CN113941371A - Method for preparing cordierite monolithic catalyst in variable-temperature vacuum coating mode - Google Patents
Method for preparing cordierite monolithic catalyst in variable-temperature vacuum coating mode Download PDFInfo
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- CN113941371A CN113941371A CN202111134000.7A CN202111134000A CN113941371A CN 113941371 A CN113941371 A CN 113941371A CN 202111134000 A CN202111134000 A CN 202111134000A CN 113941371 A CN113941371 A CN 113941371A
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- 229910052878 cordierite Inorganic materials 0.000 title claims abstract description 233
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 title claims abstract description 233
- 239000003054 catalyst Substances 0.000 title claims abstract description 114
- 238000000034 method Methods 0.000 title claims abstract description 46
- 238000001771 vacuum deposition Methods 0.000 title claims abstract description 25
- 238000000576 coating method Methods 0.000 claims abstract description 155
- 239000011248 coating agent Substances 0.000 claims abstract description 144
- 239000000919 ceramic Substances 0.000 claims abstract description 102
- 238000010438 heat treatment Methods 0.000 claims abstract description 62
- 239000002002 slurry Substances 0.000 claims abstract description 33
- 238000003860 storage Methods 0.000 claims abstract description 22
- LQWKWJWJCDXKLK-UHFFFAOYSA-N cerium(3+) manganese(2+) oxygen(2-) Chemical compound [O--].[Mn++].[Ce+3] LQWKWJWJCDXKLK-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000007789 sealing Methods 0.000 claims abstract description 14
- 238000005470 impregnation Methods 0.000 claims abstract description 8
- 238000001035 drying Methods 0.000 claims description 59
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 30
- 238000007598 dipping method Methods 0.000 claims description 25
- 239000011572 manganese Substances 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 19
- 239000011259 mixed solution Substances 0.000 claims description 18
- 239000007787 solid Substances 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 11
- 238000005086 pumping Methods 0.000 claims description 11
- 239000000243 solution Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 7
- 238000002791 soaking Methods 0.000 claims description 7
- 239000006255 coating slurry Substances 0.000 claims description 3
- 238000007654 immersion Methods 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims description 2
- 230000003197 catalytic effect Effects 0.000 abstract description 8
- 230000008569 process Effects 0.000 abstract description 6
- 239000002156 adsorbate Substances 0.000 abstract description 5
- 239000007789 gas Substances 0.000 description 35
- 239000010410 layer Substances 0.000 description 32
- 229910003158 γ-Al2O3 Inorganic materials 0.000 description 22
- 238000011068 loading method Methods 0.000 description 21
- 239000011148 porous material Substances 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 17
- 239000000499 gel Substances 0.000 description 13
- 230000001105 regulatory effect Effects 0.000 description 12
- 238000012360 testing method Methods 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- 239000012855 volatile organic compound Substances 0.000 description 7
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 239000000969 carrier Substances 0.000 description 6
- 239000011247 coating layer Substances 0.000 description 6
- 238000003618 dip coating Methods 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 238000013112 stability test Methods 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- VXAUWWUXCIMFIM-UHFFFAOYSA-M aluminum;oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Al+3] VXAUWWUXCIMFIM-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 238000007664 blowing Methods 0.000 description 3
- 239000004202 carbamide Substances 0.000 description 3
- 238000007084 catalytic combustion reaction Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 238000001878 scanning electron micrograph Methods 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
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- 239000003546 flue gas Substances 0.000 description 2
- 238000001027 hydrothermal synthesis Methods 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 239000006004 Quartz sand Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
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- 230000005587 bubbling Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005524 ceramic coating Methods 0.000 description 1
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- 238000004817 gas chromatography Methods 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
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- 238000011031 large-scale manufacturing process Methods 0.000 description 1
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- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
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- 238000002203 pretreatment Methods 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000009991 scouring Methods 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
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- 238000004506 ultrasonic cleaning Methods 0.000 description 1
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- 230000003313 weakening effect Effects 0.000 description 1
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
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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
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
- B01J21/04—Alumina
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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- B01J23/32—Manganese, technetium or rhenium
- B01J23/34—Manganese
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
- B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/61—Surface area
- B01J35/613—10-100 m2/g
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- B01J37/02—Impregnation, coating or precipitation
- B01J37/0215—Coating
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- B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
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- F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
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Abstract
The invention discloses a method for preparing a cordierite monolithic catalyst in a variable-temperature vacuum coating mode, which comprises the following steps: pretreating cordierite honeycomb ceramic by adopting plasma; placing the cordierite honeycomb ceramic subjected to plasma pretreatment into a storage tank, sealing, maintaining the storage tank in a negative pressure state, heating the cordierite honeycomb ceramic, and then carrying out impregnation treatment on the cordierite honeycomb ceramic to obtain an integral catalyst cordierite carrier with a coating; the monolithic catalyst cordierite is loaded with manganese cerium oxide on a monolithic catalyst cordierite carrier by adopting impregnation treatment to obtain the cordierite monolithic catalyst. According to the invention, residual air and adsorbate in cordierite channels are effectively removed through the temperature rise and negative pressure process, so that more slurry enters the channels to fill the channels to increase the coating capacity, the contact surface of the coating and cordierite is improved, and the stability of the coating is improved. The cordierite monolithic catalyst has obvious advantages in the aspects of catalytic activity and stability.
Description
Technical Field
The invention relates to a novel functional material preparation technology, in particular to a method for preparing a cordierite monolithic catalyst in a variable-temperature vacuum coating mode.
Background
Volatile Organic Compounds (VOCs) are commonly found in the exhaust gas of petrochemical industry. The catalytic combustion technology is one of effective means for treating VOCs at the tail end due to the advantages of multiple treatment objects, high efficiency, simple process and the like. The integral catalyst has the advantages of small loss of bed pressure drop, high mass transfer efficiency, regular structure and strong machineryThe purity and the heat resistance are good, and the like, and the method is often used for purifying VOCs in the petrochemical industry. However, cordierite (2 MgO. Al) as a supporting carrier2O3·5SiO2) The surface of the honeycomb ceramic is smooth and the specific surface area is low (about 0.7 m)2·g-1) The active species loading is limited. The coating of a layer of oxide or active carbon with high specific surface area as a support carrier and the dispersion of active components of the catalyst are effective ways for improving the performance of the monolithic catalyst, and the preparation of the coating with high specific surface area, which is uniformly distributed and has a stable structure, is attracting attention of people.
The cordierite monolithic catalyst coating prepared by different coating methods has different influences on the loading rate, the uniformity of the coating thickness, the crack resistance and the stability of the coating. The traditional coating method generally comprises the steps of preparing coating slurry by a sol-gel method, soaking a pretreated cordierite support carrier in the slurry, taking out the cordierite support carrier, removing residual slurry in a pore channel by blowing with compressed air, drying and roasting to obtain the coating. However, abundant macropores exist in the cordierite honeycomb ceramic support carrier, and the cordierite honeycomb ceramic support carrier is directly immersed in slurry, so that gas in a pore channel cannot be discharged and compressed in the pore channel, and then the gas expands due to heating in the high-temperature roasting process to cause the dense cracking phenomenon of the coating, even part of the coating directly falls off, and the uniformity, stability and coating rate of the coating are directly influenced. In recent years, researchers use ultrasonic-assisted dipping technology to prepare a coating when a support carrier is coated with the coating, compared with the method of directly dipping the support carrier in slurry, the coating prepared by ultrasonic-assisted dipping slurry has higher coating rate, larger specific surface area and more mesoporous structures, the uniformity of the coating is improved, and the stability and the cracking of the coating are relieved.
In addition, researchers also grow a layer of oxide on the surface of a cordierite honeycomb ceramic supporting carrier by a hydrothermal synthesis method to be used as a transition coating to load a catalytic active component. Although the oxide coating synthesized by the hydrothermal method has controllable crystal morphology and better coating stability, the problems of complex synthesis process, high energy consumption, long synthesis process time and the like still exist in the actual industrial large-scale production.
Thus, the use of slurry impregnation to produce coatings is currently the most feasible strategy, but there is still considerable controversy over the specific method of impregnation to produce coatings.
Disclosure of Invention
The invention aims to provide a method for preparing a cordierite monolithic catalyst in a variable-temperature vacuum coating mode aiming at the defects of the existing cordierite honeycomb ceramic coating mode.
The purpose of the invention is realized by the following technical scheme:
a method for preparing a cordierite monolithic catalyst by a variable-temperature vacuum coating mode comprises the following steps: putting cordierite honeycomb ceramic into plasma generation equipment, and pretreating the cordierite honeycomb ceramic by adopting plasma; placing the cordierite honeycomb ceramic subjected to plasma pretreatment into a storage tank, sealing, maintaining the storage tank in a negative pressure state, heating the cordierite honeycomb ceramic, then carrying out impregnation treatment on the cordierite honeycomb ceramic, coating slurry on the cordierite honeycomb ceramic, and sequentially carrying out drying in the shade, drying and roasting to obtain a stable and uniform coated monolithic catalyst cordierite carrier; the monolithic catalyst cordierite is loaded with manganese cerium oxide on a monolithic catalyst cordierite carrier by adopting impregnation treatment to obtain the cordierite monolithic catalyst.
The method for preparing the cordierite monolithic catalyst by the variable-temperature vacuum coating mode comprises the following steps:
putting cordierite honeycomb ceramic into plasma generation equipment, closing a cabin door, starting a vacuum pump to pump the cabin into a negative pressure state, and pretreating the cordierite honeycomb ceramic by adopting plasma;
putting the cordierite honeycomb ceramic subjected to plasma pretreatment into a storage tank, sealing, vacuumizing to maintain the storage tank in a negative pressure state, heating in a water bath, heating the cordierite honeycomb ceramic, cooling to room temperature, introducing slurry, and coating the slurry on the cordierite honeycomb ceramic by adopting dipping treatment; pumping out the slurry;
step (3), drying the impregnated cordierite honeycomb ceramic in the shade at room temperature, and then sequentially drying and roasting to obtain the monolithic catalyst cordierite carrier with a stable and uniform coating;
and (4) putting the monolithic catalyst cordierite carrier into an active component solution for soaking, taking out, and then drying and roasting in sequence to obtain the manganese cerium oxide loaded cordierite monolithic catalyst.
As a preferred technical scheme of the method for preparing the monolithic catalyst cordierite carrier by adopting the variable-temperature vacuum coating mode, the method further comprises the following steps: and sequentially carrying out heating treatment and dipping treatment on the cordierite honeycomb ceramic subjected to plasma pretreatment for 1-3 times in a negative pressure state to obtain the monolithic catalyst cordierite carrier with 1-3 coatings.
Specifically, the monolithic catalyst cordierite carrier with 1-3 layers of coatings is obtained by treating for 1-3 times according to the step (2) and the step (3), and 3 layers are preferred.
In the step (1), the output power of the plasma generating equipment is 25-100 KW, and the working gas of the plasma is Ar: N21:1V/V mixed gas, and the treatment time is 30-150 min; the flow rate of the mixed gas in unit time for treating the cordierite honeycomb ceramic per unit volume is 0.33-0.50 L.min-1·cm-3。
Preferably, the plasma collides with cordierite surface elements to make part of Si, Mg and Al elements fall off from the cordierite surface, XRD characterization is carried out on cordierite treated at different powers and different times, and the following can be found according to the change of the characteristic peak position and the intensity of a sample: the plasma pretreated sample has no generation of new characteristic peak or position change of the characteristic peak, and the strength of the characteristic peak is weakened; with the prolonging of the treatment time, the weakening amplitude of the characteristic peak intensity is increased and then reduced, and when the pretreatment time is 60min and 90min respectively, the characteristic peak intensity of cordierite is greatly weakened, so that the plasma pretreatment time is preferably 60-90 min. By comparing the coating amount, specific surface area and other parameters of the monolithic catalyst cordierite carrier, the output power of the plasma generating equipment is preferably 75 w-100 KW.
In the step (2), the storage tank maintains negative pressure of-0.08 to-0.1 MPa (gauge pressure), and the cordierite honeycomb ceramic subjected to plasma pretreatment is subjected to heating treatment and dipping treatment in a negative pressure state.
The temperature of the heating treatment is 70-90 ℃, and the time of the heating treatment is 10-30 min, preferably 30 min.
Preferably, the heat treatment is: adopting a water bath heating mode, and heating at the temperature rising rate of 8-10 ℃ per minute-1And heating the mixture from the normal temperature to 70-90 ℃, and then heating the mixture for 10-30 min at the constant temperature.
The slurry is alumina gel with solid content of 20-25%. The single immersion time of the cordierite honeycomb ceramic is 30-60 min.
The aluminum glue is prepared from a nitric acid aqueous solution with the concentration of 0.3M, pseudo-boehmite and urea according to the mass ratio of (4-5) to (1.6-2) to (0.8-1). The preparation method comprises the following steps: mixing 0.3M nitric acid aqueous solution, pseudo-boehmite and urea, stirring for 4h, standing until no precipitate exists, putting the mixture into an oil bath kettle at the temperature of 30 ℃, stirring and aging for 1h to obtain the aluminum adhesive.
In the step (3), the drying time in the shade is 8-12 h, preferably 12 h.
The drying temperature is 50-70 ℃, preferably 60 ℃, and the drying time is 10-12 hours, preferably 12 hours.
The roasting temperature is 500-600 ℃, preferably 500 ℃, and the roasting time is 3-4 hours, preferably 3 hours.
In the step (4), the active component solution comprises Mn and Ce with the molar ratio of (8-9) to (1-2) and Ce3+The concentration is 0.5 mol.L-1The Mn/Ce mixed solution of (1).
Specifically, the Mn/Ce mixed solution is prepared from 50% of Mn (NO)3)2Solution and Ce (NO)3)3·6H2O is according toAdding the Ce (NO) with the molar ratio of Mn to Ce of (8-9) to (1-2) into deionized water and stirring to obtain the Ce3)3·6H2The O concentration is 0.5 mol.L-1The Mn/Ce mixed solution of (1).
The monolithic catalyst cordierite carrier is soaked in the active component solution for 3-4 hours.
The drying temperature is 70-80 ℃, the preferred drying temperature is 70 ℃, and the drying time is 20-24 hours, the preferred drying time is 24 hours.
The roasting temperature is 300-400 ℃, preferably 400 ℃, and the roasting time is 2-3 hours, preferably 2 hours.
The invention has the beneficial effects that:
the method utilizes the characteristic that the plasma has active chemical property to treat the cordierite honeycomb ceramic to induce the surface oxide of the cordierite honeycomb ceramic to react with the plasma, and carries out surface modification on the cordierite honeycomb ceramic. Compared with the traditional method of using water for ultrasonic cleaning or acid and alkali solution treatment, the method can avoid generating a large amount of acid and alkali chemical waste liquid.
According to the invention, a variable-temperature vacuum coating mode is utilized to treat cordierite in a high-temperature negative-pressure environment, compared with the traditional dipping coating and ultrasonic coating modes, residual air and adsorbates in cordierite channels are effectively removed in the temperature-rise negative-pressure process, so that more slurry enters the channels to fill the channels to increase the coating load capacity, meanwhile, the contact surface of the coating and a cordierite support carrier is improved, the stability of the coating is further improved, and the phenomenon that the residual gas compressed between the coating and the slurry damages the coating structure due to thermal expansion and cold contraction to cause the falling of the coating is avoided. Compared with the modes of dip coating and ultrasonic-assisted dip coating, the monolithic catalyst cordierite carrier coating obtained by variable-temperature vacuum dip coating has obvious advantages in the aspects of coating load capacity and coating stability.
Compared with the traditional immersion coating and ultrasonic coating modes, the cordierite monolithic catalyst has higher active component loading capacity and has obvious advantages in the aspects of catalytic activity and stability.
Drawings
FIG. 1 is XRD patterns of cordierite supports of monolithic catalysts obtained by different pretreatments of example 1, comparative example 2 and comparative example 3; wherein fig. 1a is an XRD pattern of a monolithic catalyst cordierite support with 1 alumina coating layer, and fig. 1b is an XRD pattern of a monolithic catalyst cordierite support with 3 alumina coating layers.
FIG. 2 is an SEM image of the coating of the monolithic catalyst cordierite carriers of example 1, comparative example 2 and comparative example 3; wherein, FIG. 2a1、b1、c1Respectively at 50 μm size of gamma-Al2O3-im1/Cord-S、γ-Al2O3-ul1/Cord-S、γ-Al2O3-va1SEM image of/Cord-S coating, FIG. 2a2、b2、c2Respectively 5 μm in size of gamma-Al2O3-im1/Cord-S、γ-Al2O3-ul1/Cord-S、γ-Al2O3-va1SEM image of/Cord-S coating.
Fig. 3 is a result of a coating load test of the coatings of the monolithic catalyst cordierite carriers in example 1, comparative example 2, and comparative example 3.
Fig. 4 shows the results of stability tests of the coatings of the monolithic catalyst cordierite carriers of example 1, comparative example 2 and comparative example 3.
FIG. 5 shows the results of the catalytic activity and stability tests of the cordierite monolith catalysts of example 1, comparative example 2 and comparative example 3; wherein fig. 5a is a result of a catalytic activity test of the cordierite monolith catalyst, and fig. 5b is a result of a stability test of the cordierite monolith catalyst.
Detailed description of the invention
The technical solution of the present invention is further explained by the following embodiments.
The model of the plasma generating equipment is BFT-1200C-PECVD.
The aluminum paste used in the examples was prepared by the following method: adding aqueous solution of nitric acid (the concentration is 0.3M), pseudo-boehmite and urea into a beaker according to the mass ratio of 5:2:1, continuously stirring for 4 hours, standing without precipitation, putting the beaker into an oil bath kettle at the temperature of 30 ℃, stirring and aging for 1 hour to prepare the alumina gel, wherein the solid content is 25%.
The Mn/Ce mixed solution used in the examples was prepared by the following method: mixing 50% Mn (NO)3)2Solution and Ce (NO)3)3·6H2Adding O into deionized water according to the molar ratio of Mn to Ce of 9:1, stirring for 30min to prepare Ce (NO)3)3·6H2The O concentration is 0.5 mol.L-1The Mn/Ce mixed solution of (1).
The cordierite monolithic catalysts of examples 2 to 9 were examined for the specific surface area of the coating layer (three layers), the ultrasonic peeling rate of the coating layer (three layers), the wear rate of the coating layer (three layers), and the loading amount of the active component of the cordierite monolithic catalyst.
Example 1
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of the gas per unit volume of cordierite honeycomb ceramic treated per unit time was 0.42L · min-1·cm-3And treating for 90min to obtain a cordierite honeycomb ceramic sample subjected to plasma pretreatment and recorded as Cord-S.
Placing the cordierite honeycomb ceramic sample Cord-S subjected to plasma pretreatment into a storage tank, sealing, vacuumizing to-0.09 MPa (gauge pressure, the same below), maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 90 deg.C, heating at constant temperature for 30min, cooling to room temperature, introducing alumina-silica gel (solid content of 25%, the same below) in the slurry tank into a sealed storage tank by using pressure difference, and soaking cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying the impregnated cordierite honeycomb ceramic in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation 3 times, and recording the obtained sample as gamma-Al2O3-va/Cord-S, where N times (N ═ 1, 2, 3) coating and N alumina coating on cordierite honeycomb ceramic samples resulted in monolithic catalysisCordierite carriers, correspondingly designated as gamma-Al2O3-vaN/Cord-S。
Putting the monolithic catalyst cordierite carrier coated with the 3-layer alumina coating into a Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ drying oven for drying for 24h, and then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain a manganese cerium oxide-loaded cordierite monolithic catalyst, which is recorded as MnCeOx/γ-Al2O3-va/Cord-S。
Comparative example 1
Cordierite honeycomb ceramic with the size of 49 × 50mm is immersed in water for ultrasonic pretreatment for 30min, taken out and dried at 100 ℃ for 12h to obtain a water-pretreated cordierite honeycomb ceramic sample which is recorded as Cord-U.
Soaking cordierite honeycomb ceramic which is only ultrasonically washed in Mn/Ce mixed solution for 3h, taking out, drying in a 70 ℃ drying oven for 24h, roasting in a muffle furnace at 400 ℃ for 2h to obtain a cordierite monolithic catalyst loaded with manganese cerium oxide, and recording the cordierite monolithic catalyst as MnCeOx/Cord-U。
Comparative example 2
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of the gas per unit volume of cordierite honeycomb ceramic treated per unit time was 0.42L · min-1·cm-3And treating for 90min to obtain a cordierite honeycomb ceramic sample subjected to plasma pretreatment and recorded as Cord-S.
Putting the cordierite subjected to plasma pretreatment into alumina gel for dipping for half an hour, taking out, blowing out redundant slurry in a pore channel, naturally drying in the shade for 12h, putting into an oven for drying at 100 ℃ for 12h, and putting into a muffle furnace for roasting at 500 ℃ for 4 h; repeating the above operation 3 times, and recording the obtained sample as gamma-Al2O3im/Cord-S, where a monolithic catalyst cordierite support, correspondingly denoted γ -Al, was obtained by coating N times (N ═ 1, 2, 3) and an N-layer alumina coating on a cordierite honeycomb ceramic sample2O3-imN/Cord-S。
Putting the monolithic catalyst cordierite carrier dipped with the 3-layer alumina coating into a Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ drying oven for drying for 24h, putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain a manganese cerium oxide-loaded cordierite monolithic catalyst, which is recorded as MnCeOx/γ-Al2O3-imN/Cord-S。
Comparative example 3
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of the gas per unit volume of cordierite honeycomb ceramic treated per unit time was 0.42L · min-1·cm-3And treating for 90min to obtain a cordierite honeycomb ceramic sample subjected to plasma pretreatment and recorded as Cord-S.
Putting a cordierite honeycomb ceramic sample subjected to plasma pretreatment into alumina gel, ultrasonically dipping for half an hour, taking out, blowing out redundant slurry in a pore channel, naturally drying in the shade for 12 hours, putting into an oven for drying at 100 ℃ for 12 hours, and putting into a muffle furnace for roasting at 500 ℃ for 4 hours; repeating the above operation 3 times, and recording the obtained sample as gamma-Al2O3ul/Cord-S, in which a monolithic catalyst cordierite support, correspondingly denoted by γ -Al, is obtained by coating N times (N ═ 1, 2, 3) and an N-layer alumina coating on a cordierite honeycomb ceramic sample2O3-ulN/Cord-S。
Putting the monolithic catalyst cordierite carrier coated with 3 layers of alumina coatings in an ultrasonic auxiliary manner into a Mn/Ce mixed solution for soaking for 3 hours, taking out, putting into a 70 ℃ drying oven for drying for 24 hours, putting into a muffle furnace for roasting at 400 ℃ for 2 hours to obtain a manganese cerium oxide-loaded cordierite monolithic catalyst, which is recorded as MnCeOx/gamma-Al2O3-ulN/Cord-S。
Application example 1
As can be seen from FIG. 1, Cord-U, γ -Al2O3-imN/Cord-S、γ-Al2O3-ulN/Cord-S and, gamma-Al2O3Characteristic peaks of four groups of samples of-vaN/Cord-S at positions of 2 theta, 10.37 degrees, 18.25 degrees, 19.01 degrees, 21.75 degrees, 26.47 degrees, 27.83 degrees, 29.35 degrees, 33.82 degrees and 38.56 degrees are all attributed to the strength of a cordierite phase characteristic peak of a mixed oxide of Si, Mg and Al (JCPD 13-0303). It is worth noting that the intensities of the characteristic peaks of the three groups of samples are significantly reduced compared to Cord-U, probably due to the amorphous structure of the alumina prepared by sol-gel, suppressing the intensities of the above characteristic peaks. The reduction amplitude of the characteristic peak intensity of the supporting carrier coating obtained by multiple coating is more obvious in comparison, and the reduction amplitude of the characteristic peak is most obvious particularly when the 2 theta is 10.37 degrees. Meaning that the coating does not change the crystal phase structure of the support carrier but causes the cordierite phase characteristic peak strength to weaken.
TABLE 1 coating parameters for monolithic catalyst cordierite carriers
As can be seen in FIG. 2, three sets of samples each seen a layer of γ -Al at 5 μm and 50 μm dimensions2O3The coating and the cordierite support the carrier skeleton structure. Comparing the coating surfaces of the three groups of samples, it was found that the exposed pore size and number of the coating surfaces of the three groups of samples were significantly different, gamma-Al2O3The size and number of pores present on the surface of the va1/Cord-S sample are significantly smaller and smaller; and gamma-Al2O3Ul1/Cord-S sample surface pore size and number vs. gamma-Al2O3The va1/Cord-S sample is obviously increased and increased; in three sets of samples, gamma-Al2O3The surface of the-im 1/Cord-S sample has the largest number of pores and the largest pore size, and the original morphology of the support carrier in the pore channels is obviously exposed, possibly because the slurry cannot completely enter the pore channels due to air and adsorbates remained in the pore channels. Based on the above, the variable-temperature vacuum coating mode is better than the dipping coating mode and the ultrasonic-assisted coating mode, and the rapid removal of air and adsorbates in the pore channels of the support carrier is facilitated in the high-temperature and negative-pressure environment, so that more air and adsorbates are facilitatedThe slurry enters the pores of the support carrier, thereby reducing the pore size and number of the support carrier surface.
As can be seen in fig. 3, and dip coating (γ -Al)2O3im/Cord-S), ultrasound-assisted coating (. gamma. -Al)2O3ul/Cord-S) coating loading of monolithic catalyst cordierite Carrier coating compared to the variable temperature vacuum coating mode to obtain a monolithic catalyst cordierite Carrier (γ -Al)2O3The coating loading of the coating of-va/Cord-S) was higher, the first coating loading reached 5.5% and the third coating loading reached 13.2%; the coating load of the coating obtained by the dip coating mode is the minimum, the first coating load is only 4.2%, and the third coating load is only 10.9%; the coating loading obtained by ultrasonic-assisted dipping is the second time, the first coating loading is only 5.1%, and the third coating loading reaches 12.4%. The inventors analyzed the above results and speculated that the variable temperature vacuum coating effectively removed the gas in the support carrier channels, allowing more slurry to enter the channels. Although the air of the supporting carrier can be removed in the ultrasonic-assisted dipping mode, part of the air remains in the pore channels of the supporting carrier, so that the coating loading amount of the coating cannot achieve the effect of variable-temperature vacuum dipping coating.
The coating stability was verified by performing an ultrasonic (ultrasonic) test and a simulated flue gas dust erosion test (smoke test) on the monolithic catalyst cordierite carriers prepared in example 1, comparative example 2 and comparative example 3, and testing the peeling rate and wear rate of the coating, and the related results are shown in fig. 4 and table 1. In the ultrasonic test, the sample is put into a 500mL beaker, 250mL deionized water is added, and ultrasonic treatment is carried out for 20min, wherein gamma-Al is generated2O3The release rate of the va/Cord-S sample coating is the lowest, the release rate of the single-coating is about 1.1%, and the release rate of the three-layer coating is about 9.8%; gamma-Al2O3The coating peeling rate of the ul/Cord-S sample is the second, and the peeling rate of the single-layer coating and the three-layer coating is about 2.2 percent and 10.4 percent respectively; gamma-Al2O3The highest coating peeling rate of the-im/Cord-S sample is achieved, the coating peeling rate of a single coating reaches about 4.2 percent, and the coating peeling rate of three coatings reaches about 13.2 percent. Indicating that the ultrasonic exfoliation rate of the coating increases with increasing coating loading. In the test of simulating flue gas dust scouring, the wind speed in the test tube is regulated and controlled to be 14.5 +/-0.5 m.s-1The concentration of the abrasive (0.3-0.4 mm diameter quartz sand) is 50 + -5 g.m-3And the test time is 20 min. The results show that gamma-Al2O3The triple layer wear rate of the va/Cord-S sample was about 5.9%; al (Al)2O3The three-layer wear rate for the ul/Cord-S sample was about 7.4%; al (Al)2O3The tri-layer wear rate for the-im/Cord-S sample was about 9.6%. The stability test result shows that the coating obtained by the variable-temperature vacuum coating mode has more obvious stability compared with the coating of the monolithic catalyst cordierite carrier obtained by dip coating and ultrasonic-assisted coating.
The cordierite monolithic catalysts prepared in example 1, comparative example 2 and comparative example 3 were subjected to activity evaluation of toluene catalytic combustion performance. The activity evaluation of the cordierite monolithic catalyst is carried out on a normal-pressure fixed bed reactor, a quartz tube (with the inner diameter of 28mm) is used as a reaction tube, a sand core is arranged in the tube, 0.5g of the cordierite monolithic catalyst is filled in the quartz tube, gaps around the catalyst are filled with glass fibers, a three-section heating furnace is adopted, the temperature is controlled by a temperature controller, and the temperature of a bed layer is monitored by a thermocouple. By bubbling through N2The reactant (toluene) is entrained at 0 ℃ with the gas mixture (N)2And O2Mixed gas, concentration 20% O2As a reaction gas, N2As a balance gas) were mixed and then fed into the reactor, the reactant concentration was 1000ppm, and the gas space velocity was 30000 mL. gcat-1·h-1Gas chromatography detection analysis of gas feed composition.
The correlation results are shown in FIG. 5. In the activity test (FIG. 5a), the concentration of VOCs was 1000ppm and the space velocity was 30000mL gcat -1·h-1The catalytic activity of all three groups of cordierite monolith catalysts increases with increasing temperature. Cordierite monolithic catalyst (MnCeOx/gamma-Al) prepared by variable-temperature vacuum coating mode2O3vaN/Cord-S) showed the best catalytic activity, followed by MnCeOx/γ -Al2O3-ulN/Cord-S and MnCeOx/γ-Al2O3imN/Cord-S, while the catalytic activity of the monolith catalyst, which was only sonicated, was the lowest. This is because the catalyst prepared by the variable temperature vacuum coating method has more slurry entering the pore channels of the supporting carrier, so that more active components are loaded on the catalyst. In the stability test (FIG. 5b), the concentration of VOCs was 1000ppm and the space velocity was 30000mL gcat -1·h-1The reaction temperature is 230 ℃, the reaction time is 50h, MnCeOx/gamma-Al2O3The activity of the-va/Cord-S cordierite monolithic catalyst is reduced from 92 percent to about 88 percent, and MnCeOx/gamma-Al2O3The activity of the-ulN/Cord-S cordierite monolithic catalyst is reduced from 90 percent to about 80 percent, and the MnCeOx/γ-Al2O3The activity of the-imN/Cord-S cordierite monolithic catalyst is reduced from 90% to about 75%, while the activity of MnCeOxThe activity of the/Cord-U cordierite monolithic catalyst is reduced from 80 percent to about 60 percent. The results show that MnCeO has 3 layers of coatingx/γ-Al2O3the-va/Cord-S cordierite monolithic catalyst has good activity and stability in catalytic combustion of VOCs.
Example 2
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of the gas per unit volume of cordierite honeycomb ceramic treated per unit time was 0.42L · min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Putting the cordierite honeycomb ceramic sample pretreated by the plasma into a storage tank, sealing, vacuumizing to-0.08 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 70 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repetition ofThe operation is carried out for 3 times in total, and 3 layers of alumina coating layers are coated on a cordierite honeycomb ceramic sample to obtain an integral catalyst cordierite carrier which is marked as gamma-Al2O3-va/Cord-S-1. The first coating load was 4.4%, and the specific surface area of the coating (three layers, the same below) was 33.2m2·g-1The ultrasonic peeling rate of the coating (three layers, the same below) is 10.0%, and the wear rate of the coating (three layers, the same below) is 7.0%.
Putting the integral catalyst cordierite carrier into the Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ oven for drying for 24h, then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain the cordierite integral catalyst loaded with the manganese cerium oxide, which is recorded as MnCeOxγ-Al2O3The active component loading is 9.5 percent of-va/Cord-S-1.
Example 3
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of gas per unit volume of cordierite treated per unit time was 0.42 l.min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Putting the cordierite honeycomb ceramic sample pretreated by the plasma into a storage tank, sealing, vacuumizing to-0.09 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 70 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation for 3 times, and coating 3 layers of alumina coating on the cordierite honeycomb ceramic sample to obtain monolithic catalyst cordierite carrier, denoted as gamma-Al2O3-va/Cord-S-2. The first coating load is 4.8 percent, and the specific surface area of the coating is 33.9m2·g-1The ultrasonic shedding rate of the coating is 10.1 percent, and the coating is appliedThe layer wear rate was 6.9%.
Putting the obtained integral catalyst cordierite carrier into the Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ drying oven for drying for 24h, and then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain the manganese cerium oxide-loaded cordierite integral catalyst, which is recorded as MnCeOx/γ-Al2O3The active component loading is 9.7 percent of-va/Cord-S-2.
Example 4
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of gas per unit volume of cordierite treated per unit time was 0.42 l.min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Placing the cordierite honeycomb ceramic sample pretreated by the plasma into a storage tank, sealing, vacuumizing to-0.1 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 70 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation for 3 times, and coating 3 layers of alumina coating on the cordierite honeycomb ceramic sample to obtain monolithic catalyst cordierite carrier, denoted as gamma-Al2O3-va/Cord-S-3. The first coating load is 5.1 percent, and the specific surface area of the coating is 34.3m2·g-1The ultrasonic shedding rate of the coating is 9.9 percent, and the wear rate of the coating is 6.5 percent.
Putting the integral catalyst cordierite carrier into the Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ oven for drying for 24h, then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain the cordierite integral catalyst loaded with the manganese cerium oxide, which is recorded as MnCeOx/γ-Al2O3The active component loading is 9.9 percent of-va/Cord-S-3.
Example 5
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of gas per unit volume of cordierite treated per unit time was 0.42 l.min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Putting the cordierite honeycomb ceramic sample pretreated by the plasma into a storage tank, sealing, vacuumizing to-0.08 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 80 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation for 3 times, and coating 3 layers of alumina coating on the cordierite honeycomb ceramic sample to obtain monolithic catalyst cordierite carrier, denoted as gamma-Al2O3-va/Cord-S-4. The first coating load is 5.3 percent, and the specific surface area of the coating is 35.0m2·g-1The ultrasonic shedding rate of the coating is 10.0 percent, and the wear rate of the coating is 5.9 percent.
Putting the integral catalyst cordierite carrier into the Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ oven for drying for 24h, then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain the cordierite integral catalyst loaded with the manganese cerium oxide, which is recorded as MnCeOx/γ-Al2O3-va/Cord-S-4. The active component loading was 9.3%.
Example 6
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) mixed gas, and gasThe flow rate of cordierite per unit volume per unit time was 0.42 L.min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Putting the cordierite honeycomb ceramic sample pretreated by the plasma into a storage tank, sealing, vacuumizing to-0.09 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 80 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation for 3 times, and coating 3 layers of alumina coating on the cordierite honeycomb ceramic sample to obtain monolithic catalyst cordierite carrier, denoted as gamma-Al2O3-va/Cord-S-5. The first coating load is 5.3 percent, and the specific surface area of the coating is 35.9m2·g-1The ultrasonic shedding rate of the coating is 9.9 percent, and the wear rate of the coating is 5.8 percent.
Putting the integral catalyst cordierite carrier into the Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ oven for drying for 24h, then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain the cordierite integral catalyst loaded with the manganese cerium oxide, which is recorded as MnCeOx/γ-Al2O3The active component loading is 9.7 percent of-va/Cord-S-5.
Example 7
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of gas per unit volume of cordierite treated per unit time was 0.42 l.min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Putting the pretreated cordierite honeycomb ceramic sample into a storage tank, sealing, vacuumizing to-0.1 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃min-1Heating to 80 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation for 3 times, and coating 3 layers of alumina coating on the cordierite honeycomb ceramic sample to obtain monolithic catalyst cordierite carrier, denoted as gamma-Al2O3-va/Cord-S-6. The first coating load is 5.6 percent, and the specific surface area of the coating is 36.0m2·g-1The ultrasonic shedding rate of the coating is 9.8 percent, and the wear rate of the coating is 5.9 percent.
Putting the integral catalyst cordierite carrier into the Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ oven for drying for 24h, then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain the cordierite integral catalyst loaded with the manganese cerium oxide, which is recorded as MnCeOx/γ-Al2O3The active component loading is 9.9 percent of-va/Cord-S-6.
Example 8
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of gas per unit volume of cordierite treated per unit time was 0.42 l.min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Putting the cordierite honeycomb ceramic sample pretreated by the plasma into a storage tank, sealing, vacuumizing to-0.08 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 90 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation for 3 times, and coating 3 layers of alumina coating on the pretreated cordierite honeycomb ceramic sample to obtain monolithic catalyst cordierite carrier, denoted as gamma-Al2O3-va/Cord-S-7. The first coating load is 5.5 percent, and the specific surface area of the coating is 36.1m2·g-1The ultrasonic shedding rate of the coating is 10.1 percent, and the wear rate of the coating is 5.9 percent.
Putting cordierite of an integral catalyst cordierite carrier into a Mn/Ce mixed solution for soaking for 3h, taking out, putting into a 70 ℃ drying oven for drying for 24h, and then putting into a muffle furnace for roasting at 400 ℃ for 2h to obtain the cordierite integral catalyst loaded with manganese cerium oxide, which is named as MnCeOx/γ-Al2O3The active component loading is 10.2 percent of-va/Cord-S-7.
Example 9
Placing cordierite honeycomb ceramic with size of 49 × 50mm into plasma generation equipment, closing cabin door, starting vacuum pump to pump cabin into negative pressure state, regulating output power of plasma generation equipment to 75KW, and making plasma working gas into Ar and N2(Ar:N21:1V/V) and the flow rate of gas per unit volume of cordierite treated per unit time was 0.42 l.min-1·cm-3And treating for 90min to obtain a plasma pretreated cordierite honeycomb ceramic sample.
Placing the cordierite honeycomb ceramic sample pretreated by the plasma into a storage tank, sealing, vacuumizing to-0.1 MPa, maintaining a negative pressure state, and heating in a water bath manner at a heating rate of 10 ℃ per minute-1Heating to 90 deg.C, heating at constant temperature for 30min, cooling to room temperature, and introducing alumina gel (solid content of 25%) to soak cordierite honeycomb ceramic for 30 min; pumping out the slurry, drying in the shade at room temperature for 12h, drying at 60 ℃ for 12h, and roasting at 500 ℃ for 3 h; repeating the above operation for 3 times, and coating 3 layers of alumina coating on the cordierite honeycomb ceramic sample to obtain monolithic catalyst cordierite carrier, denoted as gamma-Al2O3-va/Cord-S-8. The first coating load is 5.7 percent, and the specific surface area of the coating is 36.4m2·g-1The ultrasonic shedding rate of the coating is 9.9 percent, and the wear rate of the coating is 5.8 percent.
Putting the monolithic catalyst cordierite carrier into the Mn/Ce mixed solution for dipping for 3h, taking out, putting into a 70 ℃ oven for drying for 24h, and then putting into a muffle furnace for roasting at 400 ℃ for 2h, obtaining the cordierite monolithic catalyst loaded with the manganese cerium oxide, and recording the cordierite monolithic catalyst as MnCeOx/γ-Al2O3The active component loading is 10.5 percent of-va/Cord-S-8.
Claims (10)
1. A method for preparing a cordierite monolithic catalyst in a variable-temperature vacuum coating mode is characterized by comprising the following steps: the method comprises the following steps: putting cordierite honeycomb ceramic into plasma generation equipment, and pretreating the cordierite honeycomb ceramic by adopting plasma; placing the cordierite honeycomb ceramic subjected to plasma pretreatment into a storage tank, sealing, maintaining the storage tank in a negative pressure state, heating the cordierite honeycomb ceramic, then carrying out impregnation treatment on the cordierite honeycomb ceramic, coating slurry on the cordierite honeycomb ceramic, and sequentially carrying out drying in the shade, drying and roasting to obtain the monolithic catalyst cordierite carrier with the coating; the monolithic catalyst cordierite is loaded with manganese cerium oxide on a monolithic catalyst cordierite carrier by adopting impregnation treatment to obtain the cordierite monolithic catalyst.
2. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:
putting cordierite honeycomb ceramic into plasma generation equipment, closing a cabin door, starting a vacuum pump to pump the cabin into a negative pressure state, and pretreating the cordierite honeycomb ceramic by adopting plasma;
putting the cordierite honeycomb ceramic subjected to plasma pretreatment into a storage tank, sealing, vacuumizing to maintain the storage tank in a negative pressure state, heating in a water bath, heating the cordierite honeycomb ceramic, cooling to room temperature, introducing slurry, and coating the slurry on the cordierite honeycomb ceramic by adopting dipping treatment; pumping out the slurry;
step (3), drying the impregnated cordierite honeycomb ceramic in the shade at room temperature, and then sequentially drying and roasting to obtain the monolithic catalyst cordierite carrier with the coating;
and (4) putting the monolithic catalyst cordierite carrier into an active component solution for soaking, taking out, and then drying and roasting in sequence to obtain the manganese cerium oxide loaded cordierite monolithic catalyst.
3. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 1 or 2, wherein the method comprises the following steps: and sequentially carrying out heating treatment and dipping treatment on the cordierite honeycomb ceramic subjected to plasma pretreatment for 1-3 times in a negative pressure state to obtain the monolithic catalyst cordierite carrier with 1-3 coatings.
4. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 1 or 2, wherein the method comprises the following steps: the output power of the plasma generating equipment is 25-100 KW, and the working gas of the plasma is Ar: N2The treatment time is 30-150 min under the condition of 1:1V/V mixed gas.
5. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 4, wherein the method comprises the following steps: the output power of the plasma generating equipment is 75-100 KW, and the working gas of the plasma is Ar: N2The treatment time is 60-90 min under the condition of 1:1V/V mixed gas.
6. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 4, wherein the method comprises the following steps: the flow rate of the mixed gas in unit time for treating the cordierite honeycomb ceramic per unit volume is 0.33-0.50 L.min-1·cm-3。
7. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 1 or 2, wherein the method comprises the following steps: maintaining the negative pressure of the storage tank at-0.08 to-0.1 MPa (gauge pressure); the temperature of the heating treatment is 70-90 ℃, and the time of the heating treatment is 10-30 min; the slurry is alumina gel with solid content of 20-25%; the single immersion time of the cordierite honeycomb ceramic is 30-60 min.
8. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 7, wherein the method comprises the following steps: the heating treatment comprises the following steps: adopting a water bath heating mode, and heating at the temperature rising rate of 8-10 ℃ per minute-1And heating the mixture from the normal temperature to 70-90 ℃, and then heating the mixture for 10-30 min at the constant temperature.
9. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 1 or 2, wherein the method comprises the following steps: the active component solution is a Mn/Ce mixed solution with the molar ratio of Mn to Ce being (8-9) to (1-2).
10. The method for preparing the cordierite monolithic catalyst by the variable temperature vacuum coating mode according to claim 1 or 2, wherein the method comprises the following steps: the monolithic catalyst cordierite carrier is soaked in the active component solution for 3-4 h; after dipping, drying at the temperature of 70-80 ℃ for 20-24 h; the roasting temperature is 300-400 ℃, and the roasting time is 2-3 h.
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