Preparation of iron-cobalt oxide catalyst and application of iron-cobalt oxide catalyst in catalytic ozonation of VOCs (Volatile Organic Compounds)

Abstract

The invention discloses preparation of an iron-cobalt oxide catalyst and application of the iron-cobalt oxide catalyst in catalytic ozonation of VOCs, and belongs to the technical field of materials. The method for synthesizing the catalyst by using an impregnation and calcination method comprises the following steps: adding water into ferric salt and cobalt salt according to a certain proportion for ultrasonic dissolution, after the salt is dissolved, putting honeycomb ceramic into the brown yellow solution for impregnation treatment, blowing off residual liquid, and drying; performing repeated treatment; and calcining the treated honeycomb ceramic to obtain the iron-cobalt oxide catalyst. The catalyst is low in catalysis cost for low-concentration VOCs under the action of ozone, and compared with a traditional method, the catalyst can be operated at the room temperature to achieve the high removal rate, and the risk of secondary pollution is reduced while low energy consumption is achieved.

Description

Technical Field

[0001] The 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 one of the important sources of indoor and outdoor air pollution. Materials and chemicals used in industry, human activities and buildings are considered the main causes of air pollution. Among volatile organic compounds (VOCs), ethyl acetate and toluene are common pollutants in paint, printing and other factories. The emission of a large amount of waste gas pollutants poses a serious threat to humans and the environment. Especially with the urbanization of human lifestyles, it is necessary to use air purification technology to provide people with clean air.

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

[0004] In view of the above technical problems, the present invention proposes a preparation method of an iron-cobalt oxide catalyst and its application in catalytic ozonation of VOCs. The catalyst has low catalytic cost for ozonation of low-concentration VOCs and can be operated 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, and when the solution turns brown-yellow, immerse the honeycomb ceramic in the brown-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, the complete conversion of ozonated VOCs can be achieved 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 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 cost of the metal salt is low, and industrial large-scale preparation and production can be realized in the future.

[0020] The present invention applies the iron-cobalt oxide catalyst to the application of catalytic ozonation of VOCs at room temperature, achieving 100% catalytic decomposition activity for toluene and ethyl acetate at room temperature, and its performance is better than that of reported catalysts; in addition, the integral catalyst also has a high removal rate for ozone at room temperature, reducing secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] Figure 1 The picture and 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 an XPS graph of Co2P in the iron-cobalt oxide catalyst prepared in Example 1 of the present invention;

[0027] Figure 6 The activity curve of the iron-cobalt oxide catalyst prepared in Example 1 of the present invention for catalyzing the decomposition of toluene by ozonation;

[0028] Figure 7 The 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 The 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] Fig. 9 The activity curve of the iron-cobalt oxide catalyst for degrading ozone prepared in Example 1 of the present invention;

[0031] Fig.10 It 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 for 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 should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation 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 a conflict with any incorporated document, the content 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 of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary 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 embodiment of 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. When the solution turns brown-yellow, the honeycomb ceramic is immersed in the obtained brown-yellow solution, the remaining liquid is blown off, and the honeycomb ceramic is placed in an oven for drying. The treatment is repeated (i.e., the process of "immersion-blowing off the remaining 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. The preparation method of honeycomb ceramics of various materials can adopt the corresponding conventional molding process. Honeycomb ceramics need to be pretreated before use, such as water washing and dust removal, alkali washing and oil removal, drying and other steps to avoid surface impurities from adversely affecting the subsequent attachment of iron and cobalt oxides, while ensuring the stability of the loaded iron oxides and extending the cycle life of the catalyst. The pretreatment steps can all adopt conventional technical means in the art.

[0040] Cordierite honeycomb ceramics have high catalytic activity and stability, can maintain efficient catalytic activity in a wide temperature range, and have high porosity, which is convenient for the attachment of iron-cobalt oxides and can provide more active sites. In addition, cordierite honeycomb ceramics have excellent mechanical strength and thermal stability, which can ensure the service life of the catalyst. In the preferred embodiment of the present invention, cordierite honeycomb ceramics are typically but not restrictively selected as an 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 between the above ratios. The iron salt is ferric nitrate nonahydrate, and the concentration of the prepared salt solution is 0.6 mol / L; the cobalt salt is cobalt nitrate hexahydrate, and the concentration of the prepared salt solution is 0.12 mol / L.

[0042] In a 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 a preferred embodiment of the present invention, the calcination treatment parameters 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 (e.g. 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 advanced oxidation project based on ozone. The catalyst can significantly improve the oxidation efficiency of pollutants and achieve their mineralization in the presence of ozone. Compared with traditional methods, this technology can achieve high removal rates at lower ozone consumption while reducing the risk of secondary pollution to ensure its practicality in industrial applications.

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

[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 embodiments.

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

[0053] Example 1

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

[0055] 24.2394 g of ferric nitrate nonahydrate (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 brown-yellow, the honeycomb ceramic was immersed in the brown-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, and 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 catalyst structure and morphology are characterized. Figure 1 It can be seen from the scanning electron microscope that the prepared iron-cobalt oxide monolithic catalyst has no clear morphology and is evenly loaded on the cordierite honeycomb ceramic, and its surface elements are 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 trioxide, 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] The same as Example 1, except that the calcination temperature was adjusted from 400°C to 600°C to obtain an iron-cobalt oxide catalyst, denoted as Co1Fe5O x -600.

[0059] Comparative Example 2

[0060] Same as Example 1, except that ferric nitrate nonahydrate and cobalt nitrate hexahydrate are mixed in a molar ratio of 10:1 and then added to water to dissolve to obtain an iron-cobalt oxide catalyst, denoted as Co1Fe 10 O x .

[0061] Comparative Example 3

[0062] Using the reported catalyst FeMnO x The synthesis method is derived from the "FeMnO 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 as above was applied to the room temperature catalytic ozonation of VOCs.

[0065] Figure 6 The catalytic ozonation decomposition activity of ethyl acetate under dry gas components was tested by the iron-cobalt oxide catalyst. The test conditions were as follows: the test gas was ethyl acetate, the total gas flow rate was controlled to be 50 mL / min, of which the oxygen flow rate was 30 mL / min, the ozone concentration was 800 ppm, the N2 as the 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 is detected and analyzed by gas chromatography, and the ozone concentration is 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 under wet gas components was tested by the Fe-Co oxide catalyst. The test conditions were as follows: the test gas was ethyl acetate, the total gas flow rate was controlled to be 50 mL / min, of which 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 = 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 ozonation decomposition activity of toluene by iron-cobalt oxide catalyst was tested. The test conditions were as follows: the test gas was toluene, 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 is detected and analyzed by gas chromatography, and the ozone concentration is detected by an ozone detector. Figure 8 It can be seen from the catalyst activity curve 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] Fig. 9 The decomposition activity of iron-cobalt oxide catalyst to ozone at room temperature and different humidity was tested. The test conditions were: 16ppm ozone, flow rate of 1.2L / min, and air velocity of 18950h -1 , humidity RH = 1%, 25%, 50%, 75%, the ozone concentration in the tail gas is detected by an ozone detector. Fig. 9 It can be seen from the catalyst activity curve that the catalyst can achieve an ozone conversion rate of more than 99% at room temperature when the humidity is 1%, and can maintain basically unchanged for 8.5 hours, which shows that the catalyst has a good removal rate under dry gas conditions; it can reach an ozone conversion rate of more than 55% at room temperature when the humidity is 25%, and can maintain basically unchanged for 6 hours; it can reach an ozone conversion rate of more than 10% at room temperature when the humidity is 50%, and can maintain basically unchanged for 6 hours; it can reach an ozone conversion rate of basically 0 at room temperature when the humidity is 75%. It shows that the catalyst prepared by the present invention shows a good removal effect under dry gas, and still has a certain removal rate for ozone under low humidity conditions.

[0072] Application Example 5

[0073] Fig.10The catalytic ozonation decomposition activity of the iron cobalt oxide catalyst Co1Fe5Ox in Example 1 and the catalyst 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 as the 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 is detected and analyzed by gas chromatography, and the ozone concentration is detected by an ozone detector. Fig.10 It can be seen from the catalyst activity curve 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 only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing an iron-cobalt oxide catalyst, characterized in that: The following steps are involved: Add water to dissolve the iron salt and cobalt salt with ultrasonic, and when the solution turns brown-yellow, immerse the honeycomb ceramic in the brown-yellow solution, blow off the remaining liquid, and dry it; Repeat processing; The treated honeycomb ceramic is calcined to obtain an iron-cobalt oxide catalyst.

2. The method for preparing the iron-cobalt oxide catalyst according to claim 1, characterized in that: The molar ratio of the iron salt to the cobalt salt is 5:(1-1.2).

3. The method for preparing the iron-cobalt oxide catalyst according to claim 2, 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.

4. The method for preparing the iron-cobalt oxide catalyst according to claim 1, characterized in that: The parameters of the immersion treatment are: temperature 20° C., time 10 minutes.

5. The method for preparing the iron-cobalt oxide catalyst according to claim 1, characterized in that: The temperature of the drying process is 70°C.

6. The method for preparing the iron-cobalt oxide catalyst according to claim 1, characterized in that: The parameters of the calcination treatment are: temperature 400° C., time 4 hours.

7. The method for preparing the iron-cobalt oxide catalyst according to claim 1, characterized in that: The treatment was repeated four times.

8. An iron-cobalt oxide catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the iron-cobalt oxide catalyst as claimed in claim 8 in catalytic ozonation of VOCs.

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