Preparation process of neodymium-iron-boron oil sludge solid waste for preparing VOCs catalytic oxidation catalyst, product and application thereof

Abstract

The application discloses a preparation process of a neodymium iron boron oil sludge solid waste for preparing a VOCs catalytic oxidation catalyst, and a product and application thereof. The process comprises the following steps: heat treatment of the neodymium iron boron oil sludge, treatment of the oil sludge by using an oxalic acid solution with a temperature of 60-75 DEG C to obtain a multi-rare earth oxalate; impregnation by adding manganese nitrate according to a molar ratio of rare earth to manganese of 1:3-1:6; low-temperature plasma treatment under a pure oxygen atmosphere after drying; and calcination at 300-500 DEG C. The application takes the multi-component rare earth (Nd, Pr, Ce) oxalate in the oil sludge as a precursor, combines oxygen plasma valence state regulation, and obtains a RE-Mn-O composite oxide rich in oxygen vacancies. The catalyst is used for VOCs catalytic oxidation, and T98 reaches 240 DEG C in 1000 ppm dimethylbenzene, has the advantages of high value of solid waste and low cost, and avoids the high energy consumption defect of traditional wet extraction separation.

Description

Technical Field

[0001] This invention relates to the field of multi-rare earth composite oxide catalysts for solid waste resource utilization and catalytic oxidation of volatile organic compounds, and to a preparation process, product and application of a NdFeB oil sludge solid waste VOCs catalytic oxidation catalyst. Background Technology

[0002] Neodymium iron boron (NdFeB) sludge is a cutting waste generated during the processing of rare earth permanent magnet materials. Due to its high-value rare earth elements (such as neodymium, praseodymium, and dysprosium), it is considered a valuable secondary resource, and its recycling has significant strategic and economic value. Currently, the mainstream recycling processes include pyrometallurgical regeneration, calcium diffusion reduction, and hydrometallurgy. Among these, the hydrometallurgical process is the most mature. It typically involves pre-treating the sludge with oxidative roasting, followed by a process of "acid dissolution-impurity removal-extraction separation-calcination" to extract a series of high-purity rare earth oxides. Although the hydrometallurgical process is relatively mature, the extraction and separation processes are energy-intensive, making it particularly uneconomical for NdFeB sludge that does not contain high-value heavy rare earth elements. Therefore, exploring a new, low-energy-consumption, high-value resource recovery path is of great significance.

[0003] On the other hand, with the continuous rise in the price of precious metals in the country, the industrial cost of precious metal catalysts used for the catalytic oxidation of volatile organic compounds (VOCs) is also constantly increasing. Therefore, in the field of VOCs catalytic oxidation, there is an urgent need to develop highly active transition metal oxide catalysts to replace industrially used precious metal catalysts and reduce the cost of industrial applications. Currently, the mainstream transition metal oxide catalysts reported in research mainly focus on CeO2-based composite oxide catalysts, but there are few reports on Nd2O3-based composite oxide catalysts. If the characteristics of my country's NdFeB oil sludge solid waste resources can be effectively utilized and transformed into new materials applicable to the catalytic oxidation of volatile organic compounds, it will help achieve the synergistic development of solid waste resource utilization and high-end material preparation, which would be a research project with great industrial practical value.

[0004] This invention proposes a novel approach to the recycling of NdFeB oil sludge solid waste. It utilizes the rare earth components in the NdFeB oil sludge solid waste as precursors to prepare a VOCs catalytic oxidation catalyst with highly active oxygen vacancies. The synthesis method of this catalyst is unique and low-cost, and it also simultaneously solves the problem of resource utilization of NdFeB oil sludge. Summary of the Invention

[0005] One objective of this invention is to overcome the shortcomings and deficiencies of existing technologies and provide a method for preparing a highly active oxygen vacancy catalyst, aiming to effectively utilize the multi-component rare earth elements in NdFeB oil sludge. This method enables the effective resource recovery of NdFeB oil sludge solid waste, producing a suitable VOCs catalytic oxidation catalyst, which is characterized by convenient synthesis and low cost.

[0006] The objective of this invention is achieved through the following solution: A process for preparing a NdFeB oil sludge solid waste VOCs catalytic oxidation catalyst includes the following steps: Step (1): Obtain neodymium iron boron sludge solid waste from the rare earth permanent magnet material production line, wherein the neodymium iron boron sludge solid waste includes Nd, Pr and Ce elements; perform heat treatment on the neodymium iron boron sludge solid waste; Step (2): Add oxalic acid solution to the heat-treated product, stir and react under heating conditions of 60-75°C for 1-5 hours to treat with oxalic acid, and filter and separate while hot to obtain poly-rare earth oxalate precipitate. Step (3): Using the rare earth oxalate precipitate as a carrier, according to the molar ratio of rare earth to manganese in the range of 1:3 to 1:6, add manganese nitrate solution dropwise to the rare earth oxalate mixture and impregnate for a period of time. Step (4): The product obtained in step (3) is dried and dehydrated, and then subjected to low-temperature plasma treatment in a pure oxygen atmosphere; Step (5): The product obtained in step (4) is calcined at a high temperature of 300-500°C to obtain a VOCs catalytic oxidation catalyst.

[0007] Preferably, in step (2), the concentration of the oxalic acid solution is 3 mol / L.

[0008] Preferably, in step (3), the molar ratio of rare earth to manganese is 1:3.

[0009] Preferably, in step (3), the soaking time is specifically soaking for no less than 12 hours.

[0010] Preferably, in step (4), the drying and dehydration are carried out at 100°C.

[0011] Preferably, in step (4), the low-temperature plasma treatment time is 0.5 to 5 hours; and the low-temperature plasma discharge power is 50 to 80 W.

[0012] Preferably, in step (5), the calcination time is not less than 3 hours.

[0013] Preferably, in step (1), the heat treatment specifically includes: heat treatment at 500°C for no less than 1 hour in an air atmosphere.

[0014] The present invention also provides the VOCs catalytic oxidation catalyst prepared by the above-described preparation process and the application of the VOCs catalytic oxidation catalyst, which is applied to the catalytic oxidation of volatile organic compounds with a concentration of not less than 1000 ppm.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The main body of the VOCs catalytic oxidation catalyst of the present invention comes from the multi-component rare earth elements (mainly Nd, accompanied by Pr, Ce and other components) in NdFeB oil sludge solid waste. Since the traditional wet process of separation and extraction followed by utilization is abandoned, the multi-component rare earth oxalate intermediate product of the wet process is directly used as the precursor, thus greatly reducing the energy consumption required for the process; 2. The present invention obtains a multi-rare earth-based composite oxide catalyst with abundant oxygen vacancies through oxygen plasma bombardment, which has high efficiency VOCs catalytic oxidation activity. Attached Figure Description

[0016] Figure 1 This is the full spectrum of the sample with a rare earth to manganese molar ratio of 1:3 in Example 3.

[0017] Figure 2 The image shows the O-XPS plot of the sample with a rare earth to manganese molar ratio of 1:3 in Example 3.

[0018] Figure 3 The image shows the Mn-XPS spectrum of the sample with a rare earth to manganese molar ratio of 1:3 in Example 3.

[0019] Figure 4 The image shows the Raman spectrum of the sample with a rare earth to manganese molar ratio of 1:3 in Example 3. Detailed Implementation

[0020] This invention combines wet processing, equal-volume impregnation, and low-temperature plasma preparation to obtain a multi-rare-earth-based composite oxide catalyst. In the above chemical synthesis process, the key technology for preparing a highly efficient VOCs catalytic oxidation catalyst lies in the lattice doping between components and the regulation of oxygen vacancies in the multi-rare-earth-based composite oxide. The specific reaction principle is as follows: First, multi-rare-earth oxalates are obtained through a wet process, and the crystal structure of the precipitate is controlled by adjusting the treatment temperature and time. In traditional wet processes, the recovery of rare-earth components is paramount; therefore, higher treatment temperatures and longer treatment times are beneficial for improving the recovery rate of multi-rare-earth components. However, high temperatures and long treatment times lead to larger crystal sizes and excessive crystallinity in the multi-rare-earth oxalates, which is detrimental to subsequent chemical modification. Therefore, in this process, the oxalate treatment temperature and time are controlled to obtain highly chemically active multi-rare-earth oxalates while maximizing the rare-earth yield. It is important to note that using oxalate as a carrier, the complexation between oxalate and Mn ions facilitates the dispersion of Mn ions. Highly dispersed Mn ions are more likely to undergo lattice doping with rare-earth ions, generating more oxygen vacancies. If rare-earth oxides with a nearly complete lattice structure are used as carriers, Mn ions are less likely to be effectively embedded in their lattice. Secondly, when manganese ions are introduced into poly-rare earth oxalates, the catalyst precursor is bombarded with low-temperature plasma under an oxygen atmosphere. This process promotes the decomposition of poly-rare earth oxalates and manganese nitrate to obtain composite oxides. More importantly, it oxidizes divalent manganese ions (manganese nitrate) to tetravalent manganese ions through highly oxidizing oxygen free radicals. Since the rare earth components contain trivalent Nd... 3+ Mainly, by Nd 3+ and Mn 4+ A large number of highly active oxygen vacancies can only be formed through lattice doping. Finally, calcination at an appropriate temperature stabilizes the crystal structure of the composite oxide, meeting the requirements for long-term catalyst use in the catalytic oxidation of VOCs in actual industry.

[0021] The present invention will be further analyzed below with reference to specific embodiments.

[0022] Example 1 Neodymium iron boron sludge solid waste was heat-treated at 500℃ for 1 hour in air atmosphere. 3 mol / L oxalic acid was added to the heat-treated product, and the mixture was stirred and reacted at a certain temperature for 3 hours. The product was then filtered while hot to separate poly-rare earth oxalate precipitates. Using these poly-rare earth oxalate precipitates as a carrier, manganese nitrate solution was added dropwise to the poly-rare earth oxalate mixture at a rare earth to manganese molar ratio of 1:3, and the mixture was impregnated for 12 hours. The resulting mixture was dried and dehydrated at 100℃, and then treated with low-temperature plasma at a discharge power of 65W for 1.5 hours in a pure oxygen atmosphere. Finally, the plasma-treated sample was calcined at 550℃ for 3 hours to obtain the desired VOCs catalytic oxidation catalyst, RE-Mn-O composite oxide. The obtained catalyst was then subjected to the catalytic oxidation reaction of xylene, where the xylene concentration was 1000 ppm (the remainder being air), using a T... 98 The reaction temperature (at which the conversion rate is 98%) was compared with the catalyst activity. The effect of oxalic acid treatment temperature on catalyst performance is shown in Table 1.

[0023] Table 1. Effect of oxalic acid treatment temperature on xylene catalytic oxidation performance

[0024] As shown in Table 1, the catalytic oxidation activity of the prepared catalyst for xylene decreases when the oxalic acid treatment temperature is too high. Excessive oxalic acid treatment temperature leads to larger crystal sizes and excessive crystallinity, which is detrimental to subsequent chemical modification and thus affects the catalytic activity of the catalyst.

[0025] Example 2 Neodymium iron boron sludge solid waste was heat-treated at 500℃ for 1 hour in air atmosphere. 3 mol / L oxalic acid was added to the heat-treated product, and the mixture was stirred at 75℃ for a certain time. The product was then filtered while hot to separate poly-rare earth oxalate precipitates. Using these poly-rare earth oxalate precipitates as a carrier, manganese nitrate solution was added dropwise to the poly-rare earth oxalate mixture at a rare earth to manganese molar ratio of 1:3, and the mixture was impregnated for 12 hours. The resulting mixture was dried and dehydrated at 100℃, and then treated with low-temperature plasma at a discharge power of 65W for 1.5 hours in a pure oxygen atmosphere. Finally, the plasma-treated sample was calcined at 550℃ for 3 hours to obtain the desired VOCs catalytic oxidation catalyst, RE-Mn-O composite oxide. The obtained catalyst was then subjected to the catalytic oxidation of xylene, where the xylene concentration was 1000 ppm (the remainder being air), using a T... 98 The reaction temperature (at which the conversion rate is 98%) was compared with the catalyst activity. The effect of oxalic acid treatment temperature on catalyst performance is shown in Table 2.

[0026] Table 2 Effect of oxalic acid treatment time on xylene catalytic oxidation performance

[0027] Table 2 shows that when the oxalic acid treatment time is too long, the catalytic oxidation activity of the prepared catalyst for xylene decreases. Excessive oxalic acid treatment time leads to larger crystal sizes and excessive crystallinity, which is detrimental to subsequent chemical modification and thus affects the catalytic activity of the catalyst. Considering the recovery rate of rare earth elements, a 3-hour oxalic acid treatment time is preferred.

[0028] Example 3 Neodymium iron boron sludge solid waste was heat-treated at 500℃ for 1 hour in air atmosphere. 3 mol / L oxalic acid was added to the heat-treated product, and the mixture was stirred at 75℃ for 3 hours. The product was then filtered while hot to separate poly-rare earth oxalate precipitates. Using these poly-rare earth oxalate precipitates as a carrier, manganese nitrate solution was added dropwise to the poly-rare earth oxalate mixture according to a specific molar ratio of rare earth to manganese, and the mixture was impregnated for 12 hours. The resulting mixture was dried and dehydrated at 100℃, and then treated with low-temperature plasma at a discharge power of 65W for 1.5 hours in a pure oxygen atmosphere. Finally, the plasma-treated sample was calcined at 550℃ for 3 hours to obtain the desired VOCs catalytic oxidation catalyst, RE-Mn-O composite oxide. The obtained catalyst was then subjected to the catalytic oxidation of xylene, where the xylene concentration was 1000 ppm (the remainder being air), using a T... 98 The reaction temperature (at which the conversion rate is 98%) was compared with the catalyst activity. The effect of the molar ratio of rare earth elements to manganese on catalyst performance is shown in Table 3.

[0029] Table 3. Effect of the molar ratio of rare earth elements to manganese on the catalytic oxidation performance of xylene.

[0030] As shown in Table 3, the molar ratio of rare earth elements to manganese has a significant impact on the catalytic oxidation activity of xylene. The main reason is that different doping ratios directly affect the content and activity of sample vacancy sites in the composite oxide.

[0031] In this invention, the selection of the RE:Mn molar ratio and the low-temperature plasma treatment in a pure oxygen atmosphere constitute a key coupling, which is the core of obtaining highly active oxygen vacancies in the catalyst. Table 3 shows that the RE:Mn ratio shifts from 1:3 to 6:1 (excess rare earth element, T 98 =275℃) or 1:6 (Mn excess, T 98 =252℃) both resulted in a significant decrease in activity, indicating that Nd only showed activity within this window. 3+ With Mn 4+ Only a specific lattice doping ratio can maximize oxygen vacancy production. And Mn... 4+ The generation depends on a plasma step: the strong oxidizing oxygen free radicals generated by pure oxygen plasma can oxidize Mn from manganese nitrate. 2+ In-situ oxidation to Mn 4+ , Figure 3 Mn-XPS shows Mn on the catalyst surface 4+ The proportion is high; without this step, it would be difficult to push Mn to the tetravalent state by subsequent calcination at 300–550℃ alone, and Nd... 3+ –Mn 4+ Doping chain breakage affects oxygen vacancy density; Figure 2 O-XPS confirms that the product prepared by this invention has a large number of oxygen vacancies.

[0032] Tables 4 and 5 further provide plasma parameter windows: T at a discharge power of 65W and a processing time of 1.5h. 98 Optimal (240℃), insufficient oxygen free radicals when power is reduced to 50W (T 98 =252℃), increasing to 80W or extending the etching time to 5h results in over-etching without any gain. It is evident that the doping window and the parameter window of pure oxygen plasma are not independently optimized parameters, but rather jointly serve the "Mn" parameter. 4 + –Nd 3+ The single mechanism target of "lattice doping → oxygen vacancy enrichment" has not been disclosed in the existing literature on VOCs catalytic oxidation. Currently, most non-precious metal VOCs catalysts are CeO2-based, and Nd2O3-based composite oxides are rarely reported. Furthermore, there is no coupled approach of oil sludge multi-rare earth oxalate + oxygen plasma treatment proposed in this invention.

[0033] Example 4 Neodymium iron boron sludge solid waste was heat-treated at 500℃ for 1 hour in air atmosphere. 3 mol / L oxalic acid was added to the heat-treated product, and the mixture was stirred at 75℃ for 3 hours. The product was then filtered while hot to separate poly-rare earth oxalate precipitates. Using these poly-rare earth oxalate precipitates as a carrier, manganese nitrate solution was added dropwise to the poly-rare earth oxalate mixture at a rare earth to manganese molar ratio of 1:3, and the mixture was impregnated for 12 hours. The resulting mixture was dried and dehydrated at 100℃, and then treated with low-temperature plasma at a certain discharge power under a pure oxygen atmosphere for 1.5 hours. Finally, the plasma-treated sample was calcined at 550℃ for 3 hours to obtain the desired VOCs catalytic oxidation catalyst, RE-Mn-O composite oxide. The obtained catalyst was then subjected to the catalytic oxidation of xylene, where the xylene concentration was 1000 ppm (the remainder being air), using a T... 98 The reaction temperature (at which the conversion rate is 98%) was compared with the catalyst activity. The effect of discharge power on catalyst performance is shown in Table 4.

[0034] Table 4. Effect of discharge power on xylene catalytic oxidation performance

[0035] Table 4 shows that the discharge power has a certain impact on the catalytic oxidation activity of xylene on the catalyst. The oxygen free radicals generated by the oxygen low-temperature plasma have strong oxidizing properties and can effectively oxidize divalent manganese to tetravalent manganese, which is beneficial to Nd... 3+ After being doped into its crystal lattice, a large number of highly active oxygen vacancies are eventually formed. Therefore, appropriately increasing the discharge power can increase the content of oxygen free radicals in the atmosphere, thereby enhancing its oxidation of divalent manganese.

[0036] Example 5 Neodymium iron boron sludge solid waste was heat-treated at 500℃ for 1 hour in air atmosphere. 3 mol / L oxalic acid was added to the heat-treated product, and the mixture was stirred at 75℃ for 3 hours. The product was then filtered while hot to separate poly-rare earth oxalate precipitates. Using these poly-rare earth oxalate precipitates as a carrier, manganese nitrate solution was added dropwise to the poly-rare earth oxalate mixture at a rare earth to manganese molar ratio of 1:3, and the mixture was impregnated for 12 hours. The resulting mixture was dried and dehydrated at 100℃, and then treated with low-temperature plasma at a discharge power of 65W in a pure oxygen atmosphere for a certain number of hours. Finally, the plasma-treated sample was calcined at 550℃ for 3 hours to obtain the desired VOCs catalytic oxidation catalyst, RE-Mn-O composite oxide. The obtained catalyst was then subjected to the catalytic oxidation of xylene, where the xylene concentration was 1000 ppm (the remainder being air), using a T... 98 The reaction temperature (at which the conversion rate is 98%) was compared with the catalyst activity. The effect of discharge time on catalyst performance is shown in Table 5.

[0037] Table 5. Effect of discharge time on xylene catalytic oxidation performance

[0038] Example 6 Neodymium iron boron sludge solid waste was heat-treated at 500℃ for 1 hour in air atmosphere. 3 mol / L oxalic acid was added to the heat-treated product, and the mixture was stirred at 75℃ for 3 hours. The product was then filtered while hot to separate poly-rare earth oxalate precipitates. Using these poly-rare earth oxalate precipitates as a carrier, manganese nitrate solution was added dropwise to the poly-rare earth oxalate mixture at a rare earth to manganese molar ratio of 1:3, and the mixture was impregnated for 12 hours. The resulting mixture was dried and dehydrated at 100℃, and then treated with low-temperature plasma at a discharge power of 65W for 1.5 hours in a pure oxygen atmosphere. Finally, the plasma-treated sample was calcined at a certain temperature for 3 hours to obtain the desired VOCs catalytic oxidation catalyst, RE-Mn-O composite oxide. The obtained catalyst was then subjected to the catalytic oxidation of xylene, where the xylene concentration was 1000 ppm (the remainder being air), using a T... 98 The reaction temperature (at which the conversion rate is 98%) was compared with the catalyst activity. The effect of high-temperature calcination temperature on catalyst performance is shown in Table 6.

[0039] Table 6. Effect of high-temperature calcination temperature on xylene catalytic oxidation performance

[0040] As shown in Table 6, excessively high calcination temperatures are detrimental to the catalytic oxidation of xylene on the catalyst. This is mainly because high temperatures cause rare earth oxides such as Nd₂O₃ to precipitate from the crystal lattice of the composite oxide, thereby reducing the oxygen vacancy content in the system. Therefore, preferably, the high-temperature calcination temperature should not exceed 550℃.

[0041] Example 7 Neodymium iron boron sludge solid waste was heat-treated at 500℃ for 1 hour in air. 3 mol / L oxalic acid was added to the heat-treated product, and the mixture was stirred at 75℃ for 3 hours. The product was then filtered while hot to separate multi-rare earth oxalate precipitates. These precipitates were calcined at high temperature to decompose into multi-component rare earth oxides, which served as a support. Manganese nitrate solution was added dropwise to the multi-component rare earth oxides at a rare earth to manganese molar ratio of 1:3, and the mixture was impregnated for 12 hours. The resulting mixture was dried at 100℃ and then treated with low-temperature plasma at a discharge power of 65W for 1.5 hours in a pure oxygen atmosphere. Finally, the plasma-treated sample was calcined at 550℃ for 3 hours to obtain the desired VOCs catalytic oxidation catalyst RE-Mn-O composite oxide. Simultaneously, a composite oxide catalyst was prepared using multi-rare earth oxalates and neodymium oxalate as supports, with subsequent preparation steps consistent with the above.

[0042] The obtained catalyst was used for the catalytic oxidation of xylene, wherein the xylene concentration was 1000 ppm (the remainder being air), using T... 98 The reaction temperature (at which the conversion rate is 98%) was compared with the catalyst activity. The effect of different supports on catalyst performance is shown in Table 7.

[0043] Table 7. Effect of different supports on the catalytic oxidation performance of xylene

[0044] Table 7 shows that the type of support has a significant impact on the catalytic oxidation performance of composite oxides. Catalysts prepared using oxalate as the support exhibit far superior catalytic activity compared to traditional oxide support systems. This is mainly attributed to the fact that oxalate ions facilitate the dispersion of Mn ions, and highly dispersed Mn ions are more readily involved in subsequent lattice doping with rare earth ions. In contrast, if rare earth oxides with relatively complete lattice structures are used as supports, Mn ions are less likely to be effectively embedded in their lattice. Furthermore, compared to neodymium oxalate alone, multi-rare earth oxalates containing small amounts of Ce and Pr can further enhance the lattice doping effect, thereby effectively improving catalytic activity.

[0045] This invention uses polyrare earth oxalates obtained directly from NdFeB sludge through oxalic acid treatment as a carrier to prepare RE–Mn–O composite oxides. Compared with the traditional wet process, this method produces the following advantages: Firstly, the residual oxalate ions in the oxalate carrier can react with the subsequently added Mn...2+ Complexation occurs, resulting in high dispersion of Mn ions on the support surface. This facilitates their embedding into the rare-earth lattice to form a doped structure during low-temperature plasma and calcination stages. Figure 4 Raman spectroscopy corroborates Mn 4+ –Nd 3+ Lattice doping is valid; however, if a rare earth oxide with a nearly complete lattice is used as the support, Mn is difficult to embed effectively, as shown in Table 7. 98 It deteriorates to 300°C, which is 60°C higher than that of oxalate carriers. On the other hand, the "multi-component" characteristics of oil sludge, such as Figure 1 It was confirmed that Nd, Pr, Ce, O, and Mn were added as dopants, and they also showed synergistic gains compared to the single Nd oxalate support: Table 7 shows the T samples of the pure Nd oxalate support. 98 =270℃, while the rare earth oxalate support sample containing small amounts of Ce and Pr has a temperature of T 98 =240℃, Ce 3+ / Pr 3+ With Nd 3+ Coexistence can further distort the crystal lattice and promote the generation of oxygen vacancies, an effect that cannot be obtained in a single rare earth system. Therefore, this invention achieves low-consumption resource utilization of solid waste at the source and improves the chemical activity of the precursor by synergistically utilizing two technical points: direct extraction of oxalate intermediates and multi-component coexistence.

[0046] This invention employs mild treatment conditions in both the oxalic acid treatment (60–75℃, 1–3h) and the final high-temperature calcination (300–550℃, see Table 6). This synergizes with the aforementioned "oxalate support + plasma valence state regulation": if oxalate is over-calcined and transformed into a rare earth oxide with a complete lattice, it affects Mn intercalation; if calcination exceeds 550℃, the Re–Mn ​​doped lattice constructed in the previous plasma treatment will disintegrate and oxygen vacancies will collapse. Therefore, the five-step process of this invention—oil sludge heat treatment → oxalic acid complexation → Mn equal-volume impregnation → oxygen plasma valence state pre-oxidation → low-temperature calcination for phase stabilization—is a synergistic whole with interlocked parameters. Any step deviating from this window will result in a T0... 98 The product floated to the surface. The final product was evaluated at 1000 ppm xylene (remaining air) using the T method. 98 It can reach around 240℃, which is 60℃ lower than the pure rare earth oxide carrier route and 30℃ lower than the single neodymium oxalate carrier. At the same time, the raw material cost is greatly reduced by directly utilizing oil sludge solid waste and avoiding the extraction and separation process, thus forming a three-in-one effect of solid waste resource utilization, high-performance catalyst and low preparation cost.

[0047] Figure 1The full spectrum of the sample with a rare earth to manganese molar ratio of 1:3 in Example 3 shows that the catalyst contains multiple elements such as Mn, Nd, Pr, Ce, and O. Mn is a subsequent dopant element, while Nd, Pr, and Ce are all derived from the recovered multi-component rare earth oxalate, indicating that the recovered rare earth is indeed a mixture mainly composed of Nd. Figure 2 The image shows the O-XPS diagram of the sample with a rare earth to manganese molar ratio of 1:3 in Example 3. It can be seen that the catalyst has a large number of O vacancies. Figure 3 The image shows the Mn-XPS spectrum of the sample with a rare earth to manganese molar ratio of 1:3 in Example 3. It can be seen that the catalyst surface has a high proportion of Mn. 4+ This helps it to work with Nd 3+ Lattice doping. Figure 4 The Raman spectrum of the sample with a rare earth element to manganese molar ratio of 1:3 in Example 3 further demonstrates the presence of Mn. 4+ With Nd 3+ The lattice doping between them. In summary, it can be inferred that in a sample with a rare earth to manganese molar ratio of 1:3, Nd... 3+ and Mn 4+ Only through lattice doping can a large number of highly active oxygen vacancies be formed, which meets the requirements of VOCs catalytic oxidation in industry.

Claims

1. A preparation process for a NdFeB oil sludge solid waste to prepare a VOCs catalytic oxidation catalyst, characterized in that... Includes the following steps: Step (1): Obtain neodymium iron boron sludge solid waste from the rare earth permanent magnet material production line, wherein the neodymium iron boron sludge solid waste includes Nd, Pr and Ce elements; perform heat treatment on the neodymium iron boron sludge solid waste; Step (2): Add oxalic acid solution to the heat-treated product, stir and react under heating conditions of 60-75°C for 1-5 hours to treat with oxalic acid, and filter and separate while hot to obtain poly-rare earth oxalate precipitate. Step (3): Using the rare earth oxalate precipitate as a carrier, according to the molar ratio of rare earth to manganese in the range of 1:3 to 1:6, add manganese nitrate solution dropwise to the rare earth oxalate mixture and impregnate for a period of time. Step (4): The product obtained in step (3) is dried and dehydrated, and then subjected to low-temperature plasma treatment in a pure oxygen atmosphere; Step (5): The product obtained in step (4) is calcined at a high temperature of 300-500°C to obtain a VOCs catalytic oxidation catalyst.

2. The preparation process of a NdFeB oil sludge solid waste to prepare a VOCs catalytic oxidation catalyst according to claim 1, characterized in that... In step (2), the concentration of the oxalic acid solution is 3 mol / L.

3. The preparation process of a NdFeB oil sludge solid waste to prepare VOCs catalytic oxidation catalyst according to claim 1, characterized in that... In step (3), the molar ratio of rare earth elements to manganese is specifically 1:

3.

4. The preparation process of a NdFeB oil sludge solid waste to prepare VOCs catalytic oxidation catalyst according to claim 1, characterized in that... In step (3), the soaking time specifically means soaking for no less than 12 hours.

5. The preparation process of a NdFeB oil sludge solid waste to prepare VOCs catalytic oxidation catalyst according to claim 1, characterized in that... In step (4), the drying and dehydration are carried out at 100°C.

6. The preparation process of a NdFeB oil sludge solid waste to prepare VOCs catalytic oxidation catalyst according to claim 1, characterized in that... In step (4), the low-temperature plasma treatment time is 0.5 to 5 hours; the low-temperature plasma discharge power is 50 to 80 W.

7. The preparation process of a NdFeB oil sludge solid waste to prepare VOCs catalytic oxidation catalyst according to claim 1, characterized in that... In step (5), the calcination time shall not be less than 3 hours.

8. The preparation process of a NdFeB oil sludge solid waste to prepare VOCs catalytic oxidation catalyst according to claim 1, characterized in that... In step (1), the heat treatment specifically includes: heat treatment at 500°C for no less than 1 hour in an air atmosphere.

9. A VOCs catalytic oxidation catalyst prepared by the preparation process according to any one of claims 1 to 8.

10. The application of the VOCs catalytic oxidation catalyst as described in claim 9, characterized in that, It is applied to the catalytic oxidation of volatile organic compounds with a concentration of not less than 1000 ppm.

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