CN107913700B - Low SO2/SO3Denitration catalyst with conversion rate and preparation method thereof - Google Patents

Low SO2/SO3Denitration catalyst with conversion rate and preparation method thereof Download PDF

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CN107913700B
CN107913700B CN201610884221.9A CN201610884221A CN107913700B CN 107913700 B CN107913700 B CN 107913700B CN 201610884221 A CN201610884221 A CN 201610884221A CN 107913700 B CN107913700 B CN 107913700B
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source precursor
catalyst
solution
conversion rate
denitration catalyst
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CN107913700A (en
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刘光利
巫树锋
贾媛媛
王军
唐中华
李扬
李晶蕊
刘发强
梁宝锋
杨岳
荣树茂
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China Petroleum and Natural Gas 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
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • 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
    • B01J23/16—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
    • 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 low SO2/SO3Denitration catalyst with conversion rate and preparation method thereof, wherein the specific surface area of the catalyst is 40-120 m2The preparation method comprises the steps of (1) forming a titanium source precursor into a solution, (2) forming a tungsten source precursor into a solution, mixing the solution with the solution of (1), (3) adjusting the pH value of the solution obtained in the step (2) to be alkaline, precipitating (4), adding water into a filter cake obtained in the step (3) to be adjusted into slurry, adding a vanadium source precursor solution, drying and roasting to form a powder, (5) mixing the tungsten source precursor solution with the powder of the step (4) into slurry, stirring, adding a pore-forming assistant, sealing, standing, drying, and (6) dipping a dried product of the step (5) into the silicon source precursor solution, drying and roasting. 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, can ensure high catalyst performance and has low conversion rate of sulfur dioxide/sulfur trioxide.

Description

Low SO2/SO3Conversion rateDenitration catalyst and preparation method thereof
Technical Field
The invention relates to a low SO2/SO3The invention relates to a flue gas denitration catalyst with conversion rate and a preparation method thereof, in particular to a denitration catalyst for resisting uneven vanadium deposition in flue gas and a preparation method thereof, belonging 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. GB 13223-2001 '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 low SO2/SO3A denitration catalyst with conversion rate and a preparation method thereof, aiming at overcoming the defects of unbalanced active center and SO in high-temperature flue gas of the denitration catalyst in the prior art2/SO3High conversion rate and unstable activity.
The invention provides a low SO2/SO3Method for preparing a denitration catalyst for conversion, the catalystThe preparation method of the preparation comprises the following steps:
(1) dissolving a titanium source precursor in acid to form a solution;
(2) dissolving a tungsten source precursor to form a solution, and uniformly mixing the solution with the solution in the step (1);
(3) adjusting the pH value of the solution obtained in the step (2) after uniform mixing 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;
(5) mixing the solution formed by the tungsten source precursor and the powder in the step (4) into slurry, stirring, adding a pore-forming assistant, stirring for the second time, sealing, standing and drying; and
(6) and (5) dipping the dried product in the step (5) in a silicon source precursor solution, and then drying and roasting to form the denitration catalyst.
Low SO in accordance with the invention2/SO3The preparation method of the denitration catalyst with the conversion rate comprises the following steps of (1) using titanyl sulfate or metatitanic acid as a titanium source precursor, using inorganic acid as the acid, and using TiO as a formed solution2The content is preferably 15-40 g/L.
Low SO in accordance with the invention2/SO3The preparation method of the denitration catalyst with the conversion rate 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.
Low SO in accordance with the invention2/SO3The preparation method of the denitration catalyst with the conversion rate comprises the steps of (2) and (4), wherein stirring or ultrasonic oscillation is adopted in a uniform mixing mode for 0.5-3 h, the pH value adjusting agent in the step (3) is preferably ammonia water, the pH value after adjustment is preferably more than 9.0, the stirring time in the step (5) is preferably 10-60 min, and the step(5) The preferred time of the middle sealing and standing is 8-30 h, and the preferred time of the soaking in the step (6) is 5-20 s.
Low SO in accordance with the invention2/SO3The preparation method of the denitration catalyst with the conversion rate comprises the step of preparing a vanadium source precursor solution from ammonium metavanadate, wherein the vanadium source precursor is V2O5The precursor of the titanium source is TiO2The mass ratio of the vanadium source precursor to the titanium source precursor is preferably 0.5-2.0: 100.
Low SO in accordance with the invention2/SO3The preparation method of the denitration catalyst with the conversion rate comprises the steps of (4) preferably selecting the mass content of slurry in water to be 35-55%, and (5) preferably selecting the mass content of slurry in water to be 25-40%, wherein in the step (6), the silicon source precursor solution is an alcoholic solution of tetraethoxysilane, and the mass content of tetraethoxysilane is preferably 3-15%.
Low SO in accordance with the invention2/SO3The preparation method of the denitration catalyst with the conversion rate comprises the step (5) of adding the pore-forming assistant which is polyoxyethylene or sesbania powder into the denitration catalyst with the amount equal to that of TiO2The mass ratio of (A) to (B) is preferably 0.3 to 1.0: 100.
Low SO in accordance with the invention2/SO3The preparation method of the denitration catalyst with the conversion rate is characterized in that the roasting temperature in the step (4) and the roasting temperature in the step (6) are both preferably 400-650 ℃, and the roasting time is both preferably 4-10 h.
Low SO in accordance with the invention2/SO3In the method for preparing the denitration catalyst with the conversion rate, the inorganic acid is preferably sulfuric acid or nitric acid.
The invention also provides the low SO2/SO3The catalyst prepared by the preparation method of the denitration catalyst with the conversion rate is a vanadium composite metal oxide catalyst, and the specific surface area of the catalyst is 40-120 m2The titanium dioxide/g comprises 80-98 wt% of titanium dioxide, 1-15 wt% of tungsten trioxide, 0.3-5 wt% of vanadium pentoxide and 0.1-10 wt% of silicon dioxide.
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 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;
(3) 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 meanwhile, the pore-forming assistant is added, so that the surface of catalyst particles has more tungsten oxide attached and nano-scale micropores, the non-uniform deposition of vanadium oxide on the surface of the catalyst particles in flue gas can be resisted, and high catalyst performance can be ensured.
(4) The catalyst which is not roasted twice is impregnated by adopting the silicon source precursor solution, a layer of inorganic silicon is attached to the surface of the roasted catalyst, the water resistance of the catalyst can be improved, the contact of sulfur dioxide in flue gas with an active center of the catalyst layer can be prevented, and the SO can be reduced2/SO3And (4) conversion rate.
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 is more than 40g/L, the concentration is highToo high and the mixing intensity with other materials is reduced, 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, a silicon source precursor and a pore-forming auxiliary agent, and if the tungsten source precursor is less, the dispersion of an active substance vanadium is influenced, so that the performance of the catalyst is poorer; if the pore-forming assistant is too much, the adsorption of tungsten trioxide on the particle surface is affected, and if the pore-forming assistant is too little, the surface porosity of the catalyst is affected.
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 process of contacting and mixing the fresh catalyst and the waste catalytic cracking catalyst, active substances vanadium in the waste catalytic cracking catalyst are unevenly transferred to the fresh catalyst, SO that the active substances vanadium oxide on the surface of the fresh catalyst are 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 solution235g/L of solution, adding a solution containing WO3Measuring 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, standing for 24h, and drying; and (3) putting the dried catalyst powder into an ethanol solution containing 10% of tetraethoxysilane for 15s, filtering, drying, and roasting at 620 ℃ for 8h 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 1:
will contain TiO2A total of 500g of titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution235g/L of solution, adding a solution containing WO3Measuring 22.5g of ammonium paratungstate solution, oscillating for 2 hours by ultrasonic wave, gradually adding ammonia water to adjust the pH value to 10, 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 8h to obtain a 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 2
Will contain TiO2A total of 500g of titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution230g/L of a solution containing WO was added3Measuring 22.5g of ammonium paratungstate solution, oscillating for 1.5h by ultrasonic wave, gradually adding ammonia water to adjust the pH value to 10, filtering and washing after complete precipitation; then the washed materials are made into water by deionized waterThe slurry with the rate of 50 percent is added with V2O5Measuring 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 with 35 percent of water, 3.5g of polyethylene oxide is added after stirring, the mixture is stirred for 30min, sealed and kept stand for 16h, and dried; and (3) putting the dried catalyst powder into an ethanol solution containing 5% of tetraethoxysilane for 10s, filtering, drying and roasting 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 solution230g/L of a solution containing WO was added3Measuring 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 solution230g/L of a solution containing WO was added3Measuring 20g of ammonium paratungstate solution, oscillating for 1h 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 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 WO3Metatungstic acid 5g in weightPreparing ammonium solution into slurry with water content of 30%, stirring, adding 3g of polyoxyethylene, stirring for 30min, sealing, standing for 20h, and drying; and (3) putting the dried catalyst powder into an ethanol solution containing 8% of tetraethoxysilane for 6s, filtering, 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.
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 solution220g/L of a solution containing WO3Measuring 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% water content by counting 3.5g of ammonium metatungstate solution, adding 2.5g of polyethylene oxide after stirring, stirring for 40min, sealing and standing for 20h, and drying; and (3) putting the dried catalyst powder into an ethanol solution containing 13% of tetraethoxysilane for 5s, filtering, 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,the results are shown in 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 titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution235g/L of solution, adding a solution containing WO3Measuring 10g 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 added2O52.5g of ammonium metavanadate solution is counted, ultrasonic oscillation is carried out for 1.5h while stirring, and after direct drying, roasting is carried out for 8h at the temperature of 620 ℃; mixing the calcined powder with WO3Preparing slurry with the water content of 30% by counting 2.5g of ammonium metatungstate solution, stirring, adding 4g of sesbania powder, stirring for 40min, sealing and standing for 24h, and drying; and (3) putting the dried catalyst powder into an ethanol solution containing 3% of tetraethoxysilane for 15s, filtering, drying, and roasting at 620 ℃ for 8h 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 titanyl sulfate was dissolved in the sulfuric acid solution to form a TiO-containing solution235g/L of solution, adding a solution containing WO3Measuring 25g 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 usedMaking slurry with water content of 50% with ionized water, adding V2O5Measuring 10g 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 10g of ammonium metatungstate solution into slurry with the water content of 30%, stirring, adding 4g of polyethylene oxide, stirring for 40min, sealing, standing for 24h, and drying; and (3) putting the dried catalyst powder into an ethanol solution containing 15% of tetraethoxysilane for 15s, filtering, drying, and roasting at 620 ℃ for 8h 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 BDA0001127937000000091
The catalyst prepared in the embodiment is a vanadium composite metal oxide catalyst, and the specific surface area is 40-120 m2The coating comprises the following components by weight percent, 80-98% of titanium dioxide, 1-15% of tungsten trioxide, 0.3-5% of vanadium pentoxide and 0.1-10% of silicon dioxide; 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 into the particle surface and the shallow layer, a catalyst intermediate is obtained through roasting, then a cocatalyst is introduced through strengthening under the action of a pore-forming aid, the final catalyst is obtained through roasting, and NO in catalyst evaluationxThe conversion rate of the catalyst can reach more than 99 percent when the ammonia nitrogen ratio is 1, the conversion rate of the catalyst sulfur dioxide/sulfur trioxide is lower, and SO is obtained after the catalyst is mixed with a 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 steps (5) and (6), only the vanadium-tungsten-titanium catalyst sample after the first roasting is reserved, and the denitration catalyst is subjected toAfter catalytic cracking vanadium-containing waste catalyst is mixed and treated, SO2/SO3The conversion rate is slightly increased; if no pore-forming assistant is added in the step (5), SO is added after the catalytic cracking vanadium-containing waste catalyst is mixed and treated2/SO3The conversion rate is slightly increased; if there is no impregnation step in step (6), SO of the catalyst2/SO3The conversion rate is higher. 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.
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 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;
(3) 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 meanwhile, the pore-forming assistant is added, so that the surface of catalyst particles has more tungsten oxide attached and nano-scale micropores, the non-uniform deposition of vanadium oxide on the surface of the catalyst particles in flue gas can be resisted, and high catalyst performance can be ensured.
(4) The catalyst which is not roasted twice is impregnated by adopting the silicon source precursor solution, a layer of inorganic silicon is attached to the surface of the roasted catalyst, the water resistance of the catalyst can be improved, the contact of sulfur dioxide in flue gas with an active center of the catalyst layer can be prevented, and the SO can be reduced2/SO3And (4) conversion rate.
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. Make SO2/SO3A method for producing a denitration catalyst with a reduced conversion rate, characterized in that the method for producing the catalyst comprises the steps of:
(1) dissolving a titanium source precursor in acid to form a solution, wherein the titanium source precursor in the solution is TiO2The content is 15-40 g/L;
(2) dissolving a first tungsten source precursor to form a solution, and uniformly mixing the solution with the solution in the step (1);
(3) adjusting the pH value of the solution obtained in the step (2) after uniform mixing 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 slurry to form slurry, adding a vanadium source precursor solution, mixing uniformly, and directly drying and roasting to form powder;
(5) mixing the solution formed by the second tungsten source precursor and the powder in the step (4) into slurry to form slurry, stirring, adding a pore-forming assistant, stirring for the second time, sealing, standing and drying; and
(6) dipping the dried product obtained in the step (5) in a silicon source precursor solution, and then drying and roasting to form a denitration catalyst;
wherein the first tungsten source precursor and the second tungsten source precursor are both 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 V2O5The precursor of the titanium source is TiO2And the mass ratio of the vanadium source precursor to the titanium source precursor is 0.5-2.0: 100.
2. Rendering SO according to claim 12/SO3The preparation method of the denitration catalyst with the reduced conversion rate is characterized in that in the step (1), the titanium source precursor is titanyl sulfate or metatitanic acid, and the acid is inorganic acid.
3. Rendering SO according to claim 12/SO3The preparation method of the denitration catalyst with the reduced conversion rate is characterized in that the first tungsten source precursor and the second tungsten source precursor are both ammonium paratungstate or ammonium metatungstate.
4. Rendering SO according to claim 12/SO3The preparation method of the denitration catalyst with the reduced conversion rate is characterized in that stirring or ultrasonic oscillation is adopted in the mode of uniform mixing in the step (2) and the step (4), the time is 0.5-3 h, the agent for adjusting the pH value in the step (3) is ammonia water, the adjusted pH value is more than 9.0, the stirring time in the step (5) is 10-60 min, the sealing and standing time in the step (5) is 8-30 h, and the dipping time in the step (6) is 5-20 s.
5. Rendering SO according to claim 12/SO3The preparation method of the denitration catalyst with the reduced conversion rate is characterized in that a vanadium source precursor in the vanadium source precursor solution is ammonium metavanadate.
6. Rendering SO according to claim 12/SO3The preparation method of the denitration catalyst with the reduced conversion rate is characterized in that the mass content of the slurry in the step (4) is 35-55%, the mass content of the slurry in the step (5) is 25-40%, and the silicon source precursor solution in the step (6) is an alcoholic solution of tetraethoxysilane, wherein the mass content of tetraethoxysilane is 3-15%.
7. Rendering SO according to claim 12/SO3A process for producing a denitration catalyst with a reduced conversion rate, characterized in thatThen, the titanium source precursor is made of TiO2In the step (5), the pore-forming assistant is polyoxyethylene or sesbania powder, and the mass ratio of the added amount to the titanium source precursor is 0.3-1.0: 100.
8. Rendering SO according to claim 12/SO3The preparation method of the denitration catalyst with the reduced conversion rate is characterized in that the roasting temperature in the step (4) and the roasting time in the step (6) are both 400-650 ℃, and the roasting time is 4-10 hours.
9. Rendering SO according to claim 22/SO3The preparation method of the denitration catalyst with reduced conversion rate is characterized in that the inorganic acid is sulfuric acid or nitric acid.
10. Rendering SO according to any of claims 1 to 92/SO3The catalyst prepared by the preparation method of the denitration catalyst with reduced conversion rate is characterized in that the catalyst is a vanadium composite metal oxide catalyst, and the specific surface area of the catalyst is 40-120 m2The titanium dioxide/g comprises 80-98 wt% of titanium dioxide, 1-15 wt% of tungsten trioxide, 0.3-5 wt% of vanadium pentoxide and 0.1-10 wt% of silicon dioxide.
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