A method for preparing a composite catalyst for low-temperature synergistic denitrification and dioxin removal

Abstract

The present invention discloses a method for preparing a composite catalyst for low-temperature synergistic denitration and dioxin removal. The method comprises adding a molecular sieve modified with metal oxides of cobalt, nickel, palladium, and platinum as a single or combined component to a vanadium-based denitration catalyst to obtain a modified denitration catalyst, and mixing and pasting the activated carbon powder modified with an organic alkali solution with the modified denitration catalyst, and then preparing the composite catalyst through extrusion, drying, and calcination processes. The composite catalyst of the present invention reduces the catalytic temperature of the denitration catalyst and improves the denitration efficiency of flue gas; the activity of the hydroxyl and carboxyl groups of the modified activated carbon is enhanced, and the removal efficiency of dioxins is improved; the modified activated carbon and the modified denitration catalyst are physically combined to achieve synergistic effects on NO in flue gas. X , and efficiently remove dioxins, thereby increasing the service life of the composite catalyst.

Description

Technical Field

[0001] The invention relates to the technical field of incineration tail gas purification treatment, and in particular to a method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxining. Background Art

[0002] With the improvement of my country's urbanization process, the amount of urban garbage generated is increasing, and garbage disposal is an urgent issue for urban managers. Waste incineration power generation is a low-carbon, environmentally friendly industry that can generate new electricity, but the tail gas pollution problem after waste incineration is becoming more and more serious, especially the emissions of nitrogen oxides and dioxins in the flue gas of waste incineration have become the focus of attention from all walks of life. The Ministry of Environmental Protection has successively issued more stringent limit standards, such as the "Pollution Emission Standard for Domestic Waste Incinerators GB18485-2014" promulgated in 2014. Dioxins, as a typical persistent organic pollutant (POPs for short), have environmental persistence, bioaccumulation, long-distance migration ability and biological hazards, and are listed in the first batch of control lists of the "POPs Convention". Nitrogen oxides are one of the main causes of environmental problems such as acid rain, ozone holes, and photochemical smog. Therefore, it is of great significance to develop technologies to remove nitrogen oxides and dioxins.

[0003] The activated carbon adsorption method has the advantages of simple equipment structure and high removal efficiency, and is widely used in the terminal removal of dioxins. Selective catalytic reduction (SCR) technology has been widely used in the treatment of flue gas nitrogen oxides in coal-fired power plants, non-electric industries, etc., and can reduce nitrogen oxides (NOx) in flue gas to harmless N2 and H2O. The optimal reaction temperature of conventional denitrification catalysts is 300℃-400℃, but for waste incineration power plants, the flue gas temperature entering SCR is about 180℃, so SCR catalysts must use low-temperature catalysts. At present, there are few mature low-temperature catalysts and they are expensive, which invisibly increases operating costs. Chinese patent CN107952449B discloses "a low-temperature synergistic denitration, dedioxin and demercuration honeycomb catalyst and its preparation method". The catalyst is a honeycomb catalyst, with metatitanic acid and sulfated palygorskite as carriers, copper oxide, manganese oxide, vanadium oxide as active components, and rare earth metal oxides as active additives. The catalyst can achieve synergistic denitration, dedioxin and demercuration. Under the action of the catalyst, NOx and dioxins are selectively catalytically reduced to N2, HCl and CO2, CO; the generated HCl can be used as an additive for demercuration, and elemental mercury and CO, hydrocarbons, and olefins are completely oxidized to generate mercuric chloride and CO2; although the catalyst can synergistically denitrate and dedioxin at low temperatures, the denitrification and dedioxination efficiencies need to be improved; in addition, as denitrification and dedioxination continue, the removal efficiency of the catalyst decreases rapidly and its service life decreases.

[0004] The technology of removing dioxins by activated carbon is relatively mature, but as the country's emission requirements for NOx and dioxins become increasingly stringent, many waste incineration power plants must introduce SCR technology. Therefore, the use of activated carbon to remove dioxins and SCR technology in the tail gas treatment process will greatly increase the construction and operation costs of waste power plants. Chinese patent CN108246095B discloses "a flue gas denitrification agent and its preparation method and use". Based on the total weight of the raw material components of the flue gas denitrification agent, the flue gas denitrification agent includes: 15%~30% steel slag powder; 70%~85% alkali-activated activated carbon. The metal oxides in the steel slag powder are used as catalysts, and C and CO in the activated carbon are used as reducing agents, which significantly improves the denitrification efficiency. At the same time, the weak alkaline environment further improves the denitrification efficiency, reduces costs, and develops a new type of flue gas denitrification agent. The metal oxides in steel slag powder act as catalysts, but their denitrification efficiency is low. Although the addition of activated carbon can achieve the effect of denitrification and dioxin removal at the same time, the total amount of reaction sites of the catalyst is certain. As the catalytic reaction proceeds, the life of the catalyst will inevitably be reduced. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a composite catalyst that can efficiently remove NOx and dioxins, while reducing the catalytic temperature of the catalyst, delaying the poisoning time of the composite catalyst and increasing the service life of the catalyst.

[0006] Technical solution: The present invention discloses a method for preparing a composite catalyst for low-temperature coordinated denitration and de-dioxin removal, the method comprising the following steps:

[0007] Step S1: taking a powdered molecular sieve and immersing it in an acidic solution at a solid-liquid ratio of 1:(5-20), wherein the concentration of the acidic solution is 1-5%, stirring and drying, and then calcining at a calcination temperature of 300-450°C for 1-2 h to obtain an acidified molecular sieve powder;

[0008] Step S2: taking molecular sieve powder and dissolving it in purified water at a solid-liquid ratio of 1:(5-20) to prepare a molecular sieve solution, dissolving one or a combination of cobalt salt, nickel salt, palladium salt, and platinum salt in purified water at a solid-liquid ratio of 1:(5-10) to prepare a modified solution; stirring and mixing the molecular sieve solution and the modified solution evenly, drying, and calcining at a calcination temperature of 400-650° C. for 1-4 h to prepare a modified molecular sieve powder;

[0009] Step S3: taking anatase TiO2 and immersing it in a mixed solution of a vanadium source and a molybdenum source or a tungsten source at a solid-liquid ratio of 1:(10-40) to prepare a basic solution, taking the modified molecular sieve powder prepared in step S2 and adding it to the basic solution at a solid-liquid ratio of 1:(5-20) and mixing them evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 450-550°C for 2-8h; and crushing to obtain a denitration catalyst powder;

[0010] Step S4: taking powdered activated carbon and immersing it in an organic alkali solution at a solid-liquid ratio of 1:(2-8), stirring it evenly, and then filtering and drying it to obtain modified activated carbon powder; wherein the organic alkali solution is triethylamine or diisopropylamine solution;

[0011] Step S5: Take the modified activated carbon powder in step S4 and the denitration catalyst powder in step S3 in a mass ratio of 1: (10-20), mix them evenly, add purified water to make them into a slurry, and add silicon dioxide and glass fiber and stir them evenly to form a paste. After extrusion and drying, calcine at a calcination temperature of 300-400°C for 2-4h to obtain a composite catalyst.

[0012] The preparation method of the composite catalyst of the embodiment of the present invention is based on the vanadium-based denitration catalyst and adds a single component or a two-component metal oxide modified molecular sieve, which can increase the active sites of the molecular sieve, reduce the catalytic temperature of the catalyst, and improve the denitration efficiency of the flue gas; the activity of the hydroxyl and carboxyl groups of the modified activated carbon in the composite catalyst is enhanced, and the removal efficiency of dioxins is improved. The modified activated carbon of the composite catalyst and the modified denitration catalyst are physically combined to achieve the denitration of NO in the flue gas through synergistic action. X , and efficiently remove dioxins, extending the service life of the composite catalyst.

[0013] Preferably, the metal salt in step S2 uses a single-component cobalt source or nickel source; wherein the cobalt source is Co(NO3)2·6H2O, and the nickel source is Ni(NO3)2·6 H2O.

[0014] Preferably, the mass percentage of CoO or NiO in the modified molecular sieve powder obtained in step S2 is 1%-5%.

[0015] Preferably, the metal salt in step S2 is a combination of a cobalt source or a nickel source and a palladium source or a platinum source; wherein the cobalt source is Co(NO3)2·6 H2O, the nickel source is Ni(NO3)2·6 H2O, the palladium source is Pd(NO3)2, and the platinum source is Pt(NO3)2. The use of a modified molecular sieve of a single component of metal oxide or a modified molecular sieve of a two-component metal oxide can improve the denitration efficiency of the composite catalyst and reduce the catalytic temperature of the catalyst.

[0016] Preferably, the mass percentage of CoO or NiO in the modified molecular sieve powder prepared in step S2 is 1%-5%, and the mass percentage of PdO or PtO2 is 0.1%-0.5%.

[0017] Preferably, in step S3, the mass percentage of V2O5 in the denitration catalyst powder is 1%-4%, and the mass percentage of WO3 or MoO3 is 1%-10%.

[0018] Preferably, in step S3, the vanadium source is ammonium metavanadate, the molybdenum source is ammonium heptamolybdate, and the tungsten source is ammonium metatungstate.

[0019] Preferably, the acidic solution in step S1 is phosphoric acid, hydrochloric acid or sulfuric acid solution.

[0020] Preferably, the powdered molecular sieve is any one of HY and HZSM-5 or a combination thereof. The type of powdered molecular sieve is selected according to the requirements, and its type is not limited to the types of molecular sieves given above.

[0021] Preferably, the composite catalyst is fired in step S5 in a granular or clover-shaped shape. The composite catalyst structure of this shape increases the contact area of ​​the catalyst and improves the NO X and dioxin removal efficiency.

[0022] Compared with the prior art, the present invention has the following outstanding advantages: the preparation method of the composite catalyst of the present invention is based on the vanadium-based denitration catalyst and adds a single component or a two-component metal oxide-modified molecular sieve, which can increase the active sites of the molecular sieve, reduce the catalytic temperature of the catalyst, and improve the denitration efficiency of flue gas; the activity of the hydroxyl and carboxyl groups of the modified activated carbon in the composite catalyst is enhanced, which improves the removal efficiency of dioxins. The modified activated carbon of the composite catalyst and the modified denitration catalyst are physically combined to achieve the denitration of NO in the flue gas through synergistic action. X , and efficiently remove dioxins, thereby increasing the service life of the composite catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a comparison result of the denitration efficiency of the embodiment of the composite catalyst preparation method of the present invention and the comparative example;

[0024] Figure 2 is a comparison result of dioxin removal efficiency of the embodiment of the composite catalyst preparation method of the present invention and the comparative example;

[0025] Figure 3 is a comparison of the poisoning time of some embodiments of the composite catalyst of the present invention and the comparative examples. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in combination with Figures 1-3 of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0027] Example 1: A method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxin removal according to the present invention, the preparation method comprising the following steps:

[0028] Step S1: taking a powdered molecular sieve HY and immersing it in a phosphoric acid solution with a solid-liquid ratio of 1:5, the concentration of the acidic solution is 1%, stirring and drying, and calcining it in air at a calcination temperature of 300° C. for 2 h to obtain an acidified molecular sieve powder;

[0029] Step S2: dissolving the acidified molecular sieve powder in purified water at a solid-liquid ratio of 1:5 to obtain a molecular sieve solution, dissolving Co(NO3)2·6H2O in purified water at a solid-liquid ratio of 1:5-10 to obtain a modified solution; stirring and mixing the molecular sieve solution and the modified solution, drying, and calcining in air at a calcination temperature of 650°C for 1 h to obtain a modified molecular sieve powder, wherein the mass percentage of CoO in the modified molecular sieve powder is 5%;

[0030] Step S3: taking anatase TiO2 and immersing it in a mixed solution of ammonium metavanadate and ammonium heptamolybdate at a solid-liquid ratio of 1:10 to prepare a basic solution, taking the modified molecular sieve powder of step S2 and adding it to the basic solution at a solid-liquid ratio of 1:5 and mixing them evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 500°C for 5 h; after crushing, a denitration catalyst powder is obtained, wherein the mass percentage of V2O5 is 1%, and the mass percentage of MoO3 is 1%;

[0031] Step S4: taking powdered activated carbon and immersing it in a triethylamine solution at a solid-liquid ratio of 1:2, stirring it evenly, and then filtering and drying it to obtain modified activated carbon powder;

[0032] Step S5: uniformly mixing the modified activated carbon powder obtained in step S4 and the denitration catalyst powder obtained in step S3 at a mass ratio of 1:10, adding purified water to form a slurry, adding silicon dioxide and glass fiber and stirring to form a paste, extruding and drying, and calcining at a calcination temperature of 350° C. for 3 hours to obtain a composite catalyst;

[0033] The shape of the composite catalyst formed by extrusion firing is a granular or cloverleaf shape.

[0034] The preparation method of the composite catalyst of the present invention is based on the vanadium-based denitration catalyst and the modified molecular sieve of a single component of metal oxide, which can increase the active sites of the molecular sieve, reduce the catalytic temperature of the catalyst, and improve the denitration efficiency of flue gas; the activity of the hydroxyl and carboxyl groups of the modified activated carbon in the composite catalyst is enhanced, and the removal efficiency of dioxins is improved. The modified activated carbon of the composite catalyst and the modified denitration catalyst are physically combined to achieve the denitration of NO in the flue gas through synergistic action. X , and efficiently remove dioxins, extending the service life of the composite catalyst.

[0035] Example 2: A method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxin removal according to the present invention, the preparation method comprising the following steps:

[0036] Step S1: taking a powdered molecular sieve HZSM-5 and immersing it in a hydrochloric acid solution with a solid-liquid ratio of 1:20, the concentration of the acidic solution is 2%, stirring and drying, and calcining it in air at a calcination temperature of 350 ° C for 1.5 h to obtain an acidified molecular sieve powder;

[0037] Step S2: dissolving the acidified molecular sieve powder in purified water at a solid-liquid ratio of 1:20 to obtain a molecular sieve solution, dissolving Ni(NO3)2·6H2O in purified water at a solid-liquid ratio of 1:10 to obtain a modified solution; stirring and mixing the molecular sieve solution and the modified solution, drying, and calcining at a calcination temperature of 500°C for 3 h to obtain a modified molecular sieve powder; the mass percentage of NiO in the modified molecular sieve powder is 3%;

[0038] Step S3: taking anatase TiO2 and immersing it in a mixed solution of ammonium metavanadate and ammonium metatungstate at a solid-liquid ratio of 1:40 to prepare a basic solution, taking the modified molecular sieve powder of step S2 and adding it to the basic solution at a solid-liquid ratio of 1:20 and mixing them evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 450°C for 8 h; crushing to obtain a denitration catalyst powder; the mass percentage of V2O5 in the denitration catalyst powder is 2.5%, and the mass percentage of WO3 is 5%;

[0039] Step S4: taking powdered activated carbon and immersing it in a diisopropylamine solution at a solid-liquid ratio of 1:8, stirring it evenly, and then filtering and drying it to obtain modified activated carbon powder;

[0040] Step S5: uniformly mixing the modified activated carbon powder obtained in step S4 and the denitration catalyst powder obtained in step S3 at a mass ratio of 1:15, adding purified water to form a slurry, adding silicon dioxide and glass fiber and stirring to form a paste, extruding and drying, and calcining at a calcination temperature of 300° C. for 4 hours to obtain a composite catalyst;

[0041] The shape of the composite catalyst formed by extrusion firing is a granular or cloverleaf shape.

[0042] The preparation method of the composite catalyst of the present invention is based on the vanadium-based denitration catalyst and the modified molecular sieve of a single component of metal oxide, which can increase the active sites of the molecular sieve, reduce the catalytic temperature of the catalyst, and improve the denitration efficiency of flue gas; the activity of the hydroxyl and carboxyl groups of the modified activated carbon in the composite catalyst is enhanced, and the removal efficiency of dioxins is improved. The modified activated carbon of the composite catalyst and the modified denitration catalyst are physically combined to achieve the denitration of NO in the flue gas through synergistic action. X , and efficiently remove dioxins, extending the service life of the composite catalyst.

[0043] Example 3: A method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxin removal according to the present invention, the preparation method comprising the following steps:

[0044] Step S1: taking a powdered molecular sieve HZSM-5 and immersing it in a sulfuric acid solution at a solid-liquid ratio of 1:10, the concentration of the acidic solution is 3%, stirring and drying, and calcining at a calcination temperature of 450° C. for 1 h to obtain an acidified molecular sieve powder;

[0045] Step S2: dissolving the acidified molecular sieve powder in purified water at a solid-liquid ratio of 1:10 to obtain a molecular sieve solution, dissolving Co(NO3)2·6H2O and Pd(NO3)2 in purified water at a solid-liquid ratio of 1:7 to obtain a modified solution; stirring and mixing the molecular sieve solution and the modified solution to obtain a uniform mixture, drying, and calcining at a calcination temperature of 550°C for 2h to obtain a modified molecular sieve powder; the mass percentage of CoO in the modified molecular sieve powder is 1%, and the mass percentage of PdO is 0.5%;

[0046] Step S3: taking anatase TiO2 and immersing it in a mixed solution of ammonium metavanadate and ammonium heptamolybdate at a solid-liquid ratio of 1:20 to prepare a basic solution, taking the modified molecular sieve powder of step S2 and adding it to the basic solution at a solid-liquid ratio of 1:10 and mixing them evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 550°C for 2 h; crushing to obtain a denitration catalyst powder; the mass percentage of V2O5 in the denitration catalyst powder is 3.5%, and the mass percentage of MoO3 is 8%;

[0047] Step S4: taking powdered activated carbon and immersing it in a triethylamine solution at a solid-liquid ratio of 1:5, stirring it evenly, and then filtering and drying it to obtain modified activated carbon powder;

[0048] Step S5: uniformly mixing the modified activated carbon powder obtained in step S4 and the denitration catalyst powder obtained in step S3 at a mass ratio of 1:20, adding purified water to form a slurry, adding silicon dioxide and glass fiber and stirring to form a paste, extruding and drying, and calcining at a calcination temperature of 350° C. for 3 hours to obtain a composite catalyst;

[0049] The shape of the composite catalyst formed by extrusion and sintering is granular or clover-shaped; the ratio of the denitration catalyst powder to the modified activated carbon powder in the composite catalyst is 20:1.

[0050] The preparation method of the composite catalyst of the present invention is based on the vanadium-based denitration catalyst and adds a two-component metal oxide modified molecular sieve, which can increase the active sites of the molecular sieve, reduce the catalytic temperature of the catalyst, and improve the denitration efficiency of flue gas; the activity of the hydroxyl and carboxyl groups of the modified activated carbon in the composite catalyst is enhanced, and the removal efficiency of dioxins is improved. The modified activated carbon of the composite catalyst and the modified denitration catalyst are physically combined to achieve the denitration of NO in the flue gas through synergistic action. X , and efficiently remove dioxins, extending the service life of the composite catalyst.

[0051] Example 4: A method for preparing a composite catalyst for low-temperature coordinated denitration and dioxin removal according to the present invention, the preparation method comprising the following steps:

[0052] Step S1: taking a powdered molecular sieve HZSM-5 and immersing it in a hydrochloric acid solution with a solid-liquid ratio of 1:15, the concentration of the acidic solution is 5%, stirring and drying, and calcining at a calcination temperature of 400 ° C for 1.5 h to obtain an acidified molecular sieve powder;

[0053] Step S2: dissolving the acidified molecular sieve powder in purified water at a solid-liquid ratio of 1:15 to obtain a molecular sieve solution, dissolving Co(NO3)2·6 H2O and Pt(NO3)2 in purified water at a solid-liquid ratio of 1:8 to obtain a modified solution; stirring and mixing the molecular sieve solution and the modified solution, drying, and calcining at a calcination temperature of 400°C for 4 h to obtain a modified molecular sieve powder; the mass percentage of CoO in the modified molecular sieve powder is 4%, and the mass percentage of PtO2 is 0.1%;

[0054] Step S3: taking anatase TiO2 and immersing it in a mixed solution of ammonium metavanadate and ammonium heptamolybdate at a solid-liquid ratio of 1:30 to prepare a basic solution, taking the modified molecular sieve powder of step S2 and adding it to the basic solution at a solid-liquid ratio of 1:10 and mixing them evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 500°C for 6 hours; after crushing, a denitration catalyst powder is obtained, in which the mass percentage of V2O5 is 4%, and the mass percentage of MoO3 is 10%;

[0055] Step S4: taking powdered activated carbon and immersing it in a triethylamine solution at a solid-liquid ratio of 1:5, stirring it evenly, and then filtering and drying it to obtain modified activated carbon powder;

[0056] Step S5: uniformly mix the modified activated carbon powder obtained in step S4 and the denitration catalyst powder obtained in step S3 at a mass ratio of 1:15, add purified water to make a slurry, and add silicon dioxide and glass fiber and stir evenly to form a paste. After extrusion and drying, calcine at a calcination temperature of 400°C for 2h to obtain a composite catalyst.

[0057] The shape of the composite catalyst formed by extrusion firing is a granular or cloverleaf shape.

[0058] The preparation method of the composite catalyst of the present invention is based on the vanadium-based denitration catalyst and adds a two-component metal oxide modified molecular sieve, which can increase the active sites of the molecular sieve, reduce the catalytic temperature of the catalyst, and improve the denitration efficiency of flue gas; the activity of the hydroxyl and carboxyl groups of the modified activated carbon in the composite catalyst is enhanced, and the removal efficiency of dioxins is improved. The modified activated carbon of the composite catalyst and the modified denitration catalyst are physically combined to achieve the denitration of NO in the flue gas through synergistic action. X , and efficiently remove dioxins, extending the service life of the composite catalyst.

[0059] Comparative Examples 1-4 were set up to compare the results of denitration efficiency and dioxin removal efficiency with Examples 1-4 to determine the removal efficiency of the composite catalyst of the present invention in denitration and dioxin removal.

[0060] Comparative Example 1: The preparation method of the catalyst of Comparative Example 1 comprises the following steps:

[0061] Step L1: molecular sieve powder HZSM-5 is dissolved in purified water at a solid-liquid ratio of 1:10, Co(NO3)2·6 H2O and Pd(NO3)2 are added to the solution at a solid-liquid ratio of 1:7, stirred and mixed evenly, dried, and calcined at 550°C in air for 3 h to obtain powder A; the mass percentage of CoO in powder A is 5%, and the mass percentage of PdO is 0.5%;

[0062] Step L2: Take anatase TiO2 and immerse it in a mixed solution of ammonium metavanadate and ammonium heptamolybdate in a solid-liquid ratio of 1:20. Take powder A from step L1 and add it to the solution in a solid-liquid ratio of 1:15 and mix evenly to form a paste. After extrusion and drying, calcine at a calcination temperature of 550°C for 5 h, and obtain powder B after crushing; the mass percentage of V2O5 in powder B is 3%, and the mass percentage of MoO3 is 8%.

[0063] Step L3: Mix the powder B obtained in step L2 and powdered activated carbon in a mass ratio of 20:1, add purified water to make a slurry, and add silica and glass fiber and stir evenly to form a paste. After extrusion and drying, calcine at a calcination temperature of 300°C for 3 hours to obtain catalyst powder C.

[0064] The shape of the powder C formed by extrusion and firing is a granular or cloverleaf shape.

[0065] Comparative Example 2: Step M1: Powdered molecular sieve HZSM-5 was immersed in a hydrochloric acid solution with a solid-liquid ratio of 1:10, and the concentration of the acid solution was 2%. After stirring and drying, the mixture was calcined at a calcination temperature of 350°C for 2 h to obtain powder D.

[0066] Step M2: Powder D is dissolved in purified water at a solid-liquid ratio of 1:10, Co(NO3)2·6 H2O and Pd(NO3)2 are added to the solution at a solid-liquid ratio of 1:7, and stirred and mixed evenly. After drying, the mixture is calcined in air at a calcination temperature of 600°C for 4 h to obtain powder E; the mass percentage of CoO in powder E is 5%, and the mass percentage of PdO is 0.4%;

[0067] Step M3: Take rutile TiO2 and immerse it in a mixed solution of ammonium metavanadate and ammonium heptamolybdate in a solid-liquid ratio of 1:20. Take the powder E, silicon dioxide and glass fiber of step M2 and stir the mixed solution to form a paste. After extrusion and drying, calcine it in air at a calcination temperature of 500°C for 6h; after crushing, powder F is obtained, the mass percentage of V2O5 in powder F is 3.5%, and the mass percentage of MoO3 is 8%.

[0068] The catalyst powder J is sintered into a granular or clover-leaf shape.

[0069] Comparative Example 3: Step N1: Powdered molecular sieve HZSM-5 was immersed in a hydrochloric acid solution at a solid-liquid ratio of 1:10, the concentration of the acid solution was 2%, and after being stirred and dried, it was calcined at a calcination temperature of 400°C for 2 h to obtain powder G;

[0070] Step N2: Powder G is dissolved in purified water at a solid-liquid ratio of 1:10, Co(NO3)2·6 H2O and Pd(NO3)2 are dissolved in the aqueous solution at a solid-liquid ratio of 1:7, stirred and mixed evenly, dried, and calcined at a calcination temperature of 600°C for 3h to obtain powder H; the mass percentage of CoO in powder H is 4%, and the mass percentage of PdO is 0.4%;

[0071] Step N3: taking anatase TiO2 and immersing it in a mixed solution of ammonium metavanadate and ammonium heptamolybdate at a solid-liquid ratio of 1:20, taking the powder H of step N2 and adding it into the mixed solution at a solid-liquid ratio of 1:10, stirring evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 500°C for 6h; after crushing, powder I is obtained, and the mass percentage of V2O5 in powder I is 3.5%, and the mass percentage of MoO3 is 8%;

[0072] Step N4: The powder I obtained in step N3 is mixed evenly with activated carbon powder in a mass ratio of 20:1, purified water is added to form a slurry, and silicon dioxide and glass fiber are added and stirred evenly to form a paste. After extrusion and drying, it is calcined at a calcination temperature of 350°C for 4 hours to obtain catalyst powder J.

[0073] The catalyst powder J is sintered into a granular or clover-leaf shape.

[0074] Comparative Example 4: Step P1: Powdered molecular sieve HZSM-5 was immersed in a hydrochloric acid solution with a solid-liquid ratio of 1:10, and the concentration of the hydrochloric acid solution was 3%. After being stirred and dried, the mixture was calcined at a calcination temperature of 450°C for 1 h to obtain powder K;

[0075] Step P2: Powdered activated carbon is immersed in a triethylamine solution at a solid-liquid ratio of 1:5, stirred evenly, and then filtered and dried to obtain modified activated carbon powder L;

[0076] Step P3: taking anatase TiO2 and immersing it in a mixed solution of ammonium metavanadate and ammonium heptamolybdate at a solid-liquid ratio of 1:20, taking the powder K of step P1 and adding it into the mixed solution at a solid-liquid ratio of 1:10, and mixing them evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 550°C for 8h; after crushing, a catalyst powder M is obtained, in which the mass percentage of V2O5 is 4%, and the mass percentage of MoO3 is 7%;

[0077] Step P4: The powder M obtained in step P3 and the modified activated carbon powder L obtained in step P2 are mixed evenly in a mass ratio of 20:1, purified water is added to form a slurry, and silicon dioxide and glass fiber are added and stirred evenly to form a paste. After extrusion and drying, the paste is calcined at a calcination temperature of 400°C for 3 hours to obtain catalyst powder N.

[0078] The shape of the catalyst powder N formed by extrusion and firing is a granular or cloverleaf shape.

[0079] The catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to denitration and dioxin removal experiments to obtain the denitration and dioxin removal efficiencies of the catalysts corresponding to the corresponding Examples or Comparative Examples, and aging experiments were performed.

[0080] Test 1: The catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were tested for their low-temperature denitration performance. Test conditions: test temperatures of 150°C, 180°C, 210°C, and 240°C, NH3 concentration of 500ppm, NH3 / NO concentration ratio of 1, H2O concentration of 8%, and GHSV of 60000h -1 As shown in Table 1, the denitration efficiency values ​​of the catalysts of different embodiments and comparative examples show that the vanadium-based denitration catalyst of the molecular sieve HZSM-5 modified with bimetallic oxides and acidified has high denitration efficiency and excellent denitration performance in the temperature range of 150-240°C; and has good denitration performance even after operating for 100 hours at 240°C, and the catalyst has a long operating life.

[0081] Test 2: The catalysts prepared in the above-mentioned Examples 1-4 and Comparative Examples 1-4 were tested for dioxin performance. Test conditions: a nonane solution containing dioxin was added to a fixed bed reactor at a rate of 1 µL / min, the temperature of the volatilization tube was maintained to fully volatilize the atomized dioxin, the temperature of the volatilization section was 205°C, the reaction carrier gas was a nitrogen and oxygen mixture (90% N2, 10% O2) in a certain proportion, the carrier gas flow rate was adjusted and maintained at 1 L / min by a mass flow meter, and the test temperature was 240°C. As shown in Table 2, the dioxin removal efficiency values ​​of the catalysts of different Examples and Comparative Examples, the activated carbon powder treated with an organic alkali solution has a good dioxin removal efficiency; the modified vanadium-based denitrification catalyst and the modified activated carbon have a better removal efficiency in removing dioxins.

[0082] Test 3: Aging experiments on denitration and dioxin removal performance were conducted on the catalysts prepared in Example 3 and Comparative Examples 2 and 3. Experimental conditions: The experimental time was 1h and 240h. As shown in Table 3, the composite catalyst of Example 3 still maintained a relatively high NOX and dioxin removal efficiency after 240h of the experiment; the catalyst of Comparative Example 2 did not add activated carbon, and although it also had a good denitration efficiency, the denitration efficiency dropped rapidly as the experimental time increased. The main reason was that dioxin poisoned the denitration catalyst, causing a significant decrease in the denitration performance of the catalyst; the composite catalyst of Comparative Example 3 used activated carbon that was not soaked in organic alkali solution and had high denitration and dioxin removal performance at the beginning of the experiment, but as the experimental time increased, the denitration efficiency dropped rapidly. The main reason was that dioxin did not combine with the activated carbon in a directional manner, resulting in a portion of the denitration catalyst combining with dioxin, causing its denitration efficiency to decrease.

Claims

1. A method for preparing a composite catalyst for low-temperature coordinated denitration and dioxin removal, characterized in that: The preparation method comprises the following steps: Step S1: taking a powdered molecular sieve and immersing it in an acidic solution at a solid-liquid ratio of 1:(5-20), wherein the concentration of the acidic solution is 1-5%, stirring and drying, and then calcining at a calcination temperature of 300-450°C for 1-2 h to obtain an acidified molecular sieve powder; Step S2: taking molecular sieve powder and dissolving it in purified water at a solid-liquid ratio of 1:(5-20) to prepare a molecular sieve solution, dissolving one or a combination of cobalt salt, nickel salt, palladium salt and platinum salt in purified water at a solid-liquid ratio of 1:(5-10) to prepare a modified solution; stirring and mixing the molecular sieve solution and the modified solution evenly, drying, and calcining at a calcination temperature of 400-650°C for 1-4 h to prepare a modified molecular sieve powder; wherein the metal salt adopts a single component of a cobalt source or a nickel source, or the metal salt adopts a combination of a cobalt source or a nickel source and a palladium source or a platinum source, the cobalt source is Co(NO3)2·6 H2O, and the nickel source is Ni(NO3)2·6 H2O, the palladium source is Pd(NO3)2, and the platinum source is Pt(NO3)2; the mass percentage of CoO or NiO in the prepared modified molecular sieve powder is 1%-5%, and the mass percentage of PdO or PtO2 is 0.1%-0.5%; Step S3: taking anatase TiO2 and immersing it in a mixed solution of a vanadium source and a molybdenum source or a tungsten source at a solid-liquid ratio of 1:(10-40) to prepare a basic solution, taking the modified molecular sieve powder prepared in step S2 and adding it to the basic solution at a solid-liquid ratio of 1:(5-20) and mixing them evenly to form a paste, after extrusion and drying, calcining at a calcination temperature of 450-550°C for 2-8 h; after crushing, a denitration catalyst powder is obtained, wherein the mass percentage of V2O5 in the denitration catalyst powder is 1%-4%, and the mass percentage of WO3 or MoO3 is 1%-10%; Step S4: taking powdered activated carbon and immersing it in an organic alkali solution at a solid-liquid ratio of 1:(2-8), stirring it evenly, and then filtering and drying it to obtain modified activated carbon powder; wherein the organic alkali solution is triethylamine or diisopropylamine solution; Step S5: Take the modified activated carbon powder in step S4 and the denitration catalyst powder in step S3 in a mass ratio of 1: (10-20), mix them evenly, add purified water to make them into a slurry, and add silicon dioxide and glass fiber and stir them evenly to form a paste. After extrusion and drying, calcine at a calcination temperature of 300-400°C for 2-4h to obtain a composite catalyst.

2. The method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxin removal according to claim 1, characterized in that: In step S3, the vanadium source is ammonium metavanadate, the molybdenum source is ammonium heptamolybdate, and the tungsten source is ammonium metatungstate.

3. The method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxin removal according to claim 1, characterized in that: The acidic solution in step S1 is phosphoric acid, hydrochloric acid or sulfuric acid solution.

4. The method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxin removal according to claim 1, characterized in that: The powdered molecular sieve is any one of HY and HZSM-5 or a combination thereof.

5. The method for preparing a composite catalyst for low-temperature coordinated denitration and dedioxin removal according to claim 1, characterized in that: The fired shape of the composite catalyst in step S5 is granular, triangular, square, oval or clover-shaped.

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