Method for reducing tellurium elementary substance

Abstract

The invention discloses a method for reducing tellurium elementary substance, which comprises the following steps: mixing tellurium elementary substance, alkali, a reducing agent and a solvent, reacting under heating and ultrasonic conditions, and adding the alkali and the reducing agent at least once in the reaction process, the structure of the reducing agent is shown as a general formula (1). In the general formula (1), n represents a natural number of 0-10; r represents one of hydrogen, methyl, ethyl, hydroxyethyl, phenyl and p-tolyl; m represents one of H < + >, Li < + >, Na < + >, K < + >, NH4 < + >, Be < 2 + >, Mg < 2 + >, Ca < 2 + >, Zn < 2 + > and Ba < 2 + >. According to the method, the tellurium elementary substance is efficiently reduced into the tellurium ions under the mild condition by alternately or mixedly using a plurality of reducing agents containing sulfinic acid radicals or sulfoxylate radicals.

Description

Technical Field

[0001] This invention relates to the field of organic / inorganic chemistry, and in particular to a method for reducing elemental tellurium. Background Technology

[0002] The reduction of elemental tellurium plays a crucial role in the synthesis of telluride materials and their downstream applications. Tellurium-based materials, due to their unique physical and chemical properties, have attracted widespread attention in high-tech fields such as quantum dots, solar cells, and photoresists. Tellurides are a class of materials with great application potential, widely used in electronic devices, thermoelectric materials, and radiation protection. Furthermore, the application of tellurides in solar cells has garnered significant attention, especially cadmium telluride (CdTe) thin-film solar cells, which demonstrate broad application prospects in the optoelectronic field due to their high absorption coefficient and low-cost fabrication methods.

[0003] However, traditional reduction methods for elemental tellurium face several challenges. While traditional reducing agents, such as sodium borohydride, can effectively reduce tellurium, the reaction is violent, releasing large amounts of hydrogen gas, which can easily lead to explosions and poses significant safety hazards. Furthermore, sodium borohydride is expensive and a controlled chemical, restricting its use and storage, which hinders the industrial production of tellurium materials. In addition, existing reduction processes often struggle to achieve high conversion rates and product purity, or require complex separation steps. These shortcomings impede the wider application of tellurium reduction technology in various industrial fields. Therefore, developing a safe, low-cost, and highly efficient method for the reduction of elemental tellurium could not only improve the preparation efficiency of telluride materials but also promote their application in quantum dots, solar cells, and electronic materials. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a method for reducing elemental tellurium. By alternating or mixing various reducing agents containing sulfinate or hyposulfate ions, elemental tellurium is efficiently reduced to tellurium ions under mild conditions. Sulfinate reducing agents have a long history of industrial use, are inexpensive, stable, and easy to transport.

[0005] The technical solution of the present invention is as follows: The purpose of this invention is to provide a method for reducing elemental tellurium, which involves mixing elemental tellurium, an alkali, a reducing agent, and a solvent, reacting them under heating and ultrasonic conditions, and adding an alkali and a reducing agent at least once during the reaction. The structure of the reducing agent is shown in general formula (1):

[0006] General formula (1) In general formula (1), n ​​represents a natural number from 0 to 10; R represents hydrogen, methyl, ethyl, hydroxyethyl, phenyl, p-tolyl, etc. , One of them; M is represented as H + Li + Na + K + NH4 + Be 2+ Mg 2+ Ca 2+ Zn 2+ Ba 2+ One of them.

[0007] In one embodiment of the present invention, the alkali is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, sodium carbonate, and potassium carbonate.

[0008] In one embodiment of the present invention, the solvent is one or more of water, tetrahydrofuran, dichloromethane, chloroform, pyridine, benzene, toluene, N,N-dimethylformamide, ethyl acetate, acetonitrile, and dimethyl sulfoxide.

[0009] In one embodiment of the present invention, the reducing agent is one or more of sodium methyl sulfinate, sodium ethyl sulfinate, sodium phenyl sulfinate, sodium formaldehyde sulfoxylate, sodium dithionite, and formamidinium sulfinic acid.

[0010] Sodium methyl sulfite, sodium ethyl sulfite, sodium phenyl sulfite, and sodium formaldehyde sulfoxylate are relatively stable reducing agents that can withstand prolonged heating or ultrasonic treatment; sodium dithionite and formamidinium sulfinic acid are reducing agents with strong reducing power. In this invention, the reducing agent is a sulfinic acid reducing agent, which can be divided into two categories. The first category includes sodium methyl, ethyl, and phenyl sulfinates and sodium formaldehyde sulfoxylate; the second category includes sulfinic acid reducing agents such as sodium dithionite and formamidinic acid. The first type of reducing agent is relatively stable and can withstand prolonged heating or ultrasonic treatment, thus reducing elemental Te to Te2. 2- In the case of ions, because the reaction is a heterogeneous reaction, the rate is relatively slow, thus requiring a stable reducing agent for a longer period to complete the reaction. Therefore, type I sulfinic acids are used. However, these highly stable reducing agents have weak reducing power and cannot reduce Te2+. 2- The ions are further reduced to Te 2- The presence of ions leads to a lower utilization rate of Te.

[0011] The second type of reducing agent has a strong reducing ability, but it decomposes relatively quickly in water. (The text abruptly shifts to a seemingly unrelated topic about Te2.) 2- Ions reduced to Te 2-When ions are present, the reaction is a homogeneous reaction; the second type of reducing agent, which has a fast reaction rate, short effective time, but strong reducing power, is suitable for reducing Te2. 2- The ions are further reduced to Te 2- Ions, thereby improving the reduction efficiency and utilization rate of Te.

[0012] If a type II reducing agent is applied directly to elemental Te, elemental Te will not be completely converted within the effective time of the reducing agent.

[0013] In one embodiment of the present invention, a method for reducing elemental tellurium includes the following specific steps: S1: Add alkali to the solvent, stir to dissolve, and let stand and cool to room temperature to obtain solution A; S2: Mix elemental tellurium, reducing agent 1 and solution A, and heat and stir with ultrasound. After the reaction is complete, cool to room temperature. S3: Add alkali to the solvent, stir to dissolve, and let stand and cool to room temperature to obtain solution B; S4: Add reducing agent 2 to the reaction system obtained in step S2, heat and stir for 10 min, then add solution B, sonicate and heat and stir for 1-1.5 h. After the reaction is complete, cool to room temperature to obtain -2 valent tellurium, i.e., Te²⁺. - .

[0014] In one embodiment of the present invention, in step S1, the molar ratio of alkali to elemental tellurium is 5-100:1, and in step S3, the molar ratio of alkali to elemental tellurium is 1-100:1.

[0015] In one embodiment of the present invention, in step S2, the reducing agent 1 is one or more of sodium methyl sulfinate, sodium ethyl sulfinate, sodium phenyl sulfinate, and sodium formaldehyde sulfoxylate; the molar ratio of reducing agent 1 to elemental tellurium is 1-50:1; preferably, the molar ratio of reducing agent 1 to elemental tellurium is 1-20:1.

[0016] In one embodiment of the present invention, in step S4, the reducing agent 2 is one or more of sodium dithionite and formamidine sulfinic acid; the molar ratio of the reducing agent 2 to elemental tellurium is 1-50:1, preferably, the molar ratio of the reducing agent 2 to elemental tellurium is 1-20:1.

[0017] In one embodiment of the present invention, in step S2, the temperature is heated to 70-100 °C and the reaction time is 0.5-2 h.

[0018] In one embodiment of the present invention, in step S4, the temperature is heated to a reaction temperature of 30-100 °C.

[0019] In one embodiment of the present invention, in steps S2 and S4, the ultrasonic conditions are 20-40 kHz.

[0020] In one embodiment of the present invention, after step S4 is completed, steps S3 and S4 are repeated multiple times, such as once, twice, three times or more.

[0021] In one embodiment of the present invention, the relatively stable reducing agent 1 releases electrons under alkaline conditions, reducing elemental tellurium to purple -1 valence tellurium (Te2). 2- Subsequently, reducing agent 2, which has a stronger reducing ability, will reduce Te2. 2- The ions are further reduced to colorless Te. 2- ion.

[0022] In one embodiment of the present invention, the reaction is carried out in a closed environment.

[0023] After the reaction is complete, as long as the system is kept closed, the ions in the system can exist stably, and the corresponding cations are the cations contained in the base and reducing agent added in the reaction.

[0024] The beneficial technical effects of this invention are as follows: This invention utilizes the reducing power, characteristics, stability, and performance of different sulfinic acid reducing agents under varying temperatures and acid-base conditions to achieve the complete reduction of elemental tellurium through a stepwise reduction strategy. In this process, firstly, a suitable first-type sulfinic acid reducing agent is selected and subjected to preliminary reduction under specific temperature and acid-base conditions, completely converting elemental tellurium into tellurium ions with higher valence states. Then, another or more second-type sulfinic acid reducing agents are used, combined with different reaction conditions, to further advance the reduction reaction until all elemental tellurium is completely converted into tellurium ions with the target valence state, particularly -2 valence tellurium ions.

[0025] 1. Technological advantages Mild reaction conditions: The reduction reaction of the present invention is carried out under normal pressure and at a temperature not exceeding 100°C, without the need for high pressure, high temperature or harsh chemical environment, which significantly reduces the difficulty of operation.

[0026] The reduction process is controllable: by using a variety of reducing agents containing sulfinates and their combinations, the valence state of the reduction products (-1, -2, or mixtures thereof) can be precisely controlled, providing diverse options for downstream applications.

[0027] High conversion rate and purity: Previous methods for reducing elemental tellurium either used sodium borohydride, which led to the unsafe release of hydrogen gas, or used a single sulfinic acid reducing agent, which could not convert all elemental tellurium into tellurium ions, resulting in waste of tellurium and increased costs. This invention ensures complete conversion of elemental tellurium by alternating or mixing multiple sulfinic acid reducing agents, reducing waste and improving product purity.

[0028] 2. Economic advantages: Cost reduction: The reducing agents used in this invention (such as sodium dithionite and formamidinium sulfinic acid) are inexpensive and widely available, avoiding the use of expensive and regulated sodium borohydride in traditional methods, thus significantly reducing raw material costs.

[0029] Simplified process: The reduction steps of this invention are simple, and the operation can be completed by repeatedly adding reducing agent and alkali, without the need for complex equipment and separation processes, which further reduces production costs.

[0030] 3. Safety advantages: No gas release: This invention avoids the safety hazards caused by hydrogen release in traditional methods, making the operation safer and more reliable.

[0031] Improved environmental friendliness: The reducing agent used is a non-volatile substance, and the solvent selection in the reaction system is flexible, reducing potential environmental pollution.

[0032] 4. Social and application effects: Facilitating Industrial Production: Due to the safety of the reaction conditions and the reproducibility of the method, this invention is suitable for large-scale production, providing an efficient pathway for the industrial preparation of tellurium-based materials.

[0033] Reduced energy consumption: The reaction takes place under mild conditions, which significantly reduces energy demand and improves the greenness of the process.

[0034] Improved resource utilization: By alternating or mixing various sulfinic acid reducing agents, elemental tellurium can be completely converted into tellurium ions, which greatly improves the utilization efficiency of raw materials and reduces resource waste. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the route of the method of the present invention.

[0036] Figure 2 This is a photograph of the final state of the reaction system in Comparative Example 3, in which sodium methanesulfonate was used to reduce elemental tellurium.

[0037] Figure 3 This is a photograph of the final state of the reaction system in Comparative Example 3, which involves the reduction of elemental tellurium with sodium methyl sulfinate to prepare di-n-butyl telluride.

[0038] Figure 4 This is a photograph of the final state of the reaction system in Comparative Example 10, in which elemental tellurium was reduced by formamidine sulfinic acid.

[0039] Figure 5 This is a photograph of the final state of the reaction system in Comparative Example 10, which involves the reduction of elemental tellurium with formamidinium sulfinic acid to prepare di-n-butyl tellurium ether.

[0040] Figure 6This is a final-state photograph of the reaction system in Example 3, which involves the reduction of elemental tellurium with sodium formaldehyde sulfoxylate and methanesulfinic acid to prepare di-n-butyl telluride.

[0041] Figure 7 The 1H NMR spectrum of di-n-butyl telluride prepared by reducing elemental tellurium with sodium methyl sulfinate in Comparative Example 3 dissolved in deuterated chloroform is shown at 400 M. 1 HNMR).

[0042] Figure 8 The di-n-butyl telluride prepared by reducing elemental tellurium with methanesulfinic acid in Comparative Example 10 is dissolved in deuterated chloroform, and its proton NMR spectrum is obtained at 400 M. 1 H NMR).

[0043] Figure 9 The di-n-butyl telluride prepared in Example 3 by reducing elemental tellurium with sodium formaldehyde sulfoxylate and methanesulfinic acid is dissolved in deuterated chloroform, and its proton NMR spectrum is obtained at 400 M. 1 H NMR). Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] This section aims to illustrate the reduction effect of a single sulfinic acid reducing agent and observe the reduction state of elemental Te through color changes. Experimental results show that, using a single sulfinic acid reducing agent, Te can be reduced to -1 valence tellurium (Te2+). 2- However, with the increase of the amount of sulfinic acid reducing agent, Te cannot be completely reduced to -2 valent tellurium (Te²). - This phenomenon indicates that sulfinic acid reducing agent has a certain reducing ability when used alone, but it is insufficient to completely reduce Te to the -2 valence form, and the reduction reaction cannot proceed further by adding excess sulfinic acid.

[0046] The reduction process of Te can be tracked by a color reaction. The color of the tellurium solution is directly related to the extent of its reduction reaction, because -1 valence tellurium (Te2+) 2- ) is purple, while -2 valence tellurium (Te²) - ( ) is colorless and has a very significant effect on the color of the solution. When Te is reduced to Te₂... 2- When the solid completely disappears and the solution is deep purple-black, Te can be considered to have been completely reduced to Te2. 2- When Te2 2- Further reduced to Te² -As time progresses, the purple color of the solution will gradually fade, eventually turning into pale pink, colorless, or yellow (yellow is a possible color produced by sulfinic acid reducing agents). At this point, the solution is entirely composed of Te²⁺. - By observing the color changes of the solution during the reaction process, the reduction progress and extent of Te can be visually assessed. This color change provides an effective tool for real-time monitoring of the reduction reaction and allows for the acquisition of necessary experimental data without damaging the experimental system.

[0047] Precise Te 2- The yield of the ion can be calculated by the proportion of tellurium ether molecules formed by its reaction with the haloalkane. A haloalkane in a molar ratio of two and tetrahydrofuran in an equal volume to water were added to the reaction system, and the reaction was carried out overnight at a suitable temperature. After separation, washing, and rotary evaporation, a crude product containing tellurium ether molecules was obtained. The crude product was characterized by 1H NMR spectroscopy, and the Te content was calculated by the ratio of the peak areas in the 1H NMR spectrum. 2- Ion yield.

[0048] Te 2- The yield of ions = (1 – residual haloalkane content) * 100%.

[0049] Example 1 A method for reducing elemental tellurium includes the following specific steps: Let Te be 1 mol; S1: Add 5 mol NaOH to 1L of water, stir to dissolve, and let stand and cool to room temperature to obtain solution A; S2: Mix elemental tellurium, 2.5 mol sodium methanesulfonate with solution A, sonicate at 70°C with an ultrasonic power of 240 W, heat and stir for 1 h, and after the reaction is complete, cool to room temperature; S3: Add 3 mol NaOH to 1L of water, stir to dissolve, and let stand and cool to room temperature to obtain solution B; S4: Add 2 mol of sodium dithionite to the reaction system prepared in step S2, stir at 45°C for 10 min, then add solution B, and stir at 45°C with ultrasonic power of 240 W for 1 h. After the reaction is complete, cool to room temperature to obtain a pale yellow, pale pink, or colorless solution, which is Te. 2- Ions, yield 99.9%.

[0050] Example 2 A method for reducing elemental tellurium includes the following specific steps: Let Te be 1 mol; S1: Add 4 mol NaOH to 0.5 L water and 0.5 L tetrahydrofuran, stir to dissolve, and let stand and cool to room temperature to obtain solution A; S2: Mix elemental tellurium, 2 mol sodium ethyl sulfinate with solution A, sonicate at 70°C with an ultrasonic power of 240 W, heat and stir for 1 h, and after the reaction is complete, cool to room temperature; S3: Add 2 mol NaOH to 0.5 L water and 0.5 L tetrahydrofuran, stir to dissolve, and let stand and cool to room temperature to obtain solution B; S4: Add 1 mol of sodium dithionite to the reaction system prepared in step S2, stir at 50°C for 10 min, then add solution B, sonicate at 50°C with an ultrasonic power of 240 W, stir for 0.5 h, the reaction is completed, and then cool to room temperature. S5: Add 1 mol of methanesulfinic acid to the reaction system prepared in step S4, stir at 50℃ for 10 min, then add 2 mol of NaOH, sonicate at 50℃ with an ultrasonic power of 240 W, stir for 0.5 h, and the reaction is complete. Cool to room temperature to obtain a pale yellow, pale pink, or colorless solution, which is Te. 2- Ions, yield 99.9%.

[0051] Example 3 A method for reducing elemental tellurium includes the following specific steps: Let Te be 1 mol; S1: Add 5 mol NaOH to 1 L of water, stir to dissolve, and let stand and cool to room temperature to obtain solution A; S2: Mix elemental tellurium, 2.5 mol sodium formaldehyde bisulfite with solution A, sonicate at 80°C with an ultrasonic power of 240 W, heat and stir for 1 h, and after the reaction is complete, cool to room temperature; S3: Add 1.5 mol NaOH to 1L of water, stir to dissolve, and let stand and cool to room temperature to obtain solution B; S4: Add 1 mol of formamidine sulfinic acid to the reaction system prepared in step S2, stir at 50℃ for 10 min, then add solution B, sonicate at 50℃ with an ultrasonic power of 240 W, stir for 0.5 h, the reaction is completed, and then cool to room temperature. S5: Add 1 mol of methanesulfinic acid to the reaction system prepared in step S4, stir at 50℃ for 10 min, then add 1.5 mol of NaOH, sonicate at 50℃ with an ultrasonic power of 240 W, stir for 0.5 h, and the reaction is complete. Cool to room temperature to obtain a pale yellow, pale pink, or colorless solution, which is Te. 2- Ions, yield 99.9%.

[0052] Subsequently, 2 molar ratios of bromobutane and 1 L of tetrahydrofuran were added to the pale yellow solution, and the mixture was stirred at 30°C for 16 h to obtain a solution with a grayish-yellow upper layer and a yellowish-green lower layer. Figure 6As shown. Tetrahydrofuran was removed at 40℃ and 100 mbar. Dichloromethane was added and the mixture was repeatedly shaken to extract the supernatant. The supernatant was then washed with saturated brine, and the mixture was separated to obtain a yellow oily liquid. Dichloromethane was removed by rotary evaporation at 40℃ and 100 mbar, yielding a yellow oily liquid, namely di-n-butyl telluride. One drop of di-n-butyl telluride was dissolved in 0.6 mL of deuterated chloroform, transferred to an 8 mm NMR tube, and the proton NMR spectrum was measured at 400 M. The spectrum is shown in [image missing]. Figure 9 .Depend on Figure 9 It can be seen that, 1 Four characteristic signal peaks appeared in the 1H NMR spectrum, located at 2.63, 1.72, 1.39-1.38, and 0.91 ppm, corresponding to four different hydrogen environments in the molecular structure of the target product, di-n-butyl telluride. Among them, the peak (d) at 2.63 ppm belongs to the hydrogen on the methylene group (–CH2–Te) directly attached to tellurium (d hydrogen), and due to its proximity to the highly electronegative Te atom, it exhibits a significant deshielding effect; the peak (c) at 1.72 ppm belongs to the hydrogen on the methylene group (–CH2–CH2–Te) slightly away from tellurium (c-position hydrogen), and because this hydrogen is slightly away from Te, the deshielding effect is weakened; the peak (b) at 1.39-1.38 ppm is the hydrogen on the methylene group (–CH2–CH3) adjacent to the terminal methyl group (b-position hydrogen); and the strong peak (a) at 0.91 ppm belongs to the hydrogen on the terminal methyl group (–CH3) (a-position hydrogen). The peak areas show that the integral ratios of a, b, c, and d closely match the number of hydrogen atoms in the di-n-butyl telluride structure (a:b:c:d≈6:4:4:4), indicating high product purity. In summary, this spectrum clearly demonstrates that the product is high-purity di-n-butyl telluride, and that tellurium exists in the product with a -2 valence. This indicates that under the alternating action of sodium formaldehyde bisulfite and methanesulfinic acid, elemental tellurium has been completely reduced to Te. 2- The ions reacted with bromobutane to successfully generate di-n-butyl telluride.

[0053] Comparative Example 1 Taking Te as 1 mol, Te, sodium methanesulfonate, and NaOH were mixed in a molar ratio of 1:2:4, and 1 L of water was added. The mixture was stirred at 80 °C for 2 h. A deep purple solution was obtained, which is Te2. 2- ion.

[0054] Comparative Example 2 Taking Te as 1 mol, Te, sodium formaldehyde sulfoxylate, and NaOH were mixed in a molar ratio of 1:2.5:5, and 1 L of water was added. The mixture was stirred at 70 °C with an ultrasonic power of 240 W for 1 h. A deep purple transparent solution was obtained, which is Te2. 2- ion.

[0055] Comparative Example 3 Taking Te as 1 mol, Te, sodium methanesulfonate, and NaOH were mixed in a molar ratio of 1:4:8, and 1 L of water was added. The mixture was stirred at 80 °C for 2 h. A deep purple solution was obtained, which is Te2. 2- Ions, such as Figure 2 As shown. Then, 2 molar ratios of bromobutane and 1 L of tetrahydrofuran were added to the deep purple solution, and the mixture was stirred at 30°C for 16 h, yielding a solution with an orange upper layer and a pale yellow lower layer, as shown. Figure 3 As shown.

[0056] Tetrahydrofuran was removed at 40 °C and 100 mbar. Dichloromethane was added and the mixture was repeatedly shaken to extract the supernatant. The supernatant was then washed with saturated brine, and the liquid was separated to obtain a brownish-yellow oily liquid. Dichloromethane was removed by rotary evaporation at 40 °C and 100 mbar, yielding a brownish-red oily liquid, namely di-n-butyl telluride. One drop of di-n-butyl telluride was dissolved in 0.6 mL of deuterated chloroform, transferred to an 8 mm NMR tube, and its proton NMR spectrum was measured at 400 M. The spectrum is shown below. Figure 7 The 1H NMR spectrum shows a significant amount of residual n-butane bromo, indicating that increasing the amount of reducing agent is insufficient to reduce Te2. 2- To Te 2- Ion conversion.

[0057] Comparative Example 4 Taking Te as 1 mol, Te, sodium methanesulfonate, and NaOH were mixed in a molar ratio of 1:5:10, and 1 L of water was added. The mixture was stirred at 80 °C for 2 h. A deep purple solution was obtained, which is Te2. 2- Ions. This comparative example illustrates that increasing the amount of reducing agent cannot reduce Te2+. 2- To Te 2- Ion conversion.

[0058] Comparative Example 5 Taking Te as 1 mol, Te, sodium methanesulfonate, and NaOH were mixed in a molar ratio of 1:2:8, and 1 L of water was added. The mixture was stirred at 80 °C for 2 h. A purple transparent solution was obtained, which is Te2. 2- Ions and Te² - The mixture. This comparative example illustrates that increasing the amount of alkalinity can enhance the reducing power of sulfinic acid, but it cannot reduce Te2. 2- Completely converted to Te 2- ion.

[0059] Comparative Example 6 Taking Te as 1 mol, Te, sodium formaldehyde sulfoxylate, and NaOH were mixed in a molar ratio of 1:2.5:10, and 1 L of water was added. The mixture was stirred at 80 °C with an ultrasonic power of 240 W for 2 h. A purple transparent solution was obtained, which is Te2. 2- Ions and Te² - The mixture. This comparative example illustrates that increasing the amount of alkalinity can enhance the reducing power of sulfinic acid, but it cannot reduce Te2. 2- Completely converted to Te 2- ion.

[0060] Comparative Example 7 Taking Te as 1 mol, Te, sodium dithionite, and NaOH were mixed in a molar ratio of 1:2:5, and 1 L of water was added. The mixture was stirred at 50 °C for 2 h. A solution was obtained with a yellow, transparent upper layer and a silvery, reflective lower layer. This comparative example demonstrates that sodium dithionite partially reduced elemental Te to Te²⁺. - The ions were present, but the vast majority of elemental Te failed to react.

[0061] Comparative Example 8 Taking Te as 1 mol, Te, sodium dithionite, and NaOH were mixed in a molar ratio of 1:8:20, and 1 L of water was added. The mixture was stirred at 50 °C for 2 h. A solution was obtained with a yellow, transparent upper layer and a silvery, reflective lower layer. This comparative example demonstrates that increasing the amount of sodium dithionite cannot further reduce elemental Te to Te². - ion.

[0062] Comparative Example 9 Taking Te as 1 mol, Te, sodium dithionite, and NaOH were mixed in a molar ratio of 1:8:20, and 1 L of water was added. The mixture was stirred at 80 °C for 2 h. A solution with an orange turbid upper layer and a silvery reflective lower layer was obtained. This comparative example illustrates that increasing the temperature causes sodium dithionite to become unstable and decompose.

[0063] Comparative Example 10 Taking Te as 1 mol, Te, methanesulfinic acid, and NaOH were mixed in a molar ratio of 1:2.5:10, and 1 L of water was added. The mixture was then sonicated and stirred at 50 °C for 2 h. A purple transparent solution was obtained, which is Te2. 2- Ions and Te² - Mixtures, such as Figure 4 As shown. Then, 2 molar ratios of bromobutane and 1 L of tetrahydrofuran were added to the purple transparent solution, and the mixture was stirred at 30 °C for 16 h, yielding a solution with an orange upper layer and a pale yellow lower layer. A silver solid residue remained at the bottom of the flask, as shown. Figure 5 As shown.

[0064] Tetrahydrofuran was removed at 40 °C and 100 mbar. Dichloromethane was added and the mixture was repeatedly shaken to extract the supernatant. The supernatant was then washed with saturated brine, and the liquid was separated to obtain a brownish-yellow oily liquid. Dichloromethane was removed by rotary evaporation at 40 °C and 100 mbar, yielding a brownish-red oily liquid, namely di-n-butyl telluride. One drop of di-n-butyl telluride was dissolved in 0.6 mL of deuterated chloroform, transferred to an 8 mm NMR tube, and its proton NMR spectrum was measured at 400 M. The spectrum is shown below. Figure 8 The 1H NMR spectrum shows a significant amount of residual n-bromobutane in the product, indicating that the formamidinium sulfinic acid reduced some elemental Te to Te²⁺. - The ions were present, but the vast majority of elemental Te failed to react. The properties of memidazine sulfinic acid in the reduction of elemental Te are similar to those of sodium dithionite, as described in Comparative Examples 7-9, and will not be repeated here.

[0065] Comparative Example 11 Taking Te as 1 mol, Te, sodium methyl sulfinate, and NaOH were mixed in a molar ratio of 1:2.5:5, and 1 L of water was added. The mixture was stirred for 1 h at 80 °C with an ultrasonic power of 240 W. Then, 2 mol of sodium ethyl sulfinate and 4 mol of NaOH were added, and the mixture was reacted at 80 °C for 1 h to obtain a purple transparent solution, which is Te2. 2- Ions and Te² - The mixture. This comparative example illustrates that the complete reduction of elemental Te cannot be achieved by alternating addition of the first type of reducing agent.

[0066] Comparative Example 12 Taking Te as 1 mol, Te, sodium formaldehyde sulfoxylate, and NaOH were mixed in a molar ratio of 1:2.5:5, and 1 L of water was added. The mixture was stirred at 80 °C with an ultrasonic power of 240 W for 1 h. Then, 2 mol of sodium methanesulfonate and 4 mol of NaOH were added, and the mixture was reacted at 80 °C for 1 h. Finally, 2 mol of sodium methanesulfonate and 4 mol of NaOH were added, and the mixture was reacted at 80 °C for 1 h, yielding a purple transparent solution, which is Te2. 2- Ions and Te² - The mixture. This comparative example illustrates that the complete reduction of elemental Te cannot be achieved by alternating multiple additions of the first type of reducing agent.

[0067] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for reducing elemental tellurium, characterized in that, Tellurium, alkali, reducing agent and solvent are mixed and reacted under heating and ultrasonic conditions. During the reaction, alkali and reducing agent are added at least once. The structure of the reducing agent is shown in general formula (1): General formula (1) In general formula (1), n ​​represents a natural number from 0 to 10; R represents hydrogen, methyl, ethyl, hydroxyethyl, phenyl, p-tolyl, etc. , One of them; M is represented as H + Li + Na + K + NH4 + Be 2+ Mg 2+ Ca 2+ Zn 2+ Ba 2+ One of them.

2. The method according to claim 1, characterized in that, The alkali is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, sodium carbonate, and potassium carbonate.

3. The method according to claim 1, characterized in that, The solvent is one or more of water, tetrahydrofuran, dichloromethane, chloroform, pyridine, benzene, toluene, N,N-dimethylformamide, ethyl acetate, acetonitrile, and dimethyl sulfoxide.

4. The method according to claim 1, characterized in that, The reducing agent is one or more of sodium methyl sulfinate, sodium ethyl sulfinate, sodium phenyl sulfinate, sodium formaldehyde sulfoxylate, sodium dithionite, and formamidinium sulfinic acid.

5. The method according to any one of claims 1-4, characterized in that, The specific steps include the following: S1: Add alkali to the solvent, stir to dissolve, and let stand and cool to room temperature to obtain solution A; S2: Mix elemental tellurium, reducing agent 1 and solution A, and heat and stir with ultrasound. After the reaction is complete, cool to room temperature. S3: Add alkali to the solvent, stir to dissolve, and let stand and cool to room temperature to obtain solution B; S4: Add reducing agent 2 to the reaction system obtained in step S2, heat and stir for 10 min, then add solution B, sonicate and stir for 1-1.5 h. After the reaction is complete, cool to room temperature to obtain -2 valent tellurium, i.e., Te²⁻. - .

6. The method according to claim 5, characterized in that, In step S1, the molar ratio of alkali to tellurium is 5-100:1, and in step S3, the molar ratio of alkali to tellurium is 1-100:

1.

7. The method according to claim 5, characterized in that, In step S2, reducing agent 1 is one or more of sodium methyl sulfinate, sodium ethyl sulfinate, sodium phenyl sulfinate, and sodium formaldehyde sulfoxylate; the molar ratio of reducing agent 1 to elemental tellurium is 1-50:

1. In step S4, reducing agent 2 is one or more of sodium dithionite and formamidine sulfinic acid; the molar ratio of reducing agent 2 to elemental tellurium is 1-50:

1.

8. The method according to claim 5, characterized in that, In step S2, the temperature is heated to 70-100 ℃ and the reaction time is 0.5-2 h; in step S4, the temperature is heated to 30-100 ℃.

9. The method according to claim 5, characterized in that, In steps S2 and S4, the ultrasound conditions are 20-40 kHz.

10. The method according to claim 5, characterized in that, The reaction takes place in a closed environment.

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