CN107913701B - Denitration catalyst and preparation method thereof - Google Patents

Denitration catalyst and preparation method thereof Download PDF

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CN107913701B
CN107913701B CN201610884647.4A CN201610884647A CN107913701B CN 107913701 B CN107913701 B CN 107913701B CN 201610884647 A CN201610884647 A CN 201610884647A CN 107913701 B CN107913701 B CN 107913701B
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source precursor
solution
mixing
denitration catalyst
catalyst
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CN107913701A (en
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刘光利
杨岳
李扬
贾媛媛
荣树茂
巫树锋
梁宝锋
王立蓉
唐中华
王军
李晶蕊
周霞
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Petrochina Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/30—Tungsten
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8628—Processes characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts

Abstract

The invention discloses a denitration catalyst and a preparation method thereof, and the denitration catalyst comprises the following steps: (1) dissolving a titanium source precursor to form a solution; (2) dissolving a tungsten source precursor, and uniformly mixing the tungsten source precursor with the solution in the step (1); (3) uniformly mixing the solution obtained in the step (2), adjusting the pH value of the solution to be alkaline, precipitating, filtering and washing to obtain a filter cake; (4) adding deionized water into the filter cake obtained in the step (3), mixing into a slurry, adding a vanadium source precursor solution, mixing uniformly, and directly drying and roasting to form powder; and (5) mixing the solution formed by the tungsten source precursor and the powder in the step (4) into slurry, stirring, adding the citric acid-sesbania powder compound, stirring for the second time, sealing, standing, drying and roasting to form the denitration catalyst. The denitration catalyst prepared by the invention can resist the uneven deposition of vanadium oxide on the surface of the vanadium oxide in flue gas, improve the strength of the catalyst, improve the network micropores and improve the performance of the catalyst.

Description

Denitration catalyst and preparation method thereof
Technical Field
The invention relates to a flue gas denitration catalyst and a preparation method thereof, in particular to a denitration catalyst for resisting uneven vanadium deposition in flue gas and a preparation method thereof, and belongs to the technical field of novel inorganic materials.
Background
Nitrogen Oxides (NO)x) Is one of the main atmospheric pollutants, and the emission requirements are increasingly strict. The stipulation in the 'twelve five' comprehensive working scheme for energy conservation and emission reduction in China is as follows: by 2015, the total national nitrogen oxide emissions were reduced by 10% compared to 2010. GB13223-2001 'atmospheric pollutant emission standard of thermal power plant' issued by the national environmental protection department in 9 months 2011 makes more strict requirements on NOx emission concentration of the thermal power plant: the newly built, expanded and reconstructed coal-fired boiler is specified in the third period of time, and the maximum allowable NOx emission concentration is 100mg/m3. The requirements of the emission standard of pollutants for petroleum refining industry issued by the national environmental protection department are as follows: beginning at 7 months and 1 day in 2015, the requirement of nitrogen oxide in regenerated flue gas discharged by newly-built catalytic cracking device is less than 200mg/m3Particular emission limits of less than 100mg/m3Existing enterprises of 7/1/2017 also implement the standard. Among the various flue gas denitration technologies, Selective Catalytic Reduction (SCR) is still the mainstream technology in the world, and NO thereofxThe removal rate can reach 80-90%. Among them, the denitration catalyst is the core of the SCR technology, developed countries developed a series of denitration catalysts aiming at the characteristics of coal quality, boiler type and the like in the last 80 th century, and many scientific research units and enterprises in China also carried out a series of researches aiming at the conditions of coal-fired boilers and catalytic cracking flue gas in China and developed some denitration catalysts.
CN201010537130 proposes a method for preparing a denitration catalyst by using a hydrothermal method, which comprises mixing a titanium source precursor and a tungsten source precursor, placing the mixture in an autoclave for hydrothermal reaction, filtering, washing and drying to obtain a titanium-tungsten powder denitration catalyst, and introducing vanadium, molybdenum and other elements to prepare a multi-metal oxide catalyst. The active component of the catalyst prepared by the method has small crystal grains and larger specific surface area, but the phenomenon of higher aggregation degree of the same materials can be caused because the active component is not fully mixed, and the activity of the catalyst can be influenced to a certain extent.
CN201110345605 provides a preparation method of a denitration catalyst, which comprises sequentially adding ammonium tungstate, ammonium molybdate and ammonium metavanadate into metatitanic acid slurry, performing ultrasonic pulping, adjusting the pH value to 4.0-6.5, standing, separating and drying to obtain catalyst powder. The method has simple process and low cost, but ammonium metavanadate is added as a solid, the solubility of vanadium is to be verified, and SO is high in activity although the vanadium is not uniformly dispersed2/SO3The conversion rate is higher, and the use performance of the catalyst is influenced.
CN201210400949 proposes a preparation method of titanium dioxide-tungsten trioxide composite powder, which is to add ammonium paratungstate solution into metatitanic acid slurry, stir and directly vacuum-dry to obtain a finished product. The method has simple process, but the titanium-tungsten mixing strength is lower, and the performance of the material is influenced to a certain extent.
In summary, the preparation of the denitration catalyst involves the mixing of various metal oxides, and the difference of the mixing mode and the process cannot completely distinguish the denitration performance of the catalyst, NOxThe conversion rate can reach more than 90 percent, which shows that the catalytic activity of the specific metal oxide is higher, and higher NO can still be obtained due to uneven dispersionxAnd (4) conversion rate. The quality of the overall performance of the catalyst needs to be verified from other aspects of characterization, and the preparation of the catalyst also needs to be compatible with the operability of industrial scale-up.
Disclosure of Invention
The invention mainly aims to provide a denitration catalyst and a preparation method thereof, so as to overcome the defects of low crushing strength and unbalanced active center in high-temperature flue gas of the denitration catalyst in the prior art, and the denitration catalyst can resist the uneven deposition of vanadium oxide in the flue gas on the surface, improve the strength of the catalyst, improve the network micropores and improve the performance of the catalyst.
The object of the present invention is achieved by a method for preparing a denitration catalyst, comprising the steps of:
(1) dissolving a titanium source precursor to form a solution;
(2) dissolving a tungsten source precursor, and uniformly mixing the tungsten source precursor with the solution in the step (1);
(3) uniformly mixing the solution obtained in the step (2), adjusting the pH value of the solution to be alkaline, precipitating, filtering and washing to obtain a filter cake;
(4) adding deionized water into the filter cake obtained in the step (3), mixing into a slurry, adding a vanadium source precursor solution, mixing uniformly, and directly drying and roasting to form powder; and
(5) and (3) mixing the solution formed by the tungsten source precursor and the powder in the step (4) into slurry, stirring, adding the citric acid-sesbania powder compound, stirring for the second time, sealing, standing, drying and roasting to form the denitration catalyst.
The preparation method of the denitration catalyst comprises the steps of (1) preparing a solution by using TiO, wherein the titanium source precursor is titanyl sulfate or metatitanic acid2The content is preferably 15-40 g/L.
The preparation method of the denitration catalyst comprises the steps of preparing a tungsten source precursor from WO ammonium paratungstate or ammonium metatungstate3The precursor of the titanium source is calculated as TiO2The mass ratio of the tungsten source precursor to the titanium source precursor used in the step (2) is preferably 2.0-5.0: 100, and the mass ratio of the tungsten source precursor to the titanium source precursor used in the step (5) is preferably 0.5-2: 100.
The preparation method of the denitration catalyst comprises the following steps of mechanically stirring and mixing, hydrodynamically mixing or \ and ultrasonic oscillation mixing in the steps (2), (4) and (5), wherein the mixing time of the steps (2) and (4) is preferably 0.5-3 h, the mixing time of the step (5) is preferably 10-60 min, and the sealing and standing time of the step (5) is preferably 8-30 h.
The preparation method of the denitration catalyst comprises the step (4), wherein a vanadium source precursor in the vanadium source precursor solution in the step (4) is ammonium metavanadate, and the vanadium source precursor is represented by V2O5Meter, the titanium source precursorWith TiO2The mass ratio of the vanadium source precursor to the titanium source precursor is preferably 0.5-2.0: 100.
In the preparation method of the denitration catalyst, in the steps (1) and (2), the titanium source precursor is dissolved and the tungsten source precursor is dissolved, and the solvent is preferably sulfuric acid, water, nitric acid or oxalic acid.
The preparation method of the denitration catalyst comprises the step of using TiO as the titanium source precursor2In terms of the mass ratio, the preferable ratio of the addition amount of the citric acid-sesbania powder compound to the titanium source precursor is 0.5-1.5: 100.
The preparation method of the denitration catalyst provided by the invention is characterized in that the roasting temperature in the step (4) and the roasting temperature in the step (5) are both preferably 400-650 ℃, and the roasting time is both preferably 4-10 h.
In the preparation method of the denitration catalyst, the agent used for adjusting the pH value in the step (3) is preferably ammonia water or potassium hydroxide, and the pH value after adjustment is more than 8.0.
The invention also provides a denitration catalyst, which is prepared by the preparation method of the denitration catalyst.
The invention has the beneficial effects that:
(1) by utilizing an in-situ mixing method, titanium atoms and tungsten atoms are mixed at a molecular level, so that crystals generated in a subsequent coprecipitation process have more lattice defects, the particle size of mixed metal oxides is small and uniform, the specific surface area is large, the crystal transition temperature of titanium dioxide crystals is increased, and the exertion of catalytic activity is facilitated;
(2) the method of ultrasonic-assisted mixing is adopted, so that the mixing of various materials at the atomic level is more uniform;
(3) the vanadium source is added when the titanium dioxide-tungsten trioxide coprecipitation material is not roasted, the penetration on the surface of titanium-tungsten particles is deeper, the connection is tighter, the dispersion is more uniform, and the activity of the catalyst is more stable after roasting;
(4) after the prepared vanadium-tungsten-titanium powder material is roasted for one time, a layer of tungsten trioxide covers the surface of the vanadium-tungsten-titanium powder material, and a citric acid-sesbania powder composite medicament is added, so that the surface of catalyst particles has more tungsten oxide attached, and meanwhile, the vanadium-tungsten-titanium powder material also has rich space network-shaped nano-scale micropores and higher crushing strength, not only can resist the uneven deposition of vanadium oxide on the surface of the vanadium-tungsten-titanium powder material in flue gas, but also can ensure high catalyst performance.
Detailed Description
The following examples illustrate the invention in detail: the present example is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.
Titanium source precursor solution:
in the present invention, the titanium source precursor is dissolved in sulfuric acid to form a solution, and the titanium source precursor is not particularly limited, but is usually limited to titanyl sulfate or metatitanic acid, and the solution of the titanium source precursor is made of TiO2And the content of the titanium source precursor is 15-40 g/L. If the concentration is less than 15g/L, the solution is too dilute, the combination with other materials is loose, and the production efficiency is low; if it exceeds 40g/L, the mixing strength with other materials is lowered due to too high concentration, resulting in poor fusion.
The denitration catalyst comprises the following substances in proportion:
in the invention, the denitration catalyst mainly comprises a titanium source precursor, a tungsten source precursor, a vanadium source precursor and a citric acid-sesbania powder compound, and if the tungsten source precursor is less, the dispersion of an active substance vanadium can be influenced, so that the performance of the catalyst is poorer; if the amount of the citric acid-sesbania powder composite is large, the adsorption of tungsten trioxide on the particle surface is influenced, and if the amount of the citric acid-sesbania powder composite is too small, the micropores on the catalyst surface are influenced.
The mixing process of the catalyst sample and the catalytic cracking waste catalyst comprises the following steps: crushing the prepared fresh catalyst, and screening to obtain 20-40 mesh powder; screening the catalytic cracking waste catalyst, and then taking 40-60 mesh powder, wherein the content of vanadium oxide in the catalytic cracking waste catalyst is about 1%. The two powders were mixed at a mass ratio of 1:1, mixed at 350 ℃ for 24 hours in an air atmosphere, and then sieved to obtain catalyst powders for evaluation. In the contact mixing process of fresh catalyst and waste catalytic cracking catalystActive matter vanadium in the waste catalytic cracking catalyst is unevenly transferred to the fresh catalyst, SO that active matter vanadium oxide on the surface of the fresh catalyst is intensively accumulated, the local activity of the catalyst is enhanced, and the SO of the catalyst is increased2/SO3The conversion rate and the overall performance of the denitration catalyst are reduced.
NOxConversion evaluation conditions: space velocity of 20000h-1Reaction temperature of 350 ℃ and inlet gas NOx600mg/Nm3、SO2Is 1000mg/Nm3The ammonia-nitrogen ratio is 1, and the water content is 10%.
NOx、SO2The concentration measuring method comprises the following steps: a continuous on-line flue gas analyzer, siemens ULTRAMAT 23.
SO2/SO3The conversion rate determination method comprises the following steps: limestone-gypsum wet flue gas desulfurization device performance acceptance test specification (DL/T998-2006).
The following examples are specific illustrations of the present invention, and "%" described in examples and comparative examples means mass percent.
Example 1:
will contain TiO2A total of 500g of titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 22.5g of ammonium paratungstate solution, oscillating for 2 hours by ultrasonic wave, gradually adding ammonia water to adjust the pH value to 9.5, precipitating completely, filtering and washing; then the washed materials are made into slurry with the water content of 50 percent by deionized water, and V is added2O5Measuring 4.5g of ammonium metavanadate solution, stirring and simultaneously carrying out ultrasonic oscillation for 1.5h, directly drying, and roasting at 620 ℃ for 8 h; mixing the calcined powder with WO3Preparing 7.5g of ammonium metatungstate solution into slurry with the water content of 30%, stirring, adding 4g of citric acid-sesbania powder composite agent, stirring for 40min, sealing and standing for 24h, drying, and roasting at 620 ℃ for 8h to obtain the denitration catalyst. The catalyst had a crush strength of 26.7kg/cm2Specific surface area 132m2(ii) in terms of/g. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Comparative example 1:
will contain TiO2A total of 500g of titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 22.5g of ammonium paratungstate solution, oscillating for 2 hours by ultrasonic wave, gradually adding ammonia water to adjust the pH value to 9.5, precipitating completely, filtering and washing; then the washed materials are made into slurry with the water content of 50 percent by deionized water, and V is added2O5Measuring 4.5g of ammonium metavanadate solution, stirring and simultaneously carrying out ultrasonic oscillation for 1.5h, directly drying, and roasting at 620 ℃ for 8 h; mixing the calcined powder with WO3Preparing 7.5g of ammonium metatungstate solution into slurry with the water content of 30%, stirring, adding 4g of polyethylene oxide, stirring for 40min, sealing and standing for 24h, drying, and roasting at 620 ℃ for 8h to obtain the denitration catalyst. The catalyst had a crush strength of 25.5kg/cm2Specific surface area 113m2(ii) in terms of/g. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Example 2
Will contain TiO2A total of 500g of titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 22.5g of ammonium paratungstate solution, mechanically stirring for 1.5h, gradually adding ammonia water to adjust the pH value to 10, completely precipitating, filtering and washing; then the washed materials are made into slurry with the water content of 50 percent by deionized water, and V is added2O5Measuring 4.5g of ammonium metavanadate solution, stirring and simultaneously carrying out ultrasonic oscillation for 1.5h, directly drying, and roasting at 600 ℃ for 8 h; mixing the calcined powder with WO35g of ammonium metatungstate solution is prepared into slurry containing 35% of water, 3.5g of citric acid-sesbania powder composite reagent is added after stirring, the mixture is stirred for 30min, sealed and kept stand for 16h, dried and roasted at 600 ℃ to obtain the denitration catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Comparative example 2
Will contain TiO2A total of 500g of titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution2At 35g/L solution, addContaining WO3Measuring 22.5g of ammonium paratungstate solution, oscillating for 1.5h by ultrasonic wave, gradually adding ammonia water to adjust the pH value to 9.0, completely precipitating, filtering and washing; then the washed materials are made into slurry with the water content of 50 percent by deionized water, and V is added2O5Measuring 4.5g of ammonium metavanadate solution, stirring and simultaneously carrying out ultrasonic oscillation for 1.5h, directly drying, and roasting at 600 ℃ for 8 h; mixing the calcined powder with WO35g of ammonium metatungstate solution is prepared into slurry containing 35% of water, the slurry is stirred for 30min, dried and roasted at 600 ℃ to obtain the denitration catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Example 3
Will contain TiO2A total of 500g of metatitanic acid was dissolved in a sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 20g of ammonium paratungstate solution, mechanically stirring for 1h, gradually adding ammonia water to adjust the pH value to 9.5, completely precipitating, filtering and washing; then the washed materials are made into slurry with the water content of 45 percent by deionized water, and V is added2O55g of ammonium metavanadate solution is counted, stirred and ultrasonically oscillated for 1h, and after direct drying, the solution is roasted for 6h at 550 ℃; mixing the calcined powder with WO35g of ammonium metatungstate solution is prepared into slurry with the water content of 30%, 3g of citric acid-sesbania powder composite agent is added after stirring, the mixture is stirred for 30min, sealed and kept stand for 20h, dried and roasted at 550 ℃, and the denitration catalyst is obtained. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Comparative example 3
According to CN201110345605 example 1, metatitanic acid is dispersed and pulped by dilute nitric acid, filtered to be neutral, and then water is added to pulp and disperse metatitanic acid to prepare metatitanic acid slurry. Sequentially adding ammonium tungstate, ammonium molybdate and ammonium vanadate into metatitanic acid slurry to ensure that the mass ratio of the three ammonium salts to metatitanic acid is 1/100, 1/100 and 0.1/100 respectively, then using ultrasonic beating to dissolve and disperse the added ammonium salts to ensure that the ammonium salts are fully adsorbed on the surface of metatitanic acid, and using nitric acid to adjust the pH value to 5.0. Standing, drying and carrying out heat treatment at 300 ℃ for 4 hours to obtain the catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Example 4
Will contain TiO2A total of 500g of metatitanic acid was dissolved in a sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 15g of ammonium paratungstate solution, oscillating for 1h by ultrasonic wave, gradually adding ammonia water to adjust the pH value to 10.5, completely precipitating, filtering and washing; then the washed materials are made into slurry with the water content of 40% by distilled water, and V is added2O55g of ammonium metavanadate solution is counted, stirred and ultrasonically oscillated for 1h at the same time, and is directly dried and roasted for 6h at 500 ℃; mixing the calcined powder with WO3Preparing slurry with 28% of water by using 3.5g of ammonium metatungstate solution, stirring, adding 2.5g of citric acid-sesbania powder composite agent, stirring for 40min, sealing and standing for 20h, drying, and roasting at 500 ℃ to obtain the denitration catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Comparative example 4
According to CN103143396 example 1, the honeycomb type flue gas denitration catalyst is prepared by extrusion molding and sintering the following raw materials in parts by weight: 83 parts of nano titanium dioxide, 8.3 parts of nano silicon dioxide, and WO310 parts by weight of ammonium metavanadate as V2O51 portion, 6.7 portions of glass fiber, 0.42 portion of extrusion aid, 0.17 portion of cellulose, 0.25 portion of polyoxyethylene and 0.17 portion of sesbania powder. The honeycomb catalyst is crushed to 20-40 meshes for evaluation. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Example 5
Will contain TiO2A total of 500g of metatitanic acid was dissolved in a sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 20g of ammonium metatungstate solution, oscillating for 1h by ultrasonic wave, gradually adding ammonia water to adjust pH value to9.5, filtering and washing after complete precipitation; then the washed materials are made into slurry with the water content of 40% by distilled water, and V is added2O5Measuring 4g of ammonium metavanadate solution, stirring and simultaneously carrying out ultrasonic oscillation for 1h, directly drying, and roasting at 550 ℃ for 6 h; mixing the calcined powder with WO35g of ammonium metatungstate solution is prepared into slurry with the water content of 30%, 3g of citric acid-sesbania powder composite agent is added after stirring, the mixture is stirred for 40min, sealed and kept stand for 20h, dried and roasted at 550 ℃ to obtain the denitration catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Example 6
Will contain TiO2A total of 500g of metatitanic acid was dissolved in a sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 10g of ammonium metatungstate solution, oscillating by ultrasonic waves for 0.5h, gradually adding ammonia water to adjust the pH value to 9.5, precipitating completely, filtering and washing; then the washed materials are made into slurry with the water content of 40% by distilled water, and V is added2O5Measuring 10g of ammonium metavanadate solution, stirring and simultaneously carrying out ultrasonic oscillation for 1h, directly drying, and roasting at 550 ℃ for 6 h; mixing the calcined powder with WO3Preparing 10g of ammonium metatungstate solution into slurry with the water content of 30%, stirring, adding 2.5g of citric acid-sesbania powder composite agent, stirring for 10min, sealing and standing for 20h, drying, and roasting at 550 ℃ to obtain the denitration catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Example 7
Will contain TiO2A total of 500g of metatitanic acid was dissolved in a sulfuric acid solution to form a TiO-containing solution2At 35g/L of solution, a solution containing WO was added3Measuring 25g of ammonium metatungstate solution, oscillating for 1.5h by ultrasonic wave, gradually adding ammonia water to adjust the pH value to 8.5, precipitating completely, filtering and washing; then the washed materials are made into slurry with the water content of 40% by distilled water, and V is added2O52.5g of ammonium metavanadate solution is counted, stirred and ultrasonically oscillated for 1h, and after direct drying, the solution is roasted for 6h at 550 ℃;mixing the calcined powder with WO3Preparing slurry with the water content of 30% by taking 2.5g of ammonium metatungstate solution, stirring, adding 7.5g of citric acid-sesbania powder composite agent, stirring for 40min, sealing and standing for 20h, drying, and roasting at 550 ℃ to obtain the denitration catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
Example 8
Will contain TiO2A total of 500g of metatitanic acid was dissolved in a sulfuric acid solution to form a TiO-containing solution2Adding a mixed solution containing WO at 35g/L3Measuring 17.5g of ammonium metatungstate solution, oscillating for 1.7h by ultrasonic wave, gradually adding potassium hydroxide to adjust the pH value to 9.5, precipitating completely, filtering and washing; then the washed materials are made into slurry with the water content of 40% by distilled water, and V is added2O55g of ammonium metavanadate solution is counted, stirred and ultrasonically oscillated for 1h, and after direct drying, the solution is roasted for 6h at 550 ℃; mixing the calcined powder with WO35g of ammonium metatungstate solution is prepared into slurry with the water content of 30%, 3g of citric acid-sesbania powder composite agent is added after stirring, the mixture is stirred for 40min, sealed and kept stand for 20h, dried and roasted at 550 ℃ to obtain the denitration catalyst. The obtained fresh catalyst and the catalyst after being mixed with the catalytic cracking vanadium-containing waste catalyst at high temperature are respectively evaluated, and the results are shown in the data of table 1.
TABLE 1 comparative table of evaluation data of examples and comparative examples
Figure BDA0001128060480000091
By way of examples and comparative examples it was found that: the denitration catalyst for resisting uneven vanadium deposition has a good effect, the mixing level of active substances reaches the molecular level through preliminary in-situ ultrasonic mixing, slightly-dispersed nano particles are obtained through coprecipitation, vanadium oxide is introduced to the surfaces and shallow layers of the particles, a catalyst intermediate is obtained through roasting, then a cocatalyst is introduced through strengthening under the action of a pore-forming agent (citric acid and sesbania powder compound), a final catalyst is obtained through roasting, and NO in catalyst evaluationxIn the presence of ammoniaWhen the nitrogen ratio is 1, the nitrogen ratio can reach more than 99 percent, and SO is obtained after the mixed treatment with the catalytic cracking vanadium-containing waste catalyst2/SO3The conversion rate is hardly increased, which shows that the surface of the catalyst hardly generates polycrystalline deposition of vanadium oxide, and the catalyst has excellent performance; in the preparation method of the denitration catalyst, if the denitration catalyst is not treated in the step (5), only the vanadium-tungsten-titanium catalyst sample after the first roasting is reserved, and SO is added after the catalytic cracking of the vanadium-containing waste catalyst2/SO3The conversion rate is slightly increased; if no pore-forming agent is added in the step (5), SO is added after the catalytic cracking vanadium-containing waste catalyst is mixed and treated2/SO3The conversion also increased slightly. In summary, when the fresh denitration catalyst and the treated catalyst prepared by the invention are evaluated under the same conditions, SO is2/SO3The conversion rate is lower than that of other comparative samples, and the effect of resisting the uneven deposition of vanadium oxide in smoke is good.
It can be seen from the crush strength data of the examples and comparative examples that the crush strength and specific surface area of the catalyst are increased when the polyoxyethylene is replaced by the citric acid-sesbania powder compound, and the inner micro-channels of the catalyst are further improved, and the catalytic efficiency is improved.
The invention has the beneficial effects that:
(1) by utilizing an in-situ mixing method, titanium atoms and tungsten atoms are mixed at a molecular level, so that crystals generated in a subsequent coprecipitation process have more lattice defects, the particle size of mixed metal oxides is small and uniform, the specific surface area is large, the crystal transition temperature of titanium dioxide crystals is increased, and the catalytic activity is favorably exerted.
(2) The method of ultrasonic-assisted mixing is adopted, so that the mixing of various materials at the atomic level is more uniform.
(3) The vanadium source is added when the titanium dioxide-tungsten trioxide coprecipitation material is not roasted, the penetration on the surface of titanium-tungsten particles is deeper, the connection is tighter, the dispersion is more uniform, and the activity of the catalyst is more stable after roasting;
(4) after the prepared vanadium-tungsten-titanium powder material is roasted for one time, a layer of tungsten trioxide covers the surface of the vanadium-tungsten-titanium powder material, and the citric acid-sesbania powder compound is added, so that the surface of catalyst particles has more tungsten oxide attached and also has rich nano-scale micropores with spatial reticular structures, the non-uniform deposition of vanadium oxide in flue gas on the surface of the catalyst particles can be resisted, and the performance of the catalyst can be improved.
The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. A preparation method of a denitration catalyst is characterized by comprising the following steps:
(1) dissolving a titanium source precursor to form a solution;
(2) dissolving a first tungsten source precursor, and uniformly mixing the first tungsten source precursor with the solution in the step (1);
(3) uniformly mixing the solution obtained in the step (2), adjusting the pH value of the solution to be alkaline, precipitating, filtering and washing to obtain a filter cake;
(4) adding deionized water into the filter cake obtained in the step (3), mixing into a slurry, adding a vanadium source precursor solution, mixing uniformly, and directly drying and roasting to form powder; and
(5) mixing the solution formed by the second tungsten source precursor and the powder in the step (4) into slurry, stirring, adding a citric acid-sesbania powder compound, stirring for the second time, sealing, standing, drying and roasting to form the denitration catalyst;
the precursor of the titanium source in the solution formed in the step (1) is TiO2The content is 15-40 g/L;
the first tungsten source precursor and the second tungsten source precursor are both prepared from WO3The precursor of the titanium source is calculated as TiO2Counting, wherein the mass ratio of the first tungsten source precursor to the titanium source precursor used in the step (2) is 2.0-5.0: 100, and the mass ratio of the second tungsten source precursor to the titanium source precursor used in the step (5) is 0.5-2: 100;
the vanadium source precursor is represented by V2O5Meter, thePrecursor of titanium source with TiO2And the mass ratio of the vanadium source precursor to the titanium source precursor is 0.5-2.0: 100.
2. The method of producing a denitration catalyst according to claim 1, wherein the titanium source precursor is titanyl sulfate or metatitanic acid.
3. The method of preparing a denitration catalyst according to claim 1, wherein the first tungsten source precursor and the second tungsten source precursor are both ammonium paratungstate or ammonium metatungstate.
4. The preparation method of the denitration catalyst according to claim 1, wherein the mixing manner in the step (2), the step (4) and the step (5) is mechanical stirring mixing, hydrodynamic mixing or \ and ultrasonic oscillation mixing, the mixing time in the step (2) and the step (4) is 0.5-3 h, the mixing time in the step (5) is 10-60 min, and the sealing standing time in the step (5) is 8-30 h.
5. The method for preparing a denitration catalyst according to claim 1, wherein the vanadium source precursor in the vanadium source precursor solution in the step (4) is ammonium metavanadate.
6. The method of preparing a denitration catalyst according to claim 1, wherein in the steps (1) and (2), the titanium source precursor is dissolved and the first tungsten source precursor is dissolved, and the solvent used is sulfuric acid, water, nitric acid or oxalic acid.
7. The method for producing a denitration catalyst according to claim 1, wherein the titanium source precursor is TiO2And the mass ratio of the addition amount of the citric acid-sesbania powder compound to the titanium source precursor is 0.5-1.5: 100.
8. The preparation method of the denitration catalyst according to claim 1, wherein the calcination temperature in the step (4) and the calcination time in the step (5) are both 400 to 650 ℃ and 4 to 10 hours.
9. The method of claim 1, wherein the agent used for adjusting the pH in step (3) is ammonia or potassium hydroxide, and the pH is greater than 8.0 after adjustment.
10. A denitration catalyst produced by the method for producing a denitration catalyst according to any one of claims 1 to 9.
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