A noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater and a preparation method thereof

Abstract

The present invention discloses a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater and a preparation method thereof. First, a zirconium precursor is uniformly mixed with a pore-forming agent, and then kneaded and extruded into a shape with titanium dioxide, a binder, a peptizing agent, and a shaping aid, and the obtained product is subjected to high-temperature calcination and hydrogen reduction to obtain a strip-shaped TiO2-ZrO2 support. Then, an impregnating solution containing noble metal and alkali metal is used for equal-volume impregnation, and finally, it is obtained through drying, calcination, and reduction. The present invention uses TiO2-ZrO2 as the support, which can have good stability under high-temperature acidic and alkaline reaction conditions, ensuring that the noble metal catalyst does not deactivate during long-term reactions; the pre-reduction treatment of the support increases the number of reduced TiO2, which can improve catalytic activity, enhance electron transfer, increase active sites, optimize noble metal dispersion, and improve catalyst stability, so that the noble metal catalyst can be better applied in catalytic wet oxidation reactions.

Description

Technical Field

[0001] The present invention relates to a noble metal catalyst for catalytic wet air oxidation of high-concentration organic wastewater and a preparation method thereof, belonging to the technical fields of environmental protection catalysts and wastewater treatment. Technical Background

[0002] Catalytic Wet Air Oxidation (CWAO) is a method that adds a suitable catalyst to the traditional wet oxidation treatment process to enable the oxidation reaction to be completed under milder conditions and in a shorter time. This can reduce the reaction temperature and pressure, improve the oxidation decomposition ability, accelerate the reaction rate, shorten the residence time, and thus reduce equipment corrosion and operating costs. The core technology of catalytic wet air oxidation is the development of efficient and stable catalysts. At present, catalytic wet air oxidation technology is divided into homogeneous and heterogeneous catalytic wet air oxidation according to the existence form of the catalyst. Early research mainly focused on homogeneous catalysts, and the catalysts were mostly soluble transition metal salts such as Cu, Mn, Fe, Co, and Ni. Their advantages are high activity and fast reaction speed, but they are difficult to recover and easily cause secondary pollution, resulting in problems such as complex process flow and increased wastewater treatment costs. Therefore, since the late 1970s, the research focus of catalytic wet air oxidation reaction has shifted to heterogeneous catalytic wet air oxidation reaction, and the catalysts are mainly supported noble metals (such as Pt and Ru) and transition metal oxides (such as Cu, Ce, and Mn). Although noble metal catalysts have higher costs, they have unparalleled high efficiency compared to transition metal oxides, so they are widely used in catalytic wet air oxidation reactions. However, noble metal catalysts will be poisoned due to carbonaceous deposition and metal loss in the catalytic wet air oxidation reaction, resulting in a decrease in catalyst activity and stability, directly affecting the industrial application of catalytic wet air oxidation technology. Therefore, the research and development of catalysts with low noble metal content, high activity, and high stability is the key to further promoting catalytic wet air oxidation technology.

[0003] CN108435174A discloses a catalyst for treating high-concentration organic wastewater, a preparation method thereof, and an application. The catalyst preparation method is improved in the following two aspects to reduce the noble metal loading: using APTES to functionalize and modify the surface of the carrier to form adsorption sites for adsorbing noble metal compounds; introducing an Ag promoter to alloy noble metals such as Pd and Au to reduce their agglomeration degree during calcination. The catalyst is heated to the reaction temperature of 280 °C at a heating rate of 1 °C / min in an air atmosphere, the reaction pressure is 8 MPa, the concentration of wastewater organic matter is 36509 mg / L, and the liquid hourly space velocity LHSV = 0.5 h -1 , and the air hourly space velocity is 50 h -1, a COD removal efficiency of 96.5% can be achieved. Although this catalyst can achieve a high catalytic efficiency with a low noble metal content, the preparation process route is long and not suitable for actual industrial applications.

[0004] CN103521222A discloses a heterogeneous catalytic wet oxidation catalyst and its preparation method. A mixed solution of cerium salt, zirconium salt and titanium salt is co-precipitated with ammonia water to form a gel substance, which is filtered, washed, dried and calcined to form a cerium-zirconium-titanium composite support, and noble metals are loaded onto the support by the impregnation method, and the catalyst is obtained after calcination and reduction. This catalyst can achieve a COD removal efficiency of 90.8% under the conditions of a reaction temperature of 260 °C, a reaction pressure of 7 MPa and a gas-liquid volume ratio of 150. However, a large amount of organic matter is contained in the preparation process by the sol-gel method, and toxic and harmful gases will be released during the processes such as calcination, which cannot be realized in industrial production.

[0005] CN106268789A discloses a supported noble metal ruthenium mesoporous carbon catalyst, its preparation method and its application in catalytic oxidation of phenol-containing wastewater. A phenolic resin, a template agent, hydrochloric acid and water are mixed to prepare a carbon precursor solution, and supported noble metal ruthenium is added to the carbon precursor solution, and then it is washed, dried and calcined in a non-oxidizing atmosphere to obtain the catalyst. This catalyst has a large pore volume, a high specific surface area and a relatively uniform pore size distribution, and can achieve a removal rate of 98% for a 4000 mg / L phenol solution under the working conditions of a reaction temperature of 140 °C, an oxygen partial pressure of 0.5 MPa and a reaction time of 4 h. However, a large amount of toxic and harmful gases will be generated during the anaerobic calcination of phenolic resin, and the powdery catalyst is also not conducive to industrial application.

[0006] In summary, aiming at the problems of high noble metal content and poor stability existing in the catalytic wet oxidation noble metal catalysts, the existing technologies mostly start from aspects such as improving the noble metal dispersion and regulating the composition and structure of the support. They generally have problems such as complex preparation processes and easy generation of toxic and harmful substances during the preparation process, which are not conducive to industrial production and application. Summary of the Invention

[0007] The purpose of the present invention is to provide a noble metal catalyst and a preparation method for wet catalytic oxidation of high-concentration organic wastewater, so as to overcome the defects of the existing wet catalytic oxidation noble metal catalysts and make them suitable for industrial production and application.

[0008] The preparation method of the wet catalytic oxidation noble metal catalyst of the present invention includes the following steps:

[0009] (1) Preparation of a zirconium precursor pore-forming agent

[0010] The zirconium precursor solution is mixed evenly with the pore-forming agent, followed by rotary evaporation and drying to obtain the pore-forming agent loaded with the zirconium precursor. Among them, the zirconium precursor is at least one of zirconium oxychloride, zirconyl nitrate, zirconium acetate, and zirconium acetylacetonate. The pore-forming agent is at least one of polyethylene glycol, starch, polyoxyethylene, carboxymethyl cellulose, and activated carbon. The dosage of the pore-forming agent is 5% - 100% of the mass of the zirconium precursor calculated based on the molecular weight of ZrO2.

[0011] (2)Preparation of TiO2-ZrO2 support

[0012] The pore-forming agent loaded with the zirconium precursor is first dry-mixed with titanium dioxide, binder, peptizing agent, and forming aid, then water is added for wet mixing, followed by kneading, vacuum pugging, aging, extrusion molding, drying, calcination, and reduction to obtain a strip-shaped TiO2-ZrO2 support.

[0013] Among the above raw materials, industrial titanium dioxide is used for titanium dioxide. The dosage of the zirconium precursor is calculated based on the molecular weight of ZrO2 and is 5% - 20% of the mass of titanium dioxide in the titanium dioxide.

[0014] The binder is at least one of pseudo-boehmite, silica sol, natural clay, paraffin, and polyvinyl alcohol. The dosage of the binder is 15% - 45% of the mass of titanium dioxide in the titanium dioxide. The peptizing agent is at least one of nitric acid, hydrochloric acid, formic acid, and acetic acid. The dosage of the peptizing agent is 2% - 10% of the mass of titanium dioxide in the titanium dioxide. The forming aid is at least one of sesbania powder, polyanionic cellulose, hydroxyethyl cellulose, and xanthan gum. The dosage of the forming aid is 2% - 10% of the mass of titanium dioxide in the titanium dioxide.

[0015] In the preparation process, the kneading process is to fully mix the materials in a small kneader. The vacuum pugging process is to refine and extrude the materials and degas them in a vacuum pugmill to obtain dense plastic materials. The aging is to stand at room temperature for 24 - 48 h. The extrusion molding is to carry out strip extrusion molding on a twin-screw extruder. The drying is to dry at 60 - 120 °C for 6 - 12 h. The calcination is to calcine in an air atmosphere at 400 - 650 °C for 4 - 10 h. The reduction is to reduce in a hydrogen-nitrogen mixed gas phase (the volume fraction of hydrogen in the mixed gas phase is 5% - 20%) at 300 - 800 °C for 6 - 12 h.

[0016] (3)The TiO2-ZrO2 support is impregnated with an impregnating solution containing a noble metal salt and an alkali metal, and then dried and reduced to obtain a wet catalytic oxidation noble metal catalyst.

[0017] The noble metal salt is at least one of chloride salts and acetylacetonate salts of Pt, Rh, Pd, and Ru. The dosage of the noble metal salt is calculated based on the mass percentage of the noble metal element in the catalyst being 0.05% - 1%. The alkali metal salt is at least one of sodium nitrate, potassium nitrate, and cesium nitrate, and the dosage of the alkali metal salt is calculated based on the mass percentage of the noble metal in the catalyst being 2% - 20%.

[0018] The drying is carried out at 60 - 120 °C for 12 - 24 h; the reduction is carried out in a hydrogen-nitrogen mixed gas phase (the volume fraction of hydrogen in the gas phase is 5% - 20%) at 300 - 600 °C for 2 - 5 h.

[0019] The experimental results show that the catalyst prepared by the present invention can achieve a degradation and removal efficiency of more than 90% for wastewater with a concentration of 23000 mg / L at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h, and a catalyst concentration of 4 g / L. Moreover, the noble metal loading of the catalyst of the present invention is low, the production cost is low, the catalyst has good stability, and has broad application prospects.

[0020] In summary, the technical solution of the present invention has the following advantages compared with the prior art:

[0021] (1) The noble metals on the catalyst have good dispersion and low loading. The dispersion and stability of noble metal catalysts are greatly related to the pore structure, thermal stability, and chemical stability of the carrier. Because the industrial conditions of catalytic wet air oxidation reaction are harsh, the catalyst has to be immersed in high-temperature and high-pressure wastewater for a long time, and due to the intermediate product of catalytic wet air oxidation reaction being small molecule carboxylic acid, its strong acidity is also unbearable for many common catalyst carriers. The present invention uses TiO2-ZrO2 as the carrier, which can have good stability under high-temperature acidic and alkaline reaction conditions, and can ensure that the noble metal catalyst does not deactivate during long-term reaction;

[0022] (2) The catalyst has high catalytic activity due to the large number of surface oxygen vacancies. The TiO2-ZrO2 carrier pre-reduced at high temperature in a hydrogen atmosphere can increase the number of surface oxygen vacancies of the carrier, and the oxygen vacancies play a key role in the catalytic wet air oxidation reaction. The oxygen vacancies help the oxygen in the liquid phase migrate to the catalytic active center, and can also directly participate in the oxygen activation process on the catalyst surface, resulting in the generation of highly active oxygen species such as superoxides and peroxides, thereby improving the catalytic reaction efficiency. In addition, the pre-reduction treatment of the carrier will increase the number of reduced TiO2, and the reduced TiO2 plays multiple roles in the noble metal catalytic reaction, such as improving catalytic activity, improving electron transfer, increasing active sites, optimizing noble metal dispersion, and improving the stability of noble metal catalysts, enabling the noble metal catalyst to be better applied in the catalytic wet air oxidation reaction;

[0023] (3) The catalyst can inhibit poisoning and has good stability. Adding alkali metal promoters can induce electron-rich noble metals to form noble metal-oxygen-alkali metal species with them, thereby enhancing the stability of noble metals, increasing the dispersion of noble metals, and inhibiting their agglomeration during the reaction. In addition, alkali metals can slow down the carbonaceous deposition phenomenon of noble metal catalysts and maintain the high efficiency and long-term stability of the catalysts through various ways such as adjusting the surface acidity and alkalinity of the catalyst, optimizing the active sites of the catalyst, and influencing the adsorption behavior of carbonaceous substances in the wet catalytic oxidation reaction of noble metal catalysts;

[0024] (4) The catalyst preparation process is simple and easy for industrial production. The present invention adopts a process of preloading a zirconium source on a pore-forming agent first and then kneading it with a titanium source for one-step extrusion molding. The operation is simple and the cost is low, which is suitable for large-scale production. Then, high-temperature treatment with oxygen causes the pyrolysis of the pore-forming agent loaded with zirconium precursors, expanding the pores and making zirconia evenly distributed on the surface of titanium oxide. Compared with the method of preparing a titanium-zirconium composite support by loading a zirconium source on the surface of titanium oxide, this method maximally retains the porous structure of the support, which is beneficial to improving the dispersion of noble metals, thereby reducing the noble metal loading and the catalyst cost. Compared with the common co-precipitation method and sol-gel method, this process can accurately control the particle size of the support, the preparation period is moderate, and there is no environmental problem of three-waste treatment. Specific Embodiments

[0025] The following further illustrates the preparation and application performance of the catalyst of the present invention through specific examples, but the catalyst described in the present invention is not limited to the examples.

[0026] Example 1

[0027] (1) Take 9.4 g of zirconyl nitrate and 3.2 g of zirconium oxychloride and dissolve them in distilled water, then add 2 g of activated carbon and 1 g of starch to it and stir evenly; Rotate and evaporate the mixed solution in a water bath at 60 °C for 1 h, and then dry it in an oven under an air atmosphere at 100 °C for 12 h. The obtained solid is the pore-forming agent loaded with zirconium;

[0028] (2) The pore-forming agent loaded with zirconium obtained in step (1) is dry-mixed with 100 g of industrial titanium dioxide, 32 g of pseudo-boehmite, 4 g of natural clay, 4 g of sesbania powder and 2 g of polyanionic cellulose, and then 88 g of distilled water, 6 g of nitric acid (65%) and 3 g of hydrochloric acid (37%) are added for wet mixing and kneading. After vacuum pugging and aging, it is extruded and formed on a twin-screw extruder. Then the formed carrier is air-dried for 24 h, dried at 105 °C for 12 h in an oven under air atmosphere, then calcined at 550 °C for 5 h in air atmosphere, and finally placed in a tubular furnace and reduced at 500 °C for 6 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain a strip-shaped TiO2-ZrO2 carrier;

[0029] (3) The carrier obtained in step (2) is impregnated in an aqueous solution containing 0.16 g of ruthenium chloride, 0.03 g of platinum chloride, 0.03 g of sodium nitrate and 0.02 g of potassium nitrate by the equal-volume impregnation method. The impregnation time is 12 h, and then it is air-dried for 12 h, then dried at 110 °C for 12 h in an oven under air atmosphere, and finally placed in a tubular furnace and calcined at 350 °C for 3 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain catalyst A-1;

[0030] (4) The degradation and removal efficiency of catalyst A-1 for wastewater with a concentration of 23000 mg / L is 95% at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h and a catalyst concentration of 4 g / L (Table 1).

[0031] Example 2

[0032] (1) 16.1 g of zirconium oxychloride and 8.2 g of zirconium acetate are dissolved in distilled water, and then 2 g of activated carbon and 2 g of polyethylene glycol are added and stirred evenly; the mixed solution is rotary-evaporated in a water bath at 60 °C for 1 h, and then dried at 100 °C for 24 h in an oven under air atmosphere. The obtained solid is the pore-forming agent loaded with zirconium;

[0033] (2) The pore-forming agent loaded with zirconium obtained in step (1) is dry-mixed with 100 g of industrial titanium dioxide, 25 g of pseudo-boehmite, 15 g of paraffin, 3 g of sesbania powder and 2 g of polyanionic cellulose, and then 70 g of distilled water, 7 g of nitric acid (65%) and 2 g of acetic acid are added for wet mixing and kneading. After vacuum pugging and aging, it is extruded and formed on a twin-screw extruder; then the formed carrier is air-dried for 24 h, dried at 105 °C for 12 h in an oven under air atmosphere, then calcined at 500 °C for 6 h in air atmosphere, and finally placed in a tubular furnace and reduced at 600 °C for 5 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain a strip-shaped TiO2-ZrO2 carrier;

[0034] (3) The carrier obtained in step (2) was impregnated by the equal-volume impregnation method into an aqueous solution containing 0.14 g of ruthenium chloride, 0.12 g of rhodium acetylacetonate, 0.04 g of sodium nitrate, and 0.02 g of potassium nitrate. The impregnation time was 12 h. Then it was air-dried for 12 h, then dried in an oven under an air atmosphere at 110 °C for 12 h, and finally placed in a tubular furnace and calcined at 400 °C for 3 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain catalyst A-2;

[0035] (4) The degradation and removal efficiency of catalyst A-2 for wastewater with a concentration of 23000 mg / L was 93% under the reaction temperature of 250 °C, reaction pressure of 6 MPa, reaction time of 2 h, and catalyst concentration of 4 g / L (Table 1).

[0036] Example 3

[0037] (1) 15 g of zirconium acetate and 5 g of zirconium oxyhydroxide were dissolved in distilled water, and then 2 g of activated carbon and 2 g of polyethylene oxide were added thereto and stirred evenly. The mixture was rotary evaporated in a water bath at 60 °C for 1 h, and then dried in an oven under an air atmosphere at 100 °C for 24 h. The obtained solid was the pore-forming agent loaded with zirconium;

[0038] (2) The pore-forming agent loaded with zirconium obtained in step (1) was dry-mixed with 100 g of industrial titanium dioxide, 28 g of pseudo-boehmite, 5 g of silica sol, 4 g of sesbania powder, and 2 g of hydroxyethyl cellulose, and then 80 g of distilled water and 5.2 g of nitric acid (65%) were added for wet mixing and kneading. After vacuum pugging and aging, it was extruded and formed on a twin-screw extruder. Then the formed carrier was air-dried for 24 h, dried in an oven under an air atmosphere at 105 °C for 12 h, then calcined in an air atmosphere at 500 °C for 5 h, and finally placed in a tubular furnace and reduced at 600 °C for 5 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain a strip-shaped TiO2-ZrO2 carrier;

[0039] (3) The carrier obtained in step (2) was impregnated by the equal-volume impregnation method into an aqueous solution containing 0.08 g of platinum chloride, 0.08 g of palladium chloride, 0.02 g of potassium nitrate, and 0.04 g of sodium nitrate. The impregnation time was 12 h. Then it was air-dried for 12 h, then dried in an oven under an air atmosphere at 110 °C for 12 h, and finally placed in a tubular furnace and calcined at 350 °C for 3 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain catalyst A-3;

[0040] (4) The degradation and removal efficiency of catalyst A-3 for wastewater with a concentration of 23000 mg / L was 94% under the reaction temperature of 250 °C, reaction pressure of 6 MPa, reaction time of 2 h, and catalyst concentration of 4 g / L (Table 1).

[0041] Example 4

[0042] (1) Take 12 g of zirconyl nitrate and 6 g of zirconium acetate and dissolve them in distilled water. Then add 1 g of activated carbon and 1 g of starch to it and stir evenly. Rotavaporize the mixture in a water bath at 60 °C for 1 h, and then dry it in an oven under an air atmosphere at 100 °C for 12 h. The obtained solid is the pore-forming agent loaded with zirconium;

[0043] (2) Dry-mix the pore-forming agent loaded with zirconium obtained in step (1) with 100 g of industrial titanium dioxide, 26 g of pseudoboehmite, 8 g of paraffin wax, 3 g of sesbania powder and 2 g of xanthan gum, then add 85 g of distilled water, 5 g of nitric acid (65%) and 2 g of acetic acid for wet mixing and kneading. After vacuum pugging and aging, extrude and form on a twin-screw extruder. Then air-dry the formed carrier for 24 h, dry it in an oven under an air atmosphere at 105 °C for 12 h, then calcine it in an air atmosphere at 550 °C for 5 h, and finally place it in a tubular furnace and reduce it at 400 °C for 6 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain a strip-shaped TiO2-ZrO2 carrier;

[0044] (3) Impregnate the carrier obtained in step (2) into an aqueous solution containing 0.16 g of ruthenium chloride, 0.08 g of rhodium acetylacetonate, 0.04 g of sodium nitrate and 0.01 g of potassium nitrate by the equal-volume impregnation method. The impregnation time is 12 h, then air-dry it for 12 h, then dry it in an oven under an air atmosphere at 110 °C for 12 h, and finally place it in a tubular furnace and calcine it at 300 °C for 3 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain catalyst A-4;

[0045] (4) The degradation and removal efficiency of catalyst A-4 for wastewater with a concentration of 23000 mg / L is 93% at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h and a catalyst concentration of 4 g / L (Table 1).

[0046] Example 5

[0047] (1) Take 9.4 g of zirconyl nitrate and 4.2 g of zirconium acetylacetonate and dissolve them in distilled water. Then add 4 g of activated carbon and 2 g of carboxymethyl cellulose to it and stir evenly. Rotavaporize the mixture in a water bath at 60 °C for 1 h, and then dry it in an oven under an air atmosphere at 100 °C for 12 h. The obtained solid is the pore-forming agent loaded with zirconium;

[0048] (2) The pore-forming agent loaded with zirconium obtained in step (1) is dry-mixed with 100 g of industrial titanium dioxide, 32 g of pseudo-boehmite, 6 g of polyvinyl alcohol, 5 g of sesbania powder, and 2 g of hydroxyethyl cellulose, and then 88 g of distilled water, 6 g of nitric acid (65%), and 2 g of formic acid are added for wet mixing and kneading. After vacuum pugging and aging, it is extruded into strips on a twin-screw extruder; then the formed carrier is air-dried for 24 h, dried at 105 °C for 12 h in an oven under an air atmosphere, then calcined at 500 °C for 5 h in an air atmosphere, and finally placed in a tubular furnace and reduced at 550 °C for 6 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain a strip-shaped TiO2-ZrO2 carrier;

[0049] (3) The carrier obtained in step (2) is impregnated in an aqueous solution containing 0.16 g of ruthenium chloride, 0.08 g of rhodium acetylacetonate, 0.04 g of sodium nitrate, and 0.01 g of potassium nitrate by the equal-volume impregnation method. The impregnation time is 12 h, and then it is air-dried for 12 h, then dried at 110 °C for 12 h in an oven under an air atmosphere, and finally placed in a tubular furnace and calcined at 350 °C for 3 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain catalyst A-5;

[0050] (4) The degradation and removal efficiency of catalyst A-5 for wastewater with a concentration of 23000 mg / L is 94% at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h, and a catalyst concentration of 4 g / L (Table 1).

[0051] Example 6

[0052] (1) Take 12 g of zirconyl nitrate and 3 g of zirconium acetate and dissolve them in distilled water, and then add 3 g of activated carbon and 1 g of starch and stir evenly; the mixture is rotary evaporated in a water bath at 60 °C for 1 h, and then dried at 100 °C for 12 h in an oven under an air atmosphere. The obtained solid is the pore-forming agent loaded with zirconium;

[0053] (2) The pore-forming agent loaded with zirconium obtained in step (1) is dry-mixed with 100 g of industrial titanium dioxide, 24 g of pseudo-boehmite, 6 g of natural clay, 4 g of sesbania powder, and 2 g of polyanionic cellulose, and then 76 g of distilled water, 6.5 g of nitric acid (65%), and 2 g of acetic acid are added for wet mixing and kneading. After vacuum pugging and aging, it is extruded into strips on a twin-screw extruder; then the formed carrier is air-dried for 24 h, dried at 105 °C for 12 h in an oven under an air atmosphere, then calcined at 550 °C for 5 h in an air atmosphere, and finally placed in a tubular furnace and reduced at 500 °C for 6 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction is 10%) to obtain a strip-shaped TiO2-ZrO2 carrier;

[0054] (3) The carrier obtained in step (2) was impregnated in an aqueous solution containing 0.16 g of ruthenium chloride, 0.08 g of rhodium acetylacetonate, 0.04 g of sodium nitrate, and 0.01 g of potassium nitrate by the equal-volume impregnation method. The impregnation time was 12 h, followed by air drying for 12 h, then drying in an oven under an air atmosphere at 110 °C for 12 h, and finally calcined in a tubular furnace at 350 °C for 3 h in a hydrogen-nitrogen mixed atmosphere (hydrogen volume fraction of 10%) to obtain catalyst A-6;

[0055] (4) The degradation and removal efficiency of catalyst A-6 for wastewater with a concentration of 23000 mg / L was 95% at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h, and a catalyst concentration of 4 g / L (Table 1).

[0056] Comparative Example 1

[0057] (1) 2 g of activated carbon, 100 g of industrial titanium dioxide, 32 g of pseudoboehmite, and 4 g of sesbania powder were taken for dry mixing, and then 88 g of distilled water and 6 g of nitric acid (65%) were added for wet mixing and kneading. After vacuum pugging and aging, extrusion molding was carried out on a twin-screw extruder. The formed carrier was air-dried for 24 h, dried in an oven under an air atmosphere at 105 °C for 12 h, and then calcined in an air atmosphere at 550 °C for 5 h to obtain a bar-shaped TiO2 carrier;

[0058] (2) The carrier obtained in step (1) was added to a solution containing 9.4 g of zirconyl nitrate and stirred, then rotary evaporated, dried in an oven under an air atmosphere at 105 °C for 12 h, and then calcined in an air atmosphere at 550 °C for 5 h. Finally, it was placed in a tubular furnace and reduced at 500 °C for 6 h in a hydrogen-nitrogen mixed atmosphere with a hydrogen volume fraction of 10% to obtain a bar-shaped TiO2-ZrO2 carrier;

[0059] (3) The carrier obtained in step (2) was impregnated in an aqueous solution containing 0.2 g of ruthenium chloride and 0.05 g of potassium nitrate by the equal-volume impregnation method. The impregnation time was 12 h, followed by air drying for 12 h, then drying in an oven under an air atmosphere at 110 °C for 12 h, and finally calcined in a tubular furnace at 350 °C for 3 h in a hydrogen-nitrogen mixed atmosphere with a hydrogen volume fraction of 10% to obtain catalyst DB-1;

[0060] (4) The degradation and removal efficiency of catalyst DB-1 for wastewater with a concentration of 23000 mg / L was 83% at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h, and a catalyst concentration of 4 g / L (Table 1).

[0061] Comparative Example 2

[0062] (1) Dissolve 9.4 g of zirconyl nitrate in distilled water, then add 2 g of activated carbon thereto and stir evenly. Rotavaporize the mixture in a water bath at 60 °C for 1 h, and then dry it in an oven under an air atmosphere at 100 °C for 12 h for standby;

[0063] (2) Take the solid obtained in step (1) and dry-mix it with 100 g of industrial titanium dioxide, 32 g of pseudo-boehmite and 4 g of sesbania powder, then add 88 g of distilled water and 6 g of nitric acid (65%) for wet mixing and kneading. After vacuum pugging and aging, carry out extrusion molding treatment on a twin-screw extruder. Air-dry the formed carrier in air for 24 h, dry it in an oven under an air atmosphere at 105 °C for 12 h, and then calcine it in an air atmosphere at 550 °C for 5 h to obtain a strip-shaped TiO₂-ZrO₂ carrier;

[0064] (3) Immerse the carrier obtained in step (2) in an aqueous solution containing 0.2 g of ruthenium chloride and 0.05 g of potassium nitrate by the equal-volume impregnation method for 12 h, then air-dry it for 12 h, then dry it in an oven under an air atmosphere at 110 °C for 12 h, and finally place it in a tubular furnace and calcine it in a hydrogen-nitrogen mixed atmosphere at 350 °C for 3 h, where the volume fraction of hydrogen is 10% to obtain catalyst DB-2;

[0065] (4) The degradation and removal efficiency of catalyst DB-2 for wastewater with a concentration of 23000 mg / L is 80% at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h, and a catalyst concentration of 4 g / L (Table 1).

[0066] Comparative Example 3

[0067] (1) Dissolve 9.4 g of zirconyl nitrate in distilled water, then add 2 g of activated carbon thereto and stir evenly. Rotavaporize the mixture in a water bath at 60 °C for 1 h, and then dry it in an oven under an air atmosphere at 100 °C for 12 h for standby;

[0068] (2) Take the solid obtained in step (1) and dry-mix it with 100 g of industrial titanium dioxide, 32 g of pseudo-boehmite and 4 g of sesbania powder, then add 88 g of distilled water and 6 g of nitric acid (65%) for wet mixing and kneading. After vacuum pugging and aging, carry out extrusion molding treatment on a twin-screw extruder. Air-dry the formed carrier in air for 24 h, dry it in an oven under an air atmosphere at 105 °C for 12 h, and then calcine it in an air atmosphere at 550 °C for 5 h to obtain a strip-shaped TiO₂-ZrO₂ carrier;

[0069] (3) The carrier obtained in step (2) was impregnated in an aqueous solution containing 0.2 g of ruthenium chloride by the equal-volume impregnation method. The impregnation time was 12 h, followed by air drying for 12 h, then drying in an oven under an air atmosphere at 110 °C for 12 h, and finally calcined in a tubular furnace at 350 °C for 3 h in a hydrogen-nitrogen mixed atmosphere, where the volume fraction of hydrogen was 10%, to obtain the catalyst DB-3;

[0070] (4) The degradation and removal efficiency of the catalyst DB-3 for the wastewater with a concentration of 23000 mg / L was 85% at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h, and a catalyst concentration of 4 g / L (Table 1).

[0071]

[0072] As can be seen from Table 1, the COD removal performance of the catalysts prepared in Examples 1-6 was far superior to that of Comparative Examples 1-3, and a degradation and removal efficiency of more than 90% could be achieved for the wastewater with a concentration of 23000 mg / L at a reaction temperature of 250 °C, a reaction pressure of 6 MPa, a reaction time of 2 h, and a catalyst concentration of 4 g / L.

[0073] In the present invention, titanium dioxide, binder, peptizing agent, pore-forming agent, shaping aid, zirconium precursor, platinum precursor, ruthenium precursor, palladium precursor, sodium precursor, potassium precursor, and cesium precursor are all common raw materials for preparing industrial catalysts in the prior art. The technical indicators of the raw materials can be selected according to the actual process conditions and equipment characteristics, and no special limitations are imposed in the present invention.

Claims

1. A preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater, comprising the following steps: (1)Preparation of zirconium precursor-loaded pore former: The zirconium precursor solution is mixed evenly with the pore former, followed by rotary evaporation and drying to obtain the zirconium precursor-loaded pore former; (2)Preparation of TiO2-ZrO2 support: The zirconium precursor-loaded pore former is first dry-mixed with titanium dioxide, binder, peptizing agent, and forming aid, then water is added for wet mixing, followed by kneading, vacuum pugging, aging, extrusion molding, drying, calcination, and reduction to obtain a strip-shaped TiO2-ZrO2 support; (3)The TiO2-ZrO2 support is impregnated with an impregnating solution containing noble metal salt and alkali metal salt, and then dried and reduced to obtain a wet catalytic oxidation noble metal catalyst.

2. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (1), the zirconium precursor is at least one of zirconium oxychloride, zirconyl nitrate, zirconium acetate, and zirconium acetylacetonate; the pore former is at least one of polyethylene glycol, starch, polyoxyethylene, carboxymethyl cellulose, and activated carbon, and the dosage of the pore former is 5% - 100% of the mass of ZrO2 in the zirconium precursor.

3. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (2), the dosage of the zirconium precursor is calculated based on the molecular weight of ZrO2 and is 5% - 20% of the mass of titanium dioxide in the titanium dioxide powder.

4. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (2), the binder is at least one of pseudo-boehmite, silica sol, natural clay, paraffin, and polyvinyl alcohol, and the dosage of the binder is 15% - 45% of the mass of titanium dioxide in the titanium dioxide powder.

5. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (2), the peptizing agent is at least one of nitric acid, hydrochloric acid, formic acid, and acetic acid, and the dosage of the peptizing agent is 2% - 10% of the mass of titanium dioxide in the titanium dioxide powder.

6. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (2), the forming aid is at least one of sesbania powder, polyanionic cellulose, hydroxyethyl cellulose, and xanthan gum, and the dosage of the forming aid is 2% - 10% of the mass of titanium dioxide in the titanium dioxide powder.

7. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (2), the drying is carried out at 60 - 120 °C for 6 - 12 h; the calcination is carried out in an air atmosphere at 400 - 650 °C for 4 - 10 h; the reduction is carried out in a hydrogen-nitrogen mixed gas phase at 300 - 800 °C for 6 - 12 h.

8. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (3), the noble metal salt is at least one of the chlorides and acetylacetonates of Pt, Rh, Pd, and Ru; the dosage of the noble metal salt is calculated based on the mass percentage content of the noble metal element in the catalyst being 0.05% - 1%; the alkali metal salt is at least one of sodium nitrate, potassium nitrate, and cesium nitrate, and the dosage of the alkali metal salt is calculated based on the mass percentage content of the noble metal in the catalyst being 2% - 20%.

9. The preparation method of a noble metal catalyst for wet catalytic oxidation of high-concentration organic wastewater according to claim 1, characterized in that: In step (3), the drying is carried out at 60 - 120 °C for 12 - 24 h; the reduction is carried out in a hydrogen-nitrogen mixed gas phase at 300 - 600 °C for 2 - 5 h.

10. The preparation method of any one of the noble metal catalysts for wet catalytic oxidation of high-concentration organic wastewater according to claim 7 or 9, characterized in that: In the hydrogen-nitrogen mixed gas phase, the volume fraction of hydrogen is 5% - 20%.

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