Method for preparing micron-sized zinc metastannate by wet recovery of tin and zinc from electronic waste and method for synthesizing 4-hydroxy-1-indanone

Abstract

The purpose of the present invention is to provide a method for wet recovery of tin and zinc in electronic waste to prepare micron-sized zinc metastannate and a method for synthesizing 4-hydroxy-1-indanone, which belongs to the field of metal recycling technology. The method utilizes amino coordination and carboxylic acid chelation to selectively leach tin and zinc from electronic waste under mild acidic conditions, while impurity metals such as iron and copper are retained in the residue due to differences in complex constants, achieving metal ion-level separation (selectivity>99%). Subsequently, by evaporation-crystallization regulation, the Sn-Zn complex is directionally reconstructed into micron-sized zinc metastannate. In the synthesis of indanone, micron-sized zinc metastannate forms a local proton acid environment by adsorbing trace water in the reaction system, synchronously activating the C=N bond of the imine substrate (Lewis acid site catalysis) and stabilizing the cyclization transition state (hydrogen bond directing effect), reducing the activation energy of the [4+1] cycloaddition reaction, driving the reaction equilibrium to move toward the product end, and achieving quantitative conversion of indanone under mild conditions (yield 60%).

Description

Technical Field

[0001] The present invention relates to the technical field of metal recycling, and in particular to a method for preparing micron-sized zinc metastannate by wet-process recovery of tin and zinc in electronic waste, and a method for synthesizing 4-hydroxy-1-indanone. Background Art

[0002] Tin and zinc constitute a significant amount of electronic waste. While conventional acid leaching and precipitation processes can achieve crude metal extraction, they rely on the large-scale use of highly corrosive reagents, the difficulty of selective separation due to the co-dissolution of multiple metals, and the synergistic contamination of heavy metal leachates with toxic organic compounds (such as brominated flame retardants), resulting in significant resource waste and environmental risks. The final disposal stage often uses pyrometallurgy or simple landfilling, which not only has a low metal recovery rate (<60%) and limited product added value, but is also prone to secondary hazards such as soil acidification and groundwater contamination, forming a vicious cycle of "high environmental costs and low economic benefits." Therefore, the development of green and low-cost metal sorting technologies and the construction of a system for the targeted recovery and high-value utilization of low-value metals have become key breakthroughs in improving the resource utilization efficiency of all components of electronic waste.

[0003] In the field of indanone synthesis, traditional methods such as polyphosphate cyclization and the Nazarov cyclization reaction have long faced environmental pressures, strong dependence on metal catalysts, or harsh reaction conditions. With the increasing value of 3-aminoindanone compounds in drug development, the development of green and efficient synthetic pathways has become an urgent need.

[0004] Patent CN107033016B proposes a novel strategy for constructing a 3-aminoindanone skeleton using imine derivatives and olefins as raw materials via a pentamethylcyclopentadienyl rhodium dichloride / manganese acetate catalytic system. While this method achieves molecular cyclization under mild conditions through a metal-catalyzed [4+1] cycloaddition reaction, avoiding the traditional strongly acidic environment, the use of the precious metal rhodium in the catalytic system significantly increases raw material costs, and the complex multicomponent reaction system limits product yields (approximately 65-78%). Furthermore, the large-scale use of organic solvents conflicts with the principles of green chemistry. This technical approach presents a typical "efficiency-cost" trade-off between simplifying the operational steps and improving atom economy, reflecting the core challenges commonly faced in the development of new indanone synthesis methods. Summary of the Invention

[0005] The present invention aims to provide a method for wet-process recovery of tin and zinc from electronic waste to produce micron-sized zinc metastannate, as well as a method for synthesizing 4-hydroxy-1-indanone. This method utilizes the bifunctional properties of glycine (amino coordination and carboxylic acid chelation) to selectively leach tin and zinc from electronic waste under mild acidic conditions. Subsequently, through evaporation-crystallization manipulation, the Sn-Zn complex is directionally reconstructed into micron-sized zinc metastannate (ZnSnO₃·nH₂O). The exposed Sn-O-Zn active sites and surface hydroxyl groups in its layered structure impart strong water absorption.

[0006] In the synthesis of indanone, micron-sized zinc metastannate forms a local proton acid environment by adsorbing trace water in the reaction system, simultaneously activating the C=N bond of the imine substrate (Lewis acid site catalysis) and stabilizing the cyclization transition state (hydrogen bond directing effect), thereby reducing the activation energy of the [4+1] cycloaddition reaction, driving the reaction equilibrium toward the product end, and achieving quantitative conversion of indanone under mild conditions.

[0007] To achieve the above-mentioned object of the invention, the present invention provides a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate, comprising the following steps:

[0008] S1. Grinding the electronic waste to obtain slurry;

[0009] S2. Adding an amino acid leaching agent to the slurry, adjusting the pH of the slurry to 12-14; stirring to leach tin and zinc;

[0010] S3. After the tin and zinc leaching process is completed, the leached liquid is filtered and collected;

[0011] S4. ultrasonically dissolve the leaching liquid, allow it to stand, and then dry it. When the volatilization amount of the liquid in the leaching liquid reaches 60%-80% of the initial mass of the leaching liquid, stop evaporation; filter, collect the crystalline solid, rinse, and dry it naturally to obtain micron-sized zinc metastannate.

[0012] Furthermore, the leaching agent is one or more of glycine, glutamic acid, and histidine.

[0013] Furthermore, in step S2, the concentration of the leaching agent in the slurry is 0.1-1 mol / L.

[0014] Furthermore, during the grinding process, the electronic waste is ground until the portion of the material with a particle size less than 50 mesh accounts for 90%-98% of the total mass of the mineral powder.

[0015] Furthermore, in step S1, the mass concentration of the slurry is 5%-10%.

[0016] Furthermore, in step S2, the stirring time is 1-6 hours.

[0017] Furthermore, in step S2, during stirring, the temperature of the slurry is 30°C-35°C.

[0018] The present invention also provides a method for synthesizing 4-hydroxy-1-indanone, wherein micron-sized zinc metastannate is prepared by the above method; the method comprises the following steps:

[0019] A1. The micron-sized zinc metastannate was added to a methanesulfonic acid reagent and stirred to obtain a mixed solution;

[0020] A2. Add hydroxyphenylpropionic acid to the mixed solution, stir until uniform, then heat to 40°C-45°C and react for 3-4h;

[0021] A3. After the reaction is completed, cool to room temperature; neutralize with saturated sodium bicarbonate solution, extract the organic phase with dichloromethane, dry with anhydrous magnesium sulfate, filter and concentrate the organic phase to finally obtain 4-hydroxy-1-indanone.

[0022] Furthermore, in step A1, the amount of the micron-sized zinc metastannate added is 2.0-5.0 wt% of the mass of the methanesulfonic acid reagent.

[0023] Furthermore, in step A2, the mass ratio of the hydroxyphenylpropionic acid to the mixed solution is 1:(10-40).

[0024] The beneficial effects of the present invention are:

[0025] 1. This application proposes a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate. This method utilizes the dual functional properties of glycine (amino coordination and carboxylic acid chelation) to selectively leach tin and zinc from electronic waste under mild acidic conditions. Specifically: glycine binds to Sn via NO bidentate coordination. 2+ / Zn 2+ Formation of a stable complex (Sn(gly)3 - / Zn(gly)2), while impurity metals such as iron and copper remain in the residue due to differences in complexation constants, achieving metal ion-level separation (selectivity >99%). Subsequently, through evaporation-crystallization manipulation, the Sn-Zn complex is directionally reconstructed into micron-sized zinc metastannate (ZnSnO3·nH2O). The exposed Sn-O-Zn active sites and surface hydroxyl groups in its layered structure impart strong water absorption.

[0026] 2. This application proposes a method for synthesizing 4-hydroxy-1-indanone. In the synthesis of indanone, micron-sized zinc metastannate forms a local protonic acid environment by adsorbing trace amounts of water in the reaction system, thereby simultaneously activating the C=N bond of the imine substrate (Lewis acid site catalysis) and stabilizing the cyclization transition state (hydrogen bond directing effect), thereby reducing the activation energy of the [4+1] cycloaddition reaction, driving the reaction equilibrium toward the product end, and achieving quantitative conversion of indanone under mild conditions (yield 60%).

[0027] 3. This application innovatively constructs a closed-loop "metal recycling-catalytic synthesis" system by targetedly recovering low-value metals (such as tin and zinc) from electronic waste and converting them into high-value catalysts. Replacing traditional rhodium-based catalysts with a non-precious metal catalytic system not only addresses the economic and environmental challenges of recovering low-value metals from electronic waste, but also significantly reduces reliance on precious metals in the synthesis of indanone compounds, while also reducing organic solvent usage and pollutant emissions, aligning with the sustainable development concept of "waste treatment with waste."

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0030] Figure 1 SEM photos and EDS energy spectrum of micron-sized zinc metastannate prepared in Example 1; (a) backscattered photo of the product (20 μm); (b) backscattered photo of the product (8 μm); (c) and (d) elemental surface distribution of the product (20 μm); and (e) elemental energy spectrum analysis.

[0031] Figure 2 This is the XRD pattern of the micron-sized zinc metastannate prepared in Example 1.

[0032] Figure 3 This is the XRD pattern of the product prepared in Comparative Example 1.

[0033] Figure 4These are SEM photos of the PCBs samples in Example 12 and Example 1 after leaching for 2 hours and 3 hours; among them, (a) the backscattered photo of the sample in Example 12 after leaching for 2 hours; (b) the element surface distribution diagram of the sample in Example 12 after leaching for 2 hours; (c) the backscattered photo of the sample in Example 1 after leaching for 3 hours; (d) the element surface distribution diagram of the sample in Example 1 after leaching for 3 hours.

[0034] Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of 4-hydroxy-1-indanone synthesized in Example 14. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0037] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0038] The present invention provides a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate, comprising the following steps:

[0039] S1. Grinding the electronic waste to obtain slurry;

[0040] The mass concentration of the slurry is 5%-10%.

[0041] During the grinding process, the electronic waste is ground until the particle size of the material is less than 50 mesh, which accounts for 90%-98% of the total mass of the mineral powder.

[0042] S2. Add an amino acid leaching agent to the slurry and adjust the pH of the slurry to 12-14; stir to leach tin and zinc;

[0043] During stirring, the temperature of the slurry is 30°C-35°C, and the stirring time is 1-6 hours.

[0044] The stirring speed is 100-300r / min.

[0045] Wherein, the leaching agent is one or more of glycine, glutamic acid and histidine.

[0046] The concentration of the leaching agent in the slurry is 0.1-1 mol / L.

[0047] S3. After the tin and zinc leaching process is completed, the leached liquid is filtered and collected;

[0048] S4. Ultrasonic dissolution of the leaching liquid is performed, the leaching liquid is allowed to stand, and then dried. When the volatilization amount of the liquid in the leaching liquid reaches 60%-80% of the initial mass of the leaching liquid, evaporation is stopped; the crystalline solid is collected by filtration, rinsed, and naturally dried to obtain micron-sized zinc metastannate.

[0049] The drying temperature is 40°C-60°C to slowly volatilize the water in the leaching liquid.

[0050] When rinsing, use a small amount of ethanol.

[0051] The present invention also provides a method for synthesizing 4-hydroxy-1-indanone, wherein micron-sized zinc metastannate is prepared by the above method; the method comprises the following steps:

[0052] A1. Add micron-sized zinc stannate to a methanesulfonic acid reagent and stir to obtain a mixed solution;

[0053] The addition amount of micron-sized zinc metastannate is 2.0-5.0 wt% of the mass of the methanesulfonic acid reagent.

[0054] A2. Add hydroxyphenylpropionic acid to the mixed solution, stir until uniform, then heat to 40°C-45°C and react for 3-4 hours;

[0055] The mass ratio of hydroxyphenylpropionic acid to the mixed solution is 1:(10~40).

[0056] A3. After the reaction is completed, cool to room temperature; neutralize with saturated sodium bicarbonate solution, extract the organic phase with dichloromethane, dry with anhydrous magnesium sulfate, filter and concentrate the organic phase to finally obtain 4-hydroxy-1-indanone.

[0057] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0058] Example 1

[0059] A method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate comprises the following steps:

[0060] S1. Grind electronic waste (waste printed circuit boards) to a particle size of less than 50 mesh to obtain a material; then add water to the material and stir to obtain a slurry with a concentration of 5%;

[0061] S2. Glycine was added to the slurry to a concentration of 0.5 mol / L; sodium hydroxide was then added to adjust the slurry pH to 14; thereafter, the mixture was stirred at 30°C for 3 h to leach tin and zinc;

[0062] S3. After the tin and zinc leaching process is completed, the leached liquid is filtered and collected; the concentrations of tin and zinc are measured by ICP-OES, and the leaching rates of tin and zinc are calculated.

[0063] S4. Ultrasonic dissolve the leached liquid for 0.5 h. After standing for 3 h, place it in a constant temperature drying oven set at 50°C to slowly evaporate the water in the solution. When the evaporated amount of the liquid reaches 60% of the initial mass of the leached liquid, stop evaporation, filter, collect the crystalline solid, rinse with a small amount of ethanol, and dry naturally to obtain micron-sized zinc metastannate (ZnSnO3·nH2O).

[0064] Examples 2-4 and Comparative Examples 1-5

[0065] Examples 2-4 and Comparative Examples 1-5 provide a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate. Compared with Example 1, the difference is that in step S2, the amount of glycine used is different, as shown in Table 1. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0066] Table 1 Glycine dosage and experimental results of Examples 2-4 and Comparative Examples 1-5

[0067]

[0068] Table 1 shows that glycine dosage significantly affects tin and zinc leaching and the yield of micron-sized zinc metastannate. When the glycine concentration is increased from 0.1 mol / L to 1 mol / L (Examples 1-4), the tin leaching rate increases from 80% to 90%, the zinc leaching rate remains between 93% and 94%, and the micron-sized product yield increases from 57% to 66%, indicating that appropriately increasing the glycine concentration can synergistically promote metal leaching and product synthesis.

[0069] However, excess glycine (>1 mol / L) has a negative impact: at a concentration of 3 mol / L (Comparative Example 5), while the tin leaching rate remains at 86%, the zinc leaching rate plummets from 94% to 84%, resulting in a sharp drop in product yield to 12%. Furthermore, the absence of glycine (Comparative Example 1) completely inhibits tin leaching and product formation, demonstrating its essential role as a key complexing agent.

[0070] Experimental results show that the optimal dosage range of glycine is 0.1-1 mol / L, at which point the zinc / tin leaching balance is optimal and the yield can reach more than 55%, while also having good economic feasibility.

[0071] Figure 1 This is an electron scanning microscope test and energy spectrum analysis diagram of the micron-sized zinc metastannate obtained in Example 1. It can be seen that the product is in the shape of cubes of varying sizes, with the vast majority of particles ranging in size from 3 to 5 µm. According to energy spectrum analysis, the main components of the precipitated metal product obtained are tin, zinc, oxygen, sodium, etc. Among them, the mass proportions are approximately 31.13% tin, 21.15% zinc, 36.64% oxygen, 10.33% sodium, and 0.75% copper. Through the observation window (scales are 20 µm and 8 µm, respectively), it can be observed that the micron-sized zinc metastannate has a complete crystal form, with individual crystals in the shape of cubes, and the edge length of the cubes ranges from 3 to 5 µm.

[0072] Figure 2 This is the XRD spectrum of the micron-sized zinc metastannate prepared in Example 1. As can be seen from the spectrum, the diffraction peaks can be attributed to the diffraction peaks at 19.8°, 22.5°, 32.7°, 52.6° and 57.7°, respectively, corresponding to the (111), (200), (220), (420) and (422) crystal planes of ZnSn(OH)6. The characteristic peaks of ZnSn(OH)6 have a high degree of consistency with the standard card, and the peak shape is sharp, indicating that ZnSn(OH)6 has good crystallinity and high purity. The characteristic peaks of ZnO are very weak and the peak shape is wide, indicating that the crystallinity of ZnO is not high and the content is relatively low. Its main source is the decomposition of ZnSn(OH)6 under vacuum drying conditions.

[0073] Examples 5-6 and Comparative Examples 6-8

[0074] Examples 5-6 and Comparative Examples 6-8 provide a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate. Compared with Example 1, the difference is that the slurry concentration is different, as shown in Table 2. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0075] Table 2 Slurry concentration and experimental results of Examples 5-6 and Comparative Examples 6-8

[0076]

[0077] Table 2 shows that slurry concentration significantly affects the leaching rates of tin and zinc from electronic waste and the yield of micron-sized zinc metastannate. As slurry concentration increases from 5% to 10%, the leaching rates of tin and zinc gradually decrease from 85% and 93% to 80% and 86%, respectively. Simultaneously, the product yield decreases from 60% to 50%. This indicates that high slurry concentration inhibits metal leaching efficiency and product synthesis.

[0078] When the concentration was further increased to 12% (Comparative Example 7) and 20% (Comparative Example 8), the leaching rate and yield deteriorated sharply (the tin leaching rate dropped to 59% and the yield was only 14%). This may be due to the high viscosity of the slurry, which led to the obstruction of the diffusion of the reactants or insufficient solid-liquid contact.

[0079] It is noteworthy that when the slurry concentration is below 5% (4% in Comparative Example 6), all indicators are comparable to those in Example 1 (5%), indicating that concentration changes below this critical value have no significant negative impact. Comprehensive analysis shows that overall performance is optimal when the slurry concentration is controlled within the 5%-10% range. Too high a concentration will result in a significant decrease in yield, while too low a concentration is detrimental to economic efficiency.

[0080] Examples 7-8

[0081] Compared with Example 1, the difference is that in step S2, the leaching agent used is different. The rest is basically the same as Example 1 and will not be repeated here.

[0082] Table 3 Types of leaching agents and experimental results of Examples 7-8 and Comparative Example 1

[0083]

[0084] The table above demonstrates that the type of tin-zinc leaching agent plays a key role in the tin leaching rate and the synthesis of micron-sized zinc metastannate. When glycine, glutamic acid, or histidine were used as the leaching agent (Examples 1, 7, and 8), the tin leaching rate exceeded 82%, and over 60% of the target product was consistently produced. In contrast, when no leaching agent was added (Comparative Example 1), the tin leaching rate was zero, and no product was formed.

[0085] Notably, the zinc leaching rate remained high, exceeding 87%, both with and without the reagents, suggesting that zinc leaching may be primarily dependent on other reaction conditions rather than the reagents. Different amino acid reagents exhibited similar tin leaching effects (slightly lower for glutamic acid and slightly higher for histidine), suggesting that these reagents may promote tin dissolution and product synthesis through similar complexation mechanisms.

[0086] also, Figure 3The XRD spectrum of the sample prepared in Comparative Example 1 is shown. It can be seen that the diffraction peaks of the leached sample can be attributed to the diffraction card Zn5(OH)6(CO3)2 (PDF#72-1100) in the ICDD powder diffraction database. Among them, the diffraction peaks at 12.9°, 22.3°, 24.7°, 27.8°, 31.2°, 32.6°, 36.1°, and 60.7° correspond to the (200), (111), (310), (311), (220), (021), (221), and (223) crystal planes of Zn5(OH)6(CO3)2, respectively. The source of Zn5(OH)6(CO3)2 is mainly due to the deliquescence of Zn(OH)2 and its reaction with CO2. It can be seen that in the absence of amino acid leaching agents, the zinc leaching process may mainly rely on other reaction conditions rather than tin-zinc leaching agents.

[0087] Examples 9-10 and Comparative Examples 9-11

[0088] Examples 9-10 and Comparative Examples 9-11 provide a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate. Compared with Example 1, the difference is that the pH of the slurry is different, as shown in Table 4. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0089] Table 4 pH and experimental results of the slurry in Examples 9-10 and Comparative Examples 9-11

[0090]

[0091] According to the data comparison in Table 4, the following conclusions can be drawn: The pH of the slurry significantly affects the metal leaching and product synthesis by regulating the dissociation state of glycine. When the pH is ≥ 12 (Examples 1, 9, and 10), glycine is fully dissociated into the deprotonated form (Gly) under strong alkaline conditions (pKa≈9.6). - ), its complexing ability was enhanced, maintaining a tin leaching rate of 83%-85% and stably producing micron-sized zinc metastannate (yield ≥42%). As the pH dropped to 11 and below (Comparative Examples 9-11), the dissociation degree of glycine dropped sharply (approaching the isoelectric point), losing its complexing ability for tin (tin leaching rate dropped to 0%). Simultaneously, the zinc leaching rate and product yield collapsed due to the weakening of the complexing effect.

[0092] It is worth noting that the leaching rate of zinc is more sensitive to pH than that of tin (when pH = 14 → 10, the leaching rate of zinc drops sharply from 93% to 31%), which suggests that the dissolution of zinc is more dependent on OH - The complexation drive provided by tin may still have some reactivity under partially dissociated conditions.

[0093] Examples 11-13 and Comparative Examples 12-14

[0094] Examples 11-13 and Comparative Examples 12-14 provide a method for wet recovery of tin and zinc from electronic waste to prepare micron-sized zinc metastannate. Compared with Example 1, the difference is that in step S2, the stirring reaction time is different (i.e., the leaching time is different), as shown in Table 5. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0095] Table 5 Stirring reaction time and experimental results of Examples 11-13 and Comparative Examples 12-14

[0096]

[0097] Table 5 shows that the leaching time has a significant regulatory effect on the metal leaching efficiency and product yield. The surface morphology of the PCBs samples leached for 2h / 3h is as follows: Figure 4 When the reaction time is controlled between 2 and 6 hours, the leaching rates of tin (≥80%), zinc (≥85%), and zinc metastannate yield (≥50%) all reach optimal levels, indicating that the reaction requires sufficient time to complete the metal complexation and crystallization process.

[0098] However, prolonged leaching times (Comparative Example 13, 24 hours) resulted in a sharp drop in the leaching rates of tin and zinc (61% for tin and 42% for zinc), and the product completely disappeared (yield 0%). This is presumably due to the predominance of side reactions in the alkaline environment (such as metal hydroxide precipitation or product decomposition). Furthermore, while insufficient leaching times (e.g., 0.5 hours in Comparative Example 14) partially leached the metals (72% for tin and 81% for zinc), the product yield was only 41%, indicating that the synthesis reaction requires a certain kinetic time for complete nucleation and assembly.

[0099] It is worth noting that the leaching rate of zinc is more sensitive to time (e.g., the zinc leaching rate dropped from 94% to 82% after 7 h), which may be because it is more susceptible to reverse reactions or oxidation.

[0100] like Figure 4 As shown in the figure, it can be found that after leaching for 2 h / 3 h, the tin covering the surface of nickel and copper begins to dissolve, and the layered packaging of tin is opened. At the same time, other metals (copper, nickel, etc.) do not dissolve, which proves that amino acid agents are selective for the leaching of tin.

[0101] Example 14

[0102] The application of micron-sized zinc metastannate in the synthesis of 4-hydroxy-1-indanone is as follows:

[0103] A1. Weigh 5 g of methanesulfonic acid reagent, then weigh 0.2 g of micron-sized zinc metastannate prepared in Example 1, add methanesulfonic acid, and stir for 20 min to obtain a mixed solution.

[0104] A2. The mixed solution obtained in step A1 was allowed to stand at room temperature for 30 minutes. 0.52 g of 1-hydroxyphenylpropionic acid was added to the solution to obtain a mixed solution. The solution was stirred until homogeneous. Subsequently, the solution was slowly heated to 40°C and reacted for 4 hours.

[0105] A3. After the reaction is complete, cool to room temperature. Neutralize with saturated sodium bicarbonate solution, extract the organic phase with dichloromethane, and dry over anhydrous magnesium sulfate. Filter and concentrate the organic phase to obtain 4-hydroxy-1-indanone.

[0106] Comparative Example 15

[0107] Compared with Example 14, the difference is that in step A1, micron-sized zinc metastannate is not used. The rest is substantially the same as Example 14 and will not be described again.

[0108] Table 6 Effect of catalytic system on the synthesis of 4-hydroxy-1-indanone

[0109]

[0110] As can be seen from the above table, in the reaction of synthesizing 4-hydroxy-1-indanone from 1-hydroxyphenylpropionic acid, the catalytic system has a significant effect on the product yield.

[0111] When Example 14 adopts a composite catalytic system of methanesulfonic acid and micron-sized zinc metastannate, the yield reaches 70%, while the yield of Comparative Example 1 using only methanesulfonic acid is only 9%. This shows that there is a synergistic catalytic effect between micron-sized zinc metastannate and methanesulfonic acid. The possible mechanism is: methanesulfonic acid, as a protonic acid, catalyzes the dehydration of hydroxyphenylpropionic acid to generate an olefinic acid intermediate, and then micron-sized zinc metastannate promotes the intramolecular Friedel-Crafts cyclization reaction through its solid acidic surface. The high specific surface area and abundant acidic sites of the micron material can effectively adsorb the activated reactants, while stabilizing the cyclization transition state and reducing the energy barrier. Zn in zinc metastannate 2+ The carboxylic acid group may be fixed by coordination, promoting electrophilic attack on the ortho-phenyl ring, thereby efficiently constructing the indanone five-membered ring structure. This acid-base synergistic catalytic mechanism significantly improves the cyclization efficiency, inhibits side reactions, and greatly increases the yield.

[0112] Figure 5 This is the H NMR spectrum of 4-hydroxy-1-indanone synthesized in Example 14. As can be seen, at 300 MHz, the deuterated reagent is DMSO, 9.50-1.00 (s, 1H) represents an active hydrogen on the hydroxyl group, 7.30-7.50 (t, 1H), 7.00-7.20 (t, JHz, 1H), and 6.80-6.99 (t, J1H) represent three hydrogens on the benzene ring, and 2.70-3.00 (t, 2H) and 2.40-2.60 (t, 2H) represent four hydrogens on the aliphatic five-membered ring.

[0113] Examples 15-16 and Comparative Example 16

[0114] Examples 15-16 and Comparative Example 16 provide the application of micron-sized zinc metastannate in the synthesis of 4-hydroxy-1-indanone. Compared with Example 14, the difference is that in step A1, the amount of micron-sized zinc metastannate added to the mass fraction of the methanesulfonic acid reagent is different, as shown in Table 7. The other experimental parameters and conditions are basically the same as those in Example 14 and are not repeated here.

[0115] Table 7 Mass fraction of micron-sized zinc metastannate in methanesulfonic acid reagent and experimental results in Examples 15-16 and Comparative Example 16

[0116]

[0117] As shown in the table above, a mass fraction of micron-sized zinc metastannate in the methanesulfonic acid reagent of at least 2% is required to effectively catalyze the synthesis of 4-hydroxy-1-indanone. A 2% dosage achieves a yield of 61%. Optimizing the dosage to 4%-5% yields significantly higher yields (70%-72%), representing the most preferred conditions. The extremely low yield (19%) of Comparative Example 16 (1%) demonstrates that dosages below 2% are insufficient for effective catalysis.

[0118] Examples 17-18 and Comparative Examples 17-19

[0119] Examples 17-18 and Comparative Examples 17-19 provide the use of micron-sized zinc metastannate in the synthesis of 4-hydroxy-1-indanone. Compared with Example 14, the difference is that in step A2, the mass ratio of hydroxyphenylpropionic acid to the methanesulfonic acid mixed solution of micron-sized zinc metastannate is different, as shown in Table 8. The other experimental parameters and conditions are basically the same as those in Example 14 and are not repeated here.

[0120] Table 8 Effect of the mass ratio of hydroxyphenylpropionic acid to a mixed solution of micronized zinc metastannate in methanesulfonic acid on the synthesis of 4-hydroxy-1-indanone

[0121]

[0122] From the data in Table 8, it can be seen that in the synthesis of 4-hydroxy-1-indanone, the mass ratio of 1-hydroxyphenylpropionic acid to the methanesulfonic acid mixed solution of micron-sized zinc metastannate significantly affects the product yield.

[0123] When the ratio increased from 1:5 (Comparative Example 19) to 1:40 (Example 18), the yield gradually increased from 51% to 81%. Further increasing the micronized material ratio to 1:50 or 1:100 (Comparative Examples 17-18), the yield stabilized at 81%, indicating a saturation effect in the catalytic system. This trend suggests that the addition ratio of micronized zinc metastannate must reach a certain threshold (≥1:40) to fully realize its catalytic potential: its high specific surface area and acidic sites may enhance efficiency by adsorbing and activating reactants, promoting dehydration and cyclization, and stabilizing transition states. However, excessive addition results in catalytic efficiency being reduced due to saturation of active site utilization or limited dispersion uniformity. Furthermore, the low yield in Comparative Example 19 (1:5) suggests that when the micronized material ratio is insufficient, the catalytic active sites fail to fully cover the reactants, resulting in inefficient intermediate activation.

[0124] In summary, the optimized ratio of micron materials needs to balance the active site density and dispersion, and 1:40 is the critical saturation point in the current system.

[0125] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for synthesizing 4-hydroxy-1-indanone, characterized in that: The steps include: A1. Add micron-sized zinc stannate to a methanesulfonic acid reagent and stir to obtain a mixed solution; A2. Add hydroxyphenylpropionic acid to the mixed solution, stir until uniform, then heat to 40°C-45°C and react for 3-4h; A3. After the reaction was completed, the mixture was cooled to room temperature; neutralized with saturated sodium bicarbonate solution, the organic phase was extracted with dichloromethane, dried over anhydrous magnesium sulfate, filtered and concentrated to give 4-hydroxy-1-indanone; The preparation method of the micron-sized zinc metastannate comprises the following steps: S1. Grinding the electronic waste to obtain slurry; S2. Adding an amino acid leaching agent to the slurry, adjusting the pH of the slurry to 12-14; stirring to leach tin and zinc; S3. After the tin and zinc leaching process is completed, the leached liquid is filtered and collected; S4. ultrasonically dissolve the leaching liquid, allow it to stand, and then dry it. When the volatilization amount of the liquid in the leaching liquid reaches 60%-80% of the initial mass of the leaching liquid, stop evaporation; filter, collect the crystalline solid, rinse, and dry it naturally to obtain micron-sized zinc metastannate.

2. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein In step A1, the amount of the micron-sized zinc metastannate added is 2.0-5.0 wt% of the mass of the methanesulfonic acid reagent.

3. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein In step A2, the mass ratio of the hydroxyphenylpropionic acid to the mixed solution is 1:(10-40).

4. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein The leaching agent is one or more of glycine, glutamic acid and histidine.

5. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein In step S2, the concentration of the leaching agent in the slurry is 0.1-1 mol / L.

6. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein During the grinding process, the electronic waste is ground until the particle size of the material is less than 50 mesh, which accounts for 90%-98% of the total mass of the mineral powder.

7. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein In step S1, the mass concentration of the slurry is 5%-10%.

8. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein In step S2, the stirring time is 1-6 hours.

9. The method for synthesizing 4-hydroxy-1-indanone according to claim 1, wherein In step S2, during stirring, the temperature of the slurry is 30°C-35°C.

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