CN115350708B

CN115350708B - Composite catalyst, preparation method and application thereof

Info

Publication number: CN115350708B
Application number: CN202211133045.7A
Authority: CN
Inventors: 司文哲; 张晗; 刘威; 丁云; 贾福强; 姚欢; 陆冠旗; 程传; 彭悦; 李俊华
Original assignee: Jiangsu Yangjing Environmental Protection Service Co ltd; Tsinghua University
Current assignee: Jiangsu Yangjing Environmental Protection Service Co ltd; Tsinghua University
Priority date: 2022-09-16
Filing date: 2022-09-16
Publication date: 2024-04-23
Anticipated expiration: 2042-09-16
Also published as: CN115350708A

Abstract

The invention provides a composite catalyst, a preparation method and application thereof. The composite catalyst contains copper atoms and cerium atoms, wherein, when analyzed using a powder X-ray diffraction method using cukα radiation experimental conditions, the X-ray diffraction pattern of the composite catalyst has characteristic peaks at positions of 28.64±0.2, 35.54 ±0.2, 38.7±0.2 in 2θ (°). The composite catalyst of the invention has simple structure, does not contain redundant impurities or other oxides, and can be used for catalytic oxidation of Volatile Organic Compounds (VOCs). The preparation method of the composite catalyst is simple and feasible, raw materials are easy to obtain, and the composite catalyst is suitable for mass production.

Description

Composite catalyst, preparation method and application thereof

Technical Field

The invention relates to a composite catalyst, a preparation method and application thereof, and belongs to the field of catalysts.

Background

With the acceleration of industrialization progress and the sustainable development of economy, organic pollutants in the ambient air, which are closely related to human production and life, have long plagued us, particularly Volatile Organic Compounds (VOCs); wherein, the nitrogen-containing organic waste gas is one of pollutants polluted by the atmosphere and is also a type which is difficult to treat in the organic waste gas. Taking the production of Acrylonitrile (AN) as AN example, the emission limit specified by acrylonitrile is generally "0.5mg/m ³", and the treatment requirements are very high.

At present, the nitrogen-containing organic waste gas treatment modes are two, namely a recovery method and a combustion method. The recovery method mainly comprises a pressure swing adsorption method, an absorption method, a condensation method, an active carbon adsorption method and the like. However, in the actual exhaust gas treatment, it is necessary to select the most suitable method in combination with the physical properties, chemical properties, exhaust gas concentration, exhaust gas emission amount, and the like of the exhaust gas. The secondary combustion method generally comprises a direct combustion method and a catalytic oxidation method, wherein the combustion method works on the principle that the acrylonitrile waste gas is converted into carbon dioxide, water, nitrogen and the like at a certain temperature by utilizing chemical reaction.

The core technology of catalytic combustion is the development of efficient and stable catalysts. Oxides loaded with noble metals are currently commonly used in industry as catalysts. Although the catalyst has the advantages of high activity, mature production process and the like, for nitrogenous VOCs, the catalyst is often deeply oxidized into nitrogen oxides (NOx) to cause secondary pollution. The design and development of high efficiency catalysts, particularly transition metal based catalysts, is therefore critical to this control technology.

Citation 1 discloses a core-shell structure nano copper cerium composite oxide catalyst, a preparation method and application thereof. The core-shell structure nano copper cerium composite oxide catalyst takes nano cubic CuO particles as cores, and a composite material with a CuO@Ce ₂ core-shell structure, the outer walls of which are wrapped by CeO ₂ with a mesoporous structure, has a complete core-shell structure; the particle size of the core-shell structure nano copper cerium composite oxide catalyst is between 150 and 300 nm; the thickness of the outer wall of the mesoporous structure CeO ₂ is 20nm. However, the preparation method of the core-shell structure nano copper cerium composite oxide catalyst is complex, has long and numerous steps, and is not beneficial to mass production.

Reference 2 discloses a CuO/CeO ₂ nanorod catalyst and synthesis and application thereof. The CuO/CeO ₂ nano rod catalyst is a supported catalyst, the carrier is nano cerium oxide obtained by heat treatment of CeO ₂ nano rod at 25-600 ℃, the carrier nano cerium oxide is named CeO ₂ -T, wherein T is the heat treatment temperature; cuO is loaded on a CeO ₂ -T carrier, and the mass ratio of the CuO to the CeO ₂ -T carrier is (3.0-10.0)/100. However, the method adopts a loading mode, the preparation process is complex, the method is mainly used for CO selective oxidation reaction in hydrogen-rich gas, and whether the method can be used for Volatile Organic Compounds (VOCs) is unknown.

Citation literature:

Citation 1: CN 109926060A

Citation 2: CN 114713238A

Disclosure of Invention

Problems to be solved by the invention

In view of the technical problems in the prior art, the invention firstly provides a composite catalyst which has a simple structure, does not contain excessive impurities or other oxides, and can be used for catalytic oxidation of Volatile Organic Compounds (VOCs).

Furthermore, the invention also provides a preparation method of the composite catalyst, which is simple and easy to implement, raw materials are easy to obtain, and the preparation method is suitable for mass production.

Solution for solving the problem

[1] A composite catalyst comprising copper atoms and cerium atoms, wherein,

When analyzed using powder X-ray diffraction method using cukα radiation experimental conditions, the X-ray diffraction pattern of the composite catalyst has characteristic peaks at positions of 28.64±0.2, 35.54 ±0.2, 38.7±0.2 in 2θ (°).

[2] The composite catalyst according to the above [1], wherein when analyzed using a powder X-ray diffraction method using CuK alpha radiation experimental conditions, the X-ray diffraction pattern of the composite catalyst further has characteristic peaks at least one position of 33.34.+ -. 0.2, 47.44.+ -. 0.2, 56.32.+ -. 0.2 in terms of 2-theta (°).

[3] The composite catalyst according to the above [1] or [2], wherein the molar ratio of the cerium atoms to the copper atoms is 1:0.2 to 4; and/or

[4] The composite catalyst according to the above [1] to [3], wherein the composite catalyst has an average particle diameter of 10nm to 100. Mu.m.

[5] A process for producing a composite catalyst according to any one of the above [1] to [4], which comprises the steps of:

Copper salt, cerium salt, complexing agent and nonionic surfactant are dissolved in a solvent to obtain a precursor solution;

Forming the precursor solution into a sol system;

Drying the sol system to obtain a dried product;

And carrying out heat treatment on the dried product to obtain the composite catalyst.

[6] The production method according to the above [5], wherein the nonionic surfactant comprises a polyether nonionic surfactant, preferably a block polyether nonionic surfactant.

[7] The production process according to the above [6] or [7], wherein a ratio of the complexing agent to a sum of molar amounts of the copper salt and the cerium salt is 1:1 to 1.5:1; and/or the molar ratio of the cerium salt to the copper salt is 1:0.2-4.

[8] The production method according to the above [7], wherein the drying comprises a step of washing after primary drying and then secondary drying;

preferably, the temperature of the primary drying is 100-120 ℃, and the time of the primary drying is 2-4 hours; the temperature of the secondary drying is 60-80 ℃, and the time of the secondary drying is 6-8h.

[9] The production method according to the above [5] to [8], wherein the heat treatment comprises primary calcination and secondary calcination;

preferably, the temperature of the primary calcination is 150-200 ℃, the time of the primary calcination is 4-6 hours, and the temperature rising rate of the primary calcination is 1-2 ℃/min;

The temperature of the secondary calcination is 350-400 ℃, the secondary calcination time is 1-2 h, and the temperature rising rate of the secondary calcination is 1-2 ℃/min.

[10] The use of the composite catalyst according to any one of [1] to [4] above for catalytic oxidation of volatile organic compounds, preferably for catalytic oxidation of nitrogen-containing volatile organic compounds.

ADVANTAGEOUS EFFECTS OF INVENTION

The composite catalyst of the invention has simple structure, does not contain redundant impurities or other oxides, and can be used for catalytic oxidation of Volatile Organic Compounds (VOCs).

The preparation method of the composite catalyst is simple and feasible, raw materials are easy to obtain, and the composite catalyst is suitable for mass production.

Drawings

FIG. 1 shows XRD patterns of the composite catalysts of examples 1 to 4 of the present invention;

FIG. 2 shows a reaction diagram of a composite catalyst for the catalytic oxidation of acrylonitrile;

FIG. 3 shows a scanning electron microscope image of a composite catalyst of example 1 of the present invention;

Fig. 4 shows a scanning electron microscope image of the composite catalyst of example 2 of the present invention.

Detailed Description

The following describes the present invention in detail. The following description of the technical features is based on the representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

in the present specification, the numerical range indicated by the term "numerical value a to numerical value B" means a range including the end point numerical value A, B.

In the present specification, unless specifically stated otherwise, "a plurality" of "a plurality of" etc. means a numerical value of 2 or more.

In this specification, the terms "substantially", "substantially" or "substantially" mean that the error is less than 5%, or less than 3% or less than 1% compared to the relevant perfect or theoretical standard.

In the present specification, "%" means mass% unless otherwise specified.

In the present specification, the meaning of "can" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

In this specification, "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

Reference throughout this specification to "some specific/preferred embodiments," "other specific/preferred embodiments," "an embodiment," and so forth, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the elements may be combined in any suitable manner in the various embodiments.

< First aspect >

In a first aspect the present invention provides a composite catalyst comprising copper atoms and cerium atoms, wherein,

Specifically, in the present invention, when analyzed using a powder X-ray diffraction method using cukα radiation experimental conditions, the X-ray diffraction pattern of the composite catalyst further has characteristic peaks at least one position of 33.34±0.2, 47.44 ±0.2, 56.32±0.2 in 2θ (°).

The composite catalyst of the invention has characteristic peaks of cerium oxide and diffraction peaks superimposed by monoclinic CuO. The diffraction peak corresponding to the oxide crystal form is gradually presented with the increase of the corresponding metal content and positively correlated with the content. The composite catalyst of the invention has better crystal form and can be used for catalyzing and oxidizing the nitrogen-containing volatile organic compound.

In some specific embodiments, the molar ratio of cerium atoms to copper atoms of the present invention is from 1:0.2 to 4, for example: 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, etc. When the molar ratio of cerium atoms to copper atoms is 1:0.2-4, the preparation method is favorable for obtaining the composite catalyst with the required crystal form and is favorable for catalytic oxidation of the nitrogen-containing volatile organic compounds.

Further, in the present invention, the composite catalyst has an average particle diameter of 10nm to 100 μm, for example: 100nm, 500nm, 1 μm, 10 μm, 50 μm, 80 μm, etc., preferably, the composite catalyst has an average particle diameter of 50nm to 1 μm, which may be more advantageous for catalytic oxidation of nitrogen-containing volatile organic compounds.

< Second aspect >

A second aspect of the present invention provides a method for preparing a composite catalyst according to the first aspect of the present invention, comprising the steps of:

Forming the precursor solution into a sol system;

Drying the sol system to obtain a dried product;

The present invention is not particularly limited as to the manner in which the copper salt, cerium salt, complexing agent and nonionic surfactant are dissolved in the solvent, and may be mixed in any possible manner. The solvent is not particularly limited, and may be a polar solvent commonly used in the art, for example: alcohol solvents, water, and the like, with water being preferred.

Further, in some specific embodiments, the method of preparing the precursor solution comprises the steps of:

Dissolving a complexing agent in a solvent to obtain a first mixed solution;

dissolving a nonionic surfactant in the first mixed solution to obtain a second mixed solution;

And dissolving copper salt and cerium salt in the second mixed solution to obtain a precursor solution.

In some embodiments, after the complexing agent is dissolved in the solvent, stirring, sonication, etc. may be employed to cause the complexing agent to dissolve rapidly and disperse uniformly. After the nonionic surfactant is dissolved in the first mixed solution, stirring, ultrasonic treatment and other modes can be adopted to enable the nonionic surfactant to be rapidly dissolved and uniformly dispersed. When the copper salt and the cerium salt are dissolved in the second mixed solution, stirring, ultrasonic and other modes can be adopted to ensure that the copper salt and the cerium salt are rapidly dissolved and uniformly dispersed.

Further, the copper salt and cerium salt are not particularly limited in the present invention, and may be some copper salt and cerium salt commonly used in the art. Specifically, the copper salt may be one or a combination of two or more of copper nitrate, copper nitrite, copper sulfate, copper carbonate, copper sulfite, copper acetate, copper chloride, and the like; for example: the copper salt may be one or a combination of more than two of copper nitrate, copper sulfate, copper carbonate, copper acetate or copper chloride. The cerium salt is one or more of nitrate of cerium, nitrite of cerium, sulfate of cerium, carbonate of cerium, sulfite of cerium, acetate of cerium or chloride of cerium. For example: the cerium salt may be one or a combination of more than two of cerium nitrate, cerium sulfate, cerium carbonate, cerium acetate or cerium chloride.

The nonionic surfactant is not particularly limited as long as it can realize the functions of the present invention. Further, in the present invention, the nonionic surfactant includes a polyether nonionic surfactant, preferably includes a block polyether nonionic surfactant, such as: polyoxyethylene polyoxypropylene block copolymer (F127), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), and the like. The inventors have found that when using a block polyether nonionic surfactant, it is advantageous to prepare the desired composite catalyst.

Further, the complex is not particularly limited, and may be any organic substance commonly used in the art, such as one or a combination of two or more of citric acid, EDTA-2Na, EDTA-4Na, etc., which is capable of forming a sol system.

In some specific embodiments, the ratio of the complex to the sum of the molar amounts of the copper salt and the cerium salt is from 1:1 to 1.5:1, for example: 1:1, 1:1.1, 1:1.2, 1:1.3, 1:4, 1:1.5, etc. In the present invention, the complex can be used to function as a chelate metal, thereby forming a sol gel.

Further, in the present invention, in order to obtain a composite catalyst of a desired crystal form and to facilitate catalytic oxidation of a nitrogen-containing volatile organic compound, the molar ratio of the cerium salt to the copper salt is 1:0.2 to 4, for example: 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, etc.

In the present invention, the form of the sol system is not particularly limited as long as it can form a sol. Generally, on the premise of using the complexing agent, a sol system can be formed by stirring, ultrasonic treatment, standing and other modes. In order to obtain the desired sol system more quickly, it is preferable to obtain the sol system by stirring or ultrasound. The time of stirring or ultrasonic treatment is not particularly limited as long as it is capable of forming a sol system.

In some specific embodiments, the drying comprises a step of primary drying followed by washing and then secondary drying; preferably, the temperature of the primary drying is 100-120 ℃, and the time of the primary drying is 2-4 hours; the temperature of the secondary drying is 60-80 ℃, and the time of the secondary drying is 6-8h.

For washing, washing may be performed with an alcohol solvent, specifically, the alcohol solvent includes a volatile alcohol solvent such as: methanol, ethanol, propanol, and the like. The number of times of washing is not particularly limited, and may be generally 3 to 4 times.

In some specific embodiments, the heat treatment comprises a primary calcination and a secondary calcination; the invention can obtain the composite catalyst with more excellent performance through primary calcination and secondary calcination treatment.

Preferably, the temperature of the primary calcination is 150-200 ℃, for example: 160 ℃, 170 ℃, 180 ℃, 190 ℃ and the like; the time of the primary calcination is 4 to 6 hours, for example: 4.2h, 4.5h, 4.8h, 5h, 5.2h, 5.5h, 5.8h, etc.; the temperature rising rate of the primary calcination is 1-2 ℃/min, for example: 1.2 ℃/min, 1.5 ℃/min, 1.8 ℃/min, etc.

The temperature of the secondary calcination is 350 ℃ to 400 ℃, for example: 360 ℃, 370 ℃, 380 ℃, 390 ℃ and the like; the secondary calcination time is 1 to 2 hours, for example: 1.2h, 1.5h, 1.8h, etc.; the rate of temperature rise for the secondary calcination is 1 to 2 ℃/min, for example: 1.2 ℃/min, 1.5 ℃/min, 1.8 ℃/min, etc.

Further, in the present invention, the heat treatment may be performed under an air atmosphere or an inert gas atmosphere.

< Third aspect >

In a third aspect the present invention provides the use of a composite catalyst according to the first aspect of the present invention for the catalytic oxidation of volatile organic compounds, preferably for the catalytic oxidation of nitrogen-containing oxidized volatile organic compounds. As the nitrogen-containing oxidizing volatile organic compound, acrylonitrile, acetonitrile, hydrogen cyanide and the like can be mentioned.

Examples

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

Preparation of Cu ₁Ce₁ composite catalyst

10Mmol of cerium nitrate, 10mmol of copper nitrate, 20mmol of citric acid and 2g of P123 were added to 40ml of an aqueous solution in a 100ml beaker and stirred at room temperature to form a uniform sol. The sol was then transferred to an oven at 120℃and incubated for 3h. Washing with ethanol to obtain powder for 3 times, centrifuging, and vacuum drying at 80deg.C for 6 hr. Heating the powder to 150 ℃ at 1 ℃/min in an air atmosphere, preserving heat for 5 hours, continuously heating to 350 ℃ at 1 ℃/min, and preserving heat for 1 hour to obtain the target catalyst, wherein a scanning electron microscope diagram of the target catalyst is shown in figure 3.

Example 2

Preparation of Cu ₂Ce₁ composite catalyst

In a 100ml beaker, 5mmol cerium nitrate, 10mmol copper nitrate, 17mmol citric acid and 2.5g F127 were added to 45ml aqueous solution and stirred at room temperature to form a homogeneous sol. The sol was then transferred to an oven at 110℃and incubated for 2h. The powder is obtained by ethanol cleaning for 4 times, centrifugated and dried in vacuum at 90 ℃ for 6 hours. Heating the powder to 150 ℃ at 2 ℃/min in an air atmosphere, preserving heat for 4 hours, continuously heating to 350 ℃ at 2 ℃/min, and preserving heat for 1 hour to obtain the target catalyst, wherein a scanning electron microscope diagram of the target catalyst is shown in fig. 4.

Example 3

Preparation of Cu ₃Ce₁ composite catalyst

In a 100ml beaker, 5mmol cerium nitrate, 15mmol copper nitrate, 21mmol citric acid and 3g F127 were added to a 50ml aqueous solution and stirred at room temperature to form a uniform sol. The sol was then transferred to an oven at 110℃and incubated for 2h. The powder is obtained by ethanol cleaning for 4 times, centrifugated and dried in vacuum at 90 ℃ for 8 hours. Heating the powder to 200 ℃ at 2 ℃/min in an air atmosphere, preserving heat for 5 hours, continuously heating to 400 ℃ at 2 ℃/min, and preserving heat for 2 hours to obtain the target catalyst.

Example 4

Preparation of Cu ₁Ce₂ composite catalyst

10Mmol of cerium nitrate, 5mmol of copper nitrate, 16mmol of citric acid and 4g of F127 are added to 50ml of aqueous solution in a 100ml beaker and stirred at room temperature to form a uniform sol. The sol was then transferred to an oven at 100℃and incubated for 2h. The powder is obtained by ethanol cleaning for 4 times, centrifugated and dried in vacuum at 90 ℃ for 7 hours. Heating the powder to 200 ℃ at 2 ℃/min in an air atmosphere, preserving heat for 4 hours, continuously heating to 400 ℃ at 2 ℃/min, and preserving heat for 2 hours to obtain the target catalyst.

Performance testing

1. XRD testing

FIG. 1 shows XRD patterns of the composite catalysts of examples 1 to 4 of the present invention; as can be seen from fig. 1, the main diffraction peak is a characteristic peak of ceria and a diffraction peak form superimposed by monoclinic CuO, and the diffraction peak corresponding to the oxide crystal form is gradually presented with increasing content of the corresponding metal and positively correlated with the content. The composite catalyst of the invention has better crystal form and no other metal oxide.

2. Catalytic performance test

0.1G of the composite catalyst of examples 1-4 was placed in a continuous flow fixed bed reactor, the composition of the reaction gas, in mass percent, included 2000ppm acrylonitrile, the flow rate of the reaction gas was 100mL/min, the volume space velocity was 60000h ^-1, and the corresponding acrylonitrile conversions of the catalyst at different temperatures were tested at reaction temperatures of 120-260℃respectively, and the results are shown in FIG. 2.

As can be seen from FIG. 2, the composite catalyst of the present invention catalyzes acrylonitrile T _90％ at a temperature of about 190℃to 200 ℃.

Industrial applicability

The copper cerium catalyst provided by the invention can be industrially prepared and applied as a catalytic oxidation volatile organic compound, in particular to a catalytic oxidation nitrogen-containing volatile organic compound.

The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvements in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A composite catalyst comprising copper atoms and cerium atoms, wherein,

When a powder X-ray diffraction method is used for analysis by adopting CuK alpha radiation experimental conditions, an X-ray diffraction diagram of the composite catalyst has characteristic peaks at positions of 28.64+/-0.2, 35.54 +/-0.2 and 38.7+/-0.2 of 2 theta (O);

The average grain diameter of the composite catalyst is 50nm-1 mu m;

the preparation method of the composite catalyst comprises the following steps:

Forming the precursor solution into a sol system;

Drying the sol system to obtain a dried product;

carrying out heat treatment on the dried product to obtain a composite catalyst;

The molar ratio of the cerium atoms to the copper atoms is 1:1.5-4.

2. The composite catalyst of claim 1, wherein the composite catalyst further has a characteristic peak at least one position of 33.34±0.2, 47.44 ±0.2, 56.32±0.2 in 2Θ (q) when analyzed using powder X-ray diffraction using cuka radiation experimental conditions.

3. A method for preparing the composite catalyst according to claim 1 or 2, comprising the steps of:

Forming the precursor solution into a sol system;

Drying the sol system to obtain a dried product;

4. A method of preparation according to claim 3 wherein the nonionic surfactant comprises a polyether nonionic surfactant.

5. The method of claim 4, wherein the nonionic surfactant comprises a block polyether nonionic surfactant.

6. The preparation method according to any one of claims 3 to 5, characterized in that the ratio of the complexing agent to the sum of the molar amounts of copper salt and cerium salt is 1:1 to 1.5:1; and/or the molar ratio of the cerium salt to the copper salt is 1:1.5-4.

7. The method according to claim 6, wherein the drying comprises a step of washing after primary drying and then secondary drying.

8. The preparation method according to claim 7, wherein the primary drying temperature is 100-120 ℃, and the primary drying time is 2-4 hours; the temperature of the secondary drying is 60-80 ℃, and the time of the secondary drying is 6-8h.

9. The method of any one of claims 3-5, wherein the heat treatment comprises a primary calcination and a secondary calcination.

10. The preparation method according to claim 9, wherein the primary calcination temperature is 150-200 ℃, the primary calcination time is 4-6 hours, and the primary calcination temperature rising rate is 1-2 ℃/min;

11. Use of a composite catalyst according to claim 1 or 2 for the catalytic oxidation of volatile organic compounds.

12. Use according to claim 11, characterized in that the use of the composite catalyst for the catalytic oxidation of nitrogen-containing volatile organic compounds.