A method for resourceful treatment of waste palladium catalyst

Abstract

The application provides a resource treatment method of waste palladium catalyst. The method first carries out microwave carbon removal, plasma etching and N-TiO2 light catalyst loading on the waste palladium catalyst to complete carrier loosening modification; then in a supercritical extraction kettle with an embedded ultraviolet LED lamp, a gradient strategy of 'weak complexing agent pre-washing impurity removal + strong complexing agent main palladium extraction' is adopted, combined with light catalysis-super critical synergistic effect to strengthen palladium desorption and selective extraction; then the impurity metal and weak complexing agent are recovered through reduced pressure condensation, and the palladium complex fluid is purified through a silica gel adsorption column; then the purified fluid is introduced into a loading kettle to mix with a carrier precursor suspension, hydrogen is introduced for in-situ reduction, and palladium nanoparticles are loaded, and a palladium-based catalyst applicable to industrial application is directly obtained through drying and calcination; finally, the waste carrier is microwave activated (active carbon carrier is additionally steam activated) to realize deep reuse.

Description

Technical Field

[0001] This invention belongs to the field of waste catalyst recycling and resource utilization technology, specifically relating to a resource utilization method for waste palladium catalyst. Background Technology

[0002] Palladium, a rare and precious metal, is widely used in supported catalysts in petrochemical, pharmaceutical synthesis, and automotive exhaust purification industries. With prolonged use, catalysts deactivate due to carbon buildup, poisoning, and loss of active components, resulting in large quantities of spent palladium catalysts. Current mainstream methods for recovering spent palladium catalysts include chlorine volatilization, support dissolution, selective dissolution, total dissolution, pyrometallurgical smelting, incineration, and supercritical water oxidation, but all have significant drawbacks. 1. Selective dissolution method uses inorganic solvents as extraction media, which has problems such as poor solvent diffusion and difficulty in penetrating the pores of the carrier to contact the encapsulated palladium, resulting in low palladium recovery rate. In addition, the solvent is prone to environmental pollution and has high subsequent processing costs. 2. Low-grade spent palladium catalysts (palladium content <0.1%) have high palladium dispersion and strong bonding with the support, making it difficult to achieve efficient recovery using existing methods, with recovery rates generally below 92%. 3. Industrial waste palladium catalysts are often accompanied by impurity metals such as Pt, Rh, and Cu. Existing coordination extraction systems have insufficient selectivity for palladium, and trace impurities can affect the purity of recovered palladium. 4. The palladium recovered by existing methods is mostly in powder form, which requires multiple processing steps such as pressing, sintering, and loading before it can be reused as a catalyst. The process is complicated and the palladium loss rate is 3-5%. At the same time, after the support is recovered, palladium needs to be reloaded to prepare new catalysts. The secondary loading process is energy-intensive and costly. 5. In traditional extraction processes, the desorption rate of palladium from the carrier surface is limited, resulting in long processing cycles and limiting the efficiency of large-scale applications. Summary of the Invention

[0003] Based on this, the present invention provides a method for the resource-based treatment of waste palladium catalysts, aiming to develop a waste palladium catalyst resource-based treatment process that combines high recovery rate, high selectivity, green and low consumption, and can realize in-situ regeneration of catalysts.

[0004] A first aspect of this invention provides a method for the resource recovery of spent palladium catalyst, comprising the following steps: S1. After crushing and drying the waste palladium catalyst, it is sequentially subjected to microwave treatment to remove carbon, low-temperature plasma etching in Ar atmosphere, and N-TiO2 photocatalyst loading to obtain the pretreated waste palladium catalyst. S2. Add the pretreated waste palladium catalyst and weak ligand to the supercritical extraction vessel, prewash with CO2 to remove impurities, then add a strong ligand and carry out supercritical extraction under ultraviolet light irradiation. S3. The CO2 fluid after pre-washing and impurity removal is subjected to reduced pressure condensation to recover the weak ligand and impurity metals, and the CO2 fluid after supercritical extraction is subjected to secondary adsorption purification. S4. The purified palladium-containing CO2 fluid is passed into the supported vessel, a support precursor suspension is added, and hydrogen is introduced for reduction to obtain a palladium / supported catalyst precursor, which is then dried and calcined to obtain a palladium-based catalyst. S5. Microwave activation is performed on the waste carrier after extraction, and the activated carbon carrier is further activated with water vapor. The regenerated carrier can be mixed and reused with the catalyst precursor.

[0005] Furthermore, in S1, the microwave processing power is 700-900W, the frequency is 2.45GHz, and the processing time is 5min; the low-temperature plasma etching power is 40-60W, and the processing time is 10-20min; the loading of N-TiO2 photocatalyst is 0.5-1%.

[0006] Furthermore, in S2, uniformly distributed ultraviolet LEDs with wavelengths of 360-370nm and power of 25-35W are embedded in the inner wall of the supercritical extraction vessel.

[0007] Furthermore, in S2, the weak ligand is dibutylphosphoric acid, and the amount used is 2-4% of the mass of the waste palladium catalyst; the pre-washing and impurity removal process conditions are: temperature 30-40℃, pressure 6-10MPa, stirring speed 250-350r / min, and time 20-40min.

[0008] Furthermore, in S2, the strong ligand is a complex system of trioctylphosphine oxide and fluoroacetylacetone, with a mass ratio of trioctylphosphine oxide to fluoroacetylacetone of 1:2, and the amount used is 5-8% of the mass of the spent palladium catalyst; the supercritical extraction process conditions are: temperature 40-60℃, pressure 10-15MPa, stirring rate 250-350r / min, and time 1-1.5h.

[0009] Furthermore, in S3, the CO2 fluid after pre-washing and impurity removal is depressurized to 4-6 MPa for condensation and separation; the secondary adsorption purification uses a secondary extraction column filled with silica gel adsorbent.

[0010] Furthermore, in S4, the carrier precursor suspension is one of γ-Al2O3 nanoparticle dispersion, activated carbon nanoparticle dispersion, or molecular sieve dispersion, with a solid content of 10-15% and a particle size of 20-50 nm.

[0011] Furthermore, in S4, the volume ratio of hydrogen to CO2 is 1:6-1:10, and the reduction process conditions are: temperature 80-100℃, pressure 3-5MPa, and time 0.8-1.2h.

[0012] Furthermore, in S4, the drying conditions are: temperature 110-130℃, time 1.5-2.5h; the calcination conditions are: temperature 400-500℃, time 2.5-3.5h.

[0013] Furthermore, in S5, the microwave activation power is 700-900W and the time is 8-12min; the activated carbon carrier steam activation conditions are 750-850℃ and 1.5-2.5h.

[0014] Compared with the prior art, implementing the present invention has the following beneficial effects: 1. This invention utilizes a photocatalytic-supercritical synergistic extraction mechanism, where ultraviolet light excites N-TiO2 to generate photogenerated holes, breaking the chemical bonds between palladium and the support. Combined with the high diffusivity of supercritical CO2, the extraction time is effectively shortened, and the palladium recovery rate of low-grade waste palladium catalyst (palladium content 0.05-0.1%) is improved, thus solving the problem of low-grade raw material processing. 2. By adopting a gradient coordination separation strategy of "weak coordination agent pre-washing + strong coordination agent main extraction", the precise separation of Pd from impurity metals such as Cu, Pt, and Rh was achieved, and the purity of palladium recovered reached 99.99%. At the same time, the recovery rate of impurity precious metals (such as Pt) was >90%, realizing the comprehensive recovery of multi-metal resources. 3. Innovative in-situ loading and molding technology is adopted to simultaneously load palladium nanoparticles onto the carrier precursor during the palladium reduction process, thus preparing palladium-based catalysts that can be used directly in one step. This eliminates the secondary molding and loading steps of palladium powder in traditional methods, effectively shortening the process and reducing palladium loss rate. 4. The entire process uses supercritical CO2 as a green medium, with a CO2 circulation rate of >95% and a complexing agent recovery rate of >98%. There is no wastewater, waste gas, or waste residue discharge. The trace amounts of CO2 generated during the roasting stage can be recovered and reused, achieving green closed-loop treatment. 5. Energy consumption is reduced, and the type of carrier precursor can be adjusted to meet the needs of waste palladium catalyst treatment in different fields, which is highly flexible. 6. The cost of catalyst regeneration is reduced, and the recovery of precious metal impurities can further increase the revenue per ton of raw material, resulting in significant economic value. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the implementation of a method for the resource recovery of waste palladium catalyst proposed in an embodiment of the present invention.

[0016] The following detailed embodiments will be further described in conjunction with the above-mentioned accompanying drawings. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0018] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] Please see Figure 1 The diagram below shows a process flow chart for the resource recovery method of waste palladium catalyst proposed in this embodiment of the invention. The preparation method includes the following steps: S1. After crushing and drying the waste palladium catalyst, it is then subjected to microwave treatment to remove carbon, low-temperature plasma etching in an Ar atmosphere, and N-TiO2 photocatalyst loading to obtain the pretreated waste palladium catalyst.

[0021] Among them, the spent palladium catalyst is a low-grade supported spent palladium catalyst with a palladium content of 0.05-0.5%, or the spent palladium catalyst is a multi-metal doped spent palladium catalyst containing one or more impurity metals among Pt, Rh, and Cu, with an impurity metal content of 0.01-0.05%. In addition, the support for the spent palladium catalyst is one of alumina, activated carbon, or molecular sieve.

[0022] Specifically, in S11, the waste palladium catalyst is crushed to 100-200 mesh and dried in a vacuum drying oven at 105°C for 2 hours to remove surface adsorbed water and organic matter. S12, using microwave treatment for 5 minutes, with a microwave power of 700-900W and a frequency of 2.45GHz, rapidly removes carbon from the surface of the carrier. S13 was etched by low-temperature plasma in an Ar atmosphere for 10-20 minutes with a plasma power of 40-60W. At the same time, N-TiO2 photocatalyst was loaded onto the support surface by plasma sputtering with a loading of 0.5-1%.

[0023] S2, pretreated waste palladium catalyst and weak ligand are added to the supercritical extraction vessel, CO2 is introduced for pre-washing to remove impurities, then a strong ligand is added, and supercritical extraction is carried out under ultraviolet light irradiation.

[0024] In an embodiment of the present invention, S21, the pretreated waste palladium catalyst and weak ligand are added to a supercritical extraction vessel. The inner wall of the supercritical extraction vessel is embedded with uniformly distributed ultraviolet LED lamps with a wavelength of 360-370nm and a power of 25-35W. S22, CO2 is introduced into the supercritical extraction vessel, the temperature is raised to 30-40℃, the pressure is increased to 6-10MPa, the stirring rate is 250-350r / min, and the vessel is pre-washed for impurities under continuous ultraviolet light irradiation for 20-40min; the weak ligand is dibutylphosphoric acid (DBP), and the amount used is 2-4% of the mass of the spent palladium catalyst. S23, discharge the CO2 fluid containing impurity metal-weak ligand complex, add a strong ligand to the supercritical extraction vessel, continue to introduce CO2, raise the temperature to 40-60℃, pressurize to 10-15MPa, stir at a rate of 250-350r / min, and extract palladium for 1-1.5h under continuous ultraviolet irradiation; the strong ligand is a complex system of trioctylphosphine oxide (TOPO) and fluoroacetylacetone (HFA), with a mass ratio of TOPO to HFA of 1:2, and the amount used is 5-8% of the mass of the spent palladium catalyst.

[0025] S3 involves reducing pressure and condensing the pre-washed CO2 fluid to recover the weak ligand and impurity metals, and then performing secondary adsorption purification on the supercritical CO2 fluid.

[0026] It should be noted that in S31, the CO2 fluid containing the impurity metal-weak ligand complex discharged from S22 is depressurized to 4-6 MPa and condensed to recover the weak ligand. The remaining impurity metal is dissolved in hydrochloric acid and then separated and purified using ion exchange resin. S32, the CO2 fluid containing the palladium-strong ligand complex in S23 is passed into a secondary extraction column, which is filled with silica gel adsorbent to adsorb residual trace impurity metal-weak ligand complex, thereby obtaining purified palladium-strong ligand complex CO2 fluid.

[0027] S4. The purified palladium-containing complex CO2 fluid is introduced into the supported vessel, a support precursor suspension is added, and hydrogen is introduced for reduction to obtain a palladium / supported catalyst precursor, which is then dried and calcined to obtain a palladium-based catalyst.

[0028] Specifically, in step S41, the purified palladium-strong ligand complex CO2 fluid is introduced into the loading vessel, and a carrier precursor suspension is added to the loading vessel; the carrier precursor suspension is one of γ-Al2O3 nanoparticle dispersion, activated carbon nanoparticle dispersion or molecular sieve dispersion, with a solid content of 10-15% and a particle size of 20-50 nm. S42, hydrogen gas is introduced into the loading vessel, the volume ratio of hydrogen to CO2 is 1:6-1:10, the temperature is raised to 80-100℃, the pressure is increased to 3-5MPa, and the temperature is maintained for reduction for 0.8-1.2h, so that the palladium-strong ligand complex is reduced to generate palladium nanoparticles and uniformly loaded on the surface of the carrier precursor. S43, reduce the pressure of the supported vessel to atmospheric pressure, recover CO2 and strong ligand, and obtain palladium / supported catalyst precursor; S44. The palladium / supported catalyst precursor is dried at 110-130℃ for 1.5-2.5h and calcined at 400-500℃ for 2.5-3.5h to obtain a palladium-based catalyst that can be directly used in industry.

[0029] S5 involves microwave activation of the extracted waste carrier, further steam activation of the activated carbon carrier, and the regenerated carrier can be mixed and reused with the catalyst precursor.

[0030] Specifically, in S51, the waste carrier after extraction is taken out from the supercritical extraction vessel and activated by microwave for 8-12 minutes at a microwave power of 700-900W to remove residual coordinating agent. S52, if the waste carrier is an activated carbon carrier, further activate it with steam at 750-850℃ for 1.5-2.5h to regenerate it into high specific surface area activated carbon; S53 involves mixing the regenerated support with the palladium / supported catalyst precursor prepared in S43 in a specific ratio to optimize the catalyst's mechanical strength.

[0031] To facilitate understanding of the present invention, several embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0032] Example 1 In Embodiment 1 of the present invention, a method for resource utilization treatment of waste palladium catalyst is provided. Specifically, the waste three-way catalyst for automobile exhaust purification (palladium content 0.08%, containing Pt 0.02% and Cu 0.03%, with γ-Al2O3 as the support) is used as the treatment object. Microwave treatment is performed for 5 minutes with a microwave power of 700W and a frequency of 2.45GHz to quickly remove carbon from the surface of the support. The substrate was etched with low-temperature Ar plasma for 15 minutes at a plasma power of 50W, and N-TiO2 photocatalyst was simultaneously loaded onto the support surface by plasma sputtering at a loading of 0.8%. The pretreated waste palladium catalyst and weak ligand are added to a supercritical extraction vessel. The inner wall of the supercritical extraction vessel is embedded with uniformly distributed ultraviolet LEDs with a wavelength of 360-370nm and a power of 30W. CO2 was introduced into the supercritical extraction vessel, the temperature was raised to 35°C, the pressure was increased to 8 MPa, the stirring rate was 300 r / min, and the vessel was pre-washed for 30 min under continuous ultraviolet light irradiation to remove impurities; the weak ligand was dibutylphosphoric acid (DBP), and the amount used was 3% of the mass of the spent palladium catalyst. The CO2 fluid containing the impurity metal-weak ligand complex was discharged. A strong ligand was added to the supercritical extraction vessel, and CO2 was continuously introduced. The temperature was raised to 50°C, the pressure was increased to 10 MPa, the stirring rate was 300 r / min, and palladium was extracted under continuous ultraviolet light irradiation for 1 hour. The strong ligand was a complex system of trioctylphosphine oxide (TOPO) and fluoroacetylacetone (HFA), with a mass ratio of TOPO to HFA of 1:2, and the amount used was 6% of the mass of the spent palladium catalyst. The CO2 fluid containing the impurity metal-weak ligand complex discharged above was depressurized to 5 MPa and condensed to recover the weak ligand. The remaining impurity metal was dissolved in hydrochloric acid and then separated and purified using ion exchange resin. CO2 fluid containing palladium-strong ligand complex is passed into a secondary extraction column, which is filled with silica gel adsorbent to adsorb residual trace impurity metal-weak ligand complex, thus obtaining purified palladium-strong ligand complex CO2 fluid. The purified palladium-strong ligand complex CO2 fluid was introduced into the loading vessel, and a carrier precursor suspension was added to the loading vessel; the carrier precursor suspension was a γ-Al2O3 nanoparticle dispersion with a solid content of 10% and a particle size of 20-50 nm. Hydrogen gas was introduced into the loading vessel at a volume ratio of 1:8 to CO2. The temperature was raised to 90°C and the pressure was increased to 4 MPa. The vessel was kept at this temperature for 1 hour to reduce the palladium-strong ligand complex to generate palladium nanoparticles, which were then uniformly loaded onto the surface of the carrier precursor. The pressure in the supported vessel was reduced to atmospheric pressure to recover CO2 and strong coordinating agent, yielding a palladium / supported catalyst precursor. The palladium / supported catalyst precursor was dried at 120℃ for 2 hours and calcined at 450℃ for 3 hours to obtain a palladium-based catalyst that can be directly applied in industry. The waste carrier after extraction was taken out of the supercritical extraction vessel and activated by microwave for 10 minutes at a microwave power of 800W to remove residual complexing agent. If the waste carrier is an activated carbon carrier, it can be further activated by steam at 80°C for 2 hours to regenerate it into high specific surface area activated carbon. The regenerated support was mixed with the palladium / supported catalyst precursor prepared above in a certain proportion to optimize the mechanical strength of the catalyst.

[0033] In Example 1 of this invention, the catalyst activity was tested using a CO oxidation reaction at a space velocity of 10,000 h⁻¹. -1 Experimental results showed that the palladium recovery rate was 97.1%, the palladium purity reached 99.99%, the Pt recovery rate was 90.3%, the palladium nanoparticle size was 52 nm, and the carrier specific surface area (BET) was 185 m². 2 / g, the catalyst activity is 95.2% of that of fresh catalyst. This indicates that at this microwave power, the carbon removal rate reaches 92%, the support pores remain intact, there is no support damage, the palladium desorption efficiency meets the process requirements, and the support structure is not damaged. Example 2 In Embodiment 2 of the present invention, a method for the resource utilization of waste palladium catalyst is also provided. The difference from Embodiment 1 is that the microwave power is 800W in the process of obtaining the pretreated waste palladium catalyst.

[0034] Experimental results showed that the palladium recovery rate was 98.5%, the palladium purity was 99.99%, the Pt recovery rate was 92.1%, the palladium nanoparticle size was 40 nm, and the specific surface area of ​​the carrier was 198 m². 2 / g, catalyst activity 98.3%. This indicates that this power is the optimal value, with a carbon removal rate as high as 99%, and the specific surface area of ​​the support is close to that of a fresh support (200m²). 2 The pore channel expansion is the most complete, the synergistic desorption effect of photocatalysis and supercritical extraction is the best, the palladium nanoparticle dispersion is the best, and the overall processing performance is the best.

[0035] Example 3 In Embodiment 3 of the present invention, a method for the resource utilization of waste palladium catalyst is also provided. The difference from Embodiment 1 is that the microwave power is 900W in the process of obtaining the pretreated waste palladium catalyst.

[0036] Experimental results showed that the palladium recovery rate was 97.8%, the palladium purity was 99.99%, the Pt recovery rate was 91.5%, the palladium nanoparticle size was 48 nm, and the specific surface area of ​​the carrier was 189 m². 2 / g, catalyst activity 96.7%. This indicates that excessively high microwave power can lead to localized sintering of the support, a 4.5% decrease in BET specific surface area compared to 800W, slight pore blockage, and hindered palladium diffusion, resulting in a slight decrease in recovery rate.

[0037] Example 4 In Example 4 of this invention, a method for the resource utilization of waste palladium catalyst is also provided. The difference from Example 2 is that the weak ligand is dibutylphosphoric acid (DBP), and the amount used is 2% of the mass of the waste palladium catalyst.

[0038] Experimental results showed that the palladium recovery rate was 98.2%, the palladium purity was 99.97%, the Cu removal rate was 82.5%, the palladium nanoparticle size was 43 nm, and the catalyst activity was 97.1%. This indicates that insufficient DBP dosage has a negative impact on Cu removal. 2+ Insufficient chelation, residual Cu in the solution 2+ It will co-precipitate with palladium complexes, resulting in a slight decrease in palladium purity. At the same time, trace impurities will affect the catalyst activity.

[0039] Example 5 In Example 5 of this invention, a method for the resource utilization of waste palladium catalyst is also provided. The difference from Example 2 is that the weak ligand is dibutylphosphoric acid (DBP), and the amount used is 4% of the mass of the waste palladium catalyst.

[0040] Experimental results showed that the palladium recovery rate was 97.9%, the palladium purity was 99.99%, the Cu removal rate was 96.2%, the palladium nanoparticle size was 46 nm, and the catalyst activity was 97.8%. This indicates that when DBP is used in excess, some DBP will compete with strong ligands for palladium ions, leading to a slight decrease in the amount of palladium complex formed and a slight decrease in the palladium recovery rate. It also increases the recovery cost of the ligand. Therefore, 4% is the upper limit for dosage, and it is not recommended to exceed this range.

[0041] Example 6 In Example 6 of this invention, a method for the resource utilization of waste palladium catalyst is also provided. The difference from Example 2 is that hydrogen gas is introduced into the supported vessel, and the volume ratio of hydrogen gas to CO2 is 1:6.

[0042] Experimental results showed that the palladium recovery rate was 96.3%, the palladium purity was 99.99%, the palladium nanoparticle size was 65 nm, and the catalyst activity was 94.2%. This indicates that at this ratio, the solubility of hydrogen in supercritical CO2 is insufficient, leading to incomplete reduction reaction and severe palladium particle agglomeration (significantly increased particle size), which in turn affects the catalyst activity.

[0043] Example 7 In Example 7 of this invention, a method for the resource utilization of waste palladium catalyst is also provided. The difference from Example 2 is that hydrogen gas is introduced into the supported vessel, and the volume ratio of hydrogen gas to CO2 is 1:10.

[0044] Experimental results showed that the palladium recovery rate was 98.4%, the palladium purity was 99.99%, the palladium nanoparticle size was 38 nm, and the catalyst activity was 98.6%. This indicates that at this ratio, hydrogen has the best solubility in supercritical CO2, the reduction reaction is uniform and complete, the generated palladium nanoparticles have the smallest particle size and the best dispersibility, and the catalyst activity reaches the highest level.

[0045] Comparative Example 1 Comparative Example 1 uses a traditional hydrochloric acid-sodium chlorate system to treat the same waste catalyst. The specific steps are as follows: dissolve in the hydrochloric acid-sodium chlorate system at 80°C for 3 hours, and then refine and purify with aqua regia.

[0046] Experimental results showed that the palladium recovery rate was only 88.3%, the palladium purity was 99.5%, the total treatment time was 14 hours, and 12L of wastewater was generated per 1kg of catalyst treated. This indicates that traditional methods suffer from drawbacks such as low recovery rate, insufficient product purity, lengthy processing flow, and severe wastewater pollution. These shortcomings contrast sharply with the treatment effect of this invention, highlighting its significant advantages in terms of efficiency, environmental friendliness, and economy.

[0047] It should be noted that the above test results were statistically analyzed, as shown in Table 1: Table 1

[0048] In summary, the present invention proposes a method for the resource utilization of waste palladium catalysts. This method first involves microwave decarbonization, plasma etching, and loading of an N-TiO2 photocatalyst onto the waste palladium catalyst to achieve carrier loosening modification. Subsequently, in a supercritical extraction vessel with a built-in UV LED lamp, a gradient strategy of "pre-washing with a weak ligand for impurity removal + main extraction with a strong ligand" is employed, combining photocatalysis and supercritical synergy to enhance palladium desorption and selective extraction. Then, impurity metals and weak ligands are recovered by vacuum condensation, and the palladium-containing complex stream is purified using a silica gel adsorption column. The purified fluid is then introduced into a loading vessel, mixed with a carrier precursor suspension, and subjected to in-situ hydrogen reduction to complete palladium nanoparticle loading. After drying and calcination, an industrially applicable palladium-based catalyst is directly obtained. Finally, the waste carrier is microwave activated (with additional steam activation for activated carbon carriers) to achieve deep reuse.

[0049] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for the resource-based treatment of spent palladium catalyst, characterized in that, Includes the following steps: S1. After crushing and drying the waste palladium catalyst, it is sequentially subjected to microwave treatment to remove carbon, low-temperature plasma etching in Ar atmosphere, and N-TiO2 photocatalyst loading to obtain the pretreated waste palladium catalyst. S2. Add the pretreated waste palladium catalyst and weak ligand to the supercritical extraction vessel, prewash with CO2 to remove impurities, then add a strong ligand and carry out supercritical extraction under ultraviolet light irradiation. S3. The CO2 fluid after pre-washing and impurity removal is subjected to reduced pressure condensation to recover the weak ligand and impurity metals, and the CO2 fluid after supercritical extraction is subjected to secondary adsorption purification. S4. The purified palladium-containing CO2 fluid is passed into the supported vessel, a support precursor suspension is added, and hydrogen is introduced for reduction to obtain a palladium / supported catalyst precursor, which is then dried and calcined to obtain a palladium-based catalyst. S5. Microwave activation is performed on the waste carrier after extraction, and the activated carbon carrier is further activated with water vapor. The regenerated carrier can be mixed and reused with the catalyst precursor.

2. The method for resource recovery of spent palladium catalyst according to claim 1, characterized in that, In S1, the microwave processing power is 700-900W, the frequency is 2.45GHz, and the processing time is 5min; the low-temperature plasma etching power is 40-60W, and the processing time is 10-20min; the loading of N-TiO2 photocatalyst is 0.5-1%.

3. The method for resource recovery of spent palladium catalyst according to claim 1, characterized in that, In S2, uniformly distributed ultraviolet LEDs with wavelengths of 360-370nm and power of 25-35W are embedded in the inner wall of the supercritical extraction vessel.

4. The method for resource recovery of spent palladium catalyst according to claim 3, characterized in that, In S2, the weak ligand is dibutylphosphoric acid, and the amount used is 2-4% of the mass of the waste palladium catalyst; the pre-washing and impurity removal process conditions are: temperature 30-40℃, pressure 6-10MPa, stirring speed 250-350r / min, and time 20-40min.

5. The method for resource recovery of spent palladium catalyst according to claim 4, characterized in that, In S2, the strong ligand is a complex system of trioctylphosphine oxide and fluoroacetylacetone, with a mass ratio of trioctylphosphine oxide to fluoroacetylacetone of 1:2 and an amount of 5-8% of the mass of the spent palladium catalyst. The supercritical extraction process conditions are: temperature 40-60℃, pressure 10-15MPa, stirring speed 250-350r / min, and time 1-1.5h.

6. The method for resource recovery of spent palladium catalyst according to claim 1, characterized in that, In S3, the CO2 fluid after pre-washing and impurity removal is depressurized to 4-6 MPa for condensation and separation; the secondary adsorption purification uses a secondary extraction column filled with silica gel adsorbent.

7. The method for resource recovery of spent palladium catalyst according to claim 1, characterized in that, In S4, the carrier precursor suspension is one of γ-Al2O3 nanoparticle dispersion, activated carbon nanoparticle dispersion, or molecular sieve dispersion, with a solid content of 10-15% and a particle size of 20-50 nm.

8. The method for resource recovery of spent palladium catalyst according to claim 7, characterized in that, In S4, the volume ratio of hydrogen to CO2 is 1:6-1:10, and the reduction process conditions are: temperature 80-100℃, pressure 3-5MPa, and time 0.8-1.2h.

9. The method for resource recovery of spent palladium catalyst according to claim 8, characterized in that, In S4, the drying conditions are: temperature 110-130℃, time 1.5-2.5h; the calcination conditions are: temperature 400-500℃, time 2.5-3.5h.

10. The method for resource recovery of spent palladium catalyst according to claim 1, characterized in that, In S5, the microwave activation power is 700-900W and the time is 8-12min; the activated carbon carrier steam activation conditions are 750-850℃ and 1.5-2.5h.

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