Preparation method and application of a non-noble metal sub-nanocluster catalyst

Abstract

A preparation method of a non-noble metal sub-nanocluster catalyst comprises the following steps: S1. Mix a non-noble metal salt with a binary metal oxide hollow sphere having a porous structure, impregnate and dry under vacuum conditions, and metal ions are adsorbed onto the binary metal oxide hollow sphere having a porous structure; S2. Calcinate the material obtained in step S1 under N2 conditions to load the active component metal onto the carrier. The preparation process of the present invention is simple, easy to operate, and low in cost. The prepared non-noble metal sub-nanocluster catalyst supported on a porous binary metal oxide hollow sphere has good catalytic activity and good stability for refractory organic wastewater. The present invention provides a new method for obtaining a non-noble metal catalyst with high activity and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly relates to a preparation method and application of a non-noble metal sub-nanocluster catalyst. Background Art

[0002] Water pollution caused by the discharge of refractory organic wastewater has become an urgent environmental problem. Advanced oxidation is the main technical means for treating such pollution problems. Compared with other advanced oxidation agents, electrochemical oxidation methods, etc., the low-temperature catalytic air oxidation technology uses oxygen as an oxidant and uses noble metal catalysts to accelerate the oxidation of complex organic substances under low-temperature conditions. This method has a simple, clean and economical process and has good development prospects. However, noble metal catalysts based on Au, Ag, and Ru are expensive, which limits their commercial potential. Therefore, the development of stable and inexpensive catalysts is a key step in realizing catalytic air oxidation. In order to overcome the problems of low catalytic activity of ordinary non-noble metal nanoparticles and high cost of noble metals, developing a non-noble metal catalyst with multiple exposed active sites is a feasible method. Single-atom catalysts have the highest specific surface area and high catalytic efficiency, but the smaller the particle size, the easier it is to agglomerate, which in turn affects the stability and continuous catalytic performance of the material. Therefore, catalysts can be developed in the form of sub-nanoclusters. The effective utilization of metal catalysts is a key issue for heterogeneous catalysts. Small-sized sub-nanoclusters will lay the foundation for the subsequent improvement of catalytic activity. However, currently, the clusters obtained by the ordinary impregnation preparation method of sub-nanoclusters are prone to aggregation, the hydrothermal synthesis preparation method is relatively difficult to operate, and the electrochemical deposition preparation method is relatively complex. Summary of the Invention

[0003] Aiming at the problems of low activity and unstable structure of current non-noble metal catalysts, the present invention provides a simple and effective preparation method for non-noble metal sub-nanocluster catalysts.

[0004] A preparation method for a non-noble metal sub-nanocluster catalyst includes the following steps:

[0005] S1. Mix a non-noble metal salt with a binary metal oxide hollow sphere having a porous structure, impregnate and dry under vacuum conditions, and the metal ions are adsorbed onto the binary metal oxide hollow sphere having a porous structure;

[0006] S2. Calcinate the material obtained in step S1 under N 2 conditions to load the active component metal onto the carrier.

[0007] Furthermore:

[0008] The non-noble metal salt is any one of copper chloride, copper nitrate, iron chloride, iron nitrate, cobalt chloride, cobalt nitrate, nickel chloride, and nickel nitrate.

[0009] The binary metal oxide is TiZrO 4 , TiWO x , TiCeO 4 Any one of them.

[0010] The binary metal oxide hollow sphere containing a porous structure is obtained by subjecting SiO 2 loaded with binary metal oxide to gradient calcination in a muffle furnace at 500 °C - 700 °C, treating it with a 2.5 mol / L alkali solution for 12 - 16 h, and then washing it to neutrality.

[0011] In step S1, the drying is impregnation drying at 40 °C - 80 °C, preferably 60 °C, for 20 - 24 h.

[0012] In step S2, the calcination is carried out at 400 °C under N 2 conditions.

[0013] The metal content of the active component is 1.55 wt% - 4.93 wt%.

[0014] It further includes the following steps:

[0015] S3. Effectively coating the non-noble metal sub-nanocluster catalyst with oligomeric SiO 2 .

[0016] A non-noble metal sub-nanocluster catalyst is prepared by the preparation method of the non-noble metal sub-nanocluster catalyst described above. The catalyst includes a carrier and an active component; the carrier is a porous binary metal oxide hollow sphere; the active component includes Cu, Fe, Co, and Ni.

[0017] The non-noble metal sub-nanocluster catalyst described above is applied to the catalytic degradation of refractory organic wastewater.

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

[0019] The present invention proposes an innovative solution of a "vacuum impregnation - calcination" method to embed non-noble metal sub-nanocluster active components (such as Cu, Fe, Co, Ni, etc.) into porous titanium oxide-based hollow sphere nanomaterials (such as TiZrO 4 , TiWO x , TiCeO 4 , etc.). By constructing an embedded structure to form a multi-channel confinement structure to alleviate the aggregation of active components and improve the dispersion of sub-nanoclusters; further, using oligomeric SiO 2The protection can improve the stability of the catalyst while exerting its unique catalytic oxidation performance. The pressure difference generated by the vacuum impregnation method removes impurities and moisture in the pores of the catalytic carrier from the center, increasing the dispersion and loading of metal sub-nanoclusters. This preparation method has the characteristics of simple operation, high efficiency, and low cost.

[0020] Compared with the traditional preparation methods, the preparation process of the present invention is simple and the cost is low. A non-noble metal sub-nanocluster catalyst with high activity and high stability is obtained by a more convenient method, making the non-noble metal catalyst have a broader application prospect.

[0021] The present invention can be used for the catalytic degradation of refractory organic wastewater. A series of test data prove that a non-noble metal sub-nanocluster catalyst with high activity and high stability is obtained by this method. Description of the Drawings

[0022] Figure 1 is the XRD diffraction pattern of the porous structure TiZrO 4 hollow sphere, TiZrO 4 @Cu sub-nanocluster catalyst;

[0023] Figure 2 is the electron microscope image of the TiZrO 4 @Cu sub-nanocluster catalyst with a Cu content of 4.93 wt% prepared in Example 1;

[0024] Figure 3 is the synchrotron radiation characterization image of the TiZrO 4 @Cu sub-nanocluster catalyst with a Cu content of 4.93 wt% prepared in Example 1;

[0025] Figure 4 is the TEM image of the TiZrO 2 with different SiO 4 thicknesses prepared in Example 3 2 @Cu@SiO

[0026] Figure 5 is the TiZrO 4 @Cu and TiZrO 4 @Cu@SiO 2 catalyst's electrochemical impedance image. Detailed Embodiments

[0027] The present invention will be further described in detail below through examples, but the protection scope of the present invention is not limited to the content described.

[0028] An embodiment of the present invention provides a method for preparing a non-noble metal sub-nanocluster catalyst, wherein the catalyst comprises a support and an active component; the support is a porous binary metal oxide hollow sphere; the active component comprises Cu, Fe, Co, and Ni. In this method, a metal salt is mixed with a porous binary metal oxide hollow sphere, impregnated and dried under vacuum conditions, and metal ions are adsorbed onto the porous binary metal oxide hollow sphere. After drying, it is calcined under N 2 conditions by a segmented programmed temperature rise, and a porous channel confinement structure is constructed on the surface of the binary metal oxide hollow sphere. The porous structure sites effectively anchor and confine the metal sub-nanoclusters, improving the dispersion of the sub-nanoclusters. Finally, a low-polymer SiO 2 layer is coated to enable the stable existence of the metal sub-nanoclusters and prevent them from agglomerating easily during the catalytic process. The preparation process is simple, easy to operate, and low in cost. The prepared non-noble metal sub-nanocluster catalyst supported on a porous binary metal oxide hollow sphere has good catalytic activity and stability for refractory organic wastewater. The present invention provides a new method for obtaining a non-noble metal catalyst with high activity and low cost.

[0029] Example 1: Preparation of a non-noble metal sub-nanocluster catalyst

[0030] Taking the Cu-loaded porous TiZrO 4 support as an example for detailed description

[0031] 1. At room temperature, 20 mL of deionized water, 5 mL of ammonia water, and 100 mL of isopropanol are mixed and stirred to form a clear solution; 5 mL of tetraethyl orthosilicate is added to the above solution, and it is vigorously stirred for 5 min to form a homogeneous solution, and then stirred at room temperature for 12 h. SiO 2 spheres are obtained by centrifugation, then washed 3 times with ethanol, and dried overnight under vacuum for use.

[0032] 2. Weigh 1.6 g of SiO 2 spheres and ultrasonically disperse them in 50 mL of ethanol for standby. Weigh 0.01 g of hydroxypropyl cellulose and 0.5 mL of deionized water in turn, dissolve them in 100 mL of ethanol under magnetic stirring; then add 50 mL of the SiO 2 sphere dispersion in turn, and ultrasonically disperse for 15 min; under magnetic stirring, use a syringe to add 50 mL of a mixed alcohol solution of tetrabutyl titanate (2.5 mL) and zirconium butoxide (2.5 mL) respectively, place it in a water bath at 85 °C and reflux for 2 h; the product is centrifuged and washed 3 times with ethanol and dried under vacuum; finally, SiO 2 @TiZrO 4 composite materials are obtained by calcination (calcination parameters: 5 °C / min, 500 °C for 2 h + 700 °C for 2 h, air).

[0033] 3. SiO2 @TiZrO 4 The composite material is etched in 2.5 M NaOH to remove SiO 2 After the spherical template is removed, TiZrO 4 hollow spheres are obtained for standby.

[0034] 4. Different concentrations of CuCl 2 solutions (0.074 mol / L, 0.223 mol / L, 0.372 mol / L) are impregnated in the TiZrO 4 catalyst. After vacuum impregnation and drying at 60 °C for 20 - 24 h, the temperature is increased at a rate of 5 °C / min and calcined at 400 °C under N 2 for 3 h. Finally, porous hollow sphere TiZrO 4 @Cu sub-nanocluster catalysts (the Cu content corresponding to 0.074 mol / L is 1.55 wt%, the Cu content corresponding to 0.223 mol / L is 3.08 wt%, and the Cu content corresponding to 0.374 mol / L is 4.93 wt%) are obtained. For subsequent characterization and catalysis, the Cu catalyst with 4.93 wt% is used.

[0035] Figure 1 For TiZrO 4 and TiZrO 4 @Cu catalysts, the X-ray diffraction patterns (XRD) are shown. Through stepwise calcination at 500 °C and 700 °C, the diffraction peaks of TiO 4 in TiZrO 4 and TiZrO 2 @Cu belong to the anatase type and appear at 24.9°, 37.1°, 40.5°, 53.5° and 54.9° (JCPDS NO.21 - 1272) respectively. The diffraction peaks of the tetragonal phase of ZrO 4 in TiZrO 4 and TiZrO 2 @Cu appear at 30.5°, 35.5°, 50.2° and 60.7° (JCPDS 50 - 1089). By comparing the XRD patterns, it can be found that there are new characteristic peaks in the patterns of TiZrO 4 and TiZrO 4 @Cu. According to the XRD standard card of (Ti-Zr)O 4 (JCPDS 80 - 1783), the weak diffraction peaks marked with squares belong to the diffraction peaks of (Ti-Zr)O 4 , which indicates the existence of Ti-O-Zr bonds in TiZrO 4 and TiZrO 4 @Cu. Among them, the position of the diffraction peak at 45.2° belongs to TiZrO 4The metallic Cu in @Cu. The weak intensity of the Cu metal diffraction peak indicates that the metal nanoparticles are well-dispersed on the support.

[0036] Figure 2 is TiZrO 4 The electron microscopy images of the @Cu sub-nanocluster catalyst, where (a) is the TEM image; (b) is the spherical aberration electron microscopy image. The bright spots of the cluster size in the HAADF-STEM image can confirm that the Cu sub-nanoclusters are uniformly dispersed on the surface of TiZrO 4 surface.

[0037] Figure 3 is TiZrO 4 The X-ray absorption near-edge spectroscopy (XANES) of @Cu, and the K-edge XANES curve of Cu shows that in the @Cu catalyst of TiZrO 4 the absorption edge position of the Cu atoms in the @Cu catalyst is between CuO and Cu foil, indicating that the Cu atoms in the @Cu catalyst of TiZrO 4 @Cu catalyst carry a positive charge.

[0038] The above results indicate that the Cu sub-nanoclusters are successfully synthesized in the support TiZrO 4 and exist in the porous structure, indicating that the highly stable sub-nanocluster Cu-based catalyst is successfully synthesized;

[0039] Example 2: Catalytic oxidation of organic wastewater using the sub-nanocluster Cu-based catalyst

[0040] The organic wastewater is 100 mL of a 100 mg / L humic acid solution. The reactor is carried out in a three-necked round-bottom flask and operates in a completely mixed mode. The concentration of the @Cu catalyst in the reactor is 3 g / L, the reaction temperature is 90 °C, air is introduced, and the air flow rate is 0.3 L / min. After reacting for 3 hours, the final effluent is detected, and the removal rate of total organic carbon (TOC) is 89%. 4 @Cu catalyst concentration is 3 g / L, the reaction temperature is 90 °C, air is introduced, the air flow rate is 0.3 L / min. After reacting for 3 hours, the final effluent is detected, and the removal rate of total organic carbon (TOC) is 89%.

[0041] The organic wastewater has a chemical oxygen demand (COD) of 115 mg / L of leachate solution, 100 mL. The reactor is carried out in a three-necked round-bottom flask and operates in a completely mixed mode. The concentration of the @Cu catalyst in the reactor is 3 g / L, the reaction temperature is 90 °C, pH = 3, air is introduced, and the air flow rate is 0.3 L / min. After reacting for 5 hours, the final effluent is detected, and the removal rate of COD is 80%. 4 @Cu catalyst concentration is 3 g / L, the reaction temperature is 90 °C, pH = 3, air is introduced, the air flow rate is 0.3 L / min. After reacting for 5 hours, the final effluent is detected, and the removal rate of COD is 80%.

[0042] The organic wastewater has a COD of 1353 mg / L of biogas slurry solution. The reactor is carried out in a three-necked round-bottom flask and operates in a completely mixed mode. The concentration of the @Cu catalyst in the reactor is 4@The concentration of the Cu catalyst was 3 g / L, the reaction temperature was 90 °C, air was introduced, the oxygen flow rate was 0.3 L / min, and after reacting for 5 hours, the removal rate of chemical oxygen demand (COD) in the final effluent was detected to be 63%.

[0043] Example 3: Coating of sub-nanocluster catalyst with SiO 2 Preparation

[0044] By oligomeric SiO 2 coating to further improve the stability of the sub-nanocluster catalyst, the TiZrO obtained in Example 1 4 @Cu was further coated with SiO 2 .

[0045] At room temperature, 0.5 g of the TiZrO 4 @Cu catalyst was uniformly dispersed in a mixed solution of 20 mL of deionized water and 100 mL of isopropanol; different volumes of tetraethyl orthosilicate (1.5 mL, 1.0 mL, 0.5 mL, 0.3 mL) were slowly added to the above solution using a syringe, and the mixture was vigorously stirred for 5 min to form a homogeneous solution, which was then continuously stirred at room temperature for 12 h. The product was obtained by centrifugation, then washed 3 times with ethanol, and dried overnight under vacuum for use. According to the above method, TiZrO 2 @Cu@SiO 4 catalysts coated with different oligomeric SiO 2 thicknesses were prepared.

[0046] Figure 4 For TiZrO 2 @Cu@SiO 4 catalysts with different oligomeric SiO 2 thicknesses. The TEM images can confirm that the Cu sub-nanoclusters are uniformly dispersed on the surface of TiZrO 4 and are uniformly coated with SiO 2 with different thicknesses.

[0047] Figure 5 is the electrochemical impedance diagram of the TiZrO 4 @Cu and TiZrO 4 @Cu@SiO 2 catalysts. Electrochemical impedance means are used to characterize the influence of the catalyst on the electron transfer rate on the surface of the nanomaterial. After the TiZrO 4 @Cu was coated with SiO 2 , the arc radius on the electrochemical impedance spectrum did not increase, indicating that the electron transfer ability on the catalyst surface did not decrease, further proving that SiO 2 will not affect the catalytic performance while improving the stability of the catalyst.

[0048] Example 4: Using sub-nanocluster TiZrO 4 @Cu@SiO 2 Catalytic oxidation of organic wastewater by the catalyst

[0049] The organic wastewater is a biogas slurry solution with a COD of 1353 mg / L. The reactor is carried out in a three-necked round-bottom flask and operates in a completely mixed mode. The concentration of TiZrO 4 @Cu@SiO 2 in the catalyst in the reactor is 3 g / L, the reaction temperature is 90 °C, air is introduced, the oxygen flow rate is 0.3 L / min. After reacting for 5 hours, the final effluent is detected, and the removal rate of chemical oxygen demand (COD) is 60%.

[0050] As mentioned above, these are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed with preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art, without departing from the technical solution of the present application, makes some changes or modifications using the disclosed technical content, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A preparation method of a non-noble metal sub-nanocluster catalyst, characterized in that, it comprises the following steps: S1. Mix a non-noble metal salt with a binary metal oxide hollow sphere having a porous structure, and under vacuum conditions, impregnate and dry at 40°C - 80°C for 20 - 24 h so that metal ions are adsorbed onto the binary metal oxide hollow sphere having a porous structure; the binary metal oxide is any one of TiZrO 4 , TiWO x , TiCeO 4 . S2. Calcinate the material obtained in step S1 under N 2 conditions to load the active component metal onto the support, obtaining a non-noble metal sub-nanocluster catalyst.

2. The preparation method of the non-noble metal sub-nanocluster catalyst according to claim 1, characterized in that: The non-noble metal salt is any one of copper chloride, copper nitrate, iron chloride, iron nitrate, cobalt chloride, cobalt nitrate, nickel chloride, nickel nitrate.

3. The preparation method of the non-noble metal sub-nanocluster catalyst according to claim 1, characterized in that: The binary metal oxide hollow spheres containing porous structures are prepared by subjecting SiO 2 supported binary metal oxides to gradient calcination in a muffle furnace at 500 °C - 700 °C, treating them with a 2.5 mol / L alkali solution for 12 - 16 h, and then washing them until neutrality.

4. The preparation method of the non-noble metal sub-nanocluster catalyst according to claim 1, characterized in that: In step S1, the drying is impregnation drying at 60 °C.

5. The preparation method of the non-noble metal sub-nanocluster catalyst according to claim 1, characterized in that: In step S2, the calcination is carried out at 400 °C under the condition of N 2 condition.

6. The preparation method of the non-noble metal sub-nanocluster catalyst according to claim 1, characterized in that: The active component metal content is 1.55 wt% - 4.93 wt%.

7. The preparation method of the non-noble metal sub-nanocluster catalyst according to any one of claims 1 to 6, characterized in that: It further comprises the following steps: S3. Coating the non-noble metal sub-nanocluster catalyst with oligomeric SiO 2 ​ 8. A non-noble metal sub-nanocluster catalyst, characterized in that: It is prepared by the preparation method of the non-noble metal sub-nanocluster catalyst according to any one of claims 1-7. The catalyst comprises a carrier and an active component; the carrier is a porous binary metal oxide hollow sphere; the active component comprises Cu, Fe, Co, Ni.

9. The non-noble metal sub-nanocluster catalyst according to claim 8 is applied to the catalytic degradation of refractory organic wastewater.

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