Carbon tetrafluoride catalyst as well as preparation method and application thereof

Abstract

The invention discloses a carbon tetrafluoride catalyst as well as a preparation method and application thereof, and belongs to the technical field of environment. Aiming at the problems of high reaction temperature, easy inactivation and insufficient efficiency of a traditional CF4 hydrolysis catalyst, the preparation method comprises the following steps: firstly preparing an Al2O3 nanosheet, and then sequentially loading Ga and Pt components through a step-by-step impregnation method to form the Pt-Ga / Al2O3 catalyst containing Pt-Ga double active sites. The catalyst can realize CF4 100% decomposition at 550 DEG C, is still stable after continuous operation for 100 hours, overcomes the industrial bottleneck of the traditional catalyst, and provides a feasible technical path for high-efficiency low-carbon treatment of fluorine-containing greenhouse gas CF4.

Description

Technical Field

[0001] This invention belongs to the field of environmental technology, and in particular relates to a carbon tetrafluoride catalyst, its preparation method, and its application. Background Technology

[0002] Carbon tetrafluoride (CF4) is a typical perfluorinated compound widely used in microelectronic etching, plasma cleaning, optical fiber manufacturing, and the electrolytic aluminum industry. It possesses extremely high thermodynamic stability and chemical inertness, and is recognized globally as one of the atmospheric greenhouse gases. The C–F bond energy of CF4 is as high as 543 kJ / mol, one of the strongest known chemical bonds, making it extremely difficult for CF4 to degrade naturally in the environment, posing a long-term potential threat to the climate system. Therefore, developing efficient, low-energy-consumption, and sustainable CF4 emission reduction and treatment technologies has become a key challenge in the field of environmental catalysis technology.

[0003] Currently, the main technical methods for CF4 treatment include high-temperature combustion, plasma decomposition, adsorption, electrochemical decomposition, and catalytic hydrolysis. Among these, thermocatalytic hydrolysis is considered the most promising industrial application route due to its lack of secondary pollution, adaptability to continuous industrial reactions, and the availability of recyclable HF as a product. However, traditional thermocatalytic hydrolysis still faces many challenges: high reaction temperature requirements: traditional alumina (Al2O3) catalysts, due to their low surface activity, can only achieve significant CF4 decomposition at temperatures above 650–700°C, resulting in high energy consumption and limited material lifespan; severe catalyst deactivation problems: during CF4 hydrolysis, HF generated easily undergoes irreversible reactions with the catalyst's active sites (e.g., Al–OH reacts with HF to form Al–F), causing active site poisoning and non-renewability, severely affecting catalyst lifespan; insufficient reaction rate and conversion efficiency: under actual industrial operating conditions, CF4 concentration is low and moisture content fluctuates greatly, making it difficult for conventional catalysts to provide sufficient proton sources under low moisture conditions, limiting the activation rate of C–F bonds. Against this backdrop, it is necessary to develop a highly efficient low-temperature CF4 hydrolysis catalyst. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon tetrafluoride catalyst that enhances the H2O dissociation and C–F bond activation capabilities by synergistically regulating the surface acidic environment with noble metals and main group metals, thereby achieving low-temperature and high-efficiency hydrolysis catalysis of CF4.

[0005] A second objective of this invention is to provide a method for preparing a carbon tetrafluoride catalyst; A third objective of this invention is to provide an application of a carbon tetrafluoride catalyst.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is a method for preparing a carbon tetrafluoride catalyst, comprising the following steps: S1. Preparation of Al2O3 nanosheets; S2. Load Ga components onto the Al2O3 nanosheets, and obtain Ga / Al2O3 precursor by drying and calcination; S3. Pt components are loaded onto the Ga / Al2O3 precursor, and then dried and calcined to obtain a Pt-Ga / Al2O3 catalyst.

[0007] Furthermore, in step S1, the preparation of the Al2O3 nanosheets includes: dissolving aluminum isopropoxide in isopropanol and stirring to disperse it, adding deionized water and transferring it to a reaction vessel for hydrothermal reaction, cooling, washing, centrifuging and drying the product to obtain a white precursor powder, and then calcining the white precursor powder by stepwise heating to obtain Al2O3 nanosheets.

[0008] Furthermore, in step S1, the ratio of aluminum isopropoxide to isopropanol is 0.08-0.12 g / mL, the stirring rate is 500 rpm, and the stirring time is 10-14 h; the hydrothermal reaction temperature is 100-120℃, and the reaction time is 0.5-3 h; the stepwise heating and calcination process is as follows: the temperature is increased to 550-650℃ at a rate of 4-6℃ / min, and then increased to 850-950℃ at a rate of 1-2℃ / min, and held at that temperature for 3-5 h.

[0009] Furthermore, in step S2, the specific process for obtaining the Ga / Al2O3 precursor is as follows: Al2O3 nanosheets are dispersed in deionized water and subjected to ultrasonic treatment, Ga(NO3)3 solution is added and stirred continuously, the solvent is removed by rotary evaporation and then calcined; wherein, the molar ratio of Ga to Al is 2%-35%, the ultrasonic treatment time is 20-40 min, and the stirring time is 15-45 min.

[0010] Furthermore, in step S2, the dispersion ratio of Al2O3 nanosheets in deionized water is 10g:(300-500)mL; the calcination temperature is 600-700℃, and the calcination time is 2-4h.

[0011] Furthermore, in step S3, the raw material used for supporting the Pt component is... The solution, the The mass concentration of the solution is 0.5%-2%.

[0012] Furthermore, in step S3, the drying process parameters are: temperature 70-90℃, time 6-10h; the calcination process parameters are: temperature 600-800℃, time 3-6h.

[0013] Furthermore, in step S3, The volume of solution added should be sufficient to fully wet the Ga / Al2O3 precursor.

[0014] A carbon tetrafluoride catalyst is prepared by the above-described method.

[0015] The application of a carbon tetrafluoride catalyst in the treatment of carbon tetrafluoride-containing flue gas, wherein the carbon tetrafluoride-containing flue gas has a CF4 concentration of 1500-3500 ppm, an H2O volume percentage content of 10%-50%, and a catalytic reaction temperature of 450-650℃.

[0016] Compared with existing technologies, the beneficial effects of this invention include the following: The low-temperature hydrolysis carbon tetrafluoride (CF4) catalyst prepared by this invention is significantly superior to reported conventional catalysts in terms of performance and application potential: it can achieve 100% decomposition of CF4 at a relatively low temperature of 550°C, exhibiting excellent low-temperature catalytic activity; at the same time, while maintaining 100% decomposition efficiency, the catalyst can operate stably for more than 100 hours continuously, demonstrating good thermal stability and durability; more importantly, this catalyst overcomes the industrial application bottlenecks caused by high reaction temperatures, short lifespans, or high costs of traditional systems, possessing the feasibility of large-scale production and engineering practicality, and providing a practical and feasible technical path for the efficient and low-carbon treatment of the fluorinated greenhouse gas CF4. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is the X-ray diffraction (XRD) pattern of the low-temperature hydrolysis carbon tetrafluoride catalyst of this invention.

[0019] Figure 2 This is a TEM elemental distribution spectrum of the low-temperature hydrolysis carbon tetrafluoride catalyst of the present invention, wherein (a) is Al, (b) is O, (c) is Pt, and (d) is Ga.

[0020] Figure 3 These are graphs showing the CF4 decomposition effects of the low-temperature hydrolysis carbon tetrafluoride catalyst of this invention at different temperature ranges.

[0021] Figure 4 This is a diagram showing the effect of long-term treatment of CF4 with the low-temperature hydrolysis carbon tetrafluoride catalyst of this invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This embodiment provides a carbon tetrafluoride catalyst that achieves a significant improvement in catalytic performance by constructing a Pt–Ga dual-active-site system with a well-defined structure and strong interfacial coupling. Compared to the problem of Pt species easily sintering and agglomerating, leading to deactivation, in traditional single-metal Pt-modified catalysts, the introduction of Pt–Ga dual sites can effectively enhance the dispersion stability of Pt and inhibit its migration and aggregation during the reaction process. However, in the actual construction process of bimetallic synergistic modification, challenges are often faced, such as the difficulty in precisely controlling the spatial distribution of the two metal components, poor matching of bifunctional active centers, and the inability to fully exert the synergistic effect. To address these issues, this embodiment adopts a stepwise impregnation strategy: first, a Ga / Al2O3 precursor is prepared by loading Ga components onto Al2O3, and then Pt components are introduced, ultimately successfully constructing a Pt–Ga / Al2O3 dual-site catalytic system with uniform distribution of Pt and Ga components, strong interfacial interaction, and stable structure.

[0024] In some specific embodiments, the catalyst is prepared by impregnating Al2O3 nanosheets in a solution containing Ga(NO3)3, dispersing them ultrasonically, drying them by rotary evaporation, and then calcining them to obtain the Ga / Al2O3 catalyst.

[0025] In some specific embodiments, the preparation process of the Al2O3 nanosheets is as follows: Add 8.0–12.0 g of aluminum isopropoxide to 100 mL of isopropanol solution, with an aluminum isopropoxide to isopropanol ratio of 0.08–0.12 g / mL. Stir at 500 rpm for 10–14 h. Add 8–12 mL of deionized water to the mixture, continue stirring for 10–30 min, and then transfer to a reaction vessel lined with polytetrafluoroethylene. React in an oven at 100–120 °C for 0.5–3 h. Cool, wash, centrifuge, and dry at 70–90 °C to obtain a white precursor powder. Heat the precursor to 550–650 °C at 4–6 °C / min, then to 850–950 °C at 1–2 °C / min and hold for 3–5 h to obtain Al₂O₃ nanosheets.

[0026] In some specific implementations, the subsequent processing of Al2O3 nanosheets is as follows: Subsequently, 10g of Al2O3 nanosheets were dispersed in 300-500mL of deionized water and ultrasonically dispersed for 20-40min. Ga(NO3)3 was then added to the above solution and stirred for 15-45min. The molar ratio of Ga / Al was 2%-35%. The solvent was removed by rotary evaporation, and the catalyst was calcined at 600-700℃ for 2-4h to obtain the Ga / Al2O3 catalyst. The doping of Ga on Al2O3 material and the catalyst performance are controlled by the temperature and time parameters during the preparation process. Specifically, if the calcination temperature is too low, Ga species will have difficulty overcoming the energy barrier to achieve effective doping into the Al2O3 material lattice, resulting in the failure of doping modification. If the reaction temperature is too high, it will cause sintering and agglomeration of Al2O3 material, resulting in a significant decrease in the specific surface area of ​​the catalyst, thereby reducing the number of active sites exposed on the surface and ultimately reducing its catalytic decomposition performance for CF4. Regarding calcination time, if the time is too short, the diffusion and substitution reactions of Ga species on and inside the Al2O3 material will be insufficient, easily leading to uneven Ga doping distribution and failure to form uniform active sites; if the time is too long, it will unnecessarily prolong the product preparation cycle and cause ineffective energy consumption, which does not meet the requirements of process economy. Subsequently, 10g of Ga / Al2O3 catalyst was impregnated in a solution with a mass concentration of 0.5-2%. In the solution, the Ga / Al2O3 precursor is fully wetted. The mixture is dried in an oven at 70-90℃ for 6-10 hours, and then calcined at 600-800℃ for 3-6 hours to obtain the PtGa / Al2O3 catalyst. If the temperature is too low, Pt-Ga dual sites cannot form; if the temperature is too high, Pt will sinter and agglomerate, reducing the number of Pt-Ga dual sites; if the time is too short, the distribution of Pt-Ga dual sites will be uneven; if the time is too long, it will affect the product preparation cycle and waste energy. Furthermore, in the above process, if the Ga / Al2O3 ratio is too high or too low, it will lead to either too low or too high Pt modification, both of which will adversely affect the catalyst performance. Specifically, if the Ga / Al2O3 ratio is too high, there will be an excess of tricoordinated Ga active sites that can be used to anchor Pt species, resulting in insufficient Pt modification. At this point, Pt and Ga cannot fully combine to form a sufficient number of Pt-Ga dual active sites, directly resulting in insufficient dissociation ability of the catalyst for H2O and insufficient activation ability for CF bonds. Conversely, if the proportion of Ga / Al2O3 is too low, the number of tricoordinate Ga active sites that can anchor Pt species is limited. Excessive Pt species will agglomerate due to the lack of effective anchoring sites and will not be able to form the target Pt-Ga dual active sites with Ga. This will also lead to a reduction in the actual number of Pt-Ga dual active sites, ultimately causing the catalyst's H2O dissociation efficiency and CF bond activation ability to fail to meet expectations.

[0027] This embodiment first modifies the Al2O3 support material with Ga doping. Characterization results confirm that Ga can selectively replace the three-coordinate Al sites on the Al2O3 surface, forming unsaturated three-coordinate Ga active sites. These unsaturated three-coordinate Ga sites have strong coordination binding ability and can effectively anchor the Pt species introduced in the subsequent modification process, thereby achieving the precise construction of Pt-Ga dual active sites. Given the specific substitution characteristics of Ga for the three-coordinate Al sites, and the inherent and uniformly dispersed state of the three-coordinate Al sites on the Al2O3 surface, the Pt-Ga dual active sites formed by anchoring Pt species through the above-mentioned Ga sites can be precisely controlled to ensure their uniform dispersion. In the PtGa / Al2O3 catalyst system prepared above, the Pt active sites mainly undertake the dissociation function of H2O molecules, efficiently dissociating H2O into H protons and hydroxyl groups (-OH); while the Ga active sites can utilize the H protons and hydroxyl groups generated by the above dissociation (both are active proton species that can effectively activate CF bonds) to achieve directional activation of CF bonds. This application achieves uniform distribution and atomic-level close contact of the Pt-Ga dual active sites through precise control. This structural characteristic ensures that the H2O dissociation function of Pt sites and the CF bond activation function of Ga sites form a highly efficient synergistic effect, thereby significantly improving the catalyst's dissociation efficiency for H2O and its activation ability for CF bonds. In contrast, in catalysts prepared by traditional bimetallic modification strategies, it is difficult to achieve atomic-level precise control of Pt and Ga species to form a dual active site structure. They usually exist in the form of nanoscale aggregates, resulting in an ineffective matching of the two functions. The proton-like active species generated by the dissociation of H2O from Pt sites are affected by steric hindrance and are difficult to efficiently transfer to Ga active sites, thus failing to achieve functional synergy.

[0028] This embodiment also provides a method for applying a carbon tetrafluoride catalyst, wherein the catalyst is used to treat a carbon tetrafluoride flue gas with a CF4 concentration of 1500-3500 ppm and an H2O volume percentage content of 10%-50%; and the temperature of the carbon tetrafluoride flue gas is 450-650℃.

[0029] Example 1 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted in an oven at 110 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 4 h to obtain the Ga / Al₂O₃ catalyst. XRD test results (e.g.) Figure 1 As shown in the figure, the PtGa / Al2O3 catalyst has been successfully prepared. TEM elemental surface scan analysis results (as shown in the figure) indicate that the catalyst has been successfully prepared. Figure 2 (a) to (d) show that Pt and Ga coexist uniformly in the catalyst, confirming that the PtGa sites exist in an alloy form. Gas chromatography analysis of the reaction tail gas revealed... Figure 3 As can be seen, the CF4 decomposition rate of the PtGa / Al2O3 catalyst is significantly higher than that of the Al2O3, Pt / Al2O3 and Ga / Al2O3 catalysts throughout the entire temperature range.

[0030] Electrolytic aluminum flue gas containing 2500ppm CF4 (at a rate of 33.3mL / min) -1 The flow rate is introduced into the reactor, and simultaneously passed through a steam generator at a rate of 0.008 mL / min. -1 Water vapor was introduced at a controlled rate to maintain the reaction temperature at 550℃. The reaction tail gas was analyzed by gas chromatography. Figure 4 As can be seen, the CF4 decomposition rate reached 100%, and there was no significant deactivation after more than 100 hours of continuous operation. This is significantly higher than that of Al2O3, Pt / Al2O3, and Ga / Al2O3 catalysts.

[0031] Example 2 8.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 10 h. 8 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 100 °C for 0.5 h. The resulting mixture was cooled, washed, centrifuged, and dried at 70 °C to obtain a white precursor powder. This precursor was heated to 550 °C at 4 °C / min, then to 850 °C at 1 °C / min and held for 3 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 300 mL of deionized water and sonicated for 20 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 2% was added to the solution, and stirring was continued for 15 min. The solvent was removed by rotary evaporation, and the solution was calcined at 600 °C for 2 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying in a 70°C oven for 6 hours and calcining at 600°C for 3 hours in a solution (0.5% by mass).

[0032] Example 3 12.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 14 h. 12 mL of deionized water was added to the mixture, and stirring continued for 30 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 120 °C for 3 h. The resulting mixture was cooled, washed, centrifuged, and dried at 90 °C to obtain a white precursor powder. This precursor was heated to 650 °C at 6 °C / min, then to 950 °C at 2 °C / min and held for 5 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 500 mL of deionized water and sonicated for 40 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 35% was added to the solution, and stirring continued for 45 min. The solvent was removed by rotary evaporation, and the solution was calcined at 700 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with... The PtGa / Al2O3 catalyst was obtained by drying the solution (2% by mass) in an oven at 90°C for 10 hours and then calcining it at 800°C for 6 hours.

[0033] Example 4 8.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 14 h. 12 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 120 °C for 0.5 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 850 °C at 2 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 500 mL of deionized water and sonicated for 20 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 35% was added to the solution, and stirring was continued for 15 min. The solvent was removed by rotary evaporation, and the solution was calcined at 600 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying in a 75°C oven for 7 hours and calcining at 650°C for 4.5 hours in solution (1.2% by mass).

[0034] Example 5 12.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 10 h. 8 mL of deionized water was added to the mixture, and stirring continued for 30 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 100 °C for 3 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 950 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 300 mL of deionized water and sonicated for 40 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 2% was added to the solution, and stirring continued for 45 min. The solvent was removed by rotary evaporation, and the solution was calcined at 700 °C for 2 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying in a 75°C oven for 7 hours and calcining at 650°C for 4.5 hours in solution (1.2% by mass).

[0035] Example 6 9.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 11 h. 11 mL of deionized water was added to the mixture, and stirring was continued for 15 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 105 °C for 1.5 h. The resulting mixture was cooled, washed, centrifuged, and dried at 75 °C to obtain a white precursor powder. This precursor was heated to 580 °C at 4.5 °C / min, then to 880 °C at 1.5 °C / min and held for 3.5 h to obtain Al₂O₃ nanosheets. 10 g of Al₂O₃ nanosheets were then dispersed in 350 mL of deionized water and sonicated for 25 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 10% was added to the solution, and stirring was continued for 25 min. The solvent was removed by rotary evaporation, and the solution was calcined at 620 °C for 3 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying in an oven at 85°C for 9 hours and calcining at 750°C for 5.5 hours in solution (1.8% by mass).

[0036] Example 7 11.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 13 h. 9 mL of deionized water was added to the mixture, and stirring continued for 25 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 115 °C for 2.5 h. The resulting mixture was cooled, washed, centrifuged, and dried at 85 °C to obtain a white precursor powder. This precursor was heated to 620 °C at 5.5 °C / min, then to 920 °C at 1.5 °C / min and held for 4.5 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 450 mL of deionized water and sonicated for 35 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 25% was added to the solution, and stirring continued for 35 min. The solvent was removed by rotary evaporation, and the solution was calcined at 680 °C for 3 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying the solution (1% by mass) in an oven at 80°C for 8 hours and then calcining it at 700°C for 4 hours.

[0037] Example 8 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 10 h. 12 mL of deionized water was added to the mixture, and stirring was continued for 20 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted in an oven at 100 °C for 2 h. The resulting mixture was cooled, washed, centrifuged, and dried at 90 °C to obtain a white precursor powder. This precursor was heated to 650 °C at 4 °C / min, then to 900 °C at 2 °C / min and held for 3 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 400 mL of deionized water and sonicated for 40 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 15% was added to the solution, and stirring was continued for 15 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 2 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with... The PtGa / Al2O3 catalyst was obtained by drying in a 72℃ oven for 6.5 h in solution (0.8% by mass) and then calcining at 630℃ for 3.5 h.

[0038] Example 9 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 14 h. 8 mL of deionized water was added to the mixture, and stirring continued for 20 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 120 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 70 °C to obtain a white precursor powder. This precursor was heated to 550 °C at 6 °C / min, then to 900 °C at 1 °C / min and held for 5 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 400 mL of deionized water and sonicated for 20 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring continued for 45 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying in a solution (1.9% by mass) at 88°C for 9.5 hours and then calcining at 780°C for 5.8 hours. Comparative Example 1 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 110 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. 10 g of Al₂O₃ nanosheets were then dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 1% (below the lower limit of 2%) was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying in a solution (1% by mass) at 80℃ for 8 hours and then calcining at 700℃ for 4 hours. Because the Ga / Al molar ratio was below the lower limit, Pt species agglomeration occurred, reducing the number of PtGa alloy sites. This resulted in the synthesized catalyst exhibiting poor performance in promoting H2O dissociation and C–F bond activation.

[0039] Comparative Example 2 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 110 °C in an oven for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. 10 g of Al₂O₃ nanosheets were then dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 40% (above the upper limit of 35%) was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying in a solution (1% by mass) at 80℃ for 8 hours and then calcining at 700℃ for 4 hours. Because the Ga / Al molar ratio was higher than the upper limit, the amount of Pt modification was too low, resulting in a reduced number of PtGa alloy sites and consequently, poor performance in promoting H2O dissociation and C–F bond activation.

[0040] Comparative Example 3 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted in an oven at 110 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 550 °C (below the lower limit of 600 °C) for 4 h to obtain the Ga / Al₂O₃ catalyst. Subsequently, 10g of Ga / Al2O3 catalyst was impregnated in... The PtGa / Al2O3 catalyst was obtained by drying in a solution (1% by mass) at 80℃ for 8 hours and then calcining at 700℃ for 4 hours. However, due to the excessively low calcination temperature, Ga could not be incorporated into the Al2O3 material and remained on the Al2O3 surface as Ga2O3, resulting in the unsuccessful synthesis of the Ga / Al2O3 material.

[0041] Comparative Example 4 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 110 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. The precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. 10 g of Al₂O₃ nanosheets were then dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 750 °C (above the upper limit of 700 °C) for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with… The PtGa / Al2O3 catalyst was obtained by drying the solution (1% by mass) in an oven at 80℃ for 8 hours and then calcining it at 700℃ for 4 hours. The excessively high calcination temperature of Ga / Al2O3 led to a significant decrease in the catalyst's specific surface area, reducing the exposed active sites and thus lowering the catalytic decomposition performance of CF4.

[0042] Comparative Example 5 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 110 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. 10 g of Al₂O₃ nanosheets were then dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with... The PtGa / Al2O3 catalyst was obtained by drying in a solution (1% by mass) at 80°C for 8 hours and then calcining at 550°C (below the lower limit of 600°C) for 4 hours. Due to the excessively low calcination temperature of PtGa / Al2O3, the formation of PtGa alloy sites was not observed.

[0043] Comparative Example 6 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 110 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. 10 g of Al₂O₃ nanosheets were then dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with... The PtGa / Al2O3 catalyst was obtained by drying in a solution (1% by mass) at 80°C for 8 hours and then calcining at 850°C (above the upper limit of 800°C) for 4 hours. The excessively high calcination temperature of PtGa / Al2O3 led to the sintering and agglomeration of Pt species, reducing the number of PtGa alloy sites.

[0044] Comparative Example 7 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 110 °C in an oven for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at a rate of 3 °C / min (below the lower limit of 4 °C / min), then further heated to 900 °C at a rate of 2.5 °C / min (above the upper limit of 2 °C / min) and held for 4 h to obtain Al₂O₃ nanosheets. Subsequently, 10 g of Al₂O₃ nanosheets were dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the mixture was calcined at 650 °C for 4 h to obtain the Ga / Al₂O₃ catalyst. Subsequently, 10g of Ga / Al2O3 catalyst was impregnated in... The PtGa / Al2O3 catalyst was obtained by drying the Al2O3 precursor (1% by mass) in a solution at 80℃ for 8 hours and then calcining it at 700℃ for 4 hours. Due to the excessive heating rate of the Al2O3 precursor, the synthesized Al2O3 consisted of multiple different crystal phases (γ phase and θ phase), which reduced the number of PtGa alloy sites and decreased the CF4 catalytic decomposition performance.

[0045] Comparative Example 8 ( (Solution concentration exceeds standard) 10.0 g of aluminum isopropoxide was added to 100 mL of isopropanol solution and stirred at 500 rpm for 12 h. 10 mL of deionized water was added to the mixture, and stirring was continued for 10 min. The mixture was then transferred to a 150 mL polytetrafluoroethylene-lined reactor and reacted at 110 °C for 1 h. The resulting mixture was cooled, washed, centrifuged, and dried at 80 °C to obtain a white precursor powder. This precursor was heated to 600 °C at 5 °C / min, then to 900 °C at 1 °C / min and held for 4 h to obtain Al₂O₃ nanosheets. 10 g of Al₂O₃ nanosheets were then dispersed in 400 mL of deionized water and sonicated for 30 min. Ga(NO₃)₃ with a molar ratio (Ga / Al) of 30% was added to the solution, and stirring was continued for 30 min. The solvent was removed by rotary evaporation, and the solution was calcined at 650 °C for 4 h to obtain a Ga / Al₂O₃ catalyst. 10 g of the Ga / Al₂O₃ catalyst was then impregnated with... The PtGa / Al2O3 catalyst was obtained by drying in a solution (2.5% by mass, exceeding the upper limit of 2%) at 80°C for 8 hours and then calcining at 700°C for 4 hours. Due to... Excessive solution concentration led to large-scale aggregation of Pt species, resulting in a significant reduction in the number of observed PtGa alloy sites.

[0046] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon tetrafluoride catalyst, characterized in that, Includes the following steps: S1. Preparation of Al2O3 nanosheets; S2. Load Ga components onto the Al2O3 nanosheets, and obtain Ga / Al2O3 precursor by drying and calcination; S3. Pt components are loaded onto the Ga / Al2O3 precursor, and then dried and calcined to obtain a Pt-Ga / Al2O3 catalyst.

2. The method for preparing a carbon tetrafluoride catalyst according to claim 1, characterized in that, In step S1, the preparation of the Al2O3 nanosheets includes: dissolving aluminum isopropoxide in isopropanol and stirring to disperse it, adding deionized water and transferring it to a reaction vessel for hydrothermal reaction, cooling, washing, centrifuging and drying the product to obtain a white precursor powder, and then calcining the white precursor powder by stepwise heating to obtain Al2O3 nanosheets.

3. The method for preparing a carbon tetrafluoride catalyst according to claim 2, characterized in that, In step S1, the ratio of aluminum isopropoxide to isopropanol is 0.08-0.12 g / mL, the stirring rate is 500 rpm, and the stirring time is 10-14 h; the hydrothermal reaction temperature is 100-120℃, and the reaction time is 0.5-3 h; the stepwise heating and calcination process is as follows: the temperature is increased to 550-650℃ at a rate of 4-6℃ / min, and then increased to 850-950℃ at a rate of 1-2℃ / min, and held at that temperature for 3-5 h.

4. The method for preparing a carbon tetrafluoride catalyst according to claim 1, characterized in that, In step S2, the specific process for obtaining the Ga / Al2O3 precursor is as follows: Al2O3 nanosheets are dispersed in deionized water and ultrasonically treated, Ga(NO3)3 solution is added and continuously stirred, the solvent is removed by rotary evaporation and then calcined; wherein, the molar ratio of Ga to Al is 2%-35%, the ultrasonic treatment time is 20-40 min, and the stirring time is 15-45 min.

5. The method for preparing a carbon tetrafluoride catalyst according to claim 4, characterized in that, In step S2, the dispersion ratio of Al2O3 nanosheets in deionized water is 10g:(300-500)mL; the calcination temperature is 600-700℃, and the calcination time is 2-4h.

6. The method for preparing a carbon tetrafluoride catalyst according to claim 1, characterized in that, In step S3, the raw material used for supporting the Pt component is... The solution, the The mass concentration of the solution is 0.5%-2%.

7. The method for preparing a carbon tetrafluoride catalyst according to claim 6, characterized in that, In step S3, the drying process parameters are: temperature 70-90℃, time 6-10h; the calcination process parameters are: temperature 600-800℃, time 3-6h.

8. The method for preparing a carbon tetrafluoride catalyst according to claim 6, characterized in that, In step S3, The volume of solution added should be sufficient to fully wet the Ga / Al2O3 precursor.

9. A carbon tetrafluoride catalyst, characterized in that, It is prepared by the method for preparing a carbon tetrafluoride catalyst according to any one of claims 1-8.

10. The application of the carbon tetrafluoride catalyst according to claim 9 in the treatment of carbon tetrafluoride-containing flue gas, characterized in that, The concentration of CF4 in the carbon tetrafluoride-containing flue gas is 1500-3500 ppm, the volume percentage of H2O is 10%-50%, and the catalytic reaction temperature is 450-650℃.

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