WO2017049804A1 - 低温催化去除环境污染物的催化剂及其制备方法 - Google Patents

低温催化去除环境污染物的催化剂及其制备方法 Download PDF

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WO2017049804A1
WO2017049804A1 PCT/CN2015/100224 CN2015100224W WO2017049804A1 WO 2017049804 A1 WO2017049804 A1 WO 2017049804A1 CN 2015100224 W CN2015100224 W CN 2015100224W WO 2017049804 A1 WO2017049804 A1 WO 2017049804A1
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catalyst
rare earth
nitrate
cobalt
catalyst according
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French (fr)
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上官文峰
邹谷初
陈铭夏
江治
张志翔
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上海交通大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • 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
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • 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
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/50—Silver
    • 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
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, 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
    • B01J23/70—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
    • 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
    • B01J23/8913—Cobalt and noble metals
    • 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
    • B01J2523/10—Constitutive chemical elements of heterogeneous catalysts of Group I (IA or IB) of the Periodic Table
    • B01J2523/18—Silver
    • 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
    • B01J2523/30—Constitutive chemical elements of heterogeneous catalysts of Group III (IIIA or IIIB) of the Periodic Table
    • B01J2523/37—Lanthanides
    • B01J2523/3706—Lanthanum
    • 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
    • B01J2523/30—Constitutive chemical elements of heterogeneous catalysts of Group III (IIIA or IIIB) of the Periodic Table
    • B01J2523/37—Lanthanides
    • B01J2523/3712—Cerium
    • 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
    • B01J2523/30—Constitutive chemical elements of heterogeneous catalysts of Group III (IIIA or IIIB) of the Periodic Table
    • B01J2523/37—Lanthanides
    • B01J2523/3718—Praseodymium
    • 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
    • B01J2523/80—Constitutive chemical elements of heterogeneous catalysts of Group VIII of the Periodic Table
    • B01J2523/84—Metals of the iron group
    • B01J2523/845—Cobalt

Definitions

  • the invention belongs to the technical field of environmental catalysis, and particularly relates to a catalyst for low-temperature catalytic removal of environmental pollutants and a preparation method thereof.
  • Environmental catalysis is a technology that uses catalysts to convert harmful substances in the environment into environmentally friendly products.
  • Catalytic technology is therefore widely used in the field of atmospheric environmental management.
  • the current technology for carbon monoxide treatment is mainly catalytic oxidation.
  • the catalysts used in it generally include precious metals such as Pt, which reduces the economics of the emission system.
  • the technologies for controlling nitrogen oxides mainly include hydrocarbon selective catalytic reduction (HC-SCR) and ammonia selective catalytic reduction (NH 3 -SCR).
  • HC-SCR hydrocarbon selective catalytic reduction
  • NH 3 -SCR ammonia selective catalytic reduction
  • China mainly adopts the NH 3 -SCR technology route, and its main catalysts are strong.
  • Particulate matter removal technology mainly includes oxidation catalyst (DOC) and diesel particulate filter (DPF), but the former can only remove volatile organic compounds on the surface of the particles, and the capture effect on soot is not good; the latter has the efficiency of soot capture.
  • DOC oxidation catalyst
  • DPF diesel particulate filter
  • the main DPF regeneration technologies include: electric heating regeneration, reverse jet regeneration, intake and exhaust throttle regeneration, fuel injection combustion regeneration, electric self heating regeneration, microwave heating regeneration, fuel additive assisted regeneration, continuous catalytic regeneration, etc., but the above heating regeneration
  • the technology has the defects that the filter body is easily damaged, the reliability is poor, the system is complicated, and the air-jet regeneration technology has the problems of poor low-temperature light-off performance and complicated installation; continuous regeneration is a promising regeneration mode, and its energy consumption is low.
  • the system is simple and easy to maintain.
  • the key to the application of continuous regeneration technology is to find a catalyst with excellent low temperature catalytic oxidation performance.
  • the Chinese invention patent application with the publication number 104508269A is named: a high performance SCR catalyst system, and a scavenging SOF catalyst module having a catalyst active material for removing SOF components is attached to the rear end of the diesel engine, and The SCR catalyst module having the SCR catalyst active material is continuously installed downstream to effectively remove the nitrogen oxides. But overall, the system is divided into two modules, which are more complicated and have poor economics.
  • the Chinese invention patent application with the publication number 103285854A is named: diesel exhaust particulate catalyst, and its preparation method and use method;
  • the catalyst comprises: a carrier, a catalyst supported on the catalyst carrier Agent and catalyst active ingredient.
  • the catalyst carrier is a coarse pore microsphere silica gel having high mechanical strength, the catalyst aid is a metal oxide, and the active component is metal ruthenium.
  • the main problem is that the economy of the catalyst is poor, and there are many defects such as high temperature loss and unstable catalytic performance.
  • the object of the present invention is to overcome the deficiencies of the prior art mentioned above, and to provide a catalyst with low cost and relatively simple preparation process capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof.
  • the invention is applied to the field of low-temperature catalytic removal of carbon monoxide, low-temperature catalytic removal of diesel vehicle exhaust gas particulate matter and ammonia selective catalytic reduction of nitrogen oxides.
  • the invention relates to a catalyst having the chemical formula zAg/Co 1-x M x O y , wherein M is La, Ce or Pr, 0.02 ⁇ x ⁇ 0.5, 1.33 ⁇ y ⁇ 2 , 0.05 ⁇ z ⁇ 0.3; the atomic ratio of M: Co is x: 1-x, and the atomic ratio of Ag: (Co + M) is z: 1.
  • x>0.5 rare earth oxides become the main phase of the material, which is not conducive to catalysis; when z ⁇ 0.05, it is not conducive to the activation of catalytic species.
  • z>0.3 it is not conducive to the mutual catalysis of elemental Ag and other oxides. effect.
  • the catalyst comprises a composite oxide and a surface-supported Ag thereof, the composite oxide being composed of Co 3 O 4 and a rare earth material, the rare earth material being a rare earth oxide or a rare earth perovskite type composite oxide;
  • the rare earth element in the rare earth material is M, and M is selected from La, Ce or Pr, and Ag is in a single state.
  • the rare earth oxide has a chemical formula of MO 2 or M 2 O 3
  • the rare earth perovskite-type composite oxide has a chemical formula of MCoO 3 .
  • the present invention also relates to a method for preparing a catalyst, wherein the catalyst is prepared by using a silver nitrate as a silver source, a cobalt salt as a cobalt source, and a nitrate of M as a rare earth precursor by a citric acid complex method or a coprecipitation method. And got it.
  • the citric acid complexing method uses silver nitrate as a silver source, a cobalt salt as a cobalt source, and a nitrate of M as a rare earth precursor, and the baking temperature is 500 ° C to 900 ° C.
  • the citric acid complexing method comprises: cobalt nitrate hexahydrate or cobalt acetate tetrahydrate, nitrate of M, Silver nitrate and citric acid are measured according to the ratio of (1-x):x:z:5 (where x is the stoichiometric number of M, 0.02 ⁇ x ⁇ 0.5, z is the stoichiometric amount of Ag, 0.05 ⁇ z ⁇ 0.3) It is formulated into a solution, stirred and evaporated at 70 to 90 ° C, and then calcined at a high temperature of 500 ° C to 900 ° C for 4 to 8 hours to synthesize the catalyst. When the calcination temperature is lower than 500 ° C, citric acid carbon cannot be effectively removed.
  • the coprecipitation method uses silver nitrate as a silver source, cobalt salt as a cobalt source, M nitrate as a rare earth precursor, a precipitant Na 2 CO 3 , and a pH value of 8 to 10 when aged.
  • the baking temperature is 500 ° C to 800 ° C.
  • the coprecipitation method comprises:
  • the invention also relates to the use of the catalyst for the catalytic oxidation of carbon monoxide at low temperature.
  • the invention also relates to the use of the catalyst for the low temperature catalytic oxidation to remove diesel exhaust particulates.
  • the invention also relates to the use of the catalyst for the selective catalytic reduction of nitrogen oxides by ammonia.
  • the invention adds a rare earth element to the silver-cobalt system to form a rare earth oxide or a perovskite-type composite oxide formed by the rare earth and the cobalt, and the interaction of these oxides with the elemental silver is advantageous for further improving the oxidizing property of the catalyst.
  • the present invention has the following beneficial effects:
  • the catalytic performance of the catalyst prepared by the invention in the catalytic oxidation of soot, the catalytic removal of carbon monoxide and the low-temperature selective catalytic reduction of nitrogen oxides is superior to that of Ag/Co 3 O 4 and other various transition metal oxides. .
  • the preparation process of the invention is economical and simple, and the raw materials used are low in price, which is beneficial to the promotion and application of the market.
  • the low temperature oxidation performance of the present invention is close to that of the noble metal catalyst, and can catalyze the oxidation of soot and carbon monoxide in a more economical manner.
  • the present invention is compared to Ag / Co 3 O 4 can widen the selective catalytic reduction of nitrogen oxides reaction temperature window, to enhance stability of the catalyst.
  • XRD X-ray diffraction
  • XRD X-ray diffraction
  • the embodiment relates to a catalyst capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof, and the preparation method comprises the following steps:
  • the powder solid sample was placed in a corundum crucible having a volume of 200 mL, and then the loaded crucible was placed in a muffle furnace, heated to 500 ° C at a rate of 10 ° C/min, and kept for 4 h. After cooling, it was taken out and ground in an agate mortar, and the loaded porcelain crucible was placed in a muffle furnace and heated to 500 ° C at a rate of 10 ° C/min, and kept for 4 hours. After cooling, the mill was taken out to obtain a target of 0.3Ag/Co 0.5 Pr 0.5 O y .
  • Fig. 2(b) is an X-ray diffraction (XRD) pattern of a sample 0.3Ag/Co 0.5 Pr 0.5 O y (1.33 ⁇ y ⁇ 1.7) synthesized in the present example, and it is known that the composition contains PrCoO 3 and elemental Ag. .
  • XRD X-ray diffraction
  • the embodiment relates to a catalyst capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof, and the preparation method comprises the following steps:
  • the powder solid sample was placed in a corundum crucible having a volume of 200 mL, and then the loaded crucible was placed in a muffle furnace, heated to 900 ° C at a rate of 10 ° C/min, and kept for 4 h. After cooling, it was taken out and ground in an agate mortar.
  • the sampled porcelain crucible was placed in a muffle furnace and heated to 900 ° C at a rate of 10 ° C/min for 4 h. After cooling, the mill was taken out to obtain the target 0.05Ag/Co 3 O 4 .
  • the prepared catalyst tablets are sieved to 60 mesh to 80 mesh.
  • Fig. 1(a) is an X-ray diffraction (XRD) pattern of a sample of 0.05Ag/Co 0.98 Ce 0.02 O y (1.33 ⁇ y ⁇ 1.5) synthesized in the present example, and the composition thereof contains a trace amount of CeO 2 , Co 3 O 4 and elemental Ag.
  • XRD X-ray diffraction
  • the embodiment relates to a catalyst capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof, and the preparation method comprises the following steps:
  • a 1 mol/L Na 2 CO 3 solution was added dropwise to a mixed solution of cobalt nitrate and cerium nitrate in a stirred state, and the pH of the solution was monitored using a pH meter. When the pH stabilized at 8, the dropping was stopped.
  • the obtained precipitate was aged for 10 hours, washed with deionized water and suction filtered 5 times, and the precipitate was placed at 100 ° C. Dry in an oven.
  • the powder solid sample was placed in a corundum crucible having a volume of 50 mL, and then the loaded crucible was placed in a muffle furnace, and heated to 500 ° C at a rate of 10 ° C/min for 4 h. After cooling, the mixture was taken out and ground, and 0.85 g of AgNO 3 was weighed, mixed with the calcined sample, and then deionized water was added to a water bath at 80 ° C to be evaporated to dryness.
  • the evaporated powder was calcined at 500 ° C for 2 h to obtain 0.2Ag/Co 0.8 Ce 0.2 O y .
  • the prepared catalyst tablets are sieved to 60 mesh to 80 mesh.
  • Fig. 1(b) is an X-ray diffraction (XRD) pattern of a sample 0.2Ag/Co 0.8 Ce 0.2 O y (1.33 ⁇ y ⁇ 1.6) synthesized in the present example, and the composition thereof contains Co 3 O 4 , CeO 2 and elemental Ag.
  • XRD X-ray diffraction
  • the embodiment relates to a catalyst capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof, and the preparation method comprises the following steps:
  • the powder solid sample was placed in a corundum crucible having a volume of 200 mL, and then the loaded crucible was placed in a muffle furnace, and heated to 700 ° C at a rate of 10 ° C/min for 4 h. After cooling, it was taken out and ground in an agate mortar.
  • the sampled porcelain crucible was placed in a muffle furnace and heated to 700 ° C at a rate of 10 ° C/min for 4 h. After cooling, it was taken out and ground to obtain a target of 0.2 Ag/Co 0.95 La 0.05 O y .
  • Fig. 3(b) is an X-ray diffraction (XRD) pattern of a sample 0.2Ag/Co 0.95 La 0.05 O y (1.35 ⁇ y ⁇ 2) synthesized in the present example, and the composition thereof contains Co 3 O 4 , LaCoO 3 and elemental Ag.
  • XRD X-ray diffraction
  • the embodiment relates to a catalyst capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof, and the preparation method comprises the following steps:
  • a 1 mol/L Na 2 CO 3 solution was added dropwise to a mixed solution of cobalt nitrate and cerium nitrate in a stirred state, and the pH of the solution was monitored using a pH meter. When the pH stabilized at 10, the dropwise addition was stopped.
  • the obtained precipitate was aged for 10 hours, washed with deionized water and suction filtered 5 times, and the precipitate was dried in an oven at 100 °C.
  • the powder solid sample was placed in a corundum crucible having a volume of 50 mL, and then the loaded crucible was placed in a muffle furnace, and heated to 500 ° C at a rate of 10 ° C/min for 4 h. After cooling, it was taken out and ground, and 0.34 g of AgNO 3 was weighed, mixed with the calcined sample, and then deionized water was added to a water bath at 80 ° C and stirred to dryness.
  • the evaporated powder was calcined at 500 ° C for 2 h to obtain 0.1 Ag / Co 0.9 Pr 0.1 O y .
  • the prepared catalyst tablets are sieved to 60 mesh to 80 mesh.
  • XRD X-ray diffraction
  • the embodiment relates to a catalyst capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof, and the preparation method comprises the following steps:
  • a 1 mol/L Na 2 CO 3 solution was added dropwise to a mixed solution of cobalt nitrate and cerium nitrate in a stirred state, and the pH of the solution was monitored using a pH meter. When the pH stabilized at 9, the dropping was stopped.
  • the obtained precipitate was aged for 10 hours, washed with deionized water and suction filtered 5 times, and the precipitate was dried in an oven at 100 °C.
  • the powder solid sample was placed in a corundum crucible having a volume of 100 mL, and then the loaded crucible was placed in a muffle furnace, and heated to 600 ° C at a rate of 10 ° C/min for 4 h. After cooling, it was taken out and ground on a mortar, and then 2.55 g of AgNO 3 was weighed, mixed with the calcined sample, and then deionized water was added to a water bath at 80 ° C and evaporated to dryness.
  • the evaporated powder was calcined at 600 ° C for 2 h to obtain 0.3 Ag / Co 0.7 La 0.3 O y .
  • the prepared catalyst tablets are sieved to 60 mesh to 80 mesh.
  • Fig. 3(a) is an X-ray diffraction (XRD) pattern of a sample 0.3Ag/Co 0.7 La 0.3 O y (1.33 ⁇ y ⁇ 2) synthesized in the present example, and the composition thereof contains Co 3 O 4 , LaCoO 3 and elemental Ag, a small amount of La 2 O 3 is stored.
  • the main phase of the present invention containing rare earth La is Co 3 O 4 , LaCoO 3 and elemental Ag, and a trace amount of La 2 O 3 is present .
  • the embodiment relates to a catalyst capable of low-temperature catalytic removal of various environmental pollutants and a preparation method thereof, and the preparation method comprises the following steps:
  • the powder solid sample was placed in a corundum crucible having a volume of 400 mL, and then the loaded crucible was placed in a muffle furnace, and the temperature was raised to 900 ° C at a rate of 10 ° C/min for 4 h. After cooling, it was taken out and placed in an agate mortar for grinding.
  • the sampled porcelain crucible was placed in a muffle furnace and heated to 900 ° C at a rate of 10 ° C/min for 4 h. After cooling, the mill was taken out to obtain a target of 0.1 Ag/Co 0.6 Ce 0.4 O y .
  • Fig. 1(c) is an X-ray diffraction (XRD) pattern of a sample 0.1Ag/Co 0.6 Ce 0.4 O y (1.5 ⁇ y ⁇ 1.8) synthesized in the present example, and the composition thereof contains Co 3 O 4 , CeO 2 and elemental Ag. It is also known from Examples 2 and 3 and this example that the main phase of the present invention containing rare earth Ce is Co 3 O 4 , CeO 2 and elemental Ag.
  • XRD X-ray diffraction
  • the particulate matter emitted by motor vehicle exhaust, carbon monoxide and nitrogen oxides are the main causes of the deterioration of the atmospheric environment, and the state has strengthened the system construction and formulated Strict vehicle emission standards.
  • motor vehicles need to be equipped with qualified aftertreatment devices.
  • the core of the aftertreatment device lies in the catalyst technology.
  • the catalyst technology developed by the invention can remove carbon monoxide at normal temperature, remove soot at a low temperature, and realize selective catalytic reduction of ammonia at a suitable medium temperature temperature window, which will bring greater social and economic benefits.
  • the present invention prepares a multifunctional catalyst by combining Ag with a transition metal oxide and a rare earth oxide; the preparation process of the invention is simple and economical, and is a catalyst technology with potential for large-scale application in the future. .

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Abstract

低温催化去除环境污染物的催化剂及其制备方法，所述催化剂是由Ag、Co、M、O四种元素构成的化学式为zAg/Co 1-xM xO y的化合物，其中M＝La、Ce、Pr中的一种，0.02≤x≤0.5，1.33≤y≤2，0.05≤z≤0.3，M:Co的原子比为x:(1-x)，Ag:(Co+M)的原子比为z:1；制得的催化剂能低温催化去除一氧化碳，颗粒物等常见环境污染物，通过调变x与z的值改善柴油机排放污染控制中氨选择性催化还原氮氧化物的温度窗口。

Description

[根据细则37.2由ISA制定的发明名称]　低温催化去除环境污染物的催化剂及其制备方法 技术领域
本发明属于环境催化技术领域，具体涉及一种低温催化去除环境污染物的催化剂及其制备方法。
背景技术
环境催化是一种利用催化剂将环境中有害物质转化为环境友好产物的技术。随着现代工业的发展以及汽柴油车保有量的增加，大气环境不断恶化，一氧化碳，氮氧化物，颗粒物(碳烟)的污染形势日趋严峻。这些物质不但对大气环境造成了破坏，更严重危害人类的健康。催化技术也因此被广泛应用于大气环境治理领域。
目前用于一氧化碳治理的技术主要为催化氧化，然而其应用的催化剂普遍包括Pt等贵金属，降低了排放系统经济性。治理氮氧化物的技术主要有碳氢选择性催化还原(HC-SCR)及氨选择性催化还原(NH3-SCR)，目前我国主要在采用NH3-SCR技术路线，其主要催化剂存在着强毒性，温度窗口狭窄等问题。颗粒物去除技术主要包括氧化型催化剂(DOC)和柴油机颗粒过滤器(DPF)，但前者只能去除颗粒表面的挥发性有机物，对碳烟的捕集效果不佳；后者对碳烟捕集效率较高，但需要可靠经济的再生技术。主要的DPF再生技术包括：电加热再生、逆向喷气再生、进排气节流再生、喷油助燃再生、电自加热再生、微波加热再生、燃油添加剂辅助再生、连续催化再生等，不过以上加热再生技术存在着过滤体容易损坏、可靠性差、系统复杂等缺陷，而喷气再生技术则存在低温起燃性能差、安装复杂等问题；连续再生是一种很有潜力的再生方式，其能耗低，系统简单易维护。连续再生技术应用的关键是找到一种低温催化氧化性能优异的催化剂。
经对现有技术的文献检索发现，公开号为104508269A的中国发明专利申请，名称为：高性能SCR催化剂系统，具有清除SOF成份的催化剂活性物质的清除SOF催化剂模块附着在柴油发动机后端，并连续在下游安装具有SCR催化剂活性物质的SCR催化剂模块，从而有效清除氮氧化合物。但整体而言，其系统分为两个模块，较为复杂，经济性不佳。
经对现有技术的文献检索发现，公开号为103285854A的中国发明专利申请，名称为：柴油机尾气颗粒物催化剂、及其制备方法和使用方法；该催化剂包括：载体，负载于催化剂载体上的催化剂助剂和催化剂活性成分。催化剂载体为具有较高机械强度的粗孔微球硅胶，催化剂助剂为金属氧化物，活性组分为金属钌。其主要问题在于催化剂的经济性较差，钌存在着高温流失的属性，催化性能不稳定等诸多缺陷。
经对现有技术的文献检索发现，申请号为201410328641.X，公开号为104162424A的中国发明专利申请，名称为：氧化铈负载钯催化剂的制备方法及在CO催化氧化中的应用，该专利公开了一种低温条件下完成氧化铈负载钯的工艺。但此工艺程序复杂，成本较高，在实际应用中会有较大的局限性。
发明内容
本发明目的在于克服上述现有技术存在的不足，提出了一种低成本，制备工艺相对简化的能低温催化去除多种环境污染物的催化剂及其制备方法。本发明应用于低温催化去除一氧化碳、低温催化去除柴油车尾气排放的颗粒物及氨选择性催化还原氮氧化物领域。
本发明的目的是通过以下技术方案实现的：
第一方面，本发明涉及一种催化剂，所述催化剂的化学式为zAg/Co1-xMxOy，其中M为La、Ce或Pr，0.02≤x≤0.5，1.33≤y≤2,0.05≤z≤0.3；M:Co的原子比为x:1-x，Ag:(Co+M)的原子比为z:1。当x>0.5时，稀土氧化物成为了材料的主相，不利于催化作用；z<0.05时，不利于催化物种的活化，当z>0.3时，不利于单质Ag与其他氧化物的相互催化作用。
优选的，所述催化剂包括复合氧化物及其表面负载的Ag，所述复合氧化物由Co3O4和稀土材料组成，所述稀土材料为稀土氧化物或稀土钙钛矿型复合氧化物；其中，稀土材料中的稀土元素为M，M选自La、Ce或Pr，Ag呈单质状态。
优选的，所述稀土氧化物的化学式为MO2或M2O3，所述稀土钙钛矿型复合氧化物的化学式为MCoO3。
第二方面，本发明还涉及催化剂的制备方法，所述催化剂以硝酸银作为银源，以钴盐作为钴源，M的硝酸盐作为稀土前驱体，通过柠檬酸络合法或共沉淀法制备而得。
优选的，所述柠檬酸络合法是以硝酸银作为银源，以钴盐作为钴源，M的硝酸盐作为稀土前驱体，焙烧温度为500℃～900℃。
优选的，所述柠檬酸络合法包括：将六水合硝酸钴或四水合乙酸钴、M的硝酸盐、 硝酸银与柠檬酸按(1-x):x:z:5(其中x为M的化学计量数，0.02≤x≤0.5,z为Ag的化学计量数，0.05≤z≤0.3)比例量取，配制成溶液，70～90℃下搅拌蒸干，再经500℃～900℃高温焙烧4～8小时，合成所述催化剂。当焙烧温度低于500℃时，柠檬酸结碳无法有效去除。
优选的，所述共沉淀法是以硝酸银作为银源，以钴盐作为钴源，M的硝酸盐作为稀土前驱体，沉淀剂为Na2CO3，老化时pH值稳定在8～10，焙烧温度为500℃～800℃。
优选的，所述共沉淀法包括：
S1、将硝酸钴或乙酸钴与M的硝酸盐与适量的去离子水混合配制成溶液，滴加入1～2mol/L的Na2CO3至pH＝8～10，老化9～12小时后，将沉淀抽滤烘干，在500℃～800℃高温焙烧4～6h，研磨成粉末；
S2、将所述粉末与硝酸银混合后加入去离子水，在70～90℃水浴搅拌蒸干，再在500℃～800℃高温焙烧2～4h，即得所述催化剂。
第三方面，本发明还涉及所述催化剂在低温催化氧化去除一氧化碳中的用途。
第四方面，本发明还涉及所述催化剂在低温催化氧化去除柴油机尾气颗粒物中的用途。
第五方面，本发明还涉及所述催化剂在氨选择性催化还原氮氧化物中的用途。
本发明在银-钴体系中添加稀土元素，可形成稀土氧化物或者稀土与钴形成的钙钛矿型复合氧化物，这些氧化物与单质银的相互作用有利于进一步提升催化剂的氧化性。
与现有技术相比，本发明具有如下有益效果：
1、本发明制备的催化剂在碳烟催化氧化，一氧化碳催化去除及氮氧化物低温选择性催化还原的催化性能明显优于Ag/Co3O4及其他各种过渡金属氧化物上负载Ag的材料。
2、本发明制备工艺经济简便，所用原料价格低廉，有益于市场的推广与应用。
3、本发明的低温氧化性能与贵金属催化剂的催化性能接近，能以更经济的方式，催化氧化碳烟及一氧化碳。
4、本发明相比Ag/Co3O4能拓宽氮氧化物选择性催化还原反应的温度窗口，提升催化剂的稳定性。
附图说明
通过阅读参照以下附图对非限制性实施例所作的详细描述，本发明的其它特征、目的和优点将会变得更明显：
图1为zAg/Co1-xCexOy的X射线衍射(XRD)图谱，其中，(a)x＝0.02,z＝0.05；(b)x＝0.2,z＝0.2；(c)x＝0.4,z＝0.1；
图2为zAg/Co1-xPrxOy的X射线衍射(XRD)图谱，其中(a)x＝0.1,z＝0.1；(b)x＝0.5,z＝0.3；
图3为zAg/Co1-xLaxOy的X射线衍射(XRD)图谱，其中，(a)x＝0.3,z＝0.3；(b)x＝0.05,z＝0.2。
具体实施方式
下面结合实施例对本发明进行详细说明。以下实施例将有助于本领域的技术人员进一步理解本发明，但不以任何形式限制本发明。应当指出的是，对本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干调整和改进。这些都属于本发明的保护范围。
实施例1
本实施例涉及一种能低温催化去除多种环境污染物的催化剂及其制备方法；其制备方法包括如下步骤：
1.用Co(NO3)3·6H2O作为钴源，取2.91g，用Pr(NO3)36H2O作为镨源，取3.39g，用硝酸银作为银源，取1.02g，称取一水合柠檬酸20g，放入烧杯，加入去离子水150mL搅拌分散，形成溶液。
2.将上面得到溶液80℃搅拌蒸干，并置于烘箱中干燥12h。
3.将粉末固体样放入体积为200mL的刚玉坩埚中，然后将装样的坩埚置于马弗炉中，以10℃/min的速度升温至500℃，保温4h。冷却后取出置于玛瑙研钵中研磨，再将装样的瓷坩埚置于马弗炉中以10℃/min的速度升温至500℃，保温4h。冷却后取出磨碎，获得目标物0.3Ag/Co0.5Pr0.5Oy。
4.称取0.38g0.3Ag/Co0.5Pr0.5Oy粉末与0.02g柴油车排气管取样的颗粒物混合后研磨20分钟，使其达到充分接触的状态。
5.称取上述混合物0.33g，置于材质为石英管固定床反应器中，用石英棉固定步骤4制备的混合物，反应气氛为1000ppmNO+5％O2，反应气流量为35ml/min以4℃/min的升温速率对混合的粉末加热，反应后产生的气体，用带有热导检测仪的气相色谱仪作定量分析。实验发现，颗粒物质量消耗10％所对应的温度为200℃，在268℃可以完全去除颗粒物。称取催化剂0.3Ag/Co3O4重复步骤4、5进行本实施例的对比实验，实验发现，其颗粒物质量消耗10％所对应的温度为218℃，298℃可以完全去除颗粒物。
图2(b)为本实施例合成的样品0.3Ag/Co0.5Pr0.5Oy(1.33<y<1.7)的X射线衍射(XRD)图谱，由图可知，其组分包含PrCoO3及单质Ag。
实施例2
本实施例涉及一种能低温催化去除多种环境污染物的催化剂及其制备方法；其制备方法包括如下步骤：
1.用C4H6CoO4·4H2O作为钴源，取2.431g，Ce(NO3)36H2O作为铈源，取0.0868g用用硝酸银作为银源，取0.17g，称取一水合柠檬酸20g，放入200ml烧杯，加入去离子水100mL溶解上述粉末。
2.将上面得到溶液80℃搅拌蒸干，并置于烘箱中干燥12h。
3.将粉末固体样放入体积为200mL的刚玉坩埚中，然后将装样的坩埚置于马弗炉中，以10℃/min的速度升温至900℃，保温4h。冷却后取出置于玛瑙研钵中研磨，再将装样的瓷坩埚置于马弗炉中以10℃/min的速度升温至900℃，保温4h。冷却后取出磨碎，获得目标物0.05Ag/Co3O4
4.将制得的催化剂压片筛分至60目至80目。
5.称取压片后的样品0.1g，置于材质为石英管固定床反应器中，反应气氛为1500ppmCO+8％O2，反应气流量为50ml/min以2℃/min的升温速率对混合的粉末加热，反应后产生的气体，用带有热导检测仪的气相色谱仪作定量分析。实验发现，此催化剂在45℃将一氧化碳氧化为二氧化碳。取催化剂0.05Ag/Co3O4重复步骤4、5进行本实施例的对比实验，实验发现，此催化剂在70℃能将一氧化碳完全转化。
图1(a)为本实施例合成的样品0.05Ag/Co0.98Ce0.02Oy(1.33<y<1.5)的X射线衍射(XRD)图谱，由图可知，其组分包含微量的CeO2，Co3O4及单质Ag。
实施例3
本实施例涉及一种能低温催化去除多种环境污染物的催化剂及其制备方法；其制备方法包括如下步骤：
1.用Co(NO3)3·6H2O作为钴源，取5.82g，用Ce(NO3)36H2O作为铈源，取10.861g，置于烧杯中，加入去离子水150ml，将上述粉末溶解。另配制1mol/L的Na2CO3溶液250ml待用。
2.将1mol/L的Na2CO3溶液，逐滴加入处于搅拌状态的硝酸钴与硝酸亚铈的混合溶液中，并利用pH计监控溶液的pH值。当pH值稳定在8时，停止滴加。
3.将所得到的沉淀陈化10小时后，用去离子水洗涤并抽滤5次，将沉淀置于100℃ 烘箱中烘干。
4.将粉末固体样放入体积为50mL的刚玉坩埚中，然后将装样的坩埚置于马弗炉中，以10℃/min的速度升温至500℃，保温4h。冷却后取出研磨，再称取AgNO30.85g，与焙烧后的样品混合后加入去离子水80℃水浴搅拌蒸干。
5.将蒸干后的粉末500℃焙烧2h，制得0.2Ag/Co0.8Ce0.2Oy。
6.将制得的催化剂压片筛分至60目至80目。
7.称取0.3g压片后催化剂，置于红外气体池中，气氛800ppmNO+800ppmNH3+5％O2,以升温速率3℃/min加热催化剂，到达待测实验温度后，稳定半小时，利用红外原理采集并处理信号。实验发现，此催化剂的温度窗口260℃～400℃。取催化剂0.2Ag/Co3O4重复步骤6、7进行本实施例的对比实验，实验发现，此催化剂的温度窗口为280℃～350℃。
图1(b)为本实施例合成的样品0.2Ag/Co0.8Ce0.2Oy(1.33≤y<1.6)的X射线衍射(XRD)图谱，由图可知，其组分包含Co3O4，CeO2及单质Ag。
实施例4
本实施例涉及一种能低温催化去除多种环境污染物的催化剂及其制备方法；其制备方法包括如下步骤：
1.用C4H6CoO4·4H2O作为钴源，取4.712g，用La(NO3)36H2O作为镧源，取0.37g，用硝酸银作为银源，取0.68g，称取一水合柠檬酸20g，放入烧杯，加入去离子水150mL搅拌分散，形成溶液。
2.将上面得到溶液80℃搅拌蒸干，并置于烘箱中干燥12h。
3.将粉末固体样放入体积为200mL的刚玉坩埚中，然后将装样的坩埚置于马弗炉中，以10℃/min的速度升温至700℃，保温4h。冷却后取出置于玛瑙研钵中研磨，再将装样的瓷坩埚置于马弗炉中以10℃/min的速度升温至700℃，保温4h。冷却后取出磨碎，获得目标物0.2Ag/Co0.95La0.05Oy。
4.称取0.38g0.2Ag/Co0.95La0.05Oy粉末与0.02g柴油车排气管取样的颗粒物混合后研磨20分钟，使其达到充分接触的状态。
5.称取上述混合物0.33g，置于材质为石英管固定床反应器中，用石英棉固定步骤4制备的混合物，反应气氛为2000ppmNO+5％O2，反应气流量为35ml/min以4℃/min的升温速率对混合的粉末加热，反应后产生的气体，用带有热导检测仪的气相色谱仪作定量分析。实验发现，颗粒物质量消耗10％所对应的温度为206℃，在278℃完全去除 颗粒物。称取催化剂0.2Ag/Co3O4重复步骤4、5进行本实施例的对比实验，实验发现，其颗粒物质量消耗10％所对应的温度为228℃,305℃可以完全去除颗粒物。
图3(b)为本实施例合成的样品0.2Ag/Co0.95La0.05Oy(1.35<y≤2)的X射线衍射(XRD)图谱，由图可知，其组分包含Co3O4，LaCoO3及单质Ag。
实施例5
本实施例涉及一种能低温催化去除多种环境污染物的催化剂及其制备方法；其制备方法包括如下步骤：
1.用Co(NO3)3·6H2O作为钴源，取5.238g，用Pr(NO3)36H2O作为镨源，，取0.678g，置于烧杯中，加入去离子水100ml，将上述粉末溶解。另配制1mol/L的Na2CO3溶液75ml待用。
2.将1mol/L的Na2CO3溶液，逐滴加入处于搅拌状态的硝酸钴与硝酸亚铈的混合溶液中，并利用pH计监控溶液的pH值。当pH值稳定在10时，停止滴加。
3.将所得到的沉淀陈化10小时后，用去离子水洗涤并抽滤5次，将沉淀置于100℃烘箱中烘干。
4.将粉末固体样放入体积为50mL的刚玉坩埚中，然后将装样的坩埚置于马弗炉中，以10℃/min的速度升温至500℃，保温4h。冷却后取出研磨，再称取AgNO30.34g，与焙烧后的样品混合后加入去离子水80℃水浴搅拌蒸干。
5.将蒸干后的粉末500℃焙烧2h，制得0.1Ag/Co0.9Pr0.1Oy。
6.将制得的催化剂压片筛分至60目至80目。
7.称取0.2g压片后催化剂，置于红外气体池中，气氛500ppmNO+500ppmNH3+5％O2,以升温速率3℃/min加热催化剂，到达待测实验温度后，稳定半小时，利用红外原理采集并处理信号。实验发现，此催化剂的温度窗口250℃～450℃。取催化剂0.1Ag/Co3O4重复步骤6、7进行本实施例的对比实验，实验发现，此催化剂的温度窗口为290℃～360℃。
图2(a)为本实施例合成的样品0.1Ag/Co0.9Pr0.1Oy(1.33<y<1.9)的X射线衍射(XRD)图谱，由图可知，其组分包含Co3O4、PrCoO3及单质Ag。由实施例1和本实施例还可知，含有稀土Pr的本发明主相为Co3O4，PrCoO3及单质Ag。
实施例6
本实施例涉及一种能低温催化去除多种环境污染物的催化剂及其制备方法；其制备方法包括如下步骤：
1.用Co(NO3)3·6H2O作为钴源，取10.185g，用La(NO3)36H2O作为铈源，，取5.55g，置于烧杯中，加入去离子水200ml，将上述粉末溶解。另配制1mol/L的Na2CO3溶液150ml待用。
2.将1mol/L的Na2CO3溶液，逐滴加入处于搅拌状态的硝酸钴与硝酸亚铈的混合溶液中，并利用pH计监控溶液的pH值。当pH值稳定在9时，停止滴加。
3.将所得到的沉淀陈化10小时后，用去离子水洗涤并抽滤5次，将沉淀置于100℃烘箱中烘干。
4.将粉末固体样放入体积为100mL的刚玉坩埚中，然后将装样的坩埚置于马弗炉中，以10℃/min的速度升温至600℃，保温4h。冷却后取出置于研钵玛瑙研磨，再称取AgNO32.55g，与焙烧后的样品混合后加入去离子水80℃水浴搅拌蒸干。
5.将蒸干后的粉末600℃焙烧2h，制得0.3Ag/Co0.7La0.3Oy。
6.将制得的催化剂压片筛分至60目至80目。
7.称取压片后的样品0.1g，置于材质为石英管固定床反应器中，反应气氛为1000ppmCO+8％O2，反应气流量为60ml/min以2℃/min的升温速率对混合的粉末加热，反应后产生的气体，用带有热导检测仪的气相色谱仪作定量分析。实验表明，此催化剂在30℃将一氧化碳氧化为二氧化碳。取催化剂0.3Ag/Co3O4重复步骤4、5进行本实施例的对比实验，实验发现，此催化剂在55℃能将一氧化碳完全转化。
图3(a)为本实施例合成的样品0.3Ag/Co0.7La0.3Oy(1.33<y<2)的X射线衍射(XRD)图谱，由图可知，其组分包含Co3O4，LaCoO3及单质Ag，另存微量La2O3。由实施例4和本实施例可知，含有稀土La的本发明主相为Co3O4，LaCoO3及单质Ag，另存微量La2O3。
实施例7
本实施例涉及一种能低温催化去除多种环境污染物的催化剂及其制备方法；其制备方法包括如下步骤：
1.用C4H6CoO4·4H2O作为钴源，取7.47g，用Ce(NO3)36H2O作为铈源，取17.36g，用硝酸银作为银源，取0.85g，称取一水合柠檬酸100g，放入烧杯，加入去离子水500mL搅拌分散，形成溶液。
2.将上面得到溶液80℃搅拌蒸干，并置于烘箱中干燥12h。
3.将粉末固体样放入体积为400mL的刚玉坩埚中，然后将装样的坩埚置于马弗炉中，以10℃/min的速度升温至900℃，保温4h。冷却后取出置于玛瑙研钵研磨，再将 装样的瓷坩埚置于马弗炉中以10℃/min的速度升温至900℃，保温4h。冷却后取出磨碎，获得目标物0.1Ag/Co0.6Ce0.4Oy。
4.称取0.38g0.1Ag/Co0.6Ce0.4Oy粉末与0.02g柴油车排气管取样的颗粒物混合后研磨20分钟，使其达到充分接触的状态。
5.称取上述混合物0.33g，置于材质为石英管固定床反应器中，用石英棉固定步骤4制备的混合物，反应气氛为2000ppmNO+5％O2，反应气流量为50ml/min以2℃/min的升温速率对混合的粉末加热，反应后产生的气体，用带有热导检测仪的气相色谱仪作定量分析。实验发现，颗粒物质量消耗10％所对应的温度为214℃，在282℃完全去除颗粒物。称取催化剂0.1Ag/Co3O4重复步骤4、5进行本实施例的对比实验，实验发现，其颗粒物质量消耗10％所对应的温度为238℃,在312℃可以完全去除颗粒物。
图1(c)为本实施例合成的样品0.1Ag/Co0.6Ce0.4Oy(1.5<y<1.8)的X射线衍射(XRD)图谱，由图可知，其组分包含Co3O4，CeO2及单质Ag。由实施例2、3和本实施例还可知，含有稀土Ce的本发明主相为Co3O4，CeO2及单质Ag。
伴随着工业化的深入，大气环境日趋恶化，各种污染物超标排放屡见不鲜，机动车尾气排放的颗粒物，一氧化碳及氮氧化物是大气环境变差的主要原因，国家也因此强化了制度建设，制订了严苛机动车排放标准。为了满足排放法规的要求，机动车需要加装合格的后处理装置。后处理装置的核心在于催化剂技术，本发明开发的催化剂技术能在常温去除一氧化碳，低温去除碳烟，合适的中温温度窗口实现氨选择性催化还原，将带来较大的社会效益和经济效益。
综上所述，本发明通过将Ag与过渡金属氧化物和稀土氧化物结合，制备了多功能的催化剂；本发明的制备工艺简便，经济性较佳，是未来有潜力大规模应用的催化剂技术。
以上对本发明的具体实施例进行了描述。需要理解的是，本发明并不局限于上述特定实施方式，本领域技术人员可以在权利要求的范围内做出各种变形或修改，这并不影响本发明的实质内容。

Claims (10)

  1. 一种催化剂，其特征在于，所述催化剂的化学式为zAg/Co1-xMxOy，其中M为La、Ce或Pr，0.02≤x≤0.5，1.33≤y≤2,0.05≤z≤0.3；M:Co的原子比为x:(1-x)，Ag:(Co+M)的原子比为z:1。
  2. 根据权利要求1所述的催化剂，其特征在于，所述催化剂包括复合氧化物及其表面负载的Ag，所述复合氧化物由Co3O4和/或稀土材料组成，所述稀土材料为稀土氧化物或稀土钙钛矿型复合氧化物；其中，稀土材料中的稀土元素M为La、Ce或Pr，Ag呈单质状态。
  3. 根据权利要求2所述的催化剂，其特征在于，所述稀土氧化物的化学式为MO2或M2O3，所述稀土钙钛矿型复合氧化物的化学式为MCoO3。
  4. 一种根据权利要求1～3中任一项所述的催化剂的制备方法，其特征在于，所述催化剂通过柠檬酸络合法或共沉淀法制备得到。
  5. 根据权利要求4所述的催化剂的制备方法，其特征在于，所述柠檬酸络合法是以硝酸银作为银源，以钴盐作为钴源，M的硝酸盐作为稀土前驱体，焙烧温度为500℃～900℃。
  6. 根据权利要求5所述的催化剂的制备方法，其特征在于，所述柠檬酸络合法包括：将六水合硝酸钴或四水合乙酸钴、M的硝酸盐、硝酸银与柠檬酸按(1-x)：x:z：5比例量取，配制成溶液，70～90℃下搅拌蒸干，再经500℃～900℃高温焙烧4～8小时，合成所述催化剂。
  7. 根据权利要求4所述的催化剂的制备方法，其特征在于，所述共沉淀法是以硝酸银作为银源，以钴盐作为钴源，M的硝酸盐作为稀土前驱体，沉淀剂为Na2CO3，老化时pH值稳定在8～10，焙烧温度为500℃～800℃。
  8. 根据权利要求7所述的催化剂的制备方法，其特征在于，所述共沉淀法包括：
    S1、将硝酸钴或乙酸钴与M的硝酸盐配制成溶液，滴加入Na2CO3至pH＝8～10，老化9～12小时后，将沉淀抽滤并烘干，在500℃～800℃高温焙烧4～6h，研磨成粉末；
    S2、将所述粉末与硝酸银混合后加入去离子水，在70～90℃水浴搅拌蒸干，再在500℃～800℃高温焙烧2～4h，即得所述催化剂。
  9. 一种根据权利要求1～3中任一项所述的催化剂在低温催化氧化去除一氧化碳或低温催化氧化去除柴油机尾气颗粒物中的用途。
  10. 一种根据权利要求1～3中任一项所述的催化剂在氨选择性催化还原氮氧化物中的用途。
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