Carbon-based catalyst for synergistically removing NOx and VOCs and preparation method thereof

Abstract

The invention belongs to the technical field of carbon-based catalyst materials and preparation thereof, and discloses a carbon-based catalyst for synergistically removing NOx and VOCs and a preparation method of the carbon-based catalyst for synergistically removing NOx and VOCs to solve the problem that an existing catalyst is low in efficiency of synergistically removing NOx and VOCs at low temperature. In the heat treatment process, the adsorption performance of the carbon-based catalytic material is effectively improved, meanwhile, uniform dispersion of Fe / V oxide can be effectively promoted, and then efficient removal of NOx and VOCs at the low temperature is achieved. Furthermore, by adding ammonia modification treatment, the dispersity of loaded metal particles is enhanced while the surface active sites of the catalyst are improved, and the efficiency of low-temperature denitration and catalytic oxidation reaction is further improved. The carbon-based catalyst disclosed by the invention is relatively low in preparation cost, non-toxic, relatively good in medium and low temperature activity and relatively high in N2 and NH3 selectivity, and is a low-cost environment-friendly catalyst.

Description

Technical Field

[0001] The present invention relates to a carbon-based catalytic material, in particular to a carbon-based catalyst for synergistically removing NOx and VOCs and a preparation method thereof, belonging to the technical field of carbon-based catalytic materials and their preparation. Background Art

[0002] The flue gas from the steel sintering industry or the waste incineration industry contains a large amount of NO x and VOCs, which can cause great damage to human health and the environment. To protect the atmospheric environment, we should minimize NO x and VOCs harmful pollutant emissions. In recent years, the "Air Quality Continuous Improvement Action Plan" and "National Pollution Prevention and Control Technical Guidance Catalogue" and other guiding documents have pointed out that NO x The use of high-efficiency treatment technologies such as low-temperature adsorption catalytic purification is encouraged for the treatment of VOCs.

[0003] V2O5-WO3 / TiO2 catalyst is currently the most widely used commercial SCR catalytic system, but the catalyst has a narrow active temperature window, generally 280-400°C, and is highly toxic. The temperature of sintering flue gas or waste incineration flue gas after dust removal is relatively low, usually <200°C, and the flue gas contains components such as SO2 and dust. In order to meet the activity requirements of the denitrification catalyst, the SCR purification device usually needs to be reheated or modified to heat the flue gas, which increases energy consumption and operating costs, and also limits the large-scale industrial application of this technology. Therefore, widening the collaborative control of the active temperature window, preparing new carbon-based catalysts, and efficiently and collaboratively removing pollutants such as NOx and VOCs at temperatures <200°C are currently urgent issues that need to be addressed. Chinese patent CN 115430459B, "A Synergistic Denitrification and VOCs Removal Catalyst, Preparation Method, and Application thereof," discloses a synergistic deNOx and deVOCs catalyst, its preparation method, and application. The method primarily involves ultrasonically treating a metal honeycomb substrate, washing it, drying it, and calcining it to produce a pretreated metal honeycomb substrate. The substrate is then impregnated with a mixed slurry of molecular sieves and copper, manganese, and iron salts, followed by drying and calcination to produce the synergistic denitrification and deVOCs catalyst. However, the resulting catalyst is difficult to recycle, has low catalytic efficiency at low temperatures, and is relatively expensive to produce. Summary of the Invention

[0004] In response to the problem in the prior art that the existing catalysts are not efficient in the synergistic removal of NOx and VOCs at low temperatures, the present invention provides a carbon-based catalyst for the synergistic removal of NOx and VOCs and a preparation method thereof. By simultaneously coupling iron salts, vanadium salts and potassium salts in the carbon-based raw materials and utilizing the composite effect between the metal salts, the adsorption performance of the carbon-based catalytic material can be effectively improved during the heat treatment process, and the uniform dispersion of Fe / V oxides can also be effectively promoted, thereby achieving efficient removal of NOx and VOCs at lower temperatures.

[0005] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0006] According to a first embodiment of the present invention, a method for preparing a carbon-based catalyst for synergistic removal of NOx and VOCs is provided:

[0007] A method for preparing a carbon-based catalyst for synergistically removing NOx and VOCs, the method comprising the following steps:

[0008] S1: The carbon-based raw material, iron salt, vanadium salt and potassium salt are mixed and ground into powder to obtain a dry mix, and the dry mix is ​​kneaded with a binder and a solvent to obtain a kneaded material.

[0009] S2: The mixed material is sequentially shaped and granulated, dried and heat-treated to obtain a hot material.

[0010] S3: The hot material is subjected to contact modification treatment using ammonia-containing gas to obtain a modified material, and the modified material is subjected to cooling and screening treatment to obtain the target carbon-based catalyst.

[0011] Preferably, in step S1, the carbon-based raw material is one or a mixture of raw coal and pulverized carbon. The raw coal includes, but is not limited to, one or more of bituminous coal, lignite, and anthracite. The pulverized carbon includes, but is not limited to, one or more of desulfurization and denitrification waste pulverized carbon, VOCs adsorption waste pulverized carbon, and waste pulverized carbon generated during activated carbon production and transportation.

[0012] Preferably, the carbon-based raw material is a mixture of raw coal and carbon powder, wherein the mass proportion of the raw coal is 55-85%, preferably 65-80%.

[0013] Preferably, in step S1, the iron salt is one or more of ferric nitrate, ferric oxalate, ferric carbonate, potassium ferrite and ferrocene.

[0014] Preferably, in step S1, the vanadium salt is ammonium metavanadate. And / or

[0015] Preferably, in step S1, the potassium salt is potassium carbonate and / or potassium bicarbonate.

[0016] Preferably, in step S1, the amount of iron salt used is 2-15% by mass of the carbon-based raw material, preferably 5-10%. The amount of vanadium salt and potassium salt used is such that the molar ratio of Fe element, V element and K element in the dry mix or wet mix is ​​1:0.8-1.2:1.8-3, preferably 1:0.9-1.1:2-2.5.

[0017] Preferably, in step S1, the binder is one or more of coal tar, carboxymethyl cellulose, polyvinyl alcohol, sesbania powder, starch, and resin.

[0018] Preferably, in step S1, the amount of the binder used is 1 to 15% of the mass of the dry mix, preferably 2 to 12%, and more preferably 3 to 10%.

[0019] Preferably, in step S1, the dissolving agent is one or more of distilled water, anhydrous ethanol, and acetic acid.

[0020] Preferably, in step S1, the amount of the dissolving agent used is 12-35% of the total mass of the dry mix and the binder, preferably 14-28% (ie, the moisture content of the mixed material).

[0021] Preferably, in step S1, the carbon-based raw material, iron salt, vanadium salt and potassium salt are mixed and ground so that the particle size of the ground dry mixture satisfies a 325 mesh pass rate of greater than 80%, preferably greater than 90%.

[0022] Preferably, in step S1, the mixing equipment for mixing the carbon-based raw material, iron salt, vanadium salt and potassium salt can be a vertical, horizontal or inclined mixer with stirring blades, preferably a vertical intensive mixer.

[0023] Preferably, in step S2, the material after molding and granulation is 3-15 mm spherical, quasi-spherical, cylindrical, or block-shaped particles, preferably 8-10 mm spherical, quasi-spherical, cylindrical, or block-shaped particles.

[0024] Preferably, in step S2, the moisture content of the dried material is less than 8%.

[0025] Preferably, in step S2, the heat treatment is carbonization and / or activation. The carbonization temperature is 200-950°C, preferably 300-900°C. The final carbonization temperature is 600-900°C, preferably 650-800°C. The carbonization time is 15-180 minutes, preferably 30-150 minutes. The activation temperature is 800-950°C, preferably 850-900°C. The activation time is 30-1500 minutes, preferably 60-1200 minutes. The activation medium is steam.

[0026] It should be noted that the heat treatment process can be carbonization only or carbonization combined with activation. If only carbonization is used, carbonization can be carried out in a rotary carbonization furnace or a horizontal translation-propelled electric heating furnace. The carbonization process controls the carbonization temperature to be 200-950°C, the final carbonization temperature to be 600-900°C (preferably 650-800°C), and the carbonization time to be 15-180 minutes. If carbonization combined with activation is used, carbonization can be carried out in a rotary carbonization furnace or a horizontal translation-propelled electric heating furnace. The carbonization process controls the carbonization temperature to be 200-850°C, the final carbonization temperature to be 600-800°C, and the carbonization time to be 15-180 minutes. Activation can be carried out in a vertical Slep furnace or a horizontal translation-propelled electric heating furnace. The activation process controls the activation temperature to be 800-950°C, the activation time to be 30-1440 minutes, and the activation medium is water vapor.

[0027] Preferably, in step S3, the ammonia-containing gas is a mixed gas composed of ammonia and one or more of nitrogen, carbon dioxide, and inert gases (such as helium, argon, xenon, etc.). The volume concentration of ammonia in the ammonia-containing gas is 5 to 10%, preferably 6 to 8%. The temperature of the contact modification treatment is 500 to 850° C., preferably 550 to 800° C. The duration of the contact modification treatment is 15 to 240 minutes, preferably 30 to 200 minutes. The contact modification treatment process is to fully contact and mix the ammonia-containing gas with the hot material after heat treatment to carry out a high-temperature reaction to achieve surface activation modification.

[0028] According to a second embodiment of the present invention, a method for preparing a carbon-based catalyst for synergistic removal of NOx and VOCs is provided:

[0029] A method for preparing a carbon-based catalyst for synergistically removing NOx and VOCs, the method comprising the following steps:

[0030] S1: Grind the carbon-based raw material into powder and then mix it with iron salt, vanadium salt, potassium salt and solvent to obtain a wet mixture. Ultrasonic impregnation, filtration and drying are sequentially performed on the wet mixture, and then kneading is performed with a binder to obtain a kneaded material.

[0031] S2: The mixed material is sequentially shaped and granulated, dried and heat-treated to obtain a hot material.

[0032] S3: The hot material is subjected to contact modification treatment using ammonia-containing gas to obtain a modified material, and the modified material is subjected to cooling and screening treatment to obtain the target carbon-based catalyst.

[0033] Preferably, in step S1, the carbon-based raw material is one or a mixture of raw coal and pulverized carbon. The raw coal includes, but is not limited to, one or more of bituminous coal, lignite, and anthracite. The pulverized carbon includes, but is not limited to, one or more of desulfurization and denitrification waste pulverized carbon, VOCs adsorption waste pulverized carbon, and waste pulverized carbon generated during activated carbon production and transportation.

[0034] Preferably, the carbon-based raw material is a mixture of raw coal and carbon powder, wherein the mass proportion of the raw coal is 55-85%, preferably 65-80%.

[0035] Preferably, in step S1, the iron salt is one or more of ferric nitrate, ferric oxalate, ferric carbonate, potassium ferrite and ferrocene.

[0036] Preferably, in step S1, the vanadium salt is ammonium metavanadate. And / or

[0037] Preferably, in step S1, the potassium salt is potassium carbonate and / or potassium bicarbonate.

[0038] Preferably, in step S1, the amount of iron salt used is 2-15% by mass of the carbon-based raw material, preferably 5-10%. The amount of vanadium salt and potassium salt used is such that the molar ratio of Fe element, V element and K element in the dry mix or wet mix is ​​1:0.8-1.2:1.8-3, preferably 1:0.9-1.1:2-2.5.

[0039] Preferably, in step S1, the binder is one or more of coal tar, carboxymethyl cellulose, polyvinyl alcohol, sesbania powder, starch, and resin.

[0040] Preferably, in step S1, the amount of the binder used is 1 to 15% of the mass of the wet mixture after drying, preferably 2 to 12%, and more preferably 3 to 10%.

[0041] Preferably, in step S1, the dissolving agent is one or more of distilled water, anhydrous ethanol, and acetic acid.

[0042] Preferably, in step S1, the amount of the dissolving agent used is 80-95% of the total mass of the wet mixture, preferably 85-90%.

[0043] Preferably, in step S1, the moisture content of the wet mixed material after filtering and drying is 15-25%, preferably 18-22%.

[0044] Preferably, in step S1, the carbon-based raw material, iron salt, vanadium salt and potassium salt are mixed and ground so that the particle size of the ground dry mixture satisfies a 325 mesh pass rate of greater than 80%, preferably greater than 90%.

[0045] Preferably, in step S1, the mixing equipment for mixing the carbon-based raw material, iron salt, vanadium salt and potassium salt can be a vertical, horizontal or inclined mixer with stirring blades, preferably a vertical intensive mixer.

[0046] Preferably, in step S1, the ultrasonic immersion is carried out at room temperature for 1 to 3 hours with an ultrasonic power of 100 to 200 W. The drying temperature is 50 to 90° C., and the moisture content of the dried material (referring to the content of the solvent) is 15 to 25%.

[0047] Preferably, in step S2, the material after molding and granulation is 3-15 mm spherical, quasi-spherical, cylindrical, or block-shaped particles, preferably 8-10 mm spherical, quasi-spherical, cylindrical, or block-shaped particles.

[0048] Preferably, in step S2, the moisture content of the dried material is less than 8%.

[0049] Preferably, in step S2, the heat treatment is carbonization and / or activation. The carbonization temperature is 200-950°C, preferably 300-900°C. The final carbonization temperature is 600-900°C, preferably 650-800°C. The carbonization time is 15-180 minutes, preferably 30-150 minutes. The activation temperature is 800-950°C, preferably 850-900°C. The activation time is 30-1500 minutes, preferably 60-1200 minutes. The activation medium is steam.

[0050] Preferably, in step S3, the ammonia-containing gas is a mixed gas composed of ammonia and one or more of nitrogen, carbon dioxide, and inert gas (such as helium, argon, xenon, etc.). The volume concentration of ammonia in the ammonia-containing gas is 5-10%, preferably 6-8% (the explosion limit of ammonia in air is 15-28%. When the concentration exceeds 15%, it is very likely to explode violently when encountering a fire source). The temperature of the contact modification treatment is 500-850°C, preferably 550-800°C. The duration of the contact modification treatment is 15-240min, preferably 30-200min. The contact modification treatment process is to fully contact and mix the ammonia-containing gas with the hot material after heat treatment to carry out a high-temperature reaction to achieve surface activation modification.

[0051] According to a third embodiment of the present invention, a carbon-based catalyst for synergistically removing NOx and VOCs is provided:

[0052] A carbon-based catalyst for synergistically removing NOx and VOCs is prepared according to the preparation method described in the first embodiment or the second embodiment.

[0053] In the present invention, in response to the problem that existing catalysts are inefficient in the synergistic removal of NOx and VOCs at low temperatures, the present invention proposes a carbon-based catalyst and preparation method for the efficient synergistic removal of NOx and VOCs based on a large number of carbon-based catalyst formulation optimization and process improvement studies. The carbon-based catalyst for the synergistic removal of NOx and VOCs is prepared by proportioning raw coal and carbon powder, simultaneously mixing and loading vanadium salts, potassium salts, iron salts, etc., and then undergoing high-temperature pyrolysis and ammonia modification. Compared with traditional V2O5-WO3 / TiO2 catalysts, the novel carbon-based catalyst of the present invention has a lower production cost, is non-toxic, has better medium and low temperature activity, has higher selectivity for N2 and NH3, and has better synergistic removal of NOx and VOCs performance in the range of 120 to 180°C. It is a low-cost, environmentally friendly catalyst.

[0054] In the present invention, the carbon-based materials include raw coal and carbon powder. The raw coal source is widely available and easy to obtain. Carbon powder has a good effect on adsorbing pollutants in flue gas and loading metal salts because it contains a relatively developed pore structure, a large specific surface area and a rich variety of surface functional groups. Therefore, the use of raw coal (preferably with an ash content of less than 8%) and carbon powder as carbon-based materials can not only broaden the source of raw materials and reduce production costs, but also achieve efficient utilization of waste carbon powder and further contribute to improving the comprehensive performance of the catalyst. In a preferred embodiment, both raw coal and carbon powder need to be ground to facilitate subsequent molding and granulation. Generally, raw coal, carbon powder, iron salt, vanadium salt and potassium salt can be directly mixed in proportion and then dry-mixed and ground to obtain a dry blend, and then the dry blend is kneaded with a binder and a solvent to obtain a mixed material. Alternatively, raw coal and carbon powder may be ground to obtain a milled material, and then an iron salt, a vanadium salt, a potassium salt, a solvent, and the milled material may be wet-mixed, followed by ultrasonic impregnation, filtration, drying, and kneading with a binder to obtain a kneaded material. Finally, the kneaded material may be subjected to granulation, drying, heat treatment, with or without modification, and cooling and screening to obtain a finished catalyst material having large particles (the small particles of powdery material screened out are returned to the raw material for grinding and reuse). The carbon-based catalyst of the present invention can achieve synergistic and efficient treatment of multiple pollutants such as dust, SO2, NOx, and VOCs in steel sintering flue gas or waste incineration flue gas, and can be recycled and reused.

[0055] In the present invention, when a dry grinding mixing process is adopted: the carbon-based raw material is directly mixed and ground with metal salts such as iron, vanadium, and potassium by mechanical force to form a physically encapsulated composite powder, and the metal salt is embedded in the coal matrix in the form of solid particles, which is conducive to fully and evenly mixing the raw coal, carbon powder and metal salt inside and outside. No solvent treatment is required, and steps such as dissolution, filtration, and drying are omitted, resulting in low energy consumption and a short production cycle. In addition, the carbon-based catalyst produced by direct mixed grinding will continuously update and expose its active sites as the number of cycles increases during industrial application, maintaining a more stable catalytic activity efficiency and a relatively longer active cycle.

[0056] In the present invention, when a wet stirring impregnation mixing process is adopted: the carbon-based raw material is first ground into powder and then stirred and mixed with metal salts such as iron, vanadium, potassium, and a solvent. After the metal salt is dissolved in the solvent, it penetrates into the pores of the coal powder in the form of ions. Ultrasonic impregnation is used to enhance diffusion, achieve atomic-level dispersion, avoid agglomeration, and increase the density of active sites. At the same time, the metal ions coordinate or ion exchange with the oxygen-containing functional groups (such as -COOH, -OH) on the surface of the coal to form chemical bonds. In addition, by adjusting the solvent concentration and impregnation time, the pore structure and impregnation modification effect can also be optimized.

[0057] In the present invention, by adding iron salt, vanadium salt, potassium salt, etc. to the raw materials, in the subsequent heat treatment process, the iron oxide (such as Fe2O3) generated by the pyrolysis of the iron salt and the vanadium oxide (such as V2O5) generated by the pyrolysis of the vanadium salt both have redox activity and can promote the NH3 conversion rate. In the process of promoting the SCR reaction, the iron oxide tends to activate oxygen molecules (O2) to generate active oxygen (such as O - or O2 - ), and the vanadium oxide surface can promote the adsorption and activation of reactants (such as NOx and NH3) during the electron transfer process. At the same time, the two can react at high temperature to form a composite oxide FeVO4, which has better thermal and chemical stability than a single oxide and can maintain structural integrity during high-temperature reactions. Its band structure and surface oxygen vacancies are synergistically optimized, which can enhance the synergy and catalytic efficiency of redox reactions and achieve low-temperature and efficient denitrification. For VOCs, the active oxygen generated by Fe2O3 activating O2 can promote the deep oxidation of VOCs to CO2 and H2O. At the same time, V2O5 can also promote the adsorption of VOCs and the breaking of C-H bonds. Among them, potassium salts (potassium carbonate, potassium bicarbonate) can decompose to produce gases such as CO2 during the subsequent high-temperature pyrolysis process, which can create pores in the carbon-based catalyst and expand the pore structure, increase the specific surface area, and provide more anchoring sites for Fe / V oxides. Secondly, the presence of potassium ions can inhibit the agglomeration of Fe / V oxide particles through electrostatic effects, promote their uniform dispersion inside and on the surface of the carbon-based catalyst, and thus expose more active sites.

[0058] In the present invention, the heat treatment process can be carbonization only or carbonization combined with activation. If carbonization only is used, carbonization can be carried out in a rotary carbonization furnace or a horizontal translation-propelled electric heating furnace. The carbonization process controls the carbonization temperature to be 200-950°C, the final carbonization temperature to be 600-900°C (preferably 650-800°C), and the carbonization time to be 15-180 minutes. If carbonization combined with activation is used, carbonization can be carried out in a rotary carbonization furnace or a horizontal translation-propelled electric heating furnace. The carbonization process controls the carbonization temperature to be 200-850°C, the final carbonization temperature to be 600-800°C, and the carbonization time to be 15-180 minutes. Activation can be carried out in a vertical Slep furnace or a horizontal translation-propelled electric heating furnace. The activation process controls the activation temperature to be 800-950°C, the activation time to be 30-1440 minutes, and the activation medium is water vapor. Through high-temperature heat treatment, waste carbon powder and raw coal can be melt-condensed at high temperature to form a carbon-based catalyst with a certain strength and a certain pore structure; at the same time, various chemical reactions can be achieved between the carbon and metal in the raw materials, and between metal salts, to enhance the synergistic removal of NOx and VOCs effects of the finished carbon-based catalyst.

[0059] In the present invention, the hot material after heat treatment can be directly cooled and screened to obtain a large-particle finished carbon-based catalyst, or it can be further introduced into an ammonia-containing gas while hot (the carbon-based catalyst in the initial cooling section after heat treatment has a higher temperature and residual heat) to fully contact the hot material, so that the carbon-based catalyst and ammonia can undergo a surface activation reaction at a higher temperature. Alkaline groups such as amino groups (-NH2) and imine groups (-NH-) can be introduced onto the surface of the carbon-based catalyst to enhance the surface alkalinity. In SCR denitrification, the amino groups can directly serve as adsorption sites for the reducing agent (NH3), reduce the activation energy of NOx reduction, and accelerate the low-temperature catalytic reaction of NOx and NH3 (such as 4NO+4NH3+O2→4N2+6H2O). In addition, ammonia modification can also cooperate with metal active sites, enhance the dispersibility of loaded metal (such as Fe, V, K) particles, and form new catalytic active sites through nitrogen-metal coordination bonds (such as Fe-N, VN), further enhancing the redox ability, improving the efficiency of denitrification and oxidation reactions, and promoting the catalytic oxidation of VOCs (such as benzene and formaldehyde decomposition).

[0060] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0061] 1: The present invention adds metal salts such as iron, vanadium, and potassium to the raw materials, and then obtains a carbon-based catalytic material with excellent comprehensive performance after heat treatment. Compared with traditional V2O5-WO3 / TiO2 catalysts, the carbon-based catalyst of the present invention has a lower production cost, is non-toxic, has better medium and low temperature activity, and has higher selectivity for N2 and NH3. It also has good synergistic removal of NOx and VOCs performance in the range of 120°C to 180°C, and is a low-cost environmentally friendly catalyst.

[0062] 2: The present invention further adds an ammonia modification process after the heat treatment, which can, on the one hand, increase the active sites on the catalyst surface and further improve the low-temperature catalytic activity of the catalyst. On the other hand, it can also enhance the dispersibility of the loaded metal (such as Fe, V, K) particles and form new catalytic active sites through nitrogen-metal coordination bonds (such as Fe-N, VN), further strengthening the redox ability, improving the efficiency of denitrification and oxidation reactions, and promoting the catalytic oxidation of VOCs. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a process flow chart of dry mixing of the present invention.

[0064] Figure 2 It is a process flow chart of wet mixing of the present invention. DETAILED DESCRIPTION

[0065] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0066] Example 1

[0067] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0068] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0069] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0070] Example 2

[0071] 75 kg of lignite and 25 kg of desulfurization and denitrification waste carbon powder were ground to obtain a carbon-based raw material with a 325 mesh pass rate greater than 90%. The obtained carbon-based raw material was then stirred and mixed with 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, 5 kg of potassium carbonate and 1000 kg of distilled water for 1 hour, and then ultrasonicated at room temperature (ultrasonic power of 150 W) for 2 hours, and then at 70°C until a dry mixture with a moisture content of 20% was obtained. 10 kg of starch was added to the obtained dry mixture and kneaded to obtain a mixed material.

[0072] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is carbonized at 200°C for 45 minutes to a final temperature of 800°C, and then steam is introduced into the raw material for activation treatment at 900°C for 6 hours to obtain a hot material.

[0073] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0074] Example 3

[0075] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0076] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80° C. until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200° C. to 800° C. over 45 minutes to obtain a hot material.

[0077] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0078] Example 4

[0079] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 1.9 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0080] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0081] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0082] Example 5

[0083] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.04 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0084] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0085] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0086] Example 6

[0087] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 4.56 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0088] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0089] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0090] Example 7

[0091] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 5.7 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0092] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0093] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0094] Example 8

[0095] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 4.55 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0096] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0097] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0098] Example 9

[0099] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 3.41 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0100] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0101] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0102] Example 10

[0103] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 5.68 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0104] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0105] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0106] Example 11

[0107] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 6.82 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0108] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0109] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 7%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0110] Example 12

[0111] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0112] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0113] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 5%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0114] Example 13

[0115] 75 kg of lignite, 25 kg of desulfurization and denitrification waste carbon powder, 8 kg of ferric nitrate, 3.8 kg of ammonium metavanadate, and 5 kg of potassium carbonate were mixed and ground to obtain a dry blend with a 325 mesh pass rate greater than 90%. 10 kg of starch and 35 kg of distilled water were added to the obtained dry blend and kneaded to obtain a mixed material.

[0116] The kneaded material is molded and granulated to obtain a molding material, and the molding material is dried at 80°C until a raw material with a moisture content of 7% is obtained. The obtained raw material is heated from 200°C to 800°C over 45 minutes, and then steam is introduced into it at 900°C for 6 hours for activation treatment to obtain a hot material.

[0117] During the process of cooling the hot material from 800°C to 500°C (about 50 minutes), an ammonia-containing gas composed of ammonia and nitrogen (ammonia volume concentration is 10%) is introduced. The ammonia-containing gas and the hot material are contacted and modified to obtain a modified material. The modified material is cooled and screened to obtain the target carbon-based catalyst.

[0118] Comparative Example 1

[0119] Example 1 was repeated except that the amount of ferric nitrate used was 0 kg.

[0120] Comparative Example 2

[0121] Example 1 was repeated except that the amount of ammonium metavanadate used was 0 kg.

[0122] Comparative Example 3

[0123] Example 1 was repeated except that the amount of potassium carbonate used was 0 kg.

[0124] Comparative Example 4

[0125] Example 1 was repeated except that the volume concentration of ammonia was 0%.

[0126] Catalytic performance test 1:

[0127] The catalysts prepared in each embodiment and comparative example were tested according to the following steps:

[0128] 1) Pretreatment: The catalyst is heated to 200°C in a fixed bed reactor (laboratory scale) or a microreactor system and helium is introduced to remove surface impurities.

[0129] 2) Temperature control: The reaction temperature was controlled at 160°C using a programmed temperature controller and a K-type thermocouple.

[0130] 3) Gas ratio: NO, NH3, O3 and other gases are used to simulate sintering flue gas and N2 is used as the balance gas.

[0131] 4) Space velocity control: adjust the ratio of gas flow rate to catalyst loading volume (space velocity) to 265h -1 , ensuring that the reactants are fully in contact with the catalyst surface.

[0132] 5) Gas analysis: Use nitrogen oxide and ammonia sensors or analyzers to monitor the NO and NH3 concentrations at the reactor inlet and outlet in real time.

[0133] 6) Data acquisition: At a constant temperature, record the NH3 and NO concentrations at the reactor outlet and calculate the NH3 selectivity (η) and N2 selectivity (S):

[0134] η={(inlet NO concentration-outlet NO concentration) / (inlet NH3 concentration-outlet NH3 concentration)}*(14 / 46)×100%.

[0135] S = (molar flow rate of nitrogen atoms converted to N2) / (molar flow rate of total nitrogen atoms consumed at the inlet) x 100%.

[0136] 7) After the reaction reaches stability (40 minutes of reaction), data is collected to evaluate the catalyst activity.

[0137] Table 1 shows the comparison results of nitrogen and ammonia selectivity of each catalyst

[0138]

[0139]

[0140] In Table 1, N2 selectivity refers to the proportion of target product N2 (rather than by-products such as N2O) generated after the catalyst reduces NO, that is, the proportion of the total nitrogen atoms consumed that are ultimately converted to N2.

[0141] Ammonia selectivity refers to the proportion of consumed ammonia that is used to reduce NO to produce N2.

[0142] Catalytic performance test 2:

[0143] The catalysts prepared in Examples 1-13 and Comparative Examples 1-4 were used to conduct simulation tests on the removal of NOx and VOCs, respectively. The test and calculation process of the simulated removal conversion rates of NOx and VOCs are as follows:

[0144] 1) Using a fixed-bed reactor: Simulating actual flue gas composition (containing 400 ppm NO, 50 ppm CH4, and 16% O2 by volume), the performance of each particle catalyst was tested. Denitrification and VOC removal efficiencies were evaluated by adjusting parameters such as temperature (e.g., 150°C), gas ratio (e.g., NH3 / NO molar ratio), and space velocity.

[0145] 2) The gas distribution system includes: NO / N2 mixed standard gas, methane, NH3, O2, N2 (balance gas), H2O, SO2, and CO2.

[0146] 3) Key analytical instruments include: NO / NOx analyzer: chemiluminescence analysis (CLD). NH3 analyzer: FTIR or TDLAS. Online FTIR: monitoring methane. Gas chromatography (GC-FID / PID / ECD): offline or online sampling, high-precision quantification.

[0147] 4) Test Procedure: Raise the temperature to the target temperature in the reaction gas and stabilize for 1.5 hours. Maintain fixed temperature, space velocity, oxygen concentration, etc., and vary the NH3 or CH4 concentration.

[0148] 5) Measure and calculate NOx (NO) conversion rate and VOCs (CH4) conversion rate

[0149] NOx conversion rate (%): η NOx =(1-[NOx]out / [NOx]in)×100%.

[0150] VOCs conversion rate (%): η VOC =(1-[VOCs]out / [VOCs]in)×100%.

[0151] Table 2 shows the comparison results of low temperature catalytic performance and stability of each catalyst

[0152]

[0153] It can be seen from the above table that the carbon-based catalysts prepared in various embodiments of the present invention have good low-temperature catalytic performance for NOx and VOCs and good cycle stability.

Claims

1. A method for preparing a carbon-based catalyst for synergistic removal of NOx and VOCs, characterized by: The method comprises the following steps: S1: mixing and grinding a carbon-based raw material, an iron salt, a vanadium salt, and a potassium salt to obtain a dry mix, and kneading the dry mix with a binder and a solvent to obtain a kneaded material; S2: The mixed material is sequentially granulated, dried, and heat-treated to obtain a hot material; S3: The hot material is subjected to contact modification treatment using ammonia-containing gas to obtain a modified material, and the modified material is subjected to cooling and screening treatment to obtain the target carbon-based catalyst.

2. A method for preparing a carbon-based catalyst for synergistic removal of NOx and VOCs, characterized by: The method comprises the following steps: S1: grinding the carbon-based raw material and then mixing it with iron salt, vanadium salt, potassium salt, and a solvent to obtain a wet mixture, ultrasonically impregnating the wet mixture, filtering, drying, and then kneading it with a binder to obtain a kneaded material; S2: The mixed material is sequentially granulated, dried, and heat-treated to obtain a hot material; S3: The hot material is subjected to contact modification treatment using ammonia-containing gas to obtain a modified material, and the modified material is subjected to cooling and screening treatment to obtain the target carbon-based catalyst.

3. The preparation method according to claim 1 or 2, characterized in that: In step S1, the carbon-based raw material is one of raw coal and carbon powder, or a mixture of the two; the raw coal is not limited to one or more of bituminous coal, lignite, and anthracite; the carbon powder includes but is not limited to one or more of desulfurization and denitrification waste carbon powder, VOCs adsorption waste carbon powder, and waste carbon powder generated during the production and transportation of activated carbon; Preferably, the carbon-based raw material is a mixture of raw coal and carbon powder, wherein the mass proportion of the raw coal is 55-85%, preferably 65-80%.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In step S1, the iron salt is one or more of ferric nitrate, ferric oxalate, ferric carbonate, potassium ferrite and ferrocene; and / or In step S1, the vanadium salt is ammonium metavanadate; and / or In step S1, the potassium salt is potassium carbonate and / or potassium bicarbonate.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step S1, the amount of iron salt used is 2-15% of the mass of the carbon-based raw material, preferably 5-10%; the amount of vanadium salt and potassium salt used is such that the molar ratio of Fe element, V element and K element in the dry mix or wet mix is ​​1:0.8-1.2:1.8-3, preferably 1:0.9-1.1:2-2.

5.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step S1, the binder is one or more of coal tar, carboxymethyl cellulose, polyvinyl alcohol, sesbania powder, starch, and resin; Preferably, the amount of the binder used is 1 to 15% of the mass of the dry mix or wet mix after drying, preferably 2 to 12%, and more preferably 3 to 10%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In step S1, the dissolving agent is one or more of distilled water, anhydrous ethanol, and acetic acid; Preferably, the amount of the dissolving agent is 12 to 35% of the total mass of the dry mix and the binder, preferably 14 to 28%; or the amount of the dissolving agent is 80 to 95% of the total mass of the wet mix, preferably 85 to 90%; The moisture content of the wet mixed material after filtering and drying is 15-25%, preferably 18-22%.

8. The preparation method according to any one of claims 1 to 7, characterized in that: In step S2, the material after forming and granulation is 3-15 mm spherical, quasi-spherical, cylindrical, or block-shaped particles, preferably 8-10 mm spherical, quasi-spherical, cylindrical, or block-shaped particles; and / or In step S2, the moisture content of the dried material is less than 8%; and / or In step S2, the heat treatment is carbonization and / or activation; the carbonization temperature is 200-950°C, preferably 300-900°C; the final carbonization temperature is 600-900°C, preferably 650-800°C; the carbonization time is 15-180 min, preferably 30-150 min; the activation temperature is 800-950°C, preferably 850-900°C; the activation time is 30-1500 min, preferably 60-1200 min; and the activation medium is water vapor.

9. The preparation method according to any one of claims 1 to 8, characterized in that: In step S3, the ammonia-containing gas is a mixed gas composed of ammonia and one or more of nitrogen, carbon dioxide, and inert gas; the volume concentration of ammonia in the ammonia-containing gas is 5-10%, preferably 6-8%; the temperature of the contact modification treatment is 500-850°C, preferably 550-800°C; the duration of the contact modification treatment is 15-240 min, preferably 30-200 min.

10. A carbon-based catalyst for synergistic removal of NOx and VOCs, characterized by: The carbon-based catalyst for synergistically removing NOx and VOCs is prepared according to the preparation method according to any one of claims 1-9.

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