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

Abstract

The application discloses a kind of iron cobalt oxide catalyst preparation and in catalytic ozonation VOCs application, belong to material technical field.The present application utilizes impregnation calcination method to synthesize this catalyst, including the following steps: a certain proportion of iron salt and cobalt salt are dissolved by water ultrasonic, after salt dissolution, solution becomes brown yellow, honeycomb ceramic is placed in brown yellow solution and is impregnated treatment, blows and removes residual liquid, and is treated by drying;Repeat processing;The treated honeycomb ceramic is calcined, and iron cobalt oxide catalyst is obtained.The catalyst is low in catalytic cost under the action of ozone to low concentration VOCs, compared with traditional method, can be operated at room temperature to realize high removal rate, while realizing low energy consumption, reduce the risk of secondary pollution.

Description

Technical Field

[0001] The present invention belongs to the field of material technology, and in particular relates to the preparation of an iron-cobalt oxide catalyst and its application in catalytic ozonation of VOCs. Background Art

[0002] Volatile organic compounds (VOCs) are a significant source of indoor and outdoor air pollution. Materials and chemicals used in industry, human activities, and buildings are considered the primary cause of air pollution. Among VOCs, ethyl acetate and toluene are common pollutants in paint and printing plants. The large amounts of these pollutants emitted from exhaust gases pose a serious threat to humans and the environment. This is especially true with the increasing urbanization of human lifestyles, making the use of air purification technologies necessary to provide clean air.

[0003] The thermal destruction and catalytic oxidation technologies widely used in existing technologies to remove low-concentration VOCs have the disadvantage of high energy consumption, so it is very important to find an effective method for VOCs removal. Summary of the Invention

[0004] To address the above technical issues, the present invention proposes a method for preparing an iron-cobalt oxide catalyst and its application in the catalytic ozonation of VOCs. The catalyst has low catalytic cost for the ozonation of low-concentration VOCs and can operate at room temperature.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] Technical Solution 1: A method for preparing an iron-cobalt oxide catalyst, comprising the following steps:

[0007] Add water to dissolve the iron salt and cobalt salt with ultrasonic. When the solution turns brownish yellow, immerse the honeycomb ceramic in the brownish yellow solution, blow off the remaining liquid, and dry it. Repeat the process.

[0008] The treated honeycomb ceramic is calcined to obtain an iron-cobalt oxide catalyst.

[0009] The present invention achieves catalyst modification through the strategy of synthesizing iron-cobalt mixed oxides. Cobalt doping increases the active sites on the surface of the iron oxide catalyst, thereby improving the catalytic ozonation activity. When used in the catalytic ozonation reaction, it can achieve complete conversion of ozonated VOCs at room temperature.

[0010] Furthermore, the molar ratio of the iron salt to the cobalt salt is 5:(1-1.2).

[0011] Furthermore, the iron salt is ferric nitrate nonahydrate, and the prepared salt solution concentration is 0.6 mol / L; the cobalt salt is cobalt nitrate hexahydrate, and the prepared salt solution concentration is 0.12 mol / L.

[0012] Furthermore, the parameters of the immersion treatment are: temperature 20° C., time 10 minutes.

[0013] Furthermore, the temperature of the drying process is 70°C.

[0014] Furthermore, the parameters of the calcination treatment are: temperature 400° C., time 4 hours.

[0015] Furthermore, the number of repetitions is four times.

[0016] Technical Solution 2: An iron-cobalt oxide catalyst prepared using the above preparation method.

[0017] Technical Solution Three: Application of an iron-cobalt oxide catalyst in the catalytic ozonation of VOCs.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] The present invention efficiently synthesizes the iron-cobalt oxide catalyst through a simple impregnation-high-temperature calcination method. The method is simple and efficient, the metal salt cost is low, and industrial large-scale preparation and production can be achieved in the future.

[0020] The present invention applies an iron-cobalt oxide catalyst to the room-temperature catalytic ozonation of VOCs, achieving 100% catalytic decomposition activity for toluene and ethyl acetate at room temperature, with performance superior to previously reported catalysts. Furthermore, the monolithic catalyst also has a high ozone removal rate at room temperature, reducing secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 A picture and a scanning electron microscope image of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention;

[0023] Figure 2 The XRD pattern of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention;

[0024] Figure 3 The Raman spectrum of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention;

[0025] Figure 4 This is an XPS graph of Fe2P in the iron-cobalt oxide catalyst prepared in Example 1 of the present invention;

[0026] Figure 5This is the XPS graph of Co2P in the iron-cobalt oxide catalyst prepared in Example 1 of the present invention;

[0027] Figure 6 This is an activity curve of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention for catalytic ozonation and decomposition of toluene;

[0028] Figure 7 This is an activity curve of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention for catalyzing the decomposition of ethyl acetate in ozonated dry gas;

[0029] Figure 8 This is an activity curve of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention for catalyzing the decomposition of ethyl acetate in ozonated wet air;

[0030] Figure 9 This is an activity curve of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention for degrading ozone;

[0031] Figure 10 This is an activity curve diagram of the catalysts in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention catalyzing the decomposition of ethyl acetate in ozonated wet gas. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] The present invention discloses a method for preparing an iron-cobalt oxide catalyst, comprising the following steps:

[0038] Soluble iron salt and soluble cobalt salt are dissolved by ultrasonic treatment in water. After the solution turns brownish yellow, the honeycomb ceramic is immersed in the obtained brownish yellow solution, the residual liquid is blown away, and the honeycomb ceramic is placed in an oven for drying. The treatment is repeated (i.e., the process of "immersion-blowing away residual liquid-drying" is repeated); the repeatedly treated honeycomb ceramic is calcined to obtain an iron-cobalt oxide catalyst.

[0039] In a preferred embodiment of the present invention, honeycomb ceramics include but are not limited to cordierite honeycomb ceramics, zirconium oxide honeycomb ceramics, silicon nitride honeycomb ceramics, aluminum oxide honeycomb ceramics, silicon carbide honeycomb ceramics, or zirconium phosphate honeycomb ceramics. Honeycomb ceramics made of various materials can be prepared using conventional molding processes. Honeycomb ceramics require pretreatment prior to use, such as water washing for dust removal, alkaline washing for oil removal, and drying, to prevent surface impurities from adversely affecting the subsequent adhesion of iron and cobalt oxides, while ensuring the stability of the loaded iron oxides and extending the catalyst's cycle life. All pretreatment steps can be performed using conventional techniques in the art.

[0040] Cordierite honeycomb ceramics exhibit high catalytic activity and stability, maintaining efficient catalytic activity over a wide temperature range. Their high porosity facilitates the attachment of iron and cobalt oxides, providing more active sites. Furthermore, cordierite honeycomb ceramics exhibit excellent mechanical strength and thermal stability, ensuring a long catalyst life. In preferred embodiments of the present invention, cordierite honeycomb ceramics are used as a representative, but non-limiting, example.

[0041] In a preferred embodiment of the present invention, 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 therebetween. The iron salt is ferric nitrate nonahydrate, and the prepared salt solution concentration is 0.6 mol / L; the cobalt salt is cobalt nitrate hexahydrate, and the prepared salt solution concentration is 0.12 mol / L.

[0042] In the following preferred embodiment of the present invention, the parameters of the immersion treatment are: temperature 20° C., time 10 minutes.

[0043] In a preferred embodiment of the present invention, the temperature of the drying process is 70°C.

[0044] In the following preferred embodiment of the present invention, the parameters of the calcination treatment are: temperature 400° C., time 4 hours.

[0045] In a preferred embodiment of the present invention, the number of repeated treatments is four times.

[0046] The iron-cobalt oxide catalyst is prepared by the above preparation method.

[0047] The application of the iron cobalt oxide catalyst in catalytic ozonation of VOCs. The VOCs include: toluene, ethyl acetate (including wet ethyl acetate and dry ethyl acetate) and ozone. During the application process, the test conditions are: the test gas flow rate is 50mL / min-1.2L / min (such as 50mL / min or 1.2L / min), the oxygen flow rate is 0-30mL / min (such as 0mL / min or 30mL / min), the ozone concentration is 16-800ppm (such as 16ppm or 800ppm), N2 is used as the balance gas flow rate of 36.7mL / min, the test gas concentration is 100ppm, the test gas flow rate is 100mL / min, and the volume space velocity 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.

[0048] Catalytic ozonation technology is an ozone-based advanced oxidation process. The catalyst significantly improves pollutant oxidation efficiency and mineralization in the presence of ozone. Compared to traditional methods, this technology achieves high removal rates at lower ozone consumption while reducing the risk of secondary pollution, ensuring its practicality in industrial applications.

[0049] Unless otherwise specified, the "room temperature" in the present invention refers to 20°C.

[0050] The raw materials used in the present invention are all purchased from the market.

[0051] The technical solution of the present invention is further illustrated by the following examples.

[0052] In the following examples, the honeycomb ceramic is cordierite honeycomb ceramic with a porosity of 200 mesh.

[0053] Example 1

[0054] Preparation of an iron-cobalt oxide catalyst:

[0055] 24.2394 g of ferric nitrate nine hydrate (0.06 mol) and 3.5556 g of cobalt nitrate hexahydrate (0.012 mol) were added to 100 mL of water and ultrasonically dissolved. After the solution turned brownish yellow, the honeycomb ceramic was immersed in the brownish yellow solution at room temperature for 10 minutes, the residual liquid was blown off, and it was placed in a 70°C oven for drying. The "immersion-blowing off the residual liquid-drying" steps were repeated four times. The honeycomb ceramic obtained after repeated treatment was calcined in a muffle furnace at 400°C for 4 hours to obtain an iron-cobalt oxide catalyst (Co1Fe5Ox).

[0056] The prepared iron-cobalt oxide catalysts were subjected to the following Figure 1-4 The structural morphology of the catalyst was characterized. Figure 1 Scanning electron microscope images show that the prepared iron-cobalt oxide monolithic catalyst has no clear morphology and is evenly loaded on the cordierite honeycomb ceramic, with the elements on its surface evenly distributed. Figure 2 From the XRD diagram in the figure, it can be seen that the prepared iron-cobalt oxide catalyst mainly shows the characteristic peak of iron oxide, but no characteristic peak of cobalt oxide is seen. It is speculated that the cobalt oxide in the surface catalyst is highly dispersed or the content is below the detection limit and no characteristic peak appears. Figure 3 Raman at 213 cm -1 、219cm -1 , 1250cm -1 The characteristic peak of Fe-O bond appears at 686cm -1 There are characteristic peaks of Co-O. Figure 4 and Figure 5 The XPS graph shows that the iron element in the iron-cobalt oxide catalyst mainly exists in a trivalent form, while the cobalt element mainly exists in a divalent form.

[0057] Comparative Example 1

[0058] Same as Example 1, except that the calcination temperature was adjusted from 400°C to 600°C to obtain an iron-cobalt oxide catalyst, which was recorded as Co1Fe5O x -600.

[0059] Comparative Example 2

[0060] The same as Example 1, except that ferric nitrate nine hydrate and cobalt nitrate six hydrate were mixed in a molar ratio of 10:1 and then dissolved in water to obtain an iron-cobalt oxide catalyst, which was recorded as Co1Fe 10 O x .

[0061] Comparative Example 3

[0062] Using the reported catalyst FeMnO x The synthesis method is derived from the book "Molecular Catalysis" x The specific preparation method is as follows: 35.8mmol of Fe(NO3)3 and 36.4mmol of Mn(NO3)2 are dissolved in ultrapure water at 25℃, and the honeycomb ceramic is immersed in the solution for 10min at room temperature. The remaining liquid is blown off, and the ceramic is dried in an oven at 105℃, and then calcined in a muffle furnace at 550℃ for 2h to obtain a comparative sample, which is recorded as FeMnO x .

[0063] Application Example 1

[0064] The iron-cobalt oxide catalyst prepared above was applied to the room temperature catalytic ozonation of VOCs.

[0065] Figure 6 The catalytic ozonation decomposition activity of ethyl acetate over iron-cobalt oxide catalyst was tested under dry gas components. The test conditions were as follows: the test gas was ethyl acetate, the total gas flow rate was controlled at 50 mL / min, the oxygen flow rate was 30 mL / min, the ozone concentration was 800 ppm, the N2 balance gas flow rate was 10 mL / min, the ethyl acetate concentration was 100 ppm, the test gas flow rate was 10 mL / min, and the volume space velocity was 3000 h -1 , humidity RH = 0%. The ethyl acetate concentration in the tail gas was detected and analyzed by gas chromatography, and the ozone concentration was detected by an ozone detector. Figure 6 It can be seen from the catalyst activity curve that the iron-cobalt oxide catalyst exhibits 100% catalytic ozonation activity of dry gas ethyl acetate at room temperature.

[0066] Application Example 2

[0067] Figure 7 The catalytic ozonation decomposition activity of ethyl acetate in wet gas was tested using an iron-cobalt oxide catalyst. The test conditions were as follows: the test gas was ethyl acetate, the total gas flow rate was controlled at 50 mL / min, the oxygen flow rate was 30 mL / min, the ozone concentration was 800 ppm, the N2 balance gas flow rate was 10 mL / min, the ethyl acetate concentration was 100 ppm, the test gas flow rate was 10 mL / min, and the volume space velocity was 3000 h / min. -1 , humidity RH = 30%. The ethyl acetate concentration in the tail gas was detected and analyzed by gas chromatography, and the ozone concentration was detected by an ozone detector. Figure 7 It can be seen from the catalyst activity curve that the catalyst exhibits 100% catalytic ozonation activity of wet ethyl acetate at room temperature.

[0068] Application Example 3

[0069] Figure 8 The room temperature catalytic ozonolysis activity of toluene over iron-cobalt oxide catalyst was tested. The test conditions were as follows: toluene was the test gas, the toluene concentration was 100 ppm, the toluene flow rate was 33.3 mL / min, the oxygen flow rate was 30 mL / min, the ozone concentration was 800 ppm, the N2 balance gas flow rate was 36.7 mL / min, the total gas flow rate was controlled at 100 mL / min, and the volumetric space velocity was 6000 h -1 , humidity RH = 0%. The toluene concentration in the tail gas was detected and analyzed by gas chromatography, and the ozone concentration was detected by an ozone detector. Figure 8 The catalyst activity curve shows that the catalyst exhibits 100% toluene catalytic ozonation activity at room temperature, and the catalyst activity does not decrease after 5 hours and can still maintain 100% toluene decomposition activity, showing good activity and stability.

[0070] Application Example 4

[0071] Figure 9 The decomposition activity of iron-cobalt oxide catalyst to ozone at room temperature and different humidity was tested. The test conditions were: 16 ppm ozone, flow rate of 1.2 L / min, and space velocity of 18950 h -1 , humidity RH = 1%, 25%, 50%, 75%, the ozone concentration in the tail gas is detected by an ozone detector. Figure 9 The catalyst activity curve shows that the catalyst can achieve an ozone conversion rate of over 99% at room temperature when the humidity is 1%, and can maintain essentially unchanged for 8.5 hours, indicating that the catalyst has a good removal rate under dry gas conditions; at a humidity of 25%, it can achieve an ozone conversion rate of over 55% at room temperature, and can maintain essentially unchanged for 6 hours; at a humidity of 50%, it can achieve an ozone conversion rate of over 10% at room temperature, and can maintain essentially unchanged for 6 hours; at a humidity of 75%, it can achieve an ozone conversion rate of essentially zero at room temperature. This indicates that the catalyst prepared by the present invention exhibits a good removal effect under dry gas conditions and still has a certain ozone removal rate under low humidity conditions.

[0072] Application Example 5

[0073] Figure 10The catalytic ozonation decomposition activity of the iron cobalt oxide catalyst Co1Fe5Ox in Example 1 and the catalysts in Comparative Examples 1-3 under the condition of wet gas components is compared. The test conditions are as follows: the test gas is ethyl acetate, the total gas flow rate is controlled to be 50 mL / min, the oxygen flow rate is 30 mL / min, the ozone concentration is 800 ppm, the N2 balance gas flow rate is 10 mL / min, the ethyl acetate concentration is 100 ppm, the test gas flow rate is 10 mL / min, and the volume space velocity is 3000 h -1 , humidity RH = 30%. The ethyl acetate concentration in the tail gas was detected and analyzed by gas chromatography, and the ozone concentration was detected by an ozone detector. Figure 10 The catalyst activity curve shows that, compared with the other three comparison samples, the catalyst exhibits excellent catalytic ability and exhibits 100% catalytic ozonation activity of wet ethyl acetate at room temperature.

[0074] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. Application of an iron-cobalt oxide catalyst in catalytic ozonation of VOCs, characterized in that: The preparation method of the iron-cobalt oxide catalyst comprises the following steps: Add water to dissolve the iron salt and cobalt salt with ultrasonic. When the solution turns brownish yellow, immerse the honeycomb ceramic in the brownish yellow solution, blow off the remaining liquid, and dry it. Repeat the process. calcining the treated honeycomb ceramic to obtain an iron-cobalt oxide catalyst; The molar ratio of the iron salt to the cobalt salt is 5:(1-1.2); The parameters of the calcination treatment are: temperature 400°C, time 4 hours; During the application process, the test conditions are: test gas flow rate of 50-1.2L / min, oxygen flow rate of 30mL / min, ozone concentration of 16-800ppm, N2 as balance gas, flow rate of 36.7mL / min, test gas concentration of 100ppm, test gas flow rate of 100mL / min, volume space velocity of 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, characterized in that The iron salt is ferric nitrate nonahydrate, and the prepared salt solution concentration is 0.6 mol / L; the cobalt salt is cobalt nitrate hexahydrate, and the prepared salt solution concentration is 0.12 mol / L.

3. The use according to claim 1, characterized in that The parameters of the immersion treatment are: temperature 20° C., time 10 minutes.

4. The use according to claim 1, characterized in that The temperature of the drying process is 70°C.

5. The use according to claim 1, characterized in that The treatment was repeated four times.

Images