Aluminum nitride supported cobalt nitrogen carbon catalyst, preparation method thereof and formaldehyde degradation method

Abstract

The invention discloses an aluminum nitride supported cobalt nitrogen carbon catalyst, a preparation method thereof and a method for degrading formaldehyde. The invention aims to provide the preparation method of the aluminum nitride supported cobalt nitrogen carbon catalyst, and the aluminum nitride supported cobalt nitrogen carbon catalyst has a relatively high degradation rate on formaldehyde. According to the technical scheme, the preparation method comprises the following steps: (1) preparing a mixed solution of cobalt nitrate hexahydrate, folic acid, AlN, ethanol and water; (2) stirring the solution for half an hour; (3) putting the obtained solution into a reaction kettle for hydrothermal reaction; (4) centrifuging, washing with deionized water, and freeze-drying to obtain a solid product; and (5) calcining the solid product in a nitrogen atmosphere at 800 DEG C to obtain a finished product. Belongs to the technical field of thermocatalytic materials and environmental protection.

Description

Technical Field

[0001] The invention relates to a catalyst, in particular to an aluminum nitride-supported cobalt-nitrogen-carbon catalyst. The invention also relates to a preparation method of the aluminum nitride-supported cobalt-nitrogen-carbon catalyst, and belongs to the technical field of thermal catalytic materials and environmental protection. Background Art

[0002] Formaldehyde (HCHO) is one of the most serious indoor pollutants, mainly derived from widely used interior decoration materials. Long-term exposure is harmful to human health. The preparation of efficient and stable catalysts to achieve catalytic oxidation of formaldehyde at room temperature has always been one of the important research contents in the field of environmental catalysis. At present, thermal catalytic reaction is considered to be one of the most promising degradation reaction pathways. Among them, precious metal-supported catalysts have good formaldehyde oxidation efficiency, but there are problems such as high prices, while relatively cheap transition metals have low activity. Therefore, the development of low-cost non-precious metal-based catalysts remains a challenge.

[0003] Transition metal nitrogen-doped carbon-based catalysts (MNCs) improve the electron transport capacity of transition metal-based catalysts and simulate the active sites of precious metals through changes in electronic structure such as bonding, electron transfer, hydrogen bond formation and breaking. These changes can promote the reaction, thereby improving the catalytic activity and selectivity of the catalyst. At the same time, the use of hydroxyl-rich carriers can increase the concentration of active adsorbed hydroxyl groups on the catalyst surface, thereby improving the catalyst's ability to adsorb activated water. AlN is a two-dimensional layered material that can form AlOOH during the hydrothermal process. AlOOH has rich hydroxyl groups and a high specific surface area carrier. It has been widely studied as a thermal catalyst carrier. For example, Wang used this method (AIChE J. 2022; e17895.) to design a transition metal Ni-enhanced adsorption hydroxyl-type PtNi / Al2O3 catalyst, which achieved room temperature catalytic oxidation of formaldehyde, confirming the feasibility of this method. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for preparing an aluminum nitride-supported cobalt nitrogen-carbon catalyst based on the problems currently faced by transition metal-based catalysts and having a high degradation rate for formaldehyde.

[0005] In order to achieve the above object, the first technical solution provided by the present invention is as follows: A method for preparing an aluminum nitride-supported cobalt-nitrogen-carbon catalyst comprises the following steps in sequence: (1) preparing a mixed solution of cobalt nitrate hexahydrate, folic acid, AlN, ethanol and water; (2) Stir the above solution for half an hour; (3) placing the obtained solution into a reaction kettle for hydrothermal reaction; (4) centrifuging, washing with deionized water, and freeze-drying to obtain a solid product; (5) calcining the solid product under a nitrogen atmosphere to obtain a finished product; belonging to the field of thermal catalytic materials and environmental protection technology.

[0006] Furthermore, in the preparation method of the aluminum nitride-supported cobalt nitrogen-carbon catalyst, the molar ratio of the cobalt nitrate hexahydrate, folic acid, AlN, ethanol, and water in step (1) is 1:1:1:1:1.

[0007] Furthermore, in the preparation method of the aluminum nitride-supported cobalt-nitrogen-carbon catalyst, the stirring speed in step (2) is 1000-1300 r / min.

[0008] Furthermore, in the above-mentioned preparation method of aluminum nitride-supported cobalt-nitrogen-carbon catalyst, the hydrothermal temperature in step (3) is 140° C. and the temperature is kept for 2 h.

[0009] Furthermore, in the preparation method of the above aluminum nitride-supported cobalt nitrogen-carbon catalyst, the centrifugal parameters in step (4) are: 10,000 r / min, time 3 min; the washing conditions are: washing with deionized water 3 to 5 times; the drying temperature is -60°C, and the time is 12-15 h.

[0010] Furthermore, in the preparation method of the aluminum nitride-supported cobalt-nitrogen-carbon catalyst, the calcination temperature in step (5) is 800° C. and the calcination time is 2 h.

[0011] The second technical solution provided by the present invention is an aluminum nitride-supported cobalt-nitrogen-carbon catalyst prepared by the above method.

[0012] The catalyst is used in a method for catalytically degrading formaldehyde. The catalytic conditions are: formaldehyde concentration of 100 ppm, space velocity of 22 200 mL / (g·h), and reaction temperature of 30°C.

[0013] The AlN / CoNC catalyst provided by the present invention is applied to the field of room temperature thermal catalysis. The catalyst has a certain catalytic efficiency for monomeric small molecule organic matter and can be used to degrade common organic pollutants in the air.

[0014] Compared with the prior art, the technical solution provided by the present invention has the following technical advantages: (1) Only transition metals are used in the preparation process, which greatly reduces the cost price; (2) AlN / CoNC is calcined at high temperature in nitrogen to obtain highly dispersed active sites, thereby improving its ability to adsorb oxygen and improve its ability to degrade formaldehyde; (3) The catalyst preparation cost is low, the preparation conditions are simple, the operation is convenient, and it is easy to scale up production in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the synthesis of AlN / CoNC catalyst; Figure 2 are nitrogen adsorption / desorption curves of AlN / CoNC of Examples 1-5; Figure 3 is the pore size distribution of AlN / CoNC of Examples 1-5; Figure 4 H2-TPR of AlN / CoNC of Examples 1-5; Figure 5 is the O2-TPD of AlN / CoNC of Examples 1-5. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be described in detail below through specific embodiments, but it should be clearly stated that these embodiments are for illustration and are not to be construed as limiting the scope of the present invention.

[0017] Example 1: This example provides a method for preparing an AlN / CoNC catalyst for thermal catalytic formaldehyde degradation, which is prepared by the following method: Take 0.7278g Co(NO3)2·6H2O, 1.104g folic acid, and 0.0513g AlN and add them to 55mL deionized water and 80mL ethanol solution; The above solution was stirred on a magnetic stirrer at 1000-1300 r / min for half an hour; The obtained solution was placed in a reactor for hydrothermal reaction. The hydrothermal conditions were: keeping the temperature at 140°C for two hours and cooling naturally to room temperature. Centrifuge, wash with deionized water, freeze-dry to obtain a solid product. The centrifugal parameters are: 10000 r / min, time 3min; washing conditions are: wash with deionized water 3 to 5 times; drying temperature is -60°C, time is 12-15h. ; The solid product was calcined under nitrogen atmosphere to obtain a finished product at a temperature of 800°C and a calcination time of 2 hours. The obtained sample is denoted as AlN 1 / 2 / CoNC.

[0018] Example 2: This example provides a method for preparing an AlN / CoNC catalyst for thermal catalytic formaldehyde degradation, which is prepared by the following method: Take 0.7278g Co(NO3)2·6H2O, 1.104g folic acid, and 0.1025g AlN and add them to 55mL deionized water and 80mL ethanol solution; (2) stirring the above solution on a magnetic stirrer at 1000-1300 r / min for half an hour; (3) placing the obtained solution into a reactor for hydrothermal reaction at 140° C. for two hours and then cooling naturally to room temperature; (4) Centrifugation, washing with deionized water, and freeze-drying to obtain a solid product. The centrifugation parameters are: 10,000 r / min, time 3 min; washing conditions are: washing with deionized water 3 to 5 times; drying temperature is -60°C, time is 12 to 15 h. (5) The solid product was calcined under nitrogen atmosphere to obtain a finished product at a temperature of 800° C. for 2 h. The obtained sample was denoted as AlN1 / CoNC.

[0019] Example 3: This example provides a method for preparing an AlN / CoNC catalyst for thermal catalytic formaldehyde degradation, which is prepared by the following method: (1) Take 0.7278 g Co(NO3)2·6H2O, 1.104 g folic acid, and 0.41 g AlN and add them to 55 mL deionized water and 80 mL ethanol solution; (2) stirring the above solution on a magnetic stirrer at 1000-1300 r / min for half an hour; (3) placing the obtained solution into a reactor for hydrothermal reaction at 140° C. for two hours and then cooling naturally to room temperature; (4) Centrifugation, washing with deionized water, and freeze-drying to obtain a solid product. The centrifugation parameters are: 10,000 r / min, time 3 min; washing conditions are: washing with deionized water 3 to 5 times; drying temperature is -60°C, time is 12 to 15 h. (5) The solid product was calcined in a nitrogen atmosphere to obtain a finished product at a calcination temperature of 800° C. for 2 h. The obtained sample was denoted as AlN4 / CoNC.

[0020] Example 4: This example provides a method for preparing an AlN / CoNC catalyst for thermal catalytic formaldehyde degradation, which is prepared by the following method: (1) Take 0.7278 g Co(NO3)2·6H2O, 1.104 g folic acid, and 0.82 g AlN and add them to 55 mL deionized water and 80 mL ethanol solution; (2) stirring the above solution on a magnetic stirrer at 1000-1300 r / min for half an hour; (3) placing the obtained solution into a reactor for hydrothermal reaction at 140° C. for two hours and then cooling naturally to room temperature; (4) Centrifugation, washing with deionized water, and freeze-drying to obtain a solid product. The centrifugation parameters are: 10,000 r / min, time 3 min; washing conditions are: washing with deionized water 3 to 5 times; drying temperature is -60°C, time is 12 to 15 h. (5) The solid product is calcined under nitrogen atmosphere at 800°C for 2 h to obtain a finished product. The obtained sample is denoted as AlN8 / CoNC.

[0021] Example 5: This example provides a method for preparing an AlN / CoNC catalyst for thermal catalytic formaldehyde degradation, which is prepared by the following method: (1) Take 0.1025 g AlN and add it to 55 mL deionized water and 80 mL ethanol solution; (2) stirring the above solution on a magnetic stirrer at 1000-1300 r / min for half an hour; (3) placing the obtained solution into a reactor for hydrothermal reaction at 140° C. for two hours and then cooling naturally to room temperature; (4) Centrifugation, washing with deionized water, and freeze-drying to obtain a solid product. The centrifugation parameters are: 10,000 r / min, time 3 min; washing conditions are: washing with deionized water 3 to 5 times; drying temperature is -60°C, time is 12 to 15 h. (5) The solid product is calcined under nitrogen atmosphere to obtain a finished product at a calcination temperature of 800°C and a calcination time of 2 h. The obtained sample is denoted as AlNC.

[0022] Table 1 Activity evaluation results of AlN / CoNC catalysts sample Example 1 Example 2 Example 3 Example 4 Example 5 Reaction conditions <![CDATA[Room temperature 100 ppm 2220 h -1 > <![CDATA[Room temperature 100 ppm 2220 h -1 > <![CDATA[Room temperature 100 ppm 2220 h -1 > <![CDATA[Room temperature 100 ppm 2220 h -1 > <![CDATA[Room temperature 100 ppm 2220 h -1 > Conversion rate 66 100 88 74 76 Examples 1-5 all used the hydrothermal + calcination method to prepare AlN / CoNC, and compared the effects of different AlN loadings on the catalyst activity, where only AlN was added in Example 5. As can be seen from the table, the formaldehyde conversion rates of the catalysts in Examples 1, 3, 4, and 5 under the same conditions were not as high as those in Example 2; this indicates that adding a suitable proportion of AlN is beneficial to formaldehyde catalysis. Therefore, Example 2 provides a thermal catalyst with excellent activity.

[0023] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing an aluminum nitride-supported cobalt-nitrogen-carbon catalyst, characterized in that: The following steps are included in sequence: (1) preparing a mixed solution of cobalt nitrate hexahydrate, folic acid, AlN, ethanol and water; (2) Stir the above solution for half an hour; (3) placing the obtained solution into a reaction kettle for hydrothermal reaction; (4) centrifuging, washing with deionized water, and freeze-drying to obtain a solid product; (5) calcining the solid product under a nitrogen atmosphere to obtain a finished product; The invention belongs to the technical field of thermal catalytic materials and environmental protection.

2. The method for preparing the aluminum nitride supported cobalt nitrogen carbon catalyst according to claim 1, characterized in that: The molar ratio of cobalt nitrate hexahydrate, folic acid, AlN, ethanol and water in step (1) is 1:1:1:1:

1.

3. The method for preparing the aluminum nitride supported cobalt nitrogen carbon catalyst according to claim 1, characterized in that: The stirring speed described in step (2) is 1000-1300r / min.

4. The method for preparing the aluminum nitride supported cobalt nitrogen carbon catalyst according to claim 1, characterized in that: The hydrothermal temperature in step (3) is 140°C and the temperature is kept for 2 h.

5. The method for preparing the aluminum nitride supported cobalt nitrogen carbon catalyst according to claim 1, characterized in that: The centrifugal parameters in step (4) are: 10000 r / min, time 3 min; the washing conditions are: washing with deionized water 3 to 5 times; the drying temperature is -60°C, and the time is 12-15 h.

6. The method for preparing the aluminum nitride supported cobalt nitrogen carbon catalyst according to claim 1, characterized in that: In step (5), the calcination temperature is 800° C. and the calcination time is 2 h.

7. An aluminum nitride-supported cobalt-nitrogen-carbon catalyst, characterized in that: The method is prepared by any one of claims 1 to 6.

8. A method for catalytic degradation of formaldehyde using the aluminum nitride supported cobalt nitrogen carbon catalyst according to claim 7, characterized in that: The catalytic conditions are: formaldehyde concentration of 100 ppm, space velocity of 22200 mL / (g·h), and reaction temperature of 30°C.

9. The aluminum nitride supported cobalt nitrogen carbon catalyst provided by the present invention is applied to the field of room temperature thermal catalysis. The catalyst has a certain catalytic efficiency for monomeric small molecule organic matter and can be used to degrade common organic pollutants in the air.

Images