CN108212180B - Titanium-molybdenum composite powder for medium-low temperature SCR denitration and preparation method thereof - Google Patents
Titanium-molybdenum composite powder for medium-low temperature SCR denitration and preparation method thereof Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 44
- 239000002131 composite material Substances 0.000 title claims abstract description 37
- ZPZCREMGFMRIRR-UHFFFAOYSA-N molybdenum titanium Chemical compound [Ti].[Mo] ZPZCREMGFMRIRR-UHFFFAOYSA-N 0.000 title claims abstract description 19
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 35
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Inorganic materials O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000002994 raw material Substances 0.000 claims abstract description 22
- 239000002245 particle Substances 0.000 claims abstract description 18
- 239000013078 crystal Substances 0.000 claims abstract description 6
- 238000009826 distribution Methods 0.000 claims abstract description 6
- 239000000126 substance Substances 0.000 claims abstract description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 57
- 239000002253 acid Substances 0.000 claims description 42
- QGAVSDVURUSLQK-UHFFFAOYSA-N ammonium heptamolybdate Chemical compound N.N.N.N.N.N.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[Mo].[Mo].[Mo].[Mo].[Mo].[Mo].[Mo] QGAVSDVURUSLQK-UHFFFAOYSA-N 0.000 claims description 31
- 239000012065 filter cake Substances 0.000 claims description 31
- 239000002002 slurry Substances 0.000 claims description 28
- 238000001354 calcination Methods 0.000 claims description 27
- 239000004408 titanium dioxide Substances 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 239000000463 material Substances 0.000 claims description 18
- 239000008367 deionised water Substances 0.000 claims description 17
- 229910021641 deionized water Inorganic materials 0.000 claims description 17
- 238000001914 filtration Methods 0.000 claims description 14
- 238000005507 spraying Methods 0.000 claims description 14
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 8
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 7
- 239000012467 final product Substances 0.000 claims description 5
- 238000004537 pulping Methods 0.000 claims description 5
- 229910021642 ultra pure water Inorganic materials 0.000 claims description 5
- 239000012498 ultrapure water Substances 0.000 claims description 5
- 238000013329 compounding Methods 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052717 sulfur Inorganic materials 0.000 claims description 2
- 238000010298 pulverizing process Methods 0.000 claims 2
- 239000003054 catalyst Substances 0.000 abstract description 28
- 230000008569 process Effects 0.000 abstract description 13
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000009991 scouring Methods 0.000 abstract description 3
- 239000011800 void material Substances 0.000 abstract description 3
- 239000000956 alloy Substances 0.000 abstract 2
- 229910045601 alloy Inorganic materials 0.000 abstract 2
- 238000006555 catalytic reaction Methods 0.000 abstract 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 15
- 238000005516 engineering process Methods 0.000 description 12
- 238000003756 stirring Methods 0.000 description 12
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 9
- 239000000047 product Substances 0.000 description 9
- 230000003197 catalytic effect Effects 0.000 description 7
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000003546 flue gas Substances 0.000 description 6
- 238000003825 pressing Methods 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- 238000010531 catalytic reduction reaction Methods 0.000 description 3
- 230000018044 dehydration Effects 0.000 description 3
- 238000006297 dehydration reaction Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000001125 extrusion Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 230000007062 hydrolysis Effects 0.000 description 3
- 238000006460 hydrolysis reaction Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000003916 acid precipitation Methods 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 238000006477 desulfuration reaction Methods 0.000 description 2
- 230000023556 desulfurization Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000000779 smoke Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009740 moulding (composite fabrication) Methods 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000004083 survival effect Effects 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/053—Sulfates
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- 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
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- B01D53/34—Chemical or biological purification of waste gases
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- B01J35/61—Surface area
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Abstract
The invention relates to titanium-molybdenum composite powder for medium-low temperature SCR denitration and a preparation method thereof, belonging to the field of denitration catalysts. The invention solves the technical problems of complex process and high cost in the production of the medium-low temperature SCR denitration catalyst. The invention discloses titanium-molybdenum composite powder suitable for a medium-low temperature 180-400 ℃ SCR denitration catalyst, which comprises the following chemical components in percentage by mass: TiO 2285％～95％，MoO33.0 to 10.0 percent of the total surface area of the alloy, and the specific surface area of the alloy is 80 to 120m2A crystal size of 12.0 to 16.5nm and a particle size distribution D50:0.8～1.1μm，D902.0 to 3.5 μm. TiO prepared by the invention2‑MoO3The composite powder is suitable for denitration catalyst raw material manufacturers, and the catalyst prepared from the composite powder has the advantages of high medium-low temperature catalysis efficiency, higher mechanical strength and scouring resistance strength and large void volume.
Description
Technical Field
The invention belongs to the field of denitration catalysts, and particularly relates to titanium-molybdenum composite powder for medium-low temperature SCR denitration and a preparation method thereof.
Background
With the development of economy, environmental pollution caused by energy consumption is more and more serious. Among them, the destruction of atmospheric smoke, acid rain, greenhouse effect and ozone layer has become four killers harmful to the survival of people. The smoke dust, sulfur dioxide, nitrogen oxide and other harmful substances contained in the coal-fired flue gas cause air pollution, acid rain and greenhouse effect. Harmful substances such as sulfur dioxide, nitrogen oxide and the like in China are mainly generated by a boiler coal burning process, automobile exhaust and the like. Whereby the development of denitration technology is becoming increasingly important.
The denitration technology mainly comprises an SNCR (selective non-catalytic reduction) technology and an SCR (selective catalytic reduction) technology. The SNCR technology is to spray NH or other NH-containing ammonia or urea at high temperature of 900-1100 deg.C without catalyst3OfReducing nitrogen oxides to N2. This technique requires accurate control of the temperature in the reaction zone, which is too low, low in denitration conversion, and too high, causing NH3To generate excess NOX. The SNCR technology has the common problems of high operation cost and low denitration rate. The SCR technique uses ammonia as a reducing agent for the reaction under certain conditions and with a suitable catalyst to make NOXConversion to N2And H2And O, realizing standard emission. The SCR technology has high denitration rate and lower operation cost, and is the most effective flue gas denitration technology with the most wide application at present.
Currently, the more mature SCR catalyst is the use of TiO2-WO3-V2O5The catalyst prepared from the composite powder belongs to a medium-high temperature SCR denitration catalyst, and is suitable for a tail gas temperature environment of 300-450 ℃. At present, because the power demand is increasingly large, the flue gas temperature in the power industry is higher, and a high-temperature SCR (selective catalytic reduction) technology is almost selected, so that the high-temperature denitration technology in the denitration market occupies a dominant position. However, for a part of kilns with lower flue gas temperature, if a high-temperature denitration technology is still selected, the denitration rate can be ensured only by reheating the flue gas, so that the energy consumption is overlarge. Therefore, the research on the denitration technology suitable for the medium-low temperature environment of 180-400 ℃ has great practical significance and economic value.
Patent document CN106466698A discloses a preparation method of an active carrier of a denitration catalyst, which contains more added components, has generally low catalytic efficiency at 200 ℃, and does not relate to the properties of the catalyst such as extrusion molding rate, wear rate and the like; patent document CN102247832A discloses a method for producing Al203-TiO2As a carrier, V2O5-MoO3The preparation method of the denitration catalyst which is an active component has the advantages of complex process, more added components, higher cost, no influence on the performance of the catalyst from the performance of the carrier, no relation to the mechanical strength, the extrusion molding rate, the wear rate and other performances of the catalyst.
Disclosure of Invention
Objects of the inventionProvides TiO suitable for a medium-low temperature SCR denitration catalyst2-MoO3The composite powder and the preparation method thereof overcome the defects of complex process, high cost and unsatisfactory medium-low temperature denitrification rate in the prior art for producing the medium-low temperature SCR denitration catalyst.
The invention provides titanium-molybdenum composite powder TiO for medium-low temperature SCR denitration2-MoO3The chemical composition comprises the following components in percentage by mass: TiO 2285％～95％，MoO33.0-10.0 percent of water, 0.5-2.0 percent of water, 0.5-3.0 percent of S, and Fe2O3≤100ppm，Na2O≤100ppm，K2O is less than or equal to 100ppm, the crystal size of the titanium molybdenum composite powder is 12.0-16.5 nm, and the particle size distribution D500.8 to 1.1 μm, D902.0 to 3.5 μm, and a specific surface area of 80 to 120m2The specific surface area of the calcined powder is 50-70 m after being calcined for 5 hours at the high temperature of 750 DEG C2/g。
The invention also provides a preparation method of the titanium-molybdenum composite powder for medium-low temperature SCR denitration, which comprises the following steps:
a. pulping and dispersing metatitanic acid serving as a raw material, and adjusting the pulp to be slurry with the mass fraction of 10-20% calculated by titanium dioxide;
b. adding ammonia water into the slurry obtained by the step a to adjust the pH value to 7.5-9.0;
c. b, filtering and dehydrating the slurry obtained after the treatment in the step b to obtain a blocky filter cake;
d. ammonium heptamolybdate (MoO) as raw material3The calculated content is more than or equal to 80 percent) is dissolved in deionized water to obtain an ammonium heptamolybdate solution;
e. c, mixing the solution obtained in the step d according to MoO in a final product3Uniformly spraying the mixture with the content of 3-10% on the filter cake in a spraying mode, and calcining for 5-8 h at the temperature of 150-520 ℃;
f. the calcined kiln product is crushed to obtain the TiO2-MoO3And (3) compounding powder.
Wherein the mass fraction of the raw material metatitanic acid in the step a is TiO2Calculated as 25-30 percent, and the particle diameter D500.8 to 1.5 μm.
Wherein, the metatitanic acid raw material in the step a is prepared by the preparation method in patent CN103288127A (catalyst titanium dioxide and the method for preparing the catalyst titanium dioxide and the hydrolysis method).
Preferably, the metatitanic acid raw material in the step a is subjected to multi-stage cyclone classification, and the part with the particle size being too large or too small is removed, so that the particle size D of the metatitanic acid500.8 to 1.2 μm.
Wherein, the mass fraction of the metatitanic acid in the blocky filter cake in the step c is 40-50 percent in terms of titanium dioxide.
Wherein the solution prepared from ammonium heptamolybdate in the step d is MoO3The mass percentage is 25-30%.
Wherein the resistivity used in step d is greater than 1.0 × 106Ω · cm deionized or ultrapure water.
And e, feeding the sprayed filter cake into a rotary kiln at a constant speed in the step e for segmental calcination, feeding the material into the rotary kiln from the kiln tail of the low-temperature area, and gradually moving the material to the kiln head of the high-temperature area until the material falls down from a feed opening.
Preferably, in the step e, the sprayed filter cake is calcined at 250 ℃ for 2h, calcined at 350 ℃ for 1.5h, calcined at 420 ℃ for 1h and calcined at 485 ℃ for 1 h.
The invention has the beneficial effects that:
(1) the titanium-molybdenum composite powder for low-temperature SCR denitration is suitable for medium-low-temperature (180-400 ℃) SCR denitration catalysts, and has the advantages of high specific surface area, nano-scale crystal size, uniform particle size distribution and less impurities.
(2) The invention discloses a method for preparing titanium-molybdenum composite powder for medium-low temperature SCR denitration, which comprises the steps of firstly preparing a filter cake of metatitanic acid, controlling the content of titanium dioxide in the filter cake by filtering and dehydrating, then dispersing ammonium heptamolybdate in metatitanic acid by spraying, and finally preparing TiO by calcining2-MoO3Compared with the process flow of the composite powder in which ammonium heptamolybdate is added into metatitanic acid slurry and then is subjected to filter pressing, the consumption of the ammonium heptamolybdate is reduced; compared with the mode that the ammonium heptamolybdate is directly added into metatitanic acid slurry and then directly enters the rotary kiln for calcination after drying, the method can reduce energy consumption and production cost(ii) a Economic and quality factors are also fully considered when preparing the slurry and the solution, so that the cost of the whole process is lower.
(3) In addition, in the method for preparing the titanium-molybdenum composite powder for medium-low temperature SCR denitration, materials enter the rotary kiln from the kiln tail of the low-temperature region, gradually move to the kiln head of the high-temperature region until falling from the feed opening, and have different changes such as dehydration, desulfurization, grain formation, growth and other processes at different temperature sections in the calcining process, so that the aim of full reaction is fulfilled.
(4) With the TiO of the invention2-MoO3The catalyst prepared from the composite powder has the advantages of high catalytic efficiency at medium and low temperature (180-400 ℃), high mechanical strength and scouring resistance, and large void volume.
Drawings
FIG. 1 is a graph showing the change of the denitrification rate of a catalyst prepared by an example of the present invention at different temperatures.
Detailed Description
The applicant strives to meet the realistic requirement of ensuring higher medium-low temperature denitrification rate, and prepares the titanium-molybdenum composite powder for medium-low temperature SCR denitration, which is required by the invention, through innovative improvement on the preparation method.
The invention provides titanium molybdenum composite powder for medium and low temperature SCR denitration, which comprises the following chemical components in percentage by mass: TiO 2285％～95％，MoO33.0-10.0%, crystal size of 12.0-16.5 nm, and particle size distribution D500.8 to 1.1 μm, D902.0 to 3.5 μm, and a specific surface area of 80 to 120m2/g。
By further controlling the reaction raw materials and the preparation process, the titanium-molybdenum composite powder also comprises the following components: 0.5-2.0% of water, 0.5-3.0% of S and Fe2O3(ppm)≤100，Na2O(ppm)≤100，K2O (ppm) is less than or equal to 100, and the specific surface area of the titanium-molybdenum composite powder after being calcined for 5 hours at the high temperature of 750 ℃ is 50-70 m2/g。
The specific surface area, also called aging area, of the composite powder after being calcined at the high temperature of 750 ℃ for 5 hours can reflect the high temperature resistance of the composite powder.
The invention also provides a preparation method of the titanium-molybdenum composite powder for medium-low temperature SCR denitration, which comprises the following steps:
a. pulping and dispersing metatitanic acid serving as a raw material in deionized water or ultrapure water, and adjusting to slurry with the mass fraction of 10-20% calculated by titanium dioxide;
b. adding ammonia water into the slurry obtained by the step a to adjust the pH value to 7.5-9.0;
c. b, filtering and dehydrating the slurry obtained after the treatment in the step b to obtain a blocky filter cake;
d. ammonium heptamolybdate (MoO) as raw material3Calculated content is more than or equal to 80 percent) is dissolved in deionized water to obtain ammonium heptamolybdate solution;
e. c, mixing the solution obtained in the step d according to MoO in a final product3Uniformly spraying the mixture with the content of 3-10% on a filter cake in a spraying mode, and calcining for 5-8 h at the temperature of 150-520 ℃;
f. the calcined kiln product is crushed to obtain the TiO2-MoO3And (3) compounding powder.
The particle size can indirectly react with the specific surface area, the specific surface area determines the size of a contact surface with tail gas during tail gas denitration, so that the denitration efficiency is influenced, and the particle size of the raw material metatitanic acid directly influences the particle size of the composite powder; on the other hand, the particle size of the raw metatitanic acid can affect the binding capacity of titanium dioxide and molybdenum trioxide and the denitration efficiency.
The mass fraction of the raw material metatitanic acid in the step a is TiO2Calculated as 25-30 percent, and the particle diameter D500.8 to 1.5 μm.
Preferably, the metatitanic acid as the raw material in step a is directly metatitanic acid prepared by the preparation method in patent CN103288127A (catalytic titanium dioxide and the method for preparing catalytic titanium dioxide and the hydrolysis method).
As a further preferable scheme, the raw material metatitanic acid in the step a is subjected to multi-stage cyclone separationStage, removing the over-or under-sized part to make the metatitanic acid particle diameter D500.8 to 1.2 μm.
The concentration and the pH value of the metatitanic acid slurry are adjusted in the steps a and b, so that sulfate radicals in metatitanic acid can be decomposed and removed in a subsequent calcining process through combination of the sulfate radicals and the concentration of the sulfate radicals is 10-20%, the sulfate radicals can be combined into ammonium sulfate to the maximum extent under the condition of considering the cost, the aim of the process is to perform desulfurization treatment in addition to denitration in the flue gas treatment process, and excessive S elements can cause catalyst poisoning failure.
In the step c, the step of filtering and dehydrating refers to the step of carrying out filter pressing and dehydrating treatment on the slurry by using a membrane filter press to obtain a metatitanic acid filter cake. If the titanium dioxide content in the blocky filter cake is too low, the water content is high, more fuel needs to be consumed in the subsequent calcining process for dehydration, and a large number of experiments show that in the step c, the mass fraction of the blocky filter cake, which is calculated by the titanium dioxide, is 40-50% by mass through filtering and dehydration is in a proper range by considering the factors of economy and the existing equipment.
In step d, the solution prepared from ammonium heptamolybdate is MoO3The mass percentage is 25-30%.
MoO3Too low a content can introduce more water, increase fuel consumption, MoO3Too high a content may result in MoO in the final product3Maldistribution phenomenon, and thus MoO in solutions prepared from ammonium heptamolybdate3The mass fraction should be in a suitable range.
Using a resistivity of more than 1.0X 106The reason why the deionized water or ultrapure water of omega cm dissolves ammonium heptamolybdate is to bring no other impurity components into the solution as much as possible.
And e, feeding the sprayed filter cake into a rotary kiln at a constant speed for segmental calcination, feeding the material into the rotary kiln from the kiln tail of the low-temperature area, and gradually moving the material to the kiln head of the high-temperature area until the material falls down from a feed opening. Preferably, the sprayed filter cake is calcined at 250 ℃ for 2h, calcined at 350 ℃ for 1.5h, calcined at 420 ℃ for 1h and calcined at 485 ℃ for 1 h.
In the steps d and e, firstly preparing a filter cake of metatitanic acid, controlling the content of titanium dioxide in the filter cake by filtering and dehydrating, and then introducingAmmonium heptamolybdate is dispersed in metatitanic acid by overspray, and TiO is prepared by calcination2-MoO3The ammonium heptamolybdate and the metatitanic acid filter cake are more fully and uniformly mixed by the composite powder in a spraying mode, and compared with the method of adding the ammonium heptamolybdate into metatitanic acid slurry and then performing filter pressing, the consumption of the ammonium heptamolybdate is reduced, and because the ammonium heptamolybdate is dissolved in water, the loss of the ammonium heptamolybdate can be caused in the filter pressing process; and compared with the method that the water entering the rotary kiln is directly added into the metatitanic acid slurry and then directly enters the rotary kiln for calcination after drying, the method can reduce the energy consumption and thus reduce the production cost.
The present invention will be described in further detail with reference to specific examples.
In the following examples, the raw material metatitanic acid used was metatitanic acid prepared by the method of patent CN103288127A (catalytic titanium dioxide, method for preparing catalytic titanium dioxide and hydrolysis method), the mass fraction of titanium dioxide was 25% to 30%, and the particle size D was500.8-1.5 mu m and the specific surface area of the product is 250-350 square meters per gram; the deionized water is treated with permeable membrane to obtain a resistivity of more than 1.0 × 106Omega.cm deionized water or ultrapure water; MoO in ammonium heptamolybdate used3The content is 82%.
Example 1
38Kg of metatitanic acid (TiO) was weighed2Content of 26.3%), adding into a reactor with a stirring device after cyclone classification, adding a certain amount of deionized water, and adjusting the slurry concentration to 15 wt% based on titanium dioxide; after stirring uniformly, adding ammonia water into the slurry to adjust the pH value to 8.2; filter pressing after fully stirring to obtain a blocky metatitanic acid filter cake with the mass fraction of titanium dioxide of 47.84%; 720g of ammonium heptamolybdate (in MoO)382 percent) is dissolved in 2400ml of water, and is uniformly sprayed on the metatitanic acid filter cake in a spraying mode after being uniformly stirred; calcining in a rotary kiln at 250 ℃ for 2h, at 350 ℃ for 1.5h, at 420 ℃ for 1h and at 485 ℃ for 1 h; crushing the calcined kiln falling material obtained by calcination by a crusher to prepare TiO2-MoO3And (3) a composite powder product.
Example 2
38.3Kg of metatitanic acid (TiO) was weighed226.1 percent of the content), adding the slurry into a reactor with a stirring device after cyclone classification, adding a certain amount of deionized water, and adjusting the slurry concentration to 14 percent by weight based on titanium dioxide; after stirring uniformly, adding ammonia water into the slurry to adjust the pH value to 8.8; fully stirring and filtering, wherein the filter material obtained by filtering is blocky metatitanic acid, and the mass fraction of titanium dioxide in a filter cake is 48.13%; 1.4kg of ammonium heptamolybdate is dissolved in 5000ml of deionized water, and the solution is uniformly stirred and then uniformly sprayed on a filter cake in a spraying mode; calcining in a rotary kiln at 250 ℃ for 2h, at 350 ℃ for 1.5h, at 420 ℃ for 1h and at 485 ℃ for 1 h; crushing the calcined kiln falling material obtained by calcination by a crusher to prepare powdery TiO2-MoO3And (3) a composite powder product.
Example 3
Weighing 37Kg metatitanic acid (TiO)2Content 27%), adding into a reactor with a stirring device after cyclone classification, adding a certain amount of deionized water, and adjusting the slurry concentration to 14 wt% based on titanium dioxide; after stirring uniformly, adding ammonia water into the slurry to adjust the pH value to 7.8; fully stirring and filtering, wherein the filter material obtained by filtering is blocky metatitanic acid, and the mass fraction of titanium dioxide in a filter cake is 48.26%; 1.4kg of ammonium heptamolybdate is dissolved in 5000ml of deionized water, and the solution is uniformly stirred and then uniformly sprayed on the filter cake in a spraying mode. Calcining in a rotary kiln at 250 ℃ for 2h, 350 ℃ for 1.5h, 420 ℃ for 1h and 490 ℃ for 1 h; crushing the calcined kiln falling material obtained by calcination by a crusher to prepare powdery TiO2-MoO3And (3) a composite powder product.
Example 4
36.6Kg of metatitanic acid (TiO) was weighed2Content 27.3%), adding into a reactor with a stirring device after cyclone classification, adding a certain amount of deionized water, and adjusting the slurry concentration to 15 wt% based on titanium dioxide; after stirring uniformly, adding ammonia water into the slurry to adjust the pH value to 8.0; fully stirring and filtering, wherein the filter material obtained by filtering is blocky metatitanic acid, and the mass fraction of titanium dioxide in a filter cake is 47.86%; 1.1kg of ammonium heptamolybdate is dissolved in 3800ml of deionized water, evenly stirred and evenly sprayed on the ammonium heptamolybdate by adopting a spraying modeOn the filter cake. Calcining in a rotary kiln at 250 ℃ for 2h, at 350 ℃ for 1.5h, at 420 ℃ for 1h and at 485 ℃ for 1 h; crushing the calcined kiln falling material obtained by calcination by a crusher to prepare powdery TiO2-MoO3And (3) a composite powder product.
TiO prepared in examples 1 to 42-MoO3The composite powder product was subjected to corresponding performance tests, and the results are shown in table 1.
TABLE 1
The TiO obtained in examples 1 to 4 was used2-MoO3The composite powder product is made into a catalyst through pulping and dispersing, adding a binder, physical extrusion forming, drying and shaping and roasting treatment, and the corresponding performance test is carried out on the catalyst, and the result is shown in table 2.
TABLE 2
As can be seen from Table 1, the TiO produced in the examples2-MoO3The composite powder has the advantages of high specific surface area, nano-scale crystal size, uniform particle size distribution and less impurities, and has basic conditions of the raw materials of the denitration catalyst. From Table 2 and FIG. 1, it can be seen that TiO according to the invention2-MoO3The catalyst prepared by the composite powder through the prior art has high low-temperature (180-400 ℃) catalytic efficiency, and simultaneously has higher mechanical strength, scouring resistance strength and void volume.
Claims (9)
1. The titanium-molybdenum composite powder for medium-low temperature SCR denitration is characterized by comprising the following chemical components in percentage by mass:
TiO285％～95％，MoO33.0-10.0 percent of water, 0.5-2.0 percent of water, 0.5-3.0 percent of S, and Fe2O3≤100ppm，Na2O≤100ppm，K2O is less than or equal to 100 ppm; the specific surface area is 80-120 m2A crystal size of 12.0 to 16.5nm and a particle size distribution D50:0.8～1.1μm，D902.0 to 3.5 μm; the specific surface area of the calcined powder is 50-70 m after the calcined powder is calcined at the high temperature of 750 ℃ for 5 hours2(ii)/g; the medium and low temperature is 180-400 ℃; the preparation method of the titanium-molybdenum composite powder for medium-low temperature SCR denitration comprises the following steps:
a. pulping and dispersing metatitanic acid serving as a raw material, and adjusting the pulp to be slurry with the mass fraction of 10-20% calculated by titanium dioxide;
b. adding ammonia water into the slurry obtained by the step a to adjust the pH value to 7.5-9.0;
c. b, filtering and dehydrating the slurry obtained after the treatment in the step b to obtain a blocky filter cake;
d. dissolving a raw material ammonium heptamolybdate into deionized water to obtain an ammonium heptamolybdate solution, wherein the raw material ammonium heptamolybdate is MoO3The content is more than or equal to 80 percent;
e. c, mixing the solution obtained in the step d according to MoO in a final product3C, uniformly spraying the mixture on the filter cake obtained in the step c in a spraying mode according to the content of 3-10%, and calcining the mixture for 5-8 hours at the temperature of 150-520 ℃;
f. pulverizing the calcined material to obtain TiO2-MoO3And (3) compounding powder.
2. The preparation method of the titanium molybdenum composite powder for medium and low temperature SCR denitration according to claim 1 is characterized by comprising the following steps:
a. pulping and dispersing metatitanic acid serving as a raw material, and adjusting the pulp to be slurry with the mass fraction of 10-20% calculated by titanium dioxide;
b. adding ammonia water into the slurry obtained by the step a to adjust the pH value to 7.5-9.0;
c. b, filtering and dehydrating the slurry obtained after the treatment in the step b to obtain a blocky filter cake;
d. dissolving a raw material ammonium heptamolybdate into deionized water to obtain an ammonium heptamolybdate solution, wherein the raw material ammonium heptamolybdate is MoO3The content is more than or equal to 80 percent;
e. c, mixing the solution obtained in the step d according to MoO in a final product3Content 3C, uniformly spraying the mixture on the filter cake obtained in the step c in a spraying mode according to the proportion of percent to 10 percent, and calcining the mixture for 5 to 8 hours at the temperature of between 150 and 520 ℃;
f. pulverizing the calcined material to obtain TiO2-MoO3And (3) compounding powder.
3. The method of claim 2, wherein: the mass fraction of the raw material metatitanic acid in the step a is TiO2Calculated as 25-30 percent, and the particle diameter D500.8 to 1.5 μm.
4. The method of claim 2, wherein: the particle diameter D of the raw metatitanic acid in the step a500.8 to 1.2 μm.
5. The method of claim 2, wherein: and c, the mass fraction of metatitanic acid in the blocky filter cake obtained in the step c is 40-50% by weight of titanium dioxide.
6. The method of claim 2, wherein: the ammonium heptamolybdate solution obtained in the step d is MoO3The mass percentage is 25-30%.
7. The method of claim 2, wherein: the resistivity used in the step d is more than 1.0 multiplied by 106Ω · cm deionized or ultrapure water.
8. The method of claim 2, wherein: and step e, enabling the sprayed filter cake to enter a rotary kiln at a constant speed for segmental calcination, enabling the material to enter the rotary kiln from the kiln tail of the low-temperature area, and gradually moving towards the kiln head of the high-temperature area until the material falls down from a feed opening.
9. The method of claim 8, wherein: the calcination in the step e is sequentially calcination at 250 ℃ for 2h, calcination at 350 ℃ for 1.5h, calcination at 420 ℃ for 1h and calcination at 485 ℃ for 1 h.
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