CN119406409B

CN119406409B - Preparation of an iron-cobalt oxide catalyst and its application in catalytic ozonation of VOCs

Info

Publication number: CN119406409B
Application number: CN202411707298.XA
Authority: CN
Inventors: 郭彦炳; 姜斯璆; 邱晓峰; 颜星宇; 侯冲冲; 王金龙; 罗竹
Original assignee: Wuhan Photochemical Technology Research Institute
Current assignee: Wuhan Photochemical Technology Research Institute
Priority date: 2024-11-27
Filing date: 2024-11-27
Publication date: 2025-10-21
Anticipated expiration: 2044-11-27
Also published as: CN119406409A

Abstract

The present invention discloses the preparation of an iron-cobalt oxide catalyst and its application in the catalytic ozonation of VOCs, belonging to the field of materials technology. The catalyst is synthesized using an impregnation and calcination method, comprising the following steps: ultrasonically dissolving a certain proportion of iron and cobalt salts in water, causing the solution to turn brownish-yellow after the salts dissolve; immersing a honeycomb ceramic in the brownish-yellow solution, removing the remaining liquid, and drying the solution; repeating the process; and calcining the treated honeycomb ceramic to obtain an iron-cobalt oxide catalyst. This catalyst has a low cost for catalyzing low-concentration VOCs under the action of ozone. Compared with traditional methods, it can be operated at room temperature to achieve a high removal rate, reducing energy consumption while also minimizing the risk of secondary pollution.

Description

Preparation of iron-cobalt oxide catalyst and application of iron-cobalt oxide catalyst in catalytic ozonation of VOCs

Technical Field

The invention belongs to the technical field of materials, and particularly relates to preparation of an iron-cobalt oxide catalyst and application of the iron-cobalt oxide catalyst in catalytic ozonation of VOCs.

Background

Volatile Organic Compounds (VOCs) are one of the important sources of indoor and outdoor air pollution. Materials and chemicals used in industry, human activities, and in buildings are considered to be the main cause of air pollution. Among Volatile Organic Compounds (VOCs), ethyl acetate and toluene are common pollutants for factories such as paints, printing and the like, and the emission of a large amount of exhaust gas pollutants poses serious threat to human beings and environment, particularly along with the urban realization of human life style, so that people are required to use an air purification technology in order to provide clean air for people.

The widely used technology for removing low-concentration VOCs by thermal destruction and catalytic oxidation in the prior art has the defect of high energy consumption, so that it is important to find an effective VOCs removal method.

Disclosure of Invention

Aiming at the technical problems, the invention provides a preparation method of an iron-cobalt oxide catalyst and application of the iron-cobalt oxide catalyst in catalyzing ozonization VOCs. The catalyst has low catalytic cost for low-concentration ozonization VOCs and can be operated at room temperature.

In order to achieve the above purpose, the present invention provides the following technical solutions:

The preparation method of the iron-cobalt oxide catalyst comprises the following steps:

Adding water into ferric salt and cobalt salt for ultrasonic dissolution, and after the solution turns into brown yellow, putting the honeycomb ceramics into the obtained brown yellow solution for dipping treatment, blowing off residual liquid, drying treatment and repeating the treatment;

and calcining the treated honeycomb ceramic to obtain the iron-cobalt oxide catalyst.

According to the method, modification of the catalyst is realized through a strategy of synthesizing the iron-cobalt mixed oxide, and the active site on the surface of the iron oxide catalyst is increased by cobalt doping, so that the catalytic ozonation activity is improved, and the catalyst can be used in the catalytic ozonation reaction, so that complete conversion of ozonation VOCs can be realized at room temperature.

Further, the mol ratio of the ferric salt to the cobalt salt is 5:1-1.2.

Further, the ferric salt is ferric nitrate nonahydrate, the concentration of the prepared salt solution is 0.6mol/L, the cobalt salt is cobalt nitrate hexahydrate, and the concentration of the prepared salt solution is 0.12mol/L.

Further, the parameters of the dipping treatment are that the temperature is 20 ℃ and the time is 10 minutes.

Further, the temperature of the drying treatment is 70 ℃.

Further, the calcination treatment is carried out at 400 ℃ for 4 hours.

Further, the number of repetitions is four.

The iron cobalt oxide catalyst prepared by the preparation method is provided.

The third technical proposal is the application of an iron cobalt oxide catalyst in catalyzing and ozonizing VOCs.

Compared with the prior art, the invention has the following advantages and technical effects:

The method for synthesizing the iron cobalt oxide catalyst by the simple impregnation-high-temperature calcination method is simple and efficient, has low cost of metal salt, and can realize industrialized large-scale preparation and production in the future.

The invention applies the iron cobalt oxide catalyst to the application of the room temperature catalytic ozonation VOCs, realizes 100% catalytic decomposition activity of toluene and ethyl acetate under the room temperature condition, has better performance than the reported catalyst, and has higher ozone removal rate under the room temperature, thereby reducing secondary pollution.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:

FIG. 1 is a photograph and scanning electron microscope of an iron-cobalt oxide catalyst prepared in example 1 of the present invention;

FIG. 2 is an XRD pattern of the iron cobalt oxide catalyst prepared in example 1 of the present invention;

FIG. 3 is a Raman spectrum of the iron cobalt oxide catalyst prepared in example 1 of the present invention;

FIG. 4 is an XPS chart of Fe2P in the iron cobalt oxide catalyst prepared in example 1 of the present invention;

FIG. 5 is an XPS chart of Co2P in the iron cobalt oxide catalyst prepared in example 1 of the present invention;

FIG. 6 is a graph showing the activity of the iron cobalt oxide catalyst prepared in example 1 of the present invention in catalyzing ozonization of toluene decomposition;

FIG. 7 is a graph showing the activity of the iron cobalt oxide catalyst prepared in example 1 of the present invention in catalyzing the decomposition of ethyl acetate in the ozonation dry gas;

FIG. 8 is a graph showing the activity of the iron cobalt oxide catalyst prepared in example 1 of the present invention in catalyzing the decomposition of ozonated wet ethyl acetate;

FIG. 9 is a graph showing the ozone degrading activity of the iron cobalt oxide catalyst prepared in example 1 of the present invention;

FIG. 10 is a graph showing the activity of the catalysts of examples 1, 2, and 3 of the present invention for the catalytic ozonation of wet ethyl acetate.

Detailed Description

Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.

The embodiment of the invention discloses a preparation method of an iron-cobalt oxide catalyst, which comprises the following steps:

adding water into soluble ferric salt and soluble cobalt salt to make ultrasonic dissolution, after the solution turns into brown yellow, placing the honeycomb ceramic into the obtained brown yellow solution to make impregnation treatment, blowing off residual liquid, placing it into oven to make drying treatment, repeating the treatment (i.e. repeating the process of impregnation-blowing off residual liquid-drying treatment), and calcining the repeatedly-treated honeycomb ceramic so as to obtain the invented iron-cobalt oxide catalyst.

In a preferred embodiment of the present invention, the honeycomb ceramic includes, but is not limited to, cordierite honeycomb ceramic, zirconia honeycomb ceramic, silicon nitride honeycomb ceramic, alumina honeycomb ceramic, silicon carbide honeycomb ceramic or zirconium phosphate honeycomb ceramic. The preparation method of the honeycomb ceramics with various materials adopts corresponding conventional forming technology, and the honeycomb ceramics are required to be pretreated before use, such as washing, dedusting, alkali washing, degreasing, drying and the like, so that the adverse effect of surface impurities on the subsequent iron-cobalt oxide adhesion is avoided, the stability of the loaded iron oxide is ensured, and the cycle life of the catalyst is prolonged. The pretreatment steps are all carried out by adopting the conventional technical means in the field.

The cordierite honeycomb ceramic has higher catalytic activity and stability, can keep high-efficiency catalytic activity in a wider temperature range, has higher porosity, is convenient for the adhesion of iron cobalt oxide, and can provide more active sites. In addition, the cordierite honeycomb ceramic has excellent mechanical strength and thermal stability, and can ensure the service life of the catalyst. In a preferred embodiment of the invention, cordierite honeycomb ceramics are typically, but not limitatively, selected as an example.

In a preferred embodiment of the invention below, the molar ratio of the iron salt to the cobalt salt is 5: (1-1.2), illustratively 5:1, 5:1.2 or any range between the foregoing ratios. The ferric salt is ferric nitrate nonahydrate, the concentration of the prepared salt solution is 0.6mol/L, the cobalt salt is cobalt nitrate hexahydrate, and the concentration of the prepared salt solution is 0.12mol/L.

In a preferred embodiment of the invention, the parameters of the impregnation treatment are a temperature of 20 ℃ for 10 minutes.

In a preferred embodiment of the present invention, the temperature of the drying process is 70 ℃.

In a preferred embodiment of the invention, the calcination treatment is carried out at a temperature of 400 ℃ for a period of 4 hours.

In a preferred embodiment of the invention below, the number of repetitions is four.

The iron cobalt oxide catalyst is prepared by the preparation method.

The application of the iron cobalt oxide catalyst in catalyzing and ozonating VOCs. The VOCs include toluene, ethyl acetate (including wet ethyl acetate and dry ethyl acetate), and ozone. In the application process, the test conditions are that the flow rate of the test gas is 50mL/min-1.2L/min (such as 50mL/min or 1.2L/min), the flow rate of the oxygen is 0-30mL/min (such as 0mL/min or 30 mL/min), the ozone concentration is 16-800ppm (such as 16ppm or 800 ppm), the flow rate of N ₂ serving as balance air flow is 36.7mL/min, the concentration of the test gas is 100ppm, the flow rate of the test gas is 100mL/min, the volume airspeed is 3000-18950h ^-1 (such as 3000h ^-1、6000h^-1 or 18950h ^-1), the test humidity is 0-75% (such as 0%, 1%, 25%, 50% or 75%), and the test temperature is room temperature.

Catalytic ozonation technology is an advanced oxidation project based on ozone. The catalyst can obviously improve the oxidation efficiency of pollutants under the condition of ozone existence, and mineralization of the pollutants is realized. Compared with the traditional method, the technology can realize high removal rate under lower ozone consumption, and simultaneously reduce the risk of secondary pollution so as to ensure the practicability of the technology in industrial application.

As used herein, the term "room temperature" refers to 20℃unless otherwise specified.

The raw materials used in the invention are all purchased in the market.

The technical scheme of the invention is further described by the following examples.

In the following examples, cordierite honeycomb ceramics were used as the honeycomb ceramics, and the porosity was 200 mesh.

Example 1

Preparation of iron-cobalt oxide catalyst:

24.2394g of ferric nitrate nonahydrate (0.06 mol) and 3.5556g of cobalt nitrate hexahydrate (0.012 mol) were added to 100mL of water for ultrasonic dissolution, after the solution became brown yellow, the honeycomb ceramic was put into the brown yellow solution at room temperature for immersion for 10 minutes, the residual liquid was blown off, the honeycomb ceramic was put into a 70 ℃ oven for drying, the "immersion-residual liquid blowing-drying" step was repeated four times, and the honeycomb ceramic obtained after the repeated treatment was calcined in a 400 ℃ muffle furnace for 4 hours, to obtain an iron cobalt oxide catalyst (Co ₁Fe₅ Ox).

The structural morphology of the catalysts shown in figures 1-4 is characterized for the prepared iron cobalt oxide catalysts. As can be seen from the scanning electron microscope chart of FIG. 1, the prepared iron-cobalt oxide monolithic catalyst has no definite morphology, is flatly and uniformly loaded on cordierite honeycomb ceramics, and has uniform surface element distribution. As can be seen from the XRD pattern in fig. 2, the prepared iron-cobalt oxide catalyst mainly shows characteristic peaks of iron trioxide, but no characteristic peaks of cobalt oxide are found, and it is presumed that the cobalt oxide in the surface catalyst is highly dispersed or the content is lower than the detection limit, and no characteristic peaks are found. The characteristic peak of Fe-O bond appears at 213cm ^-1、219cm^-1、1250cm^-1 in Raman of FIG. 3, and the characteristic peak of Co-O appears at 686cm ^-1. From the XPS graphs of fig. 4 and 5, it is known that the iron element in the iron-cobalt oxide catalyst exists mainly in trivalent form, while the cobalt element exists mainly in divalent form.

Comparative example 1

The difference from example 1 is that the calcination temperature is adjusted from 400 ℃ to 600 ℃ to obtain an iron cobalt oxide catalyst, designated as Co ₁Fe₅O_x -600.

Comparative example 2

The difference from example 1 is that ferric nitrate nonahydrate and cobalt nitrate hexahydrate are mixed according to the mol ratio of 10:1 and then added into water for dissolution, and an iron cobalt oxide catalyst, which is denoted as Co ₁Fe₁₀O_x, is obtained.

Comparative example 3

The reported catalyst FeMnO _x is adopted, the synthesis method is derived from the activity and mechanism research of the catalytic oxidation of toluene by FeMnO _x catalyst in molecular catalysis, and the specific preparation method comprises the steps of dissolving 35.8mmol of Fe (NO ₃)₃ and 36.4mmol of Mn (NO ₃)₂) in 25 ℃ ultrapure water, immersing honeycomb ceramics in the solution at room temperature for 10min, blowing off residual liquid, drying in a 105 ℃ oven, and roasting in a 550 ℃ muffle furnace for 2h to obtain a comparative sample which is marked as FeMnO _x.

Application example 1

The prepared iron cobalt oxide catalyst is applied to the room-temperature catalytic ozonation VOCs.

FIG. 6 shows the catalytic ozonization decomposition activity test of an iron cobalt oxide catalyst on ethyl acetate under the dry gas component under the conditions that the test gas is ethyl acetate, the total gas flow is controlled to be 50mL/min, the oxygen flow is 30mL/min, the ozone concentration is 800ppm, N ₂ is used as the balance gas flow and is 10mL/min, the ethyl acetate concentration is 100ppm, the test gas flow is 10mL/min, the volume space velocity is 3000h ^-1, and the humidity RH=0%. The concentration of ethyl acetate in the tail gas is detected and analyzed by gas chromatography, and the concentration of ozone is detected by an ozone detector. As can be seen from the catalyst activity curve of fig. 6, the iron cobalt oxide catalyst exhibited 100% catalytic ozonation dry gas ethyl acetate activity at room temperature.

Application example 2

FIG. 7 shows the activity test of the iron cobalt oxide catalyst on the catalytic ozonization decomposition of ethyl acetate under the moisture component under the conditions that the test gas is ethyl acetate, the total gas flow is controlled to be 50mL/min, the oxygen flow is 30mL/min, the ozone concentration is 800ppm, N ₂ is used as the balance gas flow and is 10mL/min, the ethyl acetate concentration is 100ppm, the test gas flow is 10mL/min, the volume space velocity is 3000h ^-1, and the humidity RH=30%. The concentration of ethyl acetate in the tail gas is detected and analyzed by gas chromatography, and the concentration of ozone is detected by an ozone detector. As can be seen from the catalyst activity curve of fig. 7, the catalyst exhibited 100% catalytic ozonation wet ethyl acetate activity at room temperature.

Application example 3

FIG. 8 shows the activity test of the iron cobalt oxide catalyst on the room temperature catalytic ozonation decomposition of toluene under the conditions that the test gas is toluene, the toluene concentration is 100ppm, the toluene flow is 33.3mL/min, the oxygen flow is 30mL/min, the ozone concentration is 800ppm, N ₂ is used as the balance air flow and 36.7mL/min, the total gas flow is controlled to be 100mL/min, the volume space velocity is 6000h ^-1, and the humidity RH=0%. The toluene concentration in the tail gas is detected and analyzed by gas chromatography, and the ozone concentration is detected by an ozone detector. As can be seen from the catalyst activity curve of FIG. 8, the catalyst shows 100% of toluene catalytic ozonation activity at room temperature, and can maintain 100% of toluene decomposition activity after 5 hours without reducing the catalyst activity, thus showing better activity and stability.

Application example 4

FIG. 9 shows the decomposition activity of iron cobalt oxide catalyst on ozone at room temperature under different humidity conditions of 16ppm ozone, flow rate of 1.2L/min, airspeed of 18950h ^-1, humidity RH=1%, 25%, 50%, 75% and ozone concentration in tail gas detected by an ozone detector. From the catalyst activity curve of FIG. 9, it can reach more than 99% ozone conversion rate at room temperature at humidity of 1% and can maintain 8.5h basically unchanged, which shows that the catalyst has better removal rate under dry gas condition, can reach more than 55% ozone conversion rate at room temperature at humidity of 25% and can maintain 6h basically unchanged, can reach more than 10% ozone conversion rate at room temperature at humidity of 50% and can maintain 6h basically unchanged, and can reach 0 at room temperature at humidity of 75%. The catalyst prepared by the method shows good removal effect under dry gas, and still has a certain removal rate for ozone under the low humidity condition.

Application example 5

FIG. 10 is a graph showing a comparison of catalytic ozonation decomposition activity of the iron cobalt oxide catalyst Co ₁Fe₅ Ox in example 1 with that of the catalysts of comparative examples 1-3 on ethyl acetate under wet gas component, under the conditions of a test gas of ethyl acetate, a total gas flow rate of 50mL/min, wherein the oxygen flow rate is 30mL/min, the ozone concentration is 800ppm, N ₂ is 10mL/min as an equilibrium gas flow rate, the ethyl acetate concentration is 100ppm, the test gas flow rate is 10mL/min, the volume space velocity is 3000h ^-1, and the humidity RH=30%. The concentration of ethyl acetate in the tail gas is detected and analyzed by gas chromatography, and the concentration of ozone is detected by an ozone detector. As can be seen from the catalyst activity curves of fig. 10, the present catalyst exhibited excellent catalytic ability and 100% catalytic ozonation wet ethyl acetate activity at room temperature, compared to the other three control samples.

The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. The application of the iron cobalt oxide catalyst in the catalytic ozonation of VOCs is characterized in that the preparation method of the iron cobalt oxide catalyst comprises the following steps:

calcining the treated honeycomb ceramic to obtain an iron-cobalt oxide catalyst;

the mol ratio of the ferric salt to the cobalt salt is 5:1-1.2;

the calcination treatment parameters are that the temperature is 400 ℃ and the time is 4 hours;

In the application process, the test conditions are that the flow rate of the test gas is 50-1.2L/min, the flow rate of the oxygen is 30mL/min, the ozone concentration is 16-800ppm, N ₂ is used as balance gas, the flow rate is 36.7mL/min, the concentration of the test gas is 100ppm, the flow rate of the test gas is 100mL/min, the volume airspeed is 3000-18950h ^-1, the test humidity is 1-75%, and the test temperature is room temperature;

The VOCs include ethyl acetate.

2. The use according to claim 1, wherein the iron salt is ferric nitrate nonahydrate and the prepared salt solution has a concentration of 0.6mol/L, the cobalt salt is cobalt nitrate hexahydrate and the prepared salt solution has a concentration of 0.12mol/L.

3. The method according to claim 1, wherein the parameters of the immersion treatment are a temperature of 20 ℃ and a time of 10 minutes.

4. The use according to claim 1, wherein the temperature of the drying process is 70 ℃.

5. The use according to claim 1, wherein the number of repetitions is four.