A method for preparing single-atom catalysts using waste pharmaceuticals containing precious metals

Abstract

The present invention relates to a method for preparing a single-atom catalyst from waste pharmaceutical products containing precious metals, belonging to the technical field of solid waste treatment. The method first co-hydrothermally treats the waste pharmaceutical products containing precious metals with biomass. The biomass is carbonized under hydrothermal conditions, and a large number of oxygen-containing functional groups are introduced at the same time. The oxygen therein belongs to hard acids, while the precious metals belong to hard bases. By virtue of the strong chemical interaction and physical adsorption between the precious metals and the oxygen-containing functional groups, the precious metals can be uniformly loaded on the surface of the biochar, and then calcined in a protective gas atmosphere, thereby forming a carbon composite material loaded with atomic-level precious metal single atoms, which is used as a single-atom catalyst for the catalytic conversion of CH4 and CO2. The method realizes the resource utilization and thorough harmless treatment of precious metals in waste pharmaceutical products containing precious metals, improves the resource utilization efficiency, greatly reduces the preparation cost of carbon-supported metal catalysts, and improves the catalytic activity.

Description

Technical Field

[0001] The present invention relates to a method for preparing a single-atom catalyst by using waste pharmaceutical products containing precious metals, and belongs to the technical field of solid waste treatment. Background Art

[0002] With the rapid development of medicine, the types and yields of pharmaceutical products have been continuously increasing. At the same time, a large number of expired and waste pharmaceutical products have been brought about. For example, the anti-cancer drugs cisplatin, carboplatin and oxaliplatin contain precious metal platinum; the drugs for treating rheumatoid arthritis contain gold compounds; and the silver sulfadiazine used for sterilization, treatment of burns and prevention of infection contains precious metal silver.

[0003] Currently, the recovery of expired pharmaceutical products, including liquid pharmaceutical products, is mainly carried out by incineration and safe landfill disposal technologies for harmless treatment. These traditional treatment means have high energy consumption and harmful pollutants will be generated and emitted during the treatment process. For example, the exhaust gas generated by incineration and the leachate generated by landfill will cause secondary pollution, and at the same time, the precious metals in the waste pharmaceutical products cannot be recovered. Therefore, it is of great significance to develop new resource utilization technical means to achieve the efficient resource utilization of waste pharmaceutical products containing precious metals.

[0004] The carbon-supported precious metal catalysts are widely used in industry, especially in the field of energy conversion. The traditional preparation methods of carbon-supported precious metal catalysts mainly include activated carbon loading, reduction of active metals and high-temperature calcination. The steps are cumbersome and concentrated acids, strong reducing agents, etc. are required. The preparation cost is high and there is a risk of secondary pollution. In addition, due to the microporous structure of the activated carbon used in the traditional preparation method, the metal usually exists in the form of nano-scale or larger particles after reduction, which seriously affects the performance of the catalyst. Summary of the Invention

[0005] In order to overcome the defects in the prior art such as high energy consumption, low resource utilization efficiency, serious pollution and inability to recover the precious metal resources in waste pharmaceutical products containing precious metals during the treatment process, the purpose of the present invention is to provide a method for preparing a single-atom catalyst by using waste pharmaceutical products containing precious metals.

[0006] To achieve the purpose of the present invention, the following technical solutions are provided.

[0007] A method for preparing a single-atom catalyst by using waste pharmaceutical products containing precious metals, the steps of the method are as follows:

[0008] (1) Mix the waste pharmaceutical products containing precious metals, deionized water and biomass evenly, and then carry out hydrothermal treatment at 180-240 °C, and perform solid-liquid separation to obtain a solid-phase product and dry it;

[0009] The biomass is at least one of soluble carbohydrates and lignocellulose; preferably, the soluble carbohydrate is at least one of glucose, fructose, and sucrose; the lignocellulose biomass is at least one of straw and wood powder;

[0010] The waste precious metal-containing medicine is an expired precious metal-containing medicine, which can be solid or liquid; the precious metals include elements of gold, silver, and platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, platinum), preferably, the precious metal is gold, silver, or platinum;

[0011] Preferably, the waste precious metal-containing medicine is at least one of expired cisplatin (Hospira Australia), carboplatin, and oxaliplatin;

[0012] Preferably, the waste precious metal-containing medicine is silver sulfadiazine;

[0013] Waste precious metal-containing medicines containing the same type of precious metal can be used alternatively or mixedly, while waste precious metal-containing medicines containing different types of precious metals cannot be mixed.

[0014] Preferably, the particle size of the solid waste precious metal-containing medicine is 60-110 mesh, and there is no particle size requirement for the liquid waste precious metal-containing medicine, which is directly mixed with the biomass; when the particle size of the solid waste precious metal-containing medicine is within 60-110 mesh, the specific surface area of the medicine is relatively large, and the precious metal can be fully loaded during the hydrothermal reaction, thus promoting the formation and loading of metal active centers.

[0015] Preferably, the mass ratio of the precious metal in the waste precious metal-containing medicine to the biomass is 1:8-1:15. Too high a precious metal addition amount will lead to problems such as too large particle size, low activity, and unstable loading of the generated precious metal particles due to the limited loading capacity of the carbon-based carrier derived from the carbonization of the biomass during the hydrothermal and calcination processes; while too low a precious metal medicine addition amount will affect the catalytic performance due to the lack of sufficient atomic particle quantity, and a large amount of reducing organic gases generated during the decomposition of the medicine and the biomass will be directly discharged without full utilization, resulting in environmental pollution and resource waste. In addition, too low a precious metal content will also lead to insufficient catalytic action of the precious metal during the calcination process, resulting in insufficient carbonization of the biomass, that is, low aromatization degree, affecting the stability of the carrier, etc.

[0016] Preferably, the mass ratio of the biomass to the deionized water is 1:4-1:9; due to the autogenous pressure of water during the hydrothermal process, too low a water content will lead to insufficient carbonization of the biomass; too high a water content will lead to hydrolysis rather than carbonization of the biomass, and at the same time, it will increase the energy consumption of the hydrothermal treatment process.

[0017] Preferably, the hydrothermal treatment time is 30 - 80 min; too low temperature and too short time are not conducive to the uniform loading of noble metals, while too high temperature and too long time will not only cause energy waste, but also lead to the collapse of the pore structure of carbon materials.

[0018] (2) Calcinate the solid-phase product dried in step (1) in a protective gas atmosphere at a calcination temperature of 550 - 850 °C and a protective gas flow rate of 0.6 - 1.2 L / min to obtain a solid mixture;

[0019] Preferably, the calcination time is 0.5 - 2 h;

[0020] The protective gas is at least one of nitrogen, helium, carbon monoxide and carbon dioxide;

[0021] (3) Wash and dry the solid mixture obtained in step (2) to obtain a single-atom catalyst.

[0022] Preferably, the drying temperature is 60 - 80 °C; too high drying temperature will cause the highly active metal atoms in the solid product to undergo oxidation reaction with air; too low calcination temperature and too short calcination time will lead to insufficient carbonization of biomass, resulting in too little reducing gas generated, leading to insufficient reduction of noble metals and unable to form active centers or the number of formed active centers is too small; while too high calcination temperature and too long calcination time will not only increase the energy consumption and cost of treatment, but also cause noble metal atoms to sinter to form sub-nanometer or even nanometer structures, reducing the reaction activity of active centers.

[0023] Reaction principle

[0024] The method first co-hydrothermally treats the noble metal-containing waste medicine and biomass. The biomass is carbonized under hydrothermal conditions, and a large number of oxygen-containing functional groups are introduced at the same time. The oxygen belongs to hard acid, while the noble metal belongs to hard base. With the strong chemical action (chemical chelation) and physical adsorption between the noble metal and the oxygen-containing functional groups, the noble metal can be uniformly loaded on the surface of biochar. At the same time, due to the degradation of biomass components during the hydrothermal treatment process, a rich pore structure is created, which helps the uniform dispersion and large loading of noble metals; then calcine in a protective gas atmosphere. During the calcination process, the noble metal can promote the carbonization of harmful components in biomass and organic components in medicine. Methane, carbon monoxide, hydrogen and small molecule hydrocarbon substances and other reducing gases are released during the degradation and carbonization of biomass. The generation and release of these gases are beneficial to the formation of a porous structure during the carbonization of biomass. At the same time, under the action of these high-temperature reducing gases and the highly active amorphous carbon obtained from the carbonization of biomass, the chelated and adsorbed metal ions can be fully reduced, so as to form a carbon composite material loaded with noble metal single atoms at the atomic level, which is used as a single-atom catalyst for the catalytic conversion of CH 4 and CO 2 catalytic conversion.

[0025] Beneficial effects

[0026] (1) The present invention provides a method for preparing a single-atom catalyst using waste noble metal-containing drugs. The method innovatively treats the waste noble metal-containing drugs through a hydrothermal synergistic calcination technique, which can maximize the dispersion of noble metals in the waste drugs. More reducing organic small molecule gases are generated during the biomass carbonization process, which is beneficial for preparing a carbon-based support with a larger specific surface area. At the same time, it promotes the in-situ reduction generation and synchronous loading of atomic-level active centers, thus maximizing the performance of the single-atom catalyst.

[0027] (2) The present invention provides a method for preparing a single-atom catalyst using waste noble metal-containing drugs. The method optimizes the mass ratio of noble metals to biomass in the waste noble metal-containing drugs. When the mass ratio of noble metals to biomass in the waste noble metal-containing drugs is 1:8 to 1:15, the amount of noble metal added is equivalent to the loading capacity of the carbon-based support derived from biomass. It will neither cause the noble metal particle size to be too large, the activity to decrease, and the loading to be unstable due to too high noble metal content, nor affect the catalytic performance of the single-atom catalyst due to insufficient noble metal content. And under the mass ratio condition, the noble metal content can meet the requirement of catalytically carbonizing the biomass sufficiently during the calcination process, improving the stability of the support.

[0028] (3) The present invention provides a method for preparing a single-atom catalyst using waste noble metal-containing drugs. The method optimizes the mass ratio of biomass to deionized water. When the mass ratio of biomass to deionized water is 1:4 to 1:9, the autogenous pressure of water during the hydrothermal process can ensure the sufficient carbonization of biomass and avoid hydrolysis, reducing the energy consumption of the hydrothermal treatment process.

[0029] (4) The present invention provides a method for preparing a single-atom catalyst using waste noble metal-containing drugs. The method optimizes the hydrothermal treatment conditions. When the hydrothermal treatment temperature is 180 - 240 °C and the hydrothermal treatment time is 30 - 80 min, it can not only meet the requirement that noble metals can be fully and evenly loaded on the support, but also will not cause the collapse of the pore structure of the support carbon material due to too high temperature and too long time.

[0030] (5) The present invention provides a method for preparing a single-atom catalyst using waste noble metal-containing drugs. The method optimizes the calcination conditions. When the calcination temperature is 550 - 850 °C and the calcination time is 0.5 - 2 h, the hydrothermally treated biomass can be fully carbonized and release a large amount of reducing gases. These reducing gases fully reduce the noble metals to form a large number of active centers. At the same time, it can avoid the sintering of noble metal atoms and reduce the reaction activity of the active centers.

[0031] (6) The present invention provides a method for preparing a single-atom catalyst using waste pharmaceutical products containing precious metals. The method prepares a carbon-supported single-atom precious metal catalyst without using strong acids or reducing agents. The steps are simple, the energy consumption cost is low, the preparation process is green and pollution-free, realizing the resource utilization and thorough harmless treatment of precious metals in waste pharmaceutical products containing precious metals, improving the resource utilization efficiency, and greatly reducing the preparation cost of the carbon-supported metal catalyst. Moreover, the single-atom catalyst prepared by the method has extremely high reaction activity and can efficiently catalyze the conversion of CO 2 and CH 4 . When the conversion time is 5 minutes, the conversion rates of CO 2 and CH 4 can reach up to 99% and 98% respectively at the highest. When the conversion time is 600 minutes, the conversion rates of CO 2 and CH 4 can still reach up to 92% and 90% respectively at the highest, having important application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 XRD pattern of the single-atom catalyst obtained in Example 1.

[0033] Figure 2 STEM pattern of the single-atom catalyst obtained in Example 1.

[0034] Figure 3 STEM pattern of the single-atom catalyst obtained in Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention will be described in detail below with reference to the drawings and specific embodiments, but it is not intended to limit the scope of the present invention.

[0036] The samples prepared in Examples 1-2 and Comparative Examples 1-2 were tested as follows:

[0037] (1) Specific surface area: Tested using an ASPS 2000 specific surface area and porosity analyzer from Micromeritics;

[0038] (2) Microscopic morphology: Tested using a Thermo Fisher Themis Z condenser spherical aberration correction electron microscope;

[0039] (3) X-ray diffraction: Tested using an XRD-7000 X-ray diffractometer from Bruker D8 advance;

[0040] (4) Inductively coupled plasma emission spectroscopy: Tested using a PerkinElmer 3000DV inductively coupled plasma emission spectrometer from Thermo Fisher;

[0041] Example 1

[0042] A method for preparing a single-atom catalyst using waste precious metal-containing drugs, the steps of the method are as follows:

[0043] (1) Thoroughly mix 3.07 g of expired cisplatin with a particle size of 60 - 100 mesh, 16 g of glucose, and 64 g of deionized water, then perform hydrothermal treatment at 180 °C for 30 min. After hydrothermal treatment, perform vacuum filtration to obtain a solid-phase product, and dry it at 105 °C for 24 h;

[0044] The mass ratio of platinum to glucose in the expired cisplatin is 1:8;

[0045] The mass ratio of glucose to deionized water is 1:4;

[0046] (2) Place the solid-phase product dried in step (1) in a tubular pyrolysis furnace, and calcine it at 550 °C for 0.5 h under nitrogen protection. The nitrogen gas flow rate is 0.6 L / min, and cool it to room temperature in a nitrogen atmosphere to obtain a solid mixture;

[0047] (3) Wash the solid mixture obtained in step (2) with distilled water multiple times and then dry it in an oven at 80 °C for 24 h to obtain a single-atom catalyst.

[0048] Perform specific surface area testing on the single-atom catalyst prepared in Example 1. The results show that the specific surface area of the single-atom catalyst can reach 420 m 2 / g;

[0049] Perform X-ray diffraction characterization on the single-atom catalyst prepared in Example 1. The results are as Figure 1 shown. No diffraction peaks of metal crystals appear in the figure, indicating that the precious metal elements do not exist in the form of crystal particles in the product.

[0050] Perform scanning transmission electron microscopy (STEM) characterization on the single-atom catalyst prepared in Example 1. The results are as Figure 2 shown. The metallic platinum in the expired cisplatin is uniformly distributed in the biomass-derived carbon material in the form of atoms.

[0051] Example 2

[0052] A method for preparing a single-atom catalyst using waste precious metal-containing drugs, the steps of the method are as follows:

[0053] (1) Thoroughly mix 2.26 g of expired silver sulfadiazine with a particle size of 60 - 100 mesh, 15 g of fructose, and 135 g of deionized water, then perform hydrothermal treatment at 240 °C for 80 min. After hydrothermal treatment, perform vacuum filtration to obtain a solid-phase product, and dry it at 105 °C for 24 h;

[0054] The mass ratio of silver to fructose in the expired silver sulfadiazine is 1:15;

[0055] The mass ratio of fructose to deionized water is 1:9;

[0056] (2) Place the solid product dried in step (1) in a tubular pyrolysis furnace, and calcine it at 850 °C for 2 h under nitrogen protection. The nitrogen gas flow rate is 1.2 L / min, and cool it to room temperature in the nitrogen atmosphere to obtain a solid mixture;

[0057] (3) Wash the solid mixture obtained in step (2) with distilled water several times and then dry it in an oven at 80 °C for 24 h to obtain a single-atom catalyst.

[0058] The specific surface area of the single-atom catalyst prepared in Example 2 was tested, and the results showed that the specific surface area of the single-atom catalyst could reach 465 m 2 / g;

[0059] The single-atom catalyst prepared in Example 2 was characterized by X-ray diffraction. The results were similar to those of Example 1, indicating that the noble metal element does not exist in the form of crystal particles in the product.

[0060] The single-atom catalyst prepared in Example 2 was characterized by scanning transmission electron microscopy (STEM). The results are as Figure 3 shown, indicating that the metallic silver in the expired silver sulfadiazine is uniformly distributed in the biomass-derived carbon material in the form of atoms.

[0061] Comparative Example 1

[0062] (1) Thoroughly mix 3.07 g of expired cisplatin (Hospira Australia) and 16 g of glucose in a mass ratio of 1:8 to obtain a solid mixture;

[0063] (2) Place the solid mixture obtained in step (1) in a tubular pyrolysis furnace, and calcine it at 550 °C for 0.5 h under nitrogen protection. The nitrogen gas flow rate is 0.6 L / min, and cool it to room temperature in the nitrogen atmosphere;

[0064] (3) Wash the product calcined in step (2) with deionized water several times and then dry it in an oven at 80 °C for 24 h to obtain a carbon-based platinum composite material.

[0065] The test results showed that the specific surface area of the carbon-based platinum composite material prepared in Comparative Example 1 was 56 m 2 / g; Part of the metallic platinum exists in the form of particles and is unevenly distributed. Comparing the results of Example 1 and Comparative Example 1, it can be seen that the hydrothermal reaction has a significant impact on the particle size, metal distribution morphology, and specific surface area of the support of the single-atom catalyst.

[0066] Comparative Example 2

[0067] (1) 2.26 g of expired silver sulfadiazine, 15 g of fructose and 135 g of deionized water were thoroughly mixed in a mass ratio of 1:15:135, and hydrothermally reacted at 240 °C for 80 min. After hydrothermal treatment, vacuum filtration was carried out to obtain a solid mixture, which was dried at 105 °C for 24 h;

[0068] (2) The mixture obtained in step (1) was placed in a tubular pyrolysis furnace and calcined at 400 °C for 2 h under nitrogen protection, with a nitrogen gas flow rate of 1.2 L / min, and cooled to room temperature in a nitrogen atmosphere;

[0069] (3) The product calcined in step (2) was washed with distilled water multiple times and then dried in an oven at 80 °C for 24 h to obtain a carbon-based silver composite material.

[0070] The test results show that the specific surface area of the carbon-based platinum composite material prepared in Comparative Example 2 is 46 m 2 / g; the results of inductively coupled plasma emission spectrometry analysis after digestion show that the obtained material basically does not contain silver element, which indicates that metallic silver is not effectively reduced and loaded onto the biochar, and a single-atom catalyst cannot be formed. Comparing the results of Example 2 and Comparative Example 2, it can be seen that the calcination temperature has a significant influence on the production of reducing gases by biomass to fully reduce precious metals to form a large number of active centers and porous carriers.

[0071] Example 3

[0072] In order to further verify the implementation effect of the present invention, the single-atom catalysts prepared in Examples 1-2 and the carbon-based precious metal composite materials prepared in Comparative Examples 1-2 were used as catalysts for the catalytic reforming reaction of CH 4 and CO 2 to obtain syngas (CO and H 2 ), and the catalytic conversion test of CO 2 and CH 4 was carried out. The specific experimental operations are as follows:

[0073]

[0074] The catalytic conversion experiment was carried out in a fixed-bed reactor (XCS-GDC-20, Beijing Zixin Technology Co., Ltd.) at atmospheric pressure, where the diameter of the quartz tube was 8 mm and the length was 1 m. In order to better fix the catalyst, 0.13 g of the catalyst was uniformly dispersed on quartz wool and placed at the center of the heating zone. The reactor was heated to 700 °C in a nitrogen atmosphere, and then CH with a molar ratio of 1:1 4 and CO 2The mixture is introduced into the reactor, and the outlet gas is directly introduced into an on-line gas chromatograph. The thermal conductivity detector of the gas chromatograph is used for component and content analysis. CO 2 and CH 4 conversion rates are shown in Table 1.

[0075] As can be seen from Table 1, the single-atom catalysts prepared in Examples 1-2 have very high reaction activities and can efficiently catalyze the conversion of CH 4 and CO 2 . At 5 min of conversion, the conversion rates of CO 2 and CH 4 can reach as high as 99% and 98% respectively. At 600 min of conversion, the conversion rates of CO 2 and CH 4 can still reach as high as 92% and 90% respectively. However, for the carbon-based noble metal composites prepared in Comparative Examples 1-2, the highest conversion rates for catalyzing the conversion of CO 2 and CH 4 can only reach 53% and 47% at most, and basically no longer catalyze the conversion after 30 min.

[0076] Table 1 Conversion rates of CO 2 and CH 4 catalyzed by the single-atom catalysts prepared in Examples 1-2 and the carbon-based noble metal composites prepared in Comparative Examples 1-2

[0077]

[0078]

Claims

1. A method for preparing a single-atom catalyst using waste precious metal-containing drugs, characterized in that: The method steps are as follows: (1) Mix waste precious metal-containing drugs, deionized water, and biomass evenly, perform hydrothermal treatment at 180-240 °C, carry out solid-liquid separation to obtain a solid-phase product and dry it; The biomass is at least one of soluble carbohydrates and lignocellulose; The waste precious metal-containing drugs are expired solid or liquid precious metal-containing drugs; (2) Calcinate the dried solid-phase product in a protective gas atmosphere, the calcination temperature is 550-850 °C, and the flow rate of the protective gas is 0.6-1.2 L / min to obtain a solid mixture; The protective gas is at least one of nitrogen, helium, carbon monoxide, and carbon dioxide; (3) Wash and dry the solid mixture to obtain a single-atom catalyst.

2. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to claim 1, characterized in that: The mass ratio of the precious metal in the waste precious metal-containing drugs to the biomass is 1:8-1:

15.

3. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to claim 1, characterized in that: The mass ratio of the biomass to the deionized water is 1:4-1:

9.

4. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to any one of claims 1 to 3, characterized in that: The waste precious metal-containing drugs are at least one of expired cisplatin, carboplatin, and oxaliplatin; or the waste precious metal-containing drugs are silver sulfadiazine.

5. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to any one of claims 1 to 3, characterized in that: The soluble carbohydrates are at least one of glucose and fructose; the lignocellulose is at least one of straw and wood powder.

6. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to any one of claims 1 to 3, characterized in that: When the waste precious metal-containing drugs are solid, the particle size is 60-110 mesh.

7. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to any one of claims 1 to 3, characterized in that: The hydrothermal treatment time is 30-80 min.

8. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to any one of claims 1 to 3, characterized in that: The waste precious metal-containing drugs are at least one of expired cisplatin, carboplatin, and oxaliplatin, or the waste precious metal-containing drugs are silver sulfadiazine; The soluble carbohydrates are at least one of glucose and fructose; the lignocellulose is at least one of straw and wood powder; When the waste precious metal-containing drugs are solid, the particle size is 60-110 mesh; The hydrothermal treatment time is 30-80 min.

9. The method for preparing a single-atom catalyst using waste precious metal-containing drugs according to claim 1, characterized in that: The calcination time is 0.5-2 h; the drying temperature in step (3) is 60-80 °C.

10. The method for preparing a single-atom catalyst by using waste noble metal-containing drugs according to claim 8, characterized in that: the calcination time is 0.5 to 2 h; the drying temperature in step (3) is 60 to 80 °C.

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