Preparation method of molecular oxygen activation catalyst and application thereof

Abstract

A preparation method of a molecular oxygen activation catalyst and application thereof. The method is as follows: Zn(NO3)2.6H2O, Na2MoO4.2H2O and Co(NO3)2.6H2O are fully dissolved in methanol, denoted as solution A; 2-methylimidazole is fully dissolved in methanol, denoted as solution B; solution B is rapidly injected into solution A, after stirring at normal temperature for 30 min, the mixed solution is hydrothermally treated at 100 DEG C for 3 h; the product is centrifuged, washed and vacuum dried at 80 DEG C for 8 h to obtain a purple powder; the powder is placed in a tube furnace and calcined at 950 DEG C in N2 for 2 h, thereby obtaining a diatomic catalyst. The prepared nitrogen-doped carbon material catalyst with bimetallic sites Co@CMCN can efficiently activate molecular oxygen, so that the molecular oxygen directly or indirectly participates in the degradation process of organic matter. The Co@CMCN / aeration system only needs to be aerated to complete the removal of ibuprofen in water, which is a very green and environmentally friendly pollutant removal method, has good environmental and economic benefits, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry and catalytic function preparation, and particularly relates to a preparation method of a novel molecular oxygen activation catalyst and application of the catalyst in degradation of ibuprofen through activation of O2. BACKGROUND

[0002] Traditional advanced oxidation processes have been widely applied to wastewater treatment plants, and oxidants such as H2O2, PMS, PS and O3 are activated to active oxygen (ROS) to directly or indirectly participate in the degradation process of organic matter. However, the above several oxidants still face limitations such as storage, transportation, production cost and the like. Therefore, from the perspective of green development, it is necessary to develop a more green and inexpensive ROS activation technology.

[0003] Oxygen (O2) is the most environmentally friendly oxidant, accounting for about 21% of air. However, it is difficult for molecular oxygen to directly participate in catalytic reactions at room temperature, mainly because: on the one hand, O2 dissolved in water has poor adsorption capacity on the surface of the catalyst, and is difficult to be captured by the active site; on the other hand, paramagnetic molecular O2 has a triplet ground state, and it is a very difficult process to activate it, which requires changing the spin triplet ground state of O2 and filling the antibonding orbital to lower the kinetic stability of O2. Therefore, how to quickly and efficiently activate molecular oxygen has become a key problem restricting the use of O2 at this stage. At present, some strategies for artificially activating O2 have been proposed, which reduce the energy barrier and accelerate the kinetics of the reaction by external energy input, so that molecular oxygen is converted into ROS through the path of electron transfer or energy transfer, thereby removing pollutants in water bodies. However, the continuous input of external energy has certain difficulties for practical application.

[0004] At present, some studies directly add metals, chemical reducing agents (HA, etc.) or chelate transition metal catalysts through chelating agent sodium tripolyphosphate (TPP) in the reaction medium to improve the O2 activation capacity of the catalyst, however, these homogeneous reaction systems also bring adverse effects on the convenience and environmental safety of the actual application of the reaction system. SUMMARY

[0005] The purpose of the present application is to solve the problems of low molecular oxygen activation efficiency and large energy loss, and to provide a preparation method of a novel molecular oxygen activation catalyst (Co@CMCN) and its application in removing pollutants in water. In the catalyst, Co and Mo species are coordinated with graphite carbon through Co-Nx and Mo-Nx, respectively, and O2 is captured and activated through Co-Nx and Mo-Nx sites. Unlike other systems that require additional energy input and homogeneous catalytic reaction systems, the Co@CMCN / Air system only needs to remove pollutants in water through aeration, which is a very green and environmentally friendly means of removing organic matter. The method involves a simple process, is non-toxic and environmentally friendly, and is suitable for popularization and application.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a novel molecular oxygen activation catalyst, the method comprising the following steps:

[0008] Step one: Zn(NO3)2·6H2O, Na2MoO4·2H2O and Co(NO3)2·6H2O are fully dissolved in methanol, denoted as solution A; 2-methylimidazole is fully dissolved in methanol, denoted as solution B;

[0009] Step two: solution B in step one is rapidly injected into solution A, after stirring at room temperature for 30-60 min, the mixed solution is transferred to a Teflon-lined stainless steel autoclave for hydrothermal treatment;

[0010] Step three: the product in step two is centrifuged, washed (with methanol and deionized water), and dried in a vacuum drying box to obtain a purple powder;

[0011] Step four: the powder in step three is placed in a tube furnace and calcined under inert gas to obtain a molecular oxygen activation catalyst (Co@CMCN). During pyrolysis, the organic linker of the MOF undergoes thermal decomposition during high-temperature annealing, and the nitrogen dopant is doped into the carbon skeleton. Subsequently, due to the low boiling point of Zn, it can be gasified to generate defects and pores, Co and Mo replace the sites of Zn, and the occupation of Zn can effectively hinder the aggregation of Co and Mo species.

[0012] Further, in step one, the concentration of solution A is 61.5 g / L, the concentration of solution B is 73.7 g / L, and the ratio of the three solutes in solution A is zinc nitrate:sodium molybdate: cobalt nitrate = 24.6:1:2.9-11.6.

[0013] Further, in step two, the stirring temperature is 25-35℃, the stirring speed is 450 r / min, the stirring time is 30 min, the hydrothermal temperature is 100℃, and the hydrothermal time is 3h; the volume ratio of solution A to solution B is 4:3.

[0014] Further, in step three, the centrifugal speed is 8000-9000 r / min, the washing agent is methanol and deionized water, the drying temperature is 50-80℃, and the drying time is 8-12h.

[0015] Further, in step four, the protective gas is N2, the calcination temperature is 950℃, the heating rate is 5℃ / min, and the calcination time is 2h.

[0016] A novel molecular oxygen activation catalyst prepared by the above method.

[0017] Application of the above-mentioned novel molecular oxygen-activated catalyst in the degradation of ibuprofen by activated O2.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention prepares a nitrogen-doped Co-Mo diatomic carbon material, which has a dodecahedral structure and cobalt and molybdenum active sites are uniformly distributed on the surface.

[0020] (2) The Co-Mo diatomic catalyst prepared in this invention opens up the transfer pathway of O2 on the catalyst surface, which can rapidly activate O2. In the Co@CMCN / Air system, molecular oxygen can be rapidly converted by the Co / Mo-N atoms on the catalyst surface. x Site trapping, and due to surface anchoring effects, molecular oxygen is activated into ·O2. - Subsequently, it adsorbs onto the catalyst surface, at which point the Mo-N at adjacent sites... x It can quickly convert O2 - In situ transformation 1 O2. Since both of these processes occur on the catalyst surface, the catalytic reaction proceeds rapidly. Furthermore, Mo-N... x The site accelerated the Co reaction process. 2+ / Co 3+ The cycling and electron transfer make the Co-Mo bimetallic structure more advantageous in this catalytic system.

[0021] (3) The catalyst prepared in this invention has the ability to efficiently activate molecular oxygen to generate... 1 O2 exhibits higher tolerance to aqueous substrates and a relatively long lifespan, and also demonstrates a high capacity for removing organic matter in high-concentration brine, indicating that this catalyst has significant application potential.

[0022] (4) The Co@CMCN catalyst prepared in this invention is magnetic, and can be directly recycled and reused using a magnet. After recycling, the catalyst still has good catalytic activity. The reusability of the Co@CMCN / Air system in ibuprofen removal was evaluated by adding a regenerated sample at the same concentration as under normal conditions. After four cycles, the ibuprofen removal efficiency can still reach more than 80%; and the cumulative inflow and outflow of Co and Mo are only 0.9 and 3.2 ug / L, respectively, indicating that the Co@CMCN catalyst can be reused, has a very broad application prospect, and will not cause secondary pollution to the environment. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope image of Co-2@CMCN obtained in Example 1;

[0024] Figure 2is an XRD pattern of Co-2@CMCN obtained in Example 1;

[0025] Figure 3 is an XRD pattern of CoCN obtained in Comparative Example 1;

[0026] Figure 4 is an XRD pattern of MoCN obtained in Comparative Example 2. DETAILED DESCRIPTION

[0027] Some examples are given below to illustrate the technical solutions described in the present application. The examples are only illustrative of the technical solutions, so as to be understood, and cannot limit the present application, which can be implemented in various different ways limited and covered by the claims.

[0028] The bimetallic site nitrogen-doped carbon material catalyst Co@CMCN prepared in the present application can efficiently activate molecular oxygen, so that the molecular oxygen directly or indirectly participates in the degradation process of organic matter as active oxygen. The Co@CMCN / aeration system only needs to be aerated to complete the removal of ibuprofen in the water body, and is a very green and environmentally friendly pollutant removal means, which has good environmental and economic benefits, and has a broad application prospect.

[0029] Example 1

[0030] A preparation method of a new molecular oxygen activation catalyst Co@CMCN (mass ratio of Na2MoO4·2H2O to Co(NO3)2·6H2O is 1:5.8) comprises the following steps:

[0031] (1) 2.46g Zn(NO3)2·6H2O, 0.10g Na2MoO4·2H2O and 0.58g Co(NO3)2·6H2O are fully dissolved in 40mL methanol, and the solution is recorded as solution A; 2.21g 2-methylimidazole is fully dissolved in 30mL methanol, and the solution is recorded as solution B;

[0032] (2) solution B in (1) is quickly injected into solution A, and after stirring at room temperature for 30min, the mixed solution is transferred to a 100mL Teflon-lined stainless steel autoclave for hydrothermal treatment, the hydrothermal temperature is 100℃, and the hydrothermal time is 3h;

[0033] (3) the product in (2) is centrifuged, washed, and dried in a vacuum drying box (80℃) for 8h to obtain a purple powder;

[0034] (4) the powder in (3) is placed in a tube furnace and calcined in N2, the calcination temperature is 950℃, the heating rate is 5℃ / min, and the calcination time is 2h, to obtain a diatomic catalyst (Co-2@CMCN).

[0035] The product obtained in the example was analyzed by X-ray diffraction characterization, and the results are shown in Figure 1 It can be observed from the figure that there are characteristic peaks of Co element. The product obtained in the example was subjected to morphology and structure characterization of the composite material by scanning electron microscopy, and the results are shown in Figure 2 The synthesized composite material is a dodecahedron structure.

[0036] Example 2

[0037] A preparation method of a new molecular oxygen activation catalyst Co@CMCN (mass ratio of Na2MoO4·2H2O and Co(NO3)2·6H2O is 1:11.6) includes the following steps:

[0038] (1) 2.46g Zn(NO3)2·6H2O, 0.10g Na2MoO4·2H2O and 1.16g Co(NO3)2·6H2O were fully dissolved in 40mL methanol, denoted as solution A; 2.21g 2-methylimidazole was fully dissolved in 30mL methanol, denoted as solution B;

[0039] (2) Solution B in (1) was quickly injected into solution A, and after stirring at room temperature for 30min, the mixed solution was transferred to a 100mL Teflon-lined stainless steel autoclave for hydrothermal treatment, the hydrothermal temperature was 100℃, and the hydrothermal time was 3h;

[0040] (3) The product in (2) was centrifuged, washed, and dried in a vacuum drying box (80℃) for 8h to obtain a purple powder;

[0041] (4) The powder in (3) was placed in a tube furnace and calcined in N2, the calcination temperature was 950℃, the heating rate was 5℃ / min, and the calcination time was 2h, to obtain a diatomic catalyst (Co-3@CMCN).

[0042] Example 3

[0043] A preparation method of a new molecular oxygen activation catalyst Co@CMCN (mass ratio of Na2MoO4·2H2O and Co(NO3)2·6H2O is 1:2.9) includes the following steps:

[0044] (1) 2.46g Zn(NO3)2·6H2O, 0.10g Na2MoO4·2H2O and 0.29g Co(NO3)2·6H2O were fully dissolved in 40mL methanol, denoted as solution A; 2.21g 2-methylimidazole was fully dissolved in 30mL methanol, denoted as solution B;

[0045] (2) The solution B in (1) was quickly injected into the solution A, and after stirring at room temperature for 30 min, the mixed solution was transferred into a 100 mL Teflon-lined stainless steel autoclave for hydrothermal treatment at 100°C for 3 h;

[0046] (3) The product in (2) was centrifuged, washed, and dried in a vacuum drying box (80°C) for 8 h to obtain a purple powder;

[0047] (4) The powder in (3) was placed in a tube furnace and calcined in N2at a calcination temperature of 950°C and a heating rate of 5°C / min for 2 h to obtain the diatomic catalyst (Co-1@CMCN).

[0048] Comparative Example 1

[0049] The preparation method of CoCN is as follows:

[0050] (1) 2.46 g of Zn(NO3)2·6H2O and 0.58 g of Co(NO3)2·6H2O were fully dissolved in 40 mL of methanol, denoted as solution A; 2.21 g of 2-methylimidazole was fully dissolved in 30 mL of methanol, denoted as solution B;

[0051] (2) The solution B in (1) was quickly injected into the solution A, and after stirring at room temperature for 30 min, the mixed solution was transferred into a 100 mL Teflon-lined stainless steel autoclave for hydrothermal treatment at 100°C for 3 h;

[0052] (3) The product in (2) was centrifuged, washed, and dried in a vacuum drying box (80°C) for 8 h to obtain a purple powder;

[0053] (4) The powder in (3) was placed in a tube furnace and calcined in N2at a calcination temperature of 950°C and a heating rate of 5°C / min for 2 h to obtain the diatomic catalyst (CoCN).

[0054] The product obtained in this example was analyzed by X-ray diffraction characterization, and the results are shown in Figure 3 , and no peak of Co element was observed in the figure.

[0055] Comparative Example 2

[0056] The preparation method of MoCN is as follows:

[0057] (1) 2.46 g of Zn(NO3)2·6H2O and 0.10 g of Na2MoO4·2H2O were fully dissolved in 40 mL of methanol, denoted as solution A; 2.21 g of 2-methylimidazole was fully dissolved in 30 mL of methanol, denoted as solution B;

[0058] (2) The solution B in (1) was quickly injected into solution A, and after stirring at room temperature for 30 min, the mixed solution was transferred to a 100 mL Teflon-lined stainless steel autoclave for hydrothermal treatment at 100°C for 3 h;

[0059] (3) The product in (2) was centrifuged, washed, and dried in a vacuum drying box (80°C) for 8 h to obtain a purple powder;

[0060] (4) The powder in (3) was placed in a tube furnace and calcined in N2at a temperature of 950°C with a heating rate of 5°C / min for 2 h to obtain the diatomic catalyst (MoCN).

[0061] The product obtained in this example was analyzed by X-ray diffraction characterization, and the results are shown in Figure 4 , and no peak of elemental Mo was observed in the figure.

[0062] Application Example

[0063] The materials obtained in Examples 1-3 and Comparative Examples 1-2 were applied to experiments for removing ibuprofen from water by activating molecular oxygen, which specifically included the following steps:

[0064] Experimental conditions: 10 mL of a 10 ppm ibuprofen solution was prepared, the pH of the solution was adjusted to 5, and 0.02 g of the material obtained in Examples 1-3 and Comparative Examples 1-2 was added as a catalyst. The experimental group and the control group were reacted under aeration (air) and N2conditions, respectively, and samples were taken at 0.5, 1, 1.5, 2, 3, and 5 min of reaction, and the concentration of residual ibuprofen in the solution was detected by liquid chromatography. The mobile phase was 20% acetic acid aqueous solution (0.1%) and 80% methanol solution, and the detection wavelength was 225 nm.

[0065] Table 1 is a comparison table of reaction rate constants and reaction efficiencies of ibuprofen removal obtained in Examples 1-3 and Comparative Examples 1-2

[0066]

[0067] As can be seen from Table 1, after adding the Co-2@CMCN catalyst, the reaction rate constant of ibuprofen removal reached 0.494 min -1 , and the removal efficiency reached 98.3%, which was greatly improved compared with the single metal catalysts CoCN and MoCN. This shows that the synergistic effect of Co-Mo double sites not only can achieve rapid activation of O2, but also can complete the rapid transport of ·O2 - on the surface of the catalyst, so that ·O2 - is rapidly converted into H2O2 on the adjacent Mo-N x site after being generated. 1O2, thereby enabling rapid removal of ibuprofen in high salt water.

[0068] The above are only implementation examples of the method, and cannot limit the scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application, therefore all equivalent technical solutions also belong to the scope of the present application, the patent protection scope of the present application should be limited by the claims, and should be included in the protection scope of the present application.

Claims

1. Use of a molecular oxygen activation catalyst in the activation of O2 to degrade ibuprofen, characterized in that: The preparation method of the molecular oxygen activation catalyst comprises the following steps: Step one: Zn(NO3)2·6H2O, Na2MoO4·2H2O and Co(NO3)2·6H2O are fully dissolved in methanol, denoted as solution A; 2-methylimidazole is fully dissolved in methanol, denoted as solution B; Step two: solution B in step one is rapidly injected into solution A, and after stirring at room temperature for 30-60 min, the mixed solution is transferred to a Teflon-lined stainless steel autoclave for hydrothermal treatment; Step three: the product in step two is centrifuged, washed, and dried in a vacuum drying box to obtain a purple powder; Step four: the powder in step three is placed in a tube furnace and calcined under N2 to obtain the molecular oxygen activation catalyst.

2. Use according to claim 1, characterized in that: In step one, the concentration of solution A is 61.5 g / L, the concentration of solution B is 73.7 g / L, and the ratio of the three solutes in solution A is zinc nitrate:sodium molybdate:cobalt nitrate = 24.6:1:2.9-11.

6.

3. Use according to claim 1, characterized in that: In step two, the stirring speed is 450 r / min, the stirring time is 30 min, the hydrothermal temperature is 100℃, and the hydrothermal time is 3 h; the volume ratio of solution A to solution B is 4:

3.

4. Use according to claim 1, characterized in that: In step three, the centrifugal speed is 8000-9000 r / min, the washing agent is methanol and deionized water, the drying temperature is 50-80℃, and the drying time is 8-12 h.

5. The use according to claim 1, characterized in that: In step four, the calcination temperature is 950℃, the heating rate is 5℃ / min, and the calcination time is 2 h.

Images