CN115178273A - Composite metal catalyst and preparation method and application thereof - Google Patents

Composite metal catalyst and preparation method and application thereof Download PDF

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CN115178273A
CN115178273A CN202210889438.4A CN202210889438A CN115178273A CN 115178273 A CN115178273 A CN 115178273A CN 202210889438 A CN202210889438 A CN 202210889438A CN 115178273 A CN115178273 A CN 115178273A
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composite metal
metal catalyst
nano
ceo
soot
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陈龙文
陈燕舞
肖皓洋
刘锋
郑雅诗
朱伟涛
黄宝宝
彭思莹
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Shunde Polytechnic
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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
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/894—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

The invention relates to the technical field of air pollution control, in particular to a composite metal catalyst and a preparation method and application thereof. The composite metal catalyst comprises Co 3 O 4 Nano-cubic of said Co 3 O 4 CeO is loaded on the surface of nano cube 2 A nanoparticle; in the composite metal catalyst, the mass ratio of the Co element to the Ce element is 1:0.03 to 0.2. The invention is prepared by mixing CeO 2 Loaded on Co 3 O 4 Nano cubic surface, adjusting and optimizing Co 3 O 4 ‑CeO 2 The interface can induce the synergistic effect of the two, greatly improve the catalytic performance, greatly reduce the combustion temperature of soot particles, have good catalytic stability and is expected to replace the precious metals such as platinum, palladium and the like in the existing soot oxidation combustion catalystThe catalyst effectively reduces the cost while ensuring the catalytic performance, and is in line with the actual industrial application.

Description

Composite metal catalyst and preparation method and application thereof
Technical Field
The invention relates to the technical field of air pollution control, in particular to a composite metal catalyst and a preparation method and application thereof.
Background
As an important source of urban atmospheric particulate pollutants, soot particles emitted by motor vehicle exhaust can have serious influence on air quality and human health. The use of a combination of a particulate trap and an oxidation catalyst has proven to be one of the most effective aftertreatment techniques for soot particulate removal. Through catalytic reaction, the combustion temperature of the carbon smoke can be obviously reduced, so that the carbon smoke can be directly oxidized and combusted in the temperature range of the exhaust gas of the motor vehicle, and the continuous regeneration and use of the particle catcher can be realized. In the method, the design and preparation of the high-efficiency catalyst are one of the key technical problems of soot oxidation combustion.
At present, the catalyst applied to soot catalytic combustion mainly comprises precious metals such as platinum, palladium and the like, and is expensive and not beneficial to industrial application. The adoption of non-noble metal catalysts generally has the problems of poor soot catalytic combustion effect, high catalytic temperature and the like, and limits the application of the catalysts.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. To this end, a first aspect of the invention proposes a composite metal catalyst. The design method of the catalyst mainly comprises oxygen vacancy engineering, hetero atom doping, mixed metal oxide loading and the like. Multicomponent hybrid structures generally exhibit a specific ability to enhance catalytic activity due to additional effects such as synergistic effects and interfacial effects, as compared to single components. Loading another metal oxide on a metal oxide results in an interface with an incomplete match in atomic position between the two different components, resulting in lattice distortion and the formation of structural defects. These defect sites facilitate improved mobility, availability and reactivity of the active oxygen species and facilitate the transfer of interfacial electrons from one oxide to another, creating more active centers and oxygen vacancies, thereby improving catalytic performance. It follows that the presence of an interface is critical to the effect of catalyst activity.
In view of the above, the invention adopts a metal oxide loaded on the surface of another metal oxide, and induces the synergistic effect of the two different metal oxides by adjusting and optimizing the size of the interface of the two metal oxides, so as to improve the electron transfer on the interface of the two metal oxides and enhance the oxygen vacancy forming capability; meanwhile, the introduction of the metal nanoparticles can enhance the metal-carrier interaction of the catalyst, greatly improve the catalytic activity and stability, and further improve the catalytic combustion performance of the carbon smoke. More specifically, since the mixed valence state of Co ion provides a donor-acceptor chemisorption site and has excellent oxygen carrying utilization ability, co 3 O 4 Is recognized as a catalyst with great application prospect. Co construction by utilizing synergistic effect and interface effect 3 O 4 Mixed multi-component systems with other metal oxides are of great interest. CeO (CeO) 2 Because of Ce 3+ /Ce 4+ The existence of redox couple makes it have excellent oxygen storage and storage capacity and abundant surface oxygen vacancy, thereby endowing it with high-efficient surface oxygen ion exchange rate, good electronic conductivity and a large amount of available active sites for moving oxygen, and is widely used as a catalytic promoter. Thus, the present invention is achieved by adding CeO 2 Loaded on Co 3 O 4 Nano cubic surface, regulating and optimizing Co 3 O 4 -CeO 2 The interface can induce the synergistic effect of the two, greatly improve the catalytic performance, greatly reduce the combustion temperature of soot particles, has good catalytic stability, is expected to replace the use of noble metals such as platinum, palladium and the like in the existing soot oxidation combustion catalyst, effectively reduces the cost while ensuring the catalytic performance, and accords with the actual industrial application.
The second aspect of the invention is to provide a preparation method of the composite metal catalyst, which has mild conditions and simple and convenient operation and can be implemented on a large scale.
The invention also provides an application of the composite metal catalyst.
Specifically, the invention adopts the following technical scheme:
a first aspect of the invention proposes a composite metal catalyst comprising Co 3 O 4 Nano-cubic of said Co 3 O 4 CeO is loaded on the surface of nano cube 2 A nanoparticle; in the composite metal catalyst, the mass ratio of the Co element to the Ce element is 1:0.03 to 0.2.
The invention is prepared by mixing CeO 2 Nanoparticles loaded on Co 3 O 4 The composite metal catalyst formed on the surface of the nano cubic block keeps the appearance of the nano cubic block, and the Co is adjusted and optimized by controlling the proportion of the nano cubic block to the composite metal catalyst 3 O 4 -CeO 2 The interface can induce the synergistic effect of the two components, greatly improve the catalytic performance, greatly reduce the combustion temperature of soot particles and have good catalytic stability.
In some examples of the present invention, the mass ratio of the Co element to the Ce element in the composite metal catalyst is 1:0.04 to 0.16, preferably 1:0.08 to 0.1. The mass ratio of Co to Ce includes, but is not limited to, 1:0.03,1:0.04,1:0.05,1:0.06,1:0.07,1:0.08,1:0.09,1:0.1,1:0.12,1:0.14,1:0.16,1:0.18,1:0.2, etc.
In some examples of the invention, the Co 3 O 4 The nano-cubic particle size is 100 to 300nm, preferably 200 to 250nm.
In some embodiments of the invention, the CeO 2 The size of the nanoparticles is 2 to 30nm, preferably 5 to 20nm.
In some examples of the invention, the composite metal catalyst further comprises simple substance Ag and/or AgO, and the simple substance Ag and/or AgO is loaded in any one or more of the regions a, b and c: a. the Co 3 O 4 The surface of the nano-cube; b. the CeO 2 The surface of the nanoparticle; c. CeO 2 Nanoparticles and Co 3 O 4 Interfaces between nano-cubes.
In some embodiments of the invention, the amount of elemental Ag and/or AgO is Co 3 O 4 1% to 5%, preferably 2% to 3%, including but not limited to 1%,2%,3%,4%,5%, etc.
The second aspect of the present invention provides a preparation method of the composite metal catalyst, comprising the following steps:
mixing the cobalt hydroxide cubic dispersion liquid with cerium salt, and reacting to obtain an intermediate; the mass ratio of the Co element of the cobalt hydroxide cuboids to the Ce element of the cerium salt is 1:0.03 to 0.2;
and calcining the intermediate to obtain the composite metal catalyst.
The invention adopts the cobalt hydroxide cuboids to react with the cerium salt and then calcine, compared with the prior art that the cobalt salt and the cerium salt are directly coprecipitated and calcined, solid solution can not be formed, but can be formed in Co 3 O 4 CeO is loaded on the surface of the nano cube through a Co-O-Ce chemical bond 2 The structure of the nano-particles forms firmer chemical bonds at the interface of the nano-particles and the nano-particles, and the ratio of the nano-particles and the nano-particles is controlled, so that Co is adjusted and optimized 3 O 4 -CeO 2 The interface can induce the synergistic effect of the two, greatly improve the catalytic performance, greatly reduce the combustion temperature of soot particles and have good catalytic stability.
In some embodiments of the invention, the cobalt hydroxide cubes have a mass ratio of Co element to Ce element of the cerium salt of 1:0.04 to 0.16, preferably 1:0.08 to 0.1. The mass ratio of cobalt hydroxide cubes to cerium salt includes, but is not limited to, 1:0.03,1:0.04,1:0.05,1:0.06,1:0.07,1:0.08,1:0.09,1:0.1,1:0.12,1:0.14,1:0.16,1:0.18,1:0.2, etc.
In some examples of the present invention, after the intermediate is calcined, a step of loading silver ions on the calcined product and calcining is further included. After loading silver ions, during calcination, the reaction occurs: ag + +Co 2+ →Ag 0 +Co 3+ ，Ag + +Ce 3+ →Ag 0 +Ce 4+ Thereby realizing the loading of the Ag simple substance. At the same time, agO may also be generated during the calcination process.
In some embodiments of the invention, the temperature at which the intermediate is calcined and the post-silver ion loading calcination is independently from 500 to 800 ℃, preferably from 550 to 600 ℃, including but not limited to 500, 550, 600, 650, 700, 750, 800 ℃, etc.; the calcination time is independently 1 to 10 hours, preferably 2 to 4 hours, including but not limited to 1,2,3,4,5,6,7,8,9, 10 hours, etc.
In some embodiments of the invention, the intermediate is calcined, and the calcination after loading with silver ions is carried out in air.
In some examples of the present invention, the solvent in the cobalt hydroxide cube dispersion is at least one of water and ethanol, preferably an aqueous ethanol solution, and the volume concentration of ethanol in the aqueous ethanol solution is 10% to 80%, preferably 30% to 60%, including but not limited to 10%,20%,30%,40%,50%,60%,70%,80%, etc. The concentration of the cubic cobalt hydroxide dispersion is 0.5 to 5mg/mL, preferably 0.5 to 2mg/mL, including but not limited to 0.5,1,1.5,2,2.5,3,3.5,4,4.5,5mg/mL and the like.
Dispersing the cobalt hydroxide cuboids in a solvent to obtain a cobalt hydroxide cuboids dispersion liquid, wherein the dispersion of the cobalt hydroxide cuboids can be promoted by means of ultrasound, stirring and the like in the dispersion process, and the ultrasound is preferred. The parameters used for the sonication can be selected according to the actual needs and the routine practice in the art. By way of example, the power of the sonication can be in the range of 200 to 1000W, preferably 400 to 600W, including but not limited to 200, 300, 400, 500, 600, 700, 800, 900, 1000W, etc.; the frequency of the sonication can be set to 20-80 KHz, preferably 30-50 KHz, including but not limited to 20, 30, 40, 50, 60, 70, 80KHz, etc.; the time of the ultrasonic treatment may be set to 1 to 10 hours, preferably 2 to 6 hours, including but not limited to 1,2,3,4,5,6,7,8,9, 10 hours, etc.
In some embodiments of the invention, the system in which the cobalt hydroxide cubed dispersion is mixed with the cerium salt comprises a dispersant comprising hexamethylenetetramine. The mass ratio of the dispersant to the cerium salt is 1:5 to 20, preferably 1:8 to 12, including but not limited to 1:5,1:8,1:10,1:12,1:14,1:16,1:18,1:20, etc. Cerium hydroxide can be formed in a mixed system of the cobalt hydroxide cubic dispersion liquid and the cerium salt, and by adding the dispersing agent and reasonably controlling the dosage of the dispersing agent, the loading of the cerium hydroxide on the surface of the cobalt hydroxide is facilitated, and the agglomeration of the cerium hydroxide can be avoided.
In some embodiments of the invention, the reaction temperature after mixing the cobalt hydroxide cuboidal dispersion with the cerium salt is from 50 to 90 ℃, preferably from 60 to 80 ℃, including but not limited to 50, 60, 70, 80, 90 ℃ and the like; the reaction time is 1 to 10 hours, preferably 2 to 5 hours, including but not limited to 1,2,3,4,5,6,7,8,9, 10 hours. The reaction is preferably carried out under a protective atmosphere (e.g. under nitrogen) under reflux.
In actual practice, the reaction is gradually heated from ambient temperature to the desired reaction temperature, and the heating rate can be set to 0.5-3 ℃/min, preferably 1-2 ℃/min, including but not limited to 0.5,1,1.5,2,2.5,3 ℃/min, etc.; stirring can be assisted in the temperature rising process. After the reaction is finished, cooling to the ambient temperature, then carrying out solid-liquid separation, washing and drying, wherein the drying temperature can be set to be 100-120 ℃, preferably 100-110 ℃, including but not limited to 100, 110, 120 ℃ and the like; the drying time may be set to 5 to 24 hours, preferably 10 to 12 hours, including but not limited to 5,7,9, 10, 12, 14, 16, 18, 20, 22, 24 hours, etc.
In some examples of the present invention, the method for loading silver ions may adopt an impregnation method, specifically: and mixing the calcined product of the intermediate with a silver ion solution and then drying.
In some examples of the invention, the amount of the species of silver ions is 1% to 5%, preferably 2% to 3%, including but not limited to 1%,2%,3%,4%,5%, etc., of the intermediate calcined product.
In some embodiments of the invention, the cobalt hydroxide cubes are prepared by: and carrying out hydrothermal reaction on the cobalt salt solution under an alkaline condition to obtain the cobalt hydroxide cubic block.
In some embodiments of the invention, the alkaline conditions have a pH of 8 to 11, preferably 8 to 10, including but not limited to 8,8.5,9,9.5, 10, 10.5, 11, etc. in the method of making the cobalt hydroxide cubes. In practice, the pH of the system can be adjusted by adding an alkali such as sodium hydroxide, potassium hydroxide, or ammonia water to the solution. As an example, the pH can be controlled between 8 and 11 (preferably 8 to 10) by controlling the concentration of sodium hydroxide in the cobalt salt solution to be 0.05 to 0.2mol/L, preferably 0.1 to 0.15 mol/L.
In some embodiments of the invention, the cobalt salt solution has a concentration of 0.2 to 1mol/L, preferably 0.3 to 0.8mol/L, including but not limited to 0.2,0.3,0.4,0.5,0.6,0.8,1mol/L, and the like.
In some embodiments of the invention, the ratio of the amount of cobalt salt to base is 3 to 5:1, preferably 3.5 to 4.5:1, including but not limited to 3:1,3.5:1,4:1,4.5:1,5:1, etc.
In some examples of the invention, the temperature of the hydrothermal reaction is 150 to 200 ℃, preferably 170 to 190 ℃, including but not limited to 150, 160, 170, 180, 190, 200 ℃ and the like.
In some embodiments of the present invention, the hydrothermal reaction is carried out for a period of time ranging from 3 to 10 hours, preferably from 4 to 6 hours, including but not limited to 3,4,5,6,7,8,9, 10 hours, etc. And after the hydrothermal reaction is finished, carrying out solid-liquid separation, washing and drying to obtain cobalt hydroxide cubic blocks. Wherein the drying temperature can be set to 100-120 ℃, preferably 100-110 ℃, including but not limited to 100, 110, 120 ℃ and the like; the drying time may be set to 5 to 24 hours, preferably 10 to 12 hours, including but not limited to 5,7,9, 10, 12, 14, 16, 18, 20, 22, 24 hours, etc.
In some examples of the invention, the cerium salt comprises any one or more of cerium nitrate and its hydrate, cerium sulfate and its hydrate, cerium chloride and its hydrate.
In some examples of the invention, the cobalt salt comprises any one or more of cobalt nitrate and hydrates thereof, cobalt sulfate and hydrates thereof, and cobalt chloride and hydrates thereof.
A third aspect of the invention is to provide the use of the composite metal catalyst in catalyzing soot combustion. The carbon smoke is carbon particulate matters generated by incomplete combustion of hydrocarbon fuel, and the composite metal catalyst can effectively catalyze the carbon smoke combustion, has high catalysis efficiency, can reduce the combustion temperature, and has good cycle performance.
The fourth aspect of the invention provides the application of the composite metal catalyst in the control of the soot emission of the tail gas of the motor vehicle.
A fifth aspect of the present invention provides a method for catalytic combustion of soot, comprising the steps of: and (3) enabling the soot to contact with the composite metal catalyst for catalytic combustion.
In some embodiments of the invention, the temperature of the catalytic combustion is 200 to 450 ℃, preferably 200 to 400 ℃, including but not limited to 200, 220, 240, 250, 300, 350, 400, 450 ℃ and the like. The composite metal catalyst of the invention is used for catalyzing soot combustion, the conversion rate of soot can reach 50% under the conditions of being lower than 300 ℃ and even being lower than 240 ℃, and the temperature for soot combustion is reduced.
In some examples of the invention, the mass ratio of soot to composite metal catalyst is 1:5 to 20, preferably 1:8 to 12, including but not limited to 1:5,1:8,1:10,1:12,1:14,1:16,1:18,1:20, etc.
In some examples of the invention, the catalytic combustion is carried out in an oxygen-containing atmosphere. Preferably, O is in said oxygen-containing atmosphere 2 Is from 5% to 30%, preferably from 5% to 15%, including but not limited to 5%,10%,15%,20%,25%,30%, etc.
In some examples of the invention, at least one of NO, water vapor may be present during the catalytic combustion process. The NO concentration may be 0 to 1000ppm, such as 0, 50, 100, 200, 300, 500, 600, 700, 800, 900, 1000ppm, and the like. The water vapor volume concentration is 0 to 50%, for example, 0%,5%,10%,15%,20%,25%,30%,35%,40%,45%,50%, etc. The tail gas of motor vehicle contains NO, water vapor and other components, and the catalytic combustion of the present invention may be carried out in tail gas of motor vehicle or similar conditions.
Compared with the prior art, the invention has the following advantages:
(1) The composite metal catalyst of the invention can be prepared by adjusting Co 3 O 4 -CeO 2 The size of the interface is used for regulating and controlling the synergistic effect between the two components, so that the catalytic performance is optimized;
(2) The composite metal catalyst of the invention shows excellent activity, stability and recyclable capability for carbon smoke catalytic combustion, improves the carbon smoke catalytic combustion performance, reduces the carbon smoke catalytic combustion temperature, is expected to replace the prior expensive noble metal catalysts such as platinum, palladium and the like, and reduces the catalyst cost
(3) The composite metal catalyst has mild preparation conditions, adopts economical and practical raw materials, and can be prepared in a large scale.
Drawings
FIG. 1 is SEM image (a) and structure schematic diagram (b) of Ag/CoCe-1.
FIG. 2 is SEM image (a) and structural schematic (b) of Ag/CoCe-2.
FIG. 3 is SEM image (a) and structural schematic (b) of Ag/CoCe-3.
Figure 4 is an XRD pattern of different catalysts.
Figure 5 is an XPS plot of different catalysts.
FIG. 6 shows soot catalytic combustion test results, wherein (a) is soot conversion at 200-450 ℃ for different catalysts, and (b) is T for different catalysts 10 、T 50 、T 90 (c) T of different catalysts under different atmospheres 50 And (d) is the cycle test result of Ag/CoCe-2.
Detailed Description
The technical solution of the present invention is further described below with reference to specific examples. The starting materials used in the following examples, unless otherwise specified, are available from conventional commercial sources; the adopted process adopts the conventional process in the field if no special indication is provided; the room temperature and the ambient temperature mentioned in the invention mean 25 +/-5 ℃.
Example 1
This example was carried out by hydrothermal method, N 2 A composite metal catalyst prepared by a protection condensation reflux method and an impregnation methodI.e. Ag/Co 3 O 4 -CeO 2 The nano cubic catalyst comprises the following specific steps:
(1) 40mmol of cobalt nitrate hexahydrate and 10mmol of sodium hydroxide are dissolved in 80mL of deionized water, stirred uniformly at room temperature, and then transferred to a high-pressure stainless steel reaction kettle to carry out hydrothermal reaction for 5 hours at 180 ℃. After the reaction is finished, the precipitate is collected by centrifugation, washed and dried at 110 ℃ for 12h to obtain the cobalt hydroxide cubed precursor.
(2) 100mg of the prepared cobalt hydroxide cuboidal precursor is dispersed in 100mL ethanol water solution with 50% volume, suspension is obtained after ultrasonic treatment for 4 hours with 500W power and 40kHz frequency, and then the suspension is transferred to a round-bottom flask.
(3) To the round bottom flask of step (2) were added 20mg of cerium nitrate hexahydrate and 2mg of hexamethylenetetramine. It was dissolved by stirring at room temperature for 0.5 h. Then heating while stirring, wherein the heating rate is 2 ℃/min. Under the nitrogen atmosphere, condensation reflux treatment was carried out for 4 hours at a treatment temperature of 80 ℃.
(4) After the electricity is turned off and the cooling is carried out, the suspension obtained by the condensation reflux treatment in the step (3) is centrifuged to collect the precipitate, and the precipitate is washed, dried (110 ℃,12 h) and calcined for 3h at the high temperature of 550 ℃ to obtain the loaded CeO 2 Co of (A) 3 O 4 Nano-cubic block.
(5) Dispersing a certain amount of the nano cubic blocks obtained in the step (4) in deionized water, adding a silver nitrate solution accounting for 2% of the amount of the nano cubic blocks, uniformly stirring at room temperature, drying, and calcining at 550 ℃ for 3 hours to obtain Ag/Co 3 O 4 -CeO 2 The nano cubic catalyst is named as Ag/CoCe-1.
The SEM image and the structural schematic diagram of Ag/CoCe-1 are shown in figure 1, and the XRD and XPS images are shown in figures 4 and 5 respectively.
Example 2
The specific procedure of example 2 was substantially the same as in example 1, except that 40mg of cerium nitrate hexahydrate and 4mg of hexamethylenetetramine were charged in the flask in the step (3). The catalyst prepared under the condition is named as Ag/CoCe-2, the SEM image and the structural schematic diagram of the catalyst are shown in figure 2, and the XRD and XPS images are respectively shown in figures 4 and 5.
Example 3
The specific procedure of example 3 is substantially the same as in example 1 except that in step (3), 80mg of cerium nitrate hexahydrate and 8mg of hexamethylenetetramine are added to the flask. The catalyst prepared under this condition is named as Ag/CoCe-3, and its SEM image is shown in FIG. 3, and XRD and XPS images are shown in FIGS. 4 and 5, respectively.
Comparative example 1
This comparative example provides an Ag/Co alloy 3 O 4 Nano cubic catalyst, which is different from example 1 in Co 3 O 4 Nano cubic block without CeO load 2 The preparation method comprises the following specific steps:
(1) 40mmol of cobalt nitrate hexahydrate and 10mmol of sodium hydroxide are dissolved in deionized water, stirred uniformly at room temperature, and then transferred to a high-pressure stainless steel reaction kettle to carry out hydrothermal reaction for 5 hours at 180 ℃. After the reaction is finished, the precipitate is collected by centrifugation, washed and dried at 110 ℃ for 12h to obtain the cobalt hydroxide cubed precursor.
(2) Calcining the cobalt hydroxide cubic precursor at 550 ℃ for 3 hours to obtain Co 3 O 4 Nano-cubic block.
(3) Dispersing a certain amount of nano cubic blocks obtained in the step (2) in deionized water, adding a silver nitrate solution with the amount of 2% of the substance, stirring uniformly at room temperature, drying, and calcining at 550 ℃ for 3 hours to obtain Ag/Co 3 O 4 The nanometer cubic catalyst is named as Ag/Co, and the XRD and XPS patterns are shown in figures 4 and 5 respectively.
Comparative example 2
This comparative example provides an Ag/CeO 2 Nano-cubic catalyst, which differs from example 1 in that it does not contain Co 3 O 4 The preparation method of the nano cube comprises the following specific steps:
(1) To 100mL of a 50% by volume aqueous ethanol solution were added 20mg of cerium nitrate hexahydrate and 2mg of hexamethylenetetramine. It was dissolved by stirring at room temperature for 0.5 h. Then heating while stirring, wherein the heating rate is 2 ℃/min. Under the nitrogen atmosphere, condensation reflux treatment was carried out for 4 hours at a treatment temperature of 80 ℃.
(2) After the electricity is turned off and the cooling is carried out, the suspension obtained by the condensation reflux treatment in the step (1) is centrifuged to collect the precipitate, and the precipitate is washed, dried (110 ℃,12 h) and calcined for 3h at the high temperature of 550 ℃ to obtain CeO 2 。
(3) Taking a certain amount of CeO obtained in the step (2) 2 Dispersing in deionized water, adding 2% silver nitrate solution, stirring at room temperature, drying, calcining at 550 deg.C for 3 hr to obtain Ag/CeO 2 The nano cubic catalyst is named as Ag/Ce, and XRD and XPS graphs of the nano cubic catalyst are respectively shown in figures 4 and 5.
Structural characterization:
(1) As can be seen from FIG. 1, ag/CoCe-1 has the appearance of nano-cubic blocks, wherein the size of the nano-cubic block is 200-250 nm, the surface of the nano-cubic block is dispersedly loaded with nano-particles with the size of 5-20 nm, and the nano-cubic block is Co 3 O 4 The nano particles on the surface of the nano cube contain CeO 2 And simple substance Ag and/or AgO.
FIGS. 2 and 3 show that Ag/CoCe-2 and Ag/CoCe-3 have similar structures to Ag/CoCe-1, except for the Co of Ag/CoCe-2 and Ag/CoCe-3 3 O 4 The number of nanoparticles on the surface of the nano-cubic block is obviously increased, but the aggregation of large particles still does not occur.
(2) XRD and XPS charts in FIG. 4 and FIG. 5 show that the chemical compositions of Ag/CoCe-1, ag/CoCe-2 and Ag/CoCe-3 contain Co 3 O 4 And CeO 2 And Ag simple substance.
Example 4
In the embodiment, the catalysts of the embodiments 1 to 3 and the comparative examples 1 and 2 are applied to catalyzing soot combustion, and the catalytic performance of the prepared catalysts is evaluated by testing the soot oxidation combustion temperature under different conditions.
The method comprises the following specific steps: a quartz tube having an inner diameter of 8mm was used as a microreactor. Before the experiment, 50mg of catalyst is weighed to be closely contacted and mixed with 5mg of soot, and then the catalyst is uniformly mixed with 200mg of quartz sand to be filled in a quartz tube, and quartz wool is used at two endsAnd (5) fixing. Introducing into 10% of 100mL/min 2 /N 2 Or (10%) o 2 /N 2 +500ppm NO), or (10% 2 /N 2 +500ppm NO +5vol.% steam), and the activity evaluation experiment is carried out in the range of 200-450 ℃. The concentration change of carbon dioxide in the reaction process is detected by an online gas chromatography, and the conversion rate of the carbon smoke is represented by dividing the integral of the carbon dioxide concentration at a certain temperature by the integral of the total concentration of the carbon dioxide after the reaction is finished.
The soot catalytic combustion test results are shown in FIG. 6, T 10 、T 50 、T 90 Denotes the temperatures at which the soot conversion reaches 10%, 50% and 90%, respectively, "10% 2 'OR' O 2 "means passing only 10% o 2 /N 2 Condition (1), "O 2 + NO "means passing through 10% 2 /N 2 +500ppm NO condition, "O 2 +NO+H 2 O "means passing through 10% O 2 /N 2 +500ppm NO +5vol.% steam. In FIG. 6 (a), at the arrow, the samples are Ag/CoCe-2, ag/CoCe-3, ag/CoCe-1, ag/Co and Ag/Ce in sequence according to the arrow direction; in FIGS. 6 (b) and (c), the samples corresponding to each set of data are Ag/Co, ag/CoCe-1, ag/CoCe-2, ag/CoCe-3 and Ag/Ce in sequence according to the arrow direction.
As can be seen from FIG. 6, in the same atmosphere, the soot-oxidized burning T of three of Ag/CoCe-1, ag/CoCe-2 and Ag/CoCe-3 50 The temperature shows a decreasing and increasing trend in turn, T of soot oxidation combustion of Ag/CoCe-2 of example 2 50 The catalyst has the lowest temperature, shows the highest catalytic activity and is mainly benefited by the fact that the catalyst has the largest Co 3 O 4 -CeO 2 And (6) an interface. T of Ag/CoCe-3 50 The temperature is higher than Ag/CoCe-2, but lower than Ag/CoCe-1. More specifically, the T of Ag/CoCe-2, ag/CoCe-3 under different atmospheres 50 The temperature is lower than 300 ℃; while passing through 10% O 2 /N 2 +500ppm NO +5vol.% water vapor, T of Ag/CoCe-2 50 The temperature is lower than 240 ℃, and the catalyst has excellent low-temperature catalytic activity. Meanwhile, after the Ag/CoCe-2 is tested for six times of cycles, the carbon smoke of the Ag/CoCe-2 is oxidized and combusted in T under different atmospheres 50 The temperature floating change interval is +/-3 ℃, and the catalyst has good catalytic stability.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such modifications are intended to be included in the scope of the present invention.

Claims (10)

1. A composite metal catalyst characterized by: the composite metal catalyst comprises Co 3 O 4 Nano-cubic of said Co 3 O 4 CeO is loaded on the surface of the nano cube 2 A nanoparticle; in the composite metal catalyst, the mass ratio of the Co element to the Ce element is 1:0.03 to 0.2.
2. The composite metal catalyst according to claim 1, characterized in that: in the composite metal catalyst, the mass ratio of the Co element to the Ce element is 1: 0.04-0.16.
3. The composite metal catalyst according to claim 1 or 2, characterized in that: the composite metal catalyst also comprises an Ag simple substance and/or AgO, and the Ag simple substance and/or AgO is loaded in any one or more of the areas a, b and c: a. the Co 3 O 4 The surface of the nano-cube; b. the CeO 2 The surface of the nanoparticle; c. CeO 2 Nanoparticles and Co 3 O 4 Interfaces between nano-cubes.
4. The composite metal catalyst according to claim 3, characterized in that: the amount of the Ag simple substance and/or AgO substance is Co 3 O 4 1 to 5 percent of the total weight of the composition.
5. The method for preparing the composite metal catalyst of any one of claims 1 to 4, wherein: the method comprises the following steps:
mixing the cobalt hydroxide cubic dispersion liquid with cerium salt, and reacting to obtain an intermediate; the mass ratio of the Co element of the cobalt hydroxide cuboids to the Ce element of the cerium salt is 1:0.03 to 0.2;
and calcining the intermediate to obtain the composite metal catalyst.
6. The method according to claim 5, wherein: after the intermediate is calcined, the method also comprises the steps of loading silver ions on the calcined product and calcining.
7. The method according to claim 6, wherein: the calcining temperature of the intermediate and the calcining temperature after the silver ion loading are respectively and independently 500-800 ℃.
8. Use of the composite metal catalyst of any one of claims 1 to 4 for catalyzing soot combustion.
9. Use of the composite metal catalyst of any one of claims 1 to 4 in the control of soot emissions from motor vehicle exhaust gases.
10. A method of catalytic combustion of soot comprising the steps of: the soot is brought into contact with the composite metal catalyst of any one of claims 1 to 4 to perform catalytic combustion.
CN202210889438.4A 2022-07-27 2022-07-27 Composite metal catalyst and preparation method and application thereof Pending CN115178273A (en)

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