CN108160107B - Ceramic carrier active coating method for removing NOx in diesel vehicle tail gas through in-situ synthesis - Google Patents
Ceramic carrier active coating method for removing NOx in diesel vehicle tail gas through in-situ synthesis Download PDFInfo
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- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 30
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- 239000000203 mixture Substances 0.000 claims abstract description 5
- 238000003837 high-temperature calcination Methods 0.000 claims abstract description 4
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- 238000007781 pre-processing Methods 0.000 claims abstract description 3
- 125000002924 primary amino group Chemical group [H]N([H])* 0.000 claims abstract description 3
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- 238000001035 drying Methods 0.000 claims description 14
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- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 12
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- 238000007664 blowing Methods 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 8
- 238000001354 calcination Methods 0.000 claims description 8
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 238000007598 dipping method Methods 0.000 claims description 6
- 239000002270 dispersing agent Substances 0.000 claims description 6
- 238000004070 electrodeposition Methods 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 229910052684 Cerium Inorganic materials 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 239000011651 chromium Substances 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 239000010949 copper Substances 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 2
- -1 cerium ions Chemical class 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 230000009471 action Effects 0.000 abstract description 5
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- 239000007789 gas Substances 0.000 description 25
- 239000007788 liquid Substances 0.000 description 22
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- VGBWDOLBWVJTRZ-UHFFFAOYSA-K cerium(3+);triacetate Chemical compound [Ce+3].CC([O-])=O.CC([O-])=O.CC([O-])=O VGBWDOLBWVJTRZ-UHFFFAOYSA-K 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 7
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- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 6
- 238000007654 immersion Methods 0.000 description 6
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- OPQARKPSCNTWTJ-UHFFFAOYSA-L copper(ii) acetate Chemical compound [Cu+2].CC([O-])=O.CC([O-])=O OPQARKPSCNTWTJ-UHFFFAOYSA-L 0.000 description 4
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 229910001868 water Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- YCIMNLLNPGFGHC-UHFFFAOYSA-N catechol Chemical compound OC1=CC=CC=C1O YCIMNLLNPGFGHC-UHFFFAOYSA-N 0.000 description 2
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 2
- PHFQLYPOURZARY-UHFFFAOYSA-N chromium trinitrate Chemical compound [Cr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O PHFQLYPOURZARY-UHFFFAOYSA-N 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 102000001621 Mucoproteins Human genes 0.000 description 1
- 108010093825 Mucoproteins Proteins 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- WYYQVWLEPYFFLP-UHFFFAOYSA-K chromium(3+);triacetate Chemical compound [Cr+3].CC([O-])=O.CC([O-])=O.CC([O-])=O WYYQVWLEPYFFLP-UHFFFAOYSA-K 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
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- 239000011232 storage material Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/82—Phosphates
- B01J29/84—Aluminophosphates containing other elements, e.g. metals, boron
- B01J29/85—Silicoaluminophosphates [SAPO compounds]
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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
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
- B01D53/9413—Processes characterised by a specific catalyst
- B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
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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
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/48—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing arsenic, antimony, bismuth, vanadium, niobium tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
- B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
- B01J29/76—Iron group metals or copper
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
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- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/01—Engine exhaust gases
- B01D2258/012—Diesel engines and lean burn gasoline engines
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
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Abstract
The invention relates to a method for removing NOx ceramic carrier active coating in tail gas of diesel vehicles by in-situ synthesis, which is characterized by comprising the following steps: firstly, preprocessing molecular sieve powder by dopamine solution to form polydopamine on the surface of the molecular sieve, then utilizing the strong hydrophilicity and cohesiveness of the polydopamine to firmly load the molecular sieve on a ceramic carrier, and finally, passing through copper ions and transition metal ions Mn+Under the coordination action with amino on polydopamine, and high-temperature calcination, finally loading a CuxO/MxO/N-doped molecular sieve mixture on the surface of the ceramic carrier in situ to prepare an active coating with a high-efficiency De-NOx effect; the method has the characteristics of simple preparation process, convenience for industrial continuous production, strong coating adhesive force and uniform active group distribution, and the prepared active coating has an excellent NOx removal effect.
Description
Technical Field
The invention relates to a ceramic carrier active coating method for removing NOx in tail gas of a diesel vehicle through in-situ synthesis, belongs to the technical field of automobile emission, and particularly belongs to the field of preparation of a carrier catalyst for SCR denitration of the tail gas of the diesel vehicle.
Background
With the gradual upgrade of environmental regulations, the limit value of NOx discharged by diesel vehicles is more and more strict, in order to meet the emission regulations, most of domestic host plants adopt SCR technology to purify NOx, and the principle is that when ammonia gas generated by urea hydrolysis or solid ammonia storage materials and NOx in tail gas pass through a carrier coated with an active coating, the NOx is rapidly reduced into nitrogen and water by the ammonia gas under the action of the active coating. In fact, the carrier in the SCR postprocessor consists of three parts, namely a ceramic carrier, a coating and an active metal component, the carrier plays the roles of supporting the coating, the active component and providing a proper catalytic reaction channel, the active component is actually a catalyst, if no coating exists, the active component has no carrier supported, if no active component exists on the coating, NOx emission is necessarily out of limit, and therefore the coating and the active component on the carrier are necessary.
Generally, the active component, the coating and the carrier are combined in two modes, wherein one mode is that the active component is firstly prepared into catalyst powder and then is adhered to the ceramic carrier, and because the catalyst and the ceramic carrier have no interaction force, the active component is particularly easy to fall off from the surface of the carrier in the running process of a vehicle, particularly under the working condition of a mine area; in another way, a coating is firstly attached to a carrier by using a binder, and then a catalyst is loaded on the ceramic carrier in an electrodeposition or in-situ mode, so that the distribution of active components is uniform, the binding force of the active components and the coating is improved, but no matter which mode is adopted, the problem of active component falling still exists because no interaction force exists between the coating and the ceramic carrier and the physical action of the binder is close to the problem, and the problem cannot be solved essentially. If the catalyst is directly synthesized in situ on the ceramic carrier in one step, the preparation process can be simplified, and the problem of coating falling is fundamentally solved.
Dopamine is a main component of a viscous substance secreted by marine mussel-like mucoprotein organisms, and is applied to the field of surface modification in recent years, but is not applied to the field of tail gas denitration. The dopamine is polymerized under certain conditions to form polydopamine containing catechol and aminoThe groups have high activity and can form strong acting force with the ceramic carrier by covalent bonds and non-covalent bonds, so that the catalyst material is firmly attached to the surface. Therefore, the design idea of the method is to firstly adopt dopamine solution to pretreat molecular sieve powder to form polydopamine on the surface of the molecular sieve, then utilize the cohesive property that the polydopamine has strong action force capable of forming covalent bonds and non-covalent bonds with a ceramic carrier, firmly load the molecular sieve carrier on the ceramic carrier, and finally, through copper ions and transition metal ions Mn+And finally, under the high-temperature calcination, synthesizing a CuxO/MxO/N-doped molecular sieve mixture on the surface of the ceramic carrier in situ under the complexing action with amino groups on the polydopamine, thereby preparing the active coating with the high-efficiency De-NOx effect.
Disclosure of Invention
The invention aims to provide a preparation method of a ceramic carrier active coating for removing NOx from tail gas of in-situ synthesis diesel vehicle, which has the characteristics of simple preparation process, convenience for industrial continuous production, strong coating adhesive force and uniform distribution of active groups, and the prepared active coating has excellent NOx removal effect.
In order to achieve the purpose, the technical scheme of the invention is realized as follows: the method for removing the ceramic carrier active coating of NOx in the tail gas of the diesel vehicle by in-situ synthesis is characterized by comprising the following steps: firstly, preprocessing molecular sieve powder by dopamine solution to form polydopamine on the surface of the molecular sieve, then utilizing the strong hydrophilicity and cohesiveness of the polydopamine to firmly load the molecular sieve on a ceramic carrier, and finally, passing through copper ions and transition metal ions Mn+Under the coordination action with amino on polydopamine, and high-temperature calcination, finally loading a CuxO/MxO/N-doped molecular sieve mixture on the surface of the ceramic carrier in situ to prepare an active coating with a high-efficiency De-NOx effect; the method comprises the following specific steps:
a) pretreating a microporous molecular sieve by using a dopamine solution to obtain PDA-molecular sieve powder, wherein the concentration of dopamine is 0.08-0.6 g/L, the treatment mode is continuous stirring, the temperature is 45-80 ℃, the treatment time is 8-24h, and the mass ratio of the molecular sieve to a dopamine solution system is 0.1-1.0;
b) the ceramic carrier is treated by ultrasonic-dipping at room temperature by adopting a uniform mixing system containing deionized water, PDA-molecular sieve powder, silica sol and a dispersing agent, wherein the solid content of the silica sol is 15-40%, the dispersing agent is industrial ethanol, the PDA-molecular sieve powder is 18-29 parts, the silica sol is 8-32 parts, and the dispersing agent is 8-20 parts;
c) blowing the ceramic carrier treated in the step b) by adopting compressed air, and drying at 80-105 ℃ to obtain the PDA-molecular sieve/ceramic carrier;
d) treating the PDA-molecular sieve powder/ceramic carrier by using an active metal solution, wherein the treatment mode is not limited to impregnation and electrodeposition, drying is carried out at the temperature of 80-105 ℃, the active metal is one or more of copper, cerium, iron and chromium, the concentration of copper ions is 0.008-0.05 mol/L, the concentration of cerium ions is 0-0.01 mol/L, the concentration of iron is 0-0.01 mol/L and the concentration of chromium is 0-0.01 mol/L;
e) calcining the carrier treated in the step d) at the temperature of 350-500 ℃ for 1-3h to obtain the ceramic carrier active coating for removing NOx in the tail gas of the diesel vehicle through in-situ synthesis.
The preparation method has the advantages that the De-NOx active coating is synthesized in situ on the ceramic carrier, and is suitable for diesel vehicle tail gas denitration.
Drawings
FIG. 1 is an EDX spectrum of an in situ synthesized diesel exhaust NOx removal ceramic washcoat prepared in example 1.
FIG. 2 is a mounting picture of the shedding rate test of the ceramic carrier active coating for removing NOx from the tail gas of the synthetic diesel vehicles prepared in examples 1-5 on a vibration test bed.
FIG. 3 shows the results of NOx activity tests on the ceramic washcoat for NOx removal from the tail gas of the synthetic diesel vehicle prepared in example 1.
FIG. 4 is a schematic diagram of the preparation principle of the present invention.
Detailed Description
In the following description of specific examples, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details.
Example 1
a) Weighing 300g of Sapo-34 molecular sieve powder, placing the Sapo-34 molecular sieve powder in a dopamine solution system with the concentration of 300g and the pH =8.0 of 0.08 g/L, continuously stirring for 8 hours at 80 ℃, and obtaining PDA-molecular sieve powder after suction filtration and drying at 105 ℃;
b) mixing and stirring a system containing 18 parts of PDA-molecular sieve powder, 8 parts of silica sol (solid content is 15%), 8 parts of ethanol and deionized water uniformly, treating a ceramic carrier by the system at room temperature, performing ultrasonic-immersion for 20min, and taking out the ceramic carrier and blowing residual liquid by using compressed air;
c) heating the ceramic carrier treated in the step b) for 2min under microwave, carrying out ultrasonic-dipping treatment for 10min according to the mode in the step b), blowing residual liquid by compressed air, and drying at 105 ℃;
d) preparing a mixed solution 20L from 242g of copper nitrate and 63.4g of cerium acetate, treating the PDA-molecular sieve powder/ceramic carrier at room temperature in an impregnation mode for 15min, taking out a purging residual liquid, heating the purging residual liquid for 2min by microwave, then impregnating the purging residual liquid into a mixed solution of copper acetate and cerium acetate again, and purging the residual liquid after 10 min;
e) calcining the carrier treated in the step d) for 3 hours at 350 ℃ to obtain the ceramic carrier active coating for removing NOx in the tail gas of the diesel vehicle through in-situ synthesis.
FIG. 1 is EDX of the ceramic carrier active coating for in situ synthesis removal of NOx from diesel vehicle exhaust prepared in example 1, and the composition of the elements in the coating can be seen;
as shown in fig. 2, the ceramic carrier active coating prepared in example 1 and used for removing NOx from the exhaust gas of diesel vehicles by in-situ synthesis is fixedly mounted on a vibration test bed, the vibration acceleration is 10g, the vibration frequency is (100 ± 5) Hz, the test time is 5h, the finished honeycomb catalyst is taken down after the experiment is finished and the quality is weighed, the carrier catalyst is taken down after the experiment is finished and the quality is weighed, the calculated coating falling rate is shown in table 1, and the falling rate of the coating prepared in example 1 is 0.2%, which shows that the coating has strong adhesive force, and the problem that the coating is easy to fall off is solved.
As shown in fig. 3, the ceramic carrier active coating prepared in example 1 for removing the diesel vehicle exhaust NOx by in-situ synthesis is subjected to a micro-reaction test, and the ratio of NO: 1000ppm, NH 3: 1000ppm, O2: 5 vol%, H2O: 10 vol%, N2 balance gas, space velocity 100000 +/-1000 h-1. The highest NOx conversion rate is 98.0%, the lowest NOx conversion rate at 150 ℃ is 61.3%, the NOx conversion rates at 215-450 ℃ can reach more than 85%, and the good NOx activity is shown, so that the use requirements of various working conditions of diesel vehicles can be met.
Comparative example 1
a) Mixing and stirring a system containing 18 parts of molecular sieve powder, 8 parts of silica sol (solid content is 15%), 8 parts of ethanol and deionized water uniformly, treating a ceramic carrier by the system at room temperature, carrying out ultrasonic-immersion for 20min, and taking out the ceramic carrier to sweep residual liquid by using compressed air;
b) heating the ceramic carrier treated in the step a) for 2min under microwave, carrying out ultrasonic-dipping treatment for 10min according to the mode in the step a), blowing residual liquid by compressed air, and drying at 105 ℃;
c) preparing a mixed solution 20L from 242g of copper nitrate and 63.4g of cerium acetate, treating the molecular sieve powder/ceramic carrier at room temperature in an impregnation mode for 15min, taking out a purging residual liquid, heating the purging residual liquid for 2min by microwave, then, impregnating the purging residual liquid into a mixed liquid of copper acetate and cerium acetate again, and purging the residual liquid after 10 min;
d) calcining the carrier treated in the step c) for 3 hours at 350 ℃ to obtain the ceramic carrier active coating for removing the NOx in the tail gas of the diesel vehicle through in-situ synthesis.
Table 1 shows the peeling rate test of example 1 and comparative example 1, the test conditions are 5 hours, the supported catalyst coating is taken down after the test is finished, and the mass of the supported catalyst coating is measured, and the calculated peeling rate of the coating is shown in table 1, the peeling rate of the coating is only 0.2% in example 1, and 2.1% in comparative example, which shows that the coating has strong adhesion under the action of polydopamine.
The ceramic carrier active coating which is prepared in the embodiment 1 and is used for removing the NOx in the diesel vehicle tail gas through in-situ synthesis is subjected to a micro-reaction test, and the ratio of NO: 1000ppm, NH 3: 1000ppm ofO2: 5 vol%, H2O: 10 vol%, N2 balance gas, space velocity 100000 +/-1000 h-1. The highest NOx conversion rate is 98.0%, the lowest NOx conversion rate at 150 ℃ is 61.3%, the NOx conversion rates at 215-450 ℃ can reach more than 85%, and the good NOx activity is shown, so that the use requirements of various working conditions of diesel vehicles can be met.
Example 2
a) Weighing 300g of SSZ-13 molecular sieve powder, placing the powder in a dopamine solution system with the concentration of 1000g and the pH =8.5 and the concentration of 0.6 g/L, continuously stirring for 24 hours at 45 ℃, and obtaining PDA-molecular sieve powder after suction filtration and drying at 105 ℃;
b) mixing and stirring a system containing 29 parts of PDA-molecular sieve powder, 32 parts of silica sol (solid content is 40%), 20 parts of ethanol and deionized water uniformly, then carrying out ultrasonic-immersion treatment on the ceramic carrier at room temperature for 10min, taking out, and blowing residual liquid by using compressed air;
c) drying the ceramic carrier treated in the step b) at 105 ℃;
d) preparing a mixed solution 20L by using 38.7g of copper nitrate and 80.8g of ferric nitrate, and loading the mixed solution on a PDA-molecular sieve powder/ceramic carrier in an electro-deposition mode, wherein the thickness of the coating is 0.08 mm;
e) calcining the carrier treated in the step d) for 2 hours at 500 ℃ to obtain the ceramic carrier active coating for removing NOx in the tail gas of the diesel vehicle through in-situ synthesis.
As shown in fig. 2, the ceramic carrier active coating prepared in example 2 and used for removing NOx from the exhaust gas of diesel vehicles by in-situ synthesis was fixedly mounted on a vibration test bed, the vibration acceleration was 10g, the vibration frequency was (100 ± 5) Hz, the test time was 5 hours, the finished honeycomb catalyst was taken off after the experiment was completed and the mass was weighed, the carrier catalyst was taken off after the experiment was completed and the mass was weighed, and the calculated coating falling rate was as shown in table 1, and the falling rate of the coating prepared in example 2 was 0.10%.
Example 3
a) Weighing 300g of ZSM5 molecular sieve powder, placing the powder in a dopamine solution system with the concentration of 900g and the pH =9.0 of 0.1 g/L, continuously stirring for 20 hours at the temperature of 60 ℃, and performing suction filtration and drying at the temperature of 100 ℃ to obtain PDA-molecular sieve powder;
b) mixing and stirring a system containing 20 parts of PDA-molecular sieve powder, 15 parts of silica sol (solid content is 40%), 10 parts of ethanol and deionized water uniformly, treating a ceramic carrier by the system at room temperature, performing ultrasonic-immersion for 15min, and taking out the ceramic carrier and blowing residual liquid by using compressed air;
c) heating the ceramic carrier treated in the step b) for 2min under microwave, carrying out ultrasonic-dipping treatment for the second time for 5min according to the mode in the step b), blowing residual liquid by compressed air, and drying at 105 ℃;
d) preparing a mixed solution 20L from 121g of copper nitrate and 45.8g of chromium acetate, treating the PDA-molecular sieve powder/ceramic carrier at room temperature by adopting an impregnation mode, reacting for 20min, taking out a purging residual liquid, heating for 2min by microwave, impregnating into a mixed solution of copper acetate and cerium acetate again, and purging the residual liquid after 10 min;
e) calcining the carrier treated in the step d) for 3 hours at 480 ℃ to obtain the ceramic carrier active coating for removing NOx in the tail gas of the diesel vehicle through in-situ synthesis.
As shown in fig. 2, the ceramic carrier active coating prepared in example 2 and used for removing NOx from the exhaust gas of diesel vehicles by in-situ synthesis was fixedly mounted on a vibration test bed, the vibration acceleration was 10g, the vibration frequency was (100 ± 5) Hz, the test time was 5 hours, the finished honeycomb catalyst was taken off after the experiment was completed and the mass was weighed, the carrier catalyst was taken off after the experiment was completed and the mass was weighed, and the calculated coating falling rate was as shown in table 1, and the falling rate of the coating prepared in example 3 was 0.18%.
Example 4
a) Weighing 300g of Sapo-34 molecular sieve powder, placing the Sapo-34 molecular sieve powder in a dopamine solution system with the concentration of 900g and the pH =8.5 and the concentration of 0.08 g/L, continuously stirring for 10 hours at the temperature of 60 ℃, and obtaining PDA-molecular sieve powder after suction filtration and drying at the temperature of 105 ℃;
b) mixing and stirring a system containing 25 parts of PDA-molecular sieve powder, 30 parts of silica sol (solid content is 20%), 10 parts of ethanol and deionized water uniformly, treating a ceramic carrier by the system at room temperature, performing ultrasonic-immersion for 25min, and taking out the ceramic carrier and blowing residual liquid by using compressed air;
c) drying the ceramic carrier treated in the step b) at 105 ℃;
d) preparing a mixed solution 20L containing 121g of copper nitrate, 20g of ferric nitrate, 22g of cerium nitrate and 20g of chromium nitrate, and treating the PDA-molecular sieve powder/ceramic carrier by adopting an electrodeposition mode, wherein the thickness of the coating is 0.1 mm;
e) calcining the carrier treated in the step d) for 3 hours at 480 ℃ to obtain the ceramic carrier active coating for removing NOx in the tail gas of the diesel vehicle through in-situ synthesis.
As shown in fig. 2, the ceramic carrier active coating prepared in example 2 and used for removing NOx from the exhaust gas of diesel vehicles by in-situ synthesis was fixedly mounted on a vibration test bed, the vibration acceleration was 10g, the vibration frequency was (100 ± 5) Hz, the test time was 5 hours, the finished honeycomb catalyst was taken off after the experiment was completed and the mass was weighed, the carrier catalyst was taken off after the experiment was completed and the mass was weighed, and the calculated coating falling rate was as shown in table 1, and the falling rate of the coating prepared in example 4 was 0.20%.
Example 5
a) Weighing 300g of SSZ-13 molecular sieve powder, placing the powder in a dopamine solution system with the concentration of 1000g and the pH =8.5 and the concentration of 0.2 g/L, continuously stirring for 20 hours at the temperature of 60 ℃, and performing suction filtration and drying at the temperature of 100 ℃ to obtain PDA-molecular sieve powder;
b) mixing and stirring a system containing 20 parts of PDA-molecular sieve powder, 15 parts of silica sol (solid content is 40%), 10 parts of ethanol and deionized water uniformly, treating a ceramic carrier by the system at room temperature, performing ultrasonic-immersion for 20min, and taking out the ceramic carrier and blowing residual liquid by using compressed air;
c) drying the ceramic carrier treated in the step b) at 105 ℃;
d) preparing a mixed solution 20L from 121g of copper nitrate and 32g of cerium acetate, treating the PDA-molecular sieve powder/ceramic carrier at room temperature by adopting an impregnation mode, reacting for 20min, taking out a purging residual liquid, heating for 2min by microwave, impregnating into a mixed solution of copper acetate and cerium acetate again, and purging the residual liquid after 10 min;
e) calcining the carrier treated in the step d) at 450 ℃ for 2h to obtain the ceramic carrier active coating for removing NOx in the tail gas of the diesel vehicle through in-situ synthesis.
As shown in fig. 2, the ceramic carrier active coating prepared in example 2 and used for removing NOx from the exhaust gas of diesel vehicles by in-situ synthesis was fixedly mounted on a vibration test bed, the vibration acceleration was 10g, the vibration frequency was (100 ± 5) Hz, the test time was 5 hours, the finished honeycomb catalyst was taken off after the experiment was completed and the mass was weighed, the carrier catalyst was taken off after the experiment was completed and the mass was weighed, and the calculated coating falling rate was as shown in table 1, and the falling rate of the coating prepared in example 5 was 0.15%.
Claims (1)
1. The method for removing the ceramic carrier active coating of NOx in the tail gas of the diesel vehicle by in-situ synthesis is characterized by comprising the following steps: firstly, preprocessing molecular sieve powder by dopamine solution to form polydopamine on the surface of the molecular sieve, then utilizing the strong hydrophilicity and cohesiveness of the polydopamine to firmly load the molecular sieve on a ceramic carrier, and finally, passing through copper ions and transition metal ions Mn+The coordination with amino on polydopamine is carried out, and Cu is finally loaded on the surface of the ceramic carrier in situ under the high-temperature calcinationxO/M2/nO/N-doping molecular sieve mixture, thereby preparing an active coating with the effect of efficiently removing NOx; the method comprises the following specific steps:
a) pretreating a microporous molecular sieve by using a dopamine solution to obtain polydopamine-molecular sieve powder, wherein the pH value of the dopamine solution is 8 or 8.5 or 9, the concentration of dopamine is 0.08-0.6 g/L, the treatment mode is continuous stirring, the temperature is 45-80 ℃, the treatment time is 8-24 hours, the mass ratio of the molecular sieve to the dopamine solution system is 0.1-1.0, and the molecular sieve is one of Sapo-34, SSZ-13 and ZSM 5;
b) the preparation method comprises the following steps of (1) ultrasonically dipping a ceramic carrier at room temperature by using a uniformly mixed system containing deionized water, polydopamine-molecular sieve powder, silica sol and a dispersing agent, wherein the solid content of the silica sol is 15-40%, the dispersing agent is industrial ethanol, the polydopamine-molecular sieve powder is 18-29 parts, the silica sol is 8-32 parts, and the dispersing agent is 8-20 parts;
c) blowing the ceramic carrier treated in the step b) by using compressed air, and drying at 80-105 ℃ to obtain a polydopamine-molecular sieve/ceramic carrier;
d) treating the polydopamine-molecular sieve powder/ceramic carrier by using an active metal solution, wherein the treatment mode is a dipping or electro-deposition mode, the polydopamine-molecular sieve powder/ceramic carrier is dried at the temperature of 80-105 ℃, the active metal is copper and M, wherein M is one of cerium, iron and chromium, the concentration of copper ions is 0.008-0.05 mol/L, the concentration of cerium ions is 0-0.01 mol/L, the concentration of iron is 0-0.01 mol/L, and the concentration of chromium is 0-0.01 mol/L;
e) calcining the carrier treated in the step d) at the temperature of 350-500 ℃ for 1-3h to obtain the ceramic carrier active coating for removing NOx in the tail gas of the diesel vehicle through in-situ synthesis.
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