Method for preparing high-purity phosphorus pentasulfide by low-temperature liquid phase and application thereof

Abstract

The application relates to a method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase and application thereof, and belongs to the technical field of key materials for lithium-sulfur batteries and solid-state batteries. The method solves the technical problems of high reaction temperature and large energy consumption in the existing preparation process of phosphorus pentasulfide. The method comprises the following steps: step 1, selecting phosphorus pentachloride, drying the phosphorus pentachloride, and placing the treated phosphorus pentachloride in an organic solvent to form a suspension phase or a slurry system; step 2, placing the suspension phase or the slurry system in a closed reactor; step 3, introducing a sulfur source into the reactor to make the phosphorus pentachloride and the sulfur source undergo a sulfuration reaction; step 4, keeping the deep sulfuration reaction after being heated to a set temperature to generate phosphorus pentasulfide; and step 5, cooling, solid-liquid separation and drying after the reaction to obtain a phosphorus pentasulfide solid product. The application has the advantages of mild reaction conditions, simplified process flow, high safety, recyclable solvent and suitability for continuous and large-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field of key materials for lithium-sulfur batteries and solid-state batteries, specifically relating to a method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase and its application. Background Technology

[0002] Phosphorus pentasulfide is a key inorganic sulfide used in the preparation of sulfide solid electrolytes (such as Li6PS6Cl, Li3PS4, and Li7P3S). 11 Phosphorus pentasulfide, a core precursor for solid-state batteries, directly affects the ionic conductivity, density, interfacial stability, and electrochemical performance of solid-state electrolytes due to its purity, structural stability, and impurity control level. Therefore, developing high-purity, low-chlorine, and highly stable phosphorus pentasulfide is of irreplaceable importance to the solid-state battery industry.

[0003] Currently, the commonly used methods for preparing phosphorus pentasulfide in industry and laboratories mainly include the following categories: 1. Direct high-temperature sulfidation method of red phosphorus / white phosphorus with sulfur.

[0004] This route typically requires reactions at 300℃-500℃, involving intense exothermic processes and posing safety hazards such as melt splashing and localized combustion. Due to limited heat and mass transfer in solid-solid reactions, P4S3, P4S7, and P4S are readily generated. 10 The presence of various phosphorus sulfide impurities makes the product purity unstable, making it difficult to meet the stringent requirements of solid electrolytes for raw material quality.

[0005] 2. Liquid-phase reaction of phosphorus trichloride with sulfur or sulfides.

[0006] Although the reaction temperature is low, phosphorus trichloride needs to be prepared beforehand, generating a large amount of hydrogen chloride gas as a byproduct; the phosphorus trichloride intermediate is difficult to completely convert, easily causing Cl... - High residual levels affect the structural stability and electrochemical performance of the subsequent solid electrolyte.

[0007] 3. Pyrolysis, gas-phase sulfur transfer, or multi-step staged sulfidation methods.

[0008] These methods involve complex equipment, multiple steps, and the product structure is easily affected by heat treatment conditions. They also suffer from high energy consumption and difficulty in scaling up.

[0009] For example, the patent with publication number CN110510588B, entitled "A Method for Synthesizing Phosphorus Pentasulfide Powder," mixes lithium sulfide and phosphorus pentachloride and heats them in a closed reactor. After the reaction is complete, the mixture is cooled and treated with a solvent to remove unreacted raw materials, thus preparing phosphorus pentasulfide powder. The patent with publication number CN110526224B, entitled "A Mechanical Ball Milling Synthesis Method for Phosphorus Pentasulfide Powder," under an inert atmosphere, adds phosphorus pentachloride and lithium sulfide to a sealed ball mill jar and reacts them at room temperature for a certain time. After the reaction is complete, the solid product is removed under an inert atmosphere, and the unreacted raw materials are recovered and separated to obtain phosphorus pentasulfide powder.

[0010] The aforementioned traditional routes generally suffer from bottlenecks such as uneven reaction, unstable purity, high safety risks, difficulty in handling by-products, difficulty in continuous production, and high raw material costs. They are unable to meet the demand for high-purity phosphorus pentasulfide in the new energy field, especially when used in solid electrolyte systems, where the requirements for chlorine content, moisture, and structural consistency are even more stringent. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase and its application. This method solves the problems of high reaction temperature, high energy consumption, and easy formation of various phosphorus sulfide impurities (such as P4S3, P4S7, P4S) in existing phosphorus pentasulfide preparation processes. 10 Technical challenges include difficulty in controlling chlorine content, high pressure in treating byproduct hydrogen sulfide / hydrogen chloride gas tail gas, and difficulty in achieving continuous and large-scale production.

[0012] To solve the above problems, the technical solution of the present invention is: a method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase, comprising the following steps: Step 1: Select phosphorus pentachloride with a purity ≥ 99.0 wt%, and dry it to ensure that its moisture content does not exceed 50 ppm; place the treated phosphorus pentachloride in an organic solvent to form a suspension or slurry system, with the mass fraction of phosphorus pentachloride in the solvent being 10~60 wt%; Step 2: Place the suspended phase or slurry system from Step 1 into a closed reactor (3); Step 3: Introduce a sulfur source into the reactor to allow phosphorus pentachloride to undergo a preliminary sulfidation reaction, converting phosphorus pentachloride into a phosphorus thiochloride intermediate mainly composed of phosphorus trichloride intermediate, while releasing hydrogen chloride gas. Monitor the volume fraction of hydrogen chloride gas in the tail gas online. When the concentration of hydrogen chloride gas decreases significantly and approaches stability, the preliminary sulfidation of phosphorus pentachloride is considered to be basically completed. The molar ratio of sulfur source to phosphorus pentachloride is controlled between 3:1 and 6:1. Step 4: After the initial vulcanization is completed, the temperature is slowly increased to 100℃~200℃. After the temperature is raised to the set temperature, a sulfur source is introduced to maintain the deep vulcanization reaction, so that the trichlorophosphorus intermediate is further vulcanized and polymerized to generate phosphorus pentasulfide. The hydrogen chloride gas and unreacted sulfur source generated during the reaction are continuously removed through the tail gas absorption system. Step 5: After the reaction is complete, the product is cooled and separated into solid and liquid phases to remove the solvent. After drying, solid phosphorus pentasulfide is obtained.

[0013] Preferably, the mass fraction of phosphorus pentachloride in the solvent is 20-40 wt% to ensure that the reaction system has suitable viscosity and fluidity, and to facilitate the full dissolution and diffusion of the sulfur source in the liquid phase.

[0014] Preferably, in step 1, to avoid water-induced hydrolysis and the generation of byproducts such as H3PO4 and POCl3, phosphorus pentachloride is vacuum dried at 50℃~200℃ for 2~6h before use, so that its moisture content is not higher than 50ppm.

[0015] Preferably, in step 1, the dried phosphorus pentachloride is added to an organic solvent to prepare a solution or slurry to improve mass transfer efficiency and facilitate temperature control. The organic solvent is one that does not chemically react with phosphorus pentachloride and hydrogen sulfide and is stable within the reaction temperature range.

[0016] Preferably, in step 1, the mass fraction of phosphorus pentachloride in the solvent is 20-40 wt% to ensure that the reaction system has suitable viscosity and fluidity, and to facilitate the full dissolution and diffusion of the sulfur source in the liquid phase.

[0017] Preferably, in step 1, the sulfur source is dried with concentrated sulfuric acid, phosphorus pentoxide, molecular sieve or other desiccant before use, so that its dew point is below -40°C and its water content is not higher than 10 ppm, thereby avoiding side reactions caused by moisture and product hydrolysis.

[0018] Preferably, the organic solvent in step 1 is at least one of N-methylpyrrolidone, chlorobenzene, dichlorobenzene, trichlorobenzene, o-dichlorobenzene, bromochlorobenzene, dichlorobromobenzene, dibromobenzene, tribromobenzene, chloronaphthalene, bromonaphthalene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene, tribromobenzene and their isomers, or other organic solvents that do not react with phosphorus pentachloride and have a boiling point of not less than 150°C.

[0019] Preferably, the step of drying phosphorus pentachloride in step 1 is as follows: phosphorus pentachloride is vacuum dried at 50℃~140℃ for 2~6 hours.

[0020] Preferably, in step 2, the phosphorus pentachloride suspension or slurry system obtained in step 1 is added to a corrosion-resistant closed reactor. The reactor can be an enamel-lined reactor, a glass-lined reactor, or a high-alloy steel reactor lined with fluorine material. The reactor is equipped with a temperature monitoring and control system, a stirring device, a gas flow control module, and a tail gas absorption system.

[0021] Preferably, the reactor is made of corrosion-resistant metal, enamel, or halide-resistant glass lining, and is equipped with an exhaust gas extraction system and a reflux condenser.

[0022] Preferably, in step 2, after the reactor is loaded, the air is replaced with an inert gas (nitrogen or argon) 2 to 5 times to ensure that the oxygen content is not higher than 100 ppm, so as to prevent the safety risks of oxidation side reactions and hydrogen sulfide.

[0023] Preferably, in step 3, the initial vulcanization reaction temperature is controlled at 50℃~120℃ to reduce the exothermic reaction rate and avoid local overheating that could lead to side reactions or product decomposition.

[0024] Preferably, in step 3, the molar ratio of sulfur source to phosphorus pentachloride is controlled at 3:1 to 6:1, more preferably 4:1 to 5:1, to ensure that phosphorus pentachloride is fully converted into trichlorophosphorus intermediate and to reduce the presence of residual phosphorus pentachloride.

[0025] Preferably, in step 3, the hydrogen chloride gas generated in this stage enters the alkaline absorption tower through the tail gas pipeline at the top of the reactor. The absorbent in the alkaline absorption tower can be NaOH or KOH solution, and the absorption reaction is as follows: HCl + NaOH → NaCl + H₂O This achieves efficient removal of hydrogen chloride gas, preventing its accumulation in the liquid phase and thus avoiding corrosion or side reactions.

[0026] Preferably, the sulfur source in step 3 is hydrogen sulfide gas, which is dried with concentrated sulfuric acid, phosphorus pentoxide or 4A molecular sieve before use, and the water content is not higher than 10 ppm.

[0027] Preferably, the sulfur source can be hydrogen sulfide, carbon disulfide, or a mixture of hydrogen sulfide and carbon disulfide.

[0028] Preferably, the flow rate of the sulfur source in step 3 is 0.05~0.5 L·min. -1 To ensure a continuous excess of sulfur source within the reaction system, thereby promoting the complete sulfidation of phosphorus pentachloride.

[0029] Preferably, the reaction temperature for steps 3 and 4 is 50°C to 200°C.

[0030] Preferably, in step 4, after the initial sulfidation is completed and free phosphorus pentachloride is no longer present in the system, the sulfur-chlorine-phosphorus intermediate is further subjected to deep sulfidation and polymerization reaction in the same reactor.

[0031] Preferably, in step 4, under continuous stirring and slow heating conditions, a dry sulfur source is continuously introduced to adjust the reaction temperature to 135℃~185℃, so as to drive intermediates such as trichlorophosphorus to further react with the sulfur source and undergo condensation and polymerization processes, gradually generating phosphorus pentasulfide, while releasing hydrogen chloride gas.

[0032] Preferably, in step 4, during the entire deep sulfidation process, the hydrogen chloride gas and a small amount of unreacted sulfur source generated in the tail gas continue to enter the tail gas treatment unit. The first alkaline tower mainly absorbs the hydrogen chloride gas, and the second alkaline or oxidizing absorbent (such as the NaOH / NaClO system) is used to further absorb and oxidize the sulfur source, thereby achieving the tail gas emission standard.

[0033] Preferably, the exhaust gas in step 4 undergoes two-stage absorption treatment: the first stage uses an alkaline solution, namely NaOH or KOH, to absorb hydrogen chloride gas, and the second stage uses a strong alkali or amine absorbent to absorb unreacted sulfur sources.

[0034] Preferably, in step 5, after the deep vulcanization reaction is completed, the sulfur source is stopped, and the reaction system is cooled to 40°C~80°C under inert atmosphere protection or slight positive pressure.

[0035] Preferably, in step 5, the cooling process involves continuous purging with inert gas to further remove residual hydrogen chloride gas and sulfur source, reducing their solubility in the reaction system and improving product purity. After cooling, solid phosphorus pentasulfide and organic solvent are separated by solid-liquid separation methods (such as filtration and centrifugation), and then dried at 50℃~140℃ and vacuum degree ≤−0.095MPa for 4~12h to obtain high-purity solid phosphorus pentasulfide product.

[0036] Preferably, the separated organic solvent can be recycled back to step 1 after distillation to remove a small amount of dissolved gas and low-boiling components, forming a closed-loop solvent cycle, reducing costs and reducing organic waste liquid emissions.

[0037] Another object of the present invention is to provide an application of phosphorus pentasulfide prepared by the above-mentioned method for preparing high-purity phosphorus pentasulfide in the preparation of lubricating oil additives, solid electrolyte materials, organophosphorus compounds, pesticide intermediates or high-performance sulfide functional materials.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Mild reaction conditions and significantly reduced energy consumption This invention employs a two-step sulfidation strategy involving phosphorus pentachloride and hydrogen sulfide gas. Through a gas-liquid reaction in an inert organic solvent, highly reactive phosphorus pentachloride undergoes initial sulfidation at a low temperature of 50°C to 120°C. Subsequent deep sulfidation is achieved within the range of 100°C to 200°C, yielding the target product, phosphorus pentasulfide. Compared to traditional solid-phase sulfidation methods that require direct reaction between phosphorus and sulfur at 250°C to 350°C, this invention lowers the overall reaction temperature by 150°C to 250°C, effectively reducing side reactions and energy loss caused by high temperatures. Simultaneously, the stepwise sulfidation method significantly reduces the instantaneous exothermic intensity, preventing localized overheating and the formation of impurity phases, thus providing a stable and controllable reaction environment for the preparation of high-purity phosphorus pentasulfide.

[0039] 2. Liquid media significantly improve reaction selectivity and increase kinetic efficiency. Traditional solid-solid sulfidation routes suffer from slow heat transfer, limited mass transfer, and uneven sulfidation on the phosphorus source surface, easily generating P4S3, P4S7, and P4S. 10 This invention utilizes an organic solvent to construct a uniformly dispersed liquid-phase reaction system, ensuring the complete dissolution or dispersion of phosphorus pentachloride. The excellent solubility and diffusivity of hydrogen sulfide gas significantly improve the mass transfer process. This liquid-mediated sulfidation pathway transforms the solid-solid interface reaction into a uniform and controllable gas-liquid reaction, substantially reducing the reaction diffusion barrier and improving sulfidation selectivity. This allows phosphorus pentachloride to be smoothly converted into the intermediate phosphorus trichloride and further directionally generated into phosphorus disulfide. The reaction kinetic efficiency is improved by approximately 2-4 times, the sulfidation degree is more thorough, and ultimately, a high yield and high purity of the target product are achieved.

[0040] 3. High purity, low chlorine residue, and excellent structural stability. This invention effectively reduces the chlorine content in products through a gentle sulfidation and stepwise dechlorination method, avoiding the chloride content problems caused by uneven chloride volatilization or side reactions in traditional solid-phase high-temperature sulfidation. - Residual chlorine is eliminated by removing the generated hydrogen chloride gas in real time, preventing chlorine accumulation in the liquid phase and eliminating the conditions for the formation of the chlorinated secondary phase from the process mechanism. The resulting solid phosphorus pentasulfide product has a purity ≥99wt% and a chlorine content ≤500ppm, meeting the requirements of sulfide solid electrolytes (such as Li3PS4, Li6PS5Cl, etc.) for extremely low chlorine impurities in the precursor. Furthermore, due to the mild reaction process without intense melting or localized sintering, the final phosphorus pentasulfide has a uniform structure and stable crystal phase, allowing it to be directly used for the high-quality synthesis of solid electrolytes.

[0041] 4. Significantly improved safety and environmental friendliness Traditional high-temperature synthesis routes using white phosphorus and elemental sulfur as raw materials pose a risk of combustion and explosion, with violent reactions accompanied by strong exothermic reactions. This invention employs low-temperature stepwise sulfidation, ensuring a controlled reaction process that avoids the violent exothermic reaction between high-temperature white phosphorus and sulfur, significantly improving the inherent safety of the process. Furthermore, the byproduct gases produced by this method are primarily hydrogen chloride gas and a small amount of unreacted hydrogen sulfide gas, both of which can be efficiently treated using an alkaline absorption tower or an oxidation absorption system. The entire reaction system is conducted in a closed environment, effectively preventing the safety hazards posed by the escape of hydrogen sulfide gas.

[0042] 5. Solvents can be recycled, and the process is green and closed-loop. The inert organic solvent used in this invention (such as one or more of N-methylpyrrolidone, chlorobenzene, dichlorobenzene, trichlorobenzene, bromochlorobenzene, dichlorobromobenzene, dibromobenzene, tribromobenzene, chloronaphthalene, bromonaphthalene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene, tribromobenzene and its isomers, etc.) can be recycled more than 10 times after the reaction by distillation or removal of dissolved gases. It is stable, has low loss, and avoids the generation of large amounts of waste sulfur, waste phosphorus, and difficult-to-treat mixtures generated by traditional solid-phase processes. This invention features closed-loop solvent recycling, conversion of hydrogen chloride gas tail gas into by-product salts, and complete absorption and utilization of residual hydrogen sulfide gas, making the entire process system green and environmentally friendly. The production process is highly clean and meets the requirements for environmentally friendly processes in the large-scale preparation of solid electrolyte materials.

[0043] 6. The process is stable and can realize continuous or semi-continuous industrial production. Traditional solid-phase sulfidation methods are limited by their heterogeneous, highly exothermic, and easily sintered characteristics, making continuous scale-up extremely difficult. This invention utilizes the uniform temperature field and controllable mass transfer behavior of the liquid-phase reaction system to stably control the reaction kinetics and thermal management of phosphorus pentachloride and hydrogen sulfide gas. It is suitable for modular production methods such as continuous feeding, continuous aeration, and continuous separation. Tail gas separation, solvent recycling, and solid drying can all be standardized and industrialized. This process is suitable for scaling up from kilogram-scale to ton-scale production, providing a scalable, replicable supply path for high-quality phosphorus pentasulfide feedstock in the solid electrolyte industry chain.

[0044] The phosphorus pentasulfide product prepared by the method of this invention has a purity ≥99wt%, a chlorine content ≤500ppm, and a moisture content not exceeding 0.05wt%, which can meet the requirements of sulfide solid electrolytes (such as Li3PS4, Li7P3S). 11 Requirements for precursor quality (such as Li6PS5Cl, etc.). Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is a SEM image of the phosphorus pentasulfide product in Example 2. Figure 3This is a TEM image of the phosphorus pentasulfide product in Example 3; Figure 4 This is a SEM image of the phosphorus pentasulfide product from Example 4.

[0046] Attached figures: 1. Sulfur source supply device; 2. Gas buffer / drying device; 3. Reactor; 4. Tail gas treatment system. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0048] Example 1: This example provides a method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase. By constructing a controllable gas-liquid reaction system and a stepwise sulfidation pathway, a highly selective conversion of phosphorus pentachloride to phosphorus pentasulfide is achieved, resulting in a high-purity phosphorus pentasulfide product suitable for sulfide solid electrolyte systems. The method includes the following steps: Step 1: Raw material preparation and pretreatment Industrial-grade or electronic-grade phosphorus pentachloride is selected as the phosphorus source. Preferably, the purity of phosphorus pentachloride is ≥99.0 wt%.

[0049] Preferably, to reduce the interference of moisture and impurities on the reaction, phosphorus pentachloride is vacuum dried at 80°C for 6 hours under an inert atmosphere to ensure that its moisture content does not exceed 50 ppm. The dried phosphorus pentachloride is then sealed and cooled in a drying oven for later use to prevent moisture absorption and hydrolysis. The pre-dried phosphorus pentachloride is added to an inert organic solvent to prepare the reaction solution. In this embodiment, o-dichlorobenzene is selected as the solvent, with a boiling point of approximately 180°C. O-dichlorobenzene exhibits good thermal stability and chemical inertness within the reaction temperature range (≤180°C) of this invention.

[0050] In this embodiment, 200g of phosphorus pentachloride was added to 500mL of o-dichlorobenzene and mechanically stirred for 30min under an inert atmosphere to fully dissolve or uniformly disperse it, forming a suspension or slurry system, to obtain a phosphorus pentachloride-o-dichlorobenzene solution with a mass fraction of approximately 28.6%.

[0051] Step 2: Charging and Atmosphere Control The phosphorus pentachloride-o-dichlorobenzene solution obtained in step 1 is transferred to a closed reactor 3.

[0052] Preferably, reactor 3 is a corrosion-resistant, sealed reactor with a stirrer. The inner wall of the reactor is made of glass-lined material or lined with polytetrafluoroethylene, and is equipped with a temperature probe, pressure gauge, gas flow meter, and exhaust gas outlet, which is connected to the exhaust gas treatment system 4.

[0053] Step 3: Low-temperature preliminary sulfidation (generating sulfur-chlorine-phosphorus intermediates) At 55℃, at 0.10 L·min-1 Dry hydrogen sulfide gas is slowly introduced into the reactor at a certain flow rate, allowing it to fully dissolve under stirring and come into contact with phosphorus pentachloride in the liquid phase.

[0054] Preferably, in this embodiment, the initial introduction time of hydrogen sulfide gas is controlled to be 2 hours, and the total amount of hydrogen sulfide gas introduced is approximately n(hydrogen sulfide gas):n(phosphorus pentachloride) = 4:1 by molar ratio, so as to ensure that phosphorus pentachloride is basically converted into phosphorus sulfide intermediate mainly composed of phosphorus trichloride intermediate, while releasing an equimolar amount of hydrogen chloride gas.

[0055] During the reaction, the color of the reaction system gradually changes from colorless / light yellow to light yellow to yellowish-brown, and the viscosity increases slightly. The tail gas is discharged from the top of the reactor and absorbed by the first alkaline scrubbing tower of the tail gas treatment system 4. The alkaline solution is a 10wt% NaOH solution, which mainly absorbs hydrogen chloride gas, and the following reaction occurs: HCl + NaOH → NaCl + H₂O By monitoring the volume fraction of hydrogen chloride gas in the exhaust gas online, when the concentration of hydrogen chloride gas decreases significantly and approaches stability (e.g., <0.5 vol% and remains stable for more than 30 minutes), it is considered that the initial sulfidation of phosphorus pentachloride is basically completed, the residual phosphorus pentachloride content in the reaction system is low, and trichlorophosphorus intermediates and related thiophosphorus intermediates dominate.

[0056] Step 4: Deep sulfurization reaction by heating (to produce phosphorus pentasulfide) After the initial sulfidation is completed, the hydrogen sulfide gas supply is stopped, and the temperature is slowly increased to 100℃~200℃. Once the set temperature is reached, hydrogen sulfide gas is introduced again to maintain the deep sulfidation reaction, allowing the trichlorophosphine intermediate to further sulfide-polymerize and form diphosphine pentasulfide. -1 This is to avoid excessively rapid heating that could cause localized boiling or splashing.

[0057] Preferably, the total amount of hydrogen sulfide gas introduced during the deep sulfidation stage is such that the overall molar ratio of n(hydrogen sulfide gas):n(phosphorus pentachloride) reaches 7~8:1, to ensure sufficient sulfidation and to convert residual trichlorophosphorus intermediates, phosphorus trichloride and other chlorine-containing species into a sulfide skeleton dominated by PS bonds as much as possible.

[0058] The hydrogen chloride gas generated during this process continues to enter the first alkaline scrubbing tower in the tail gas treatment system 4 along with the tail gas; the tail gas then enters the second alkaline or oxidizing absorption tower to further capture trace amounts of hydrogen sulfide gas, ensuring that the tail gas emissions meet the standards. The corresponding chemical equation is: 2PCl5 + 5H2S = P2S5 + 10HCl Step 5: Cooling, solid-liquid separation and product purification Stop the flow of hydrogen sulfide gas and switch to a low flow rate of nitrogen (e.g., 100 mL / min). -1 Purge the reactor for 30-60 minutes to remove residual hydrogen sulfide and hydrogen chloride gases from the reaction system. Then gradually cool reactor 3 to bring the system temperature down to 40-60°C.

[0059] The cooled slurry is separated into solid and liquid components by a filtration device under an inert atmosphere. The filter residue is crude phosphorus pentasulfide, and the filtrate is an organic solvent containing a small amount of inorganic salts and trace amounts of dissolved gases.

[0060] Preferably, the filter residue is washed 1-2 times with a small amount of dry organic solvent (such as o-dichlorobenzene or anhydrous diethyl ether) under an inert atmosphere (nitrogen or argon) to remove residual solvent impurities and soluble salts.

[0061] The washed filter residue was placed in a vacuum drying oven and dried for 8 hours at 80℃ and a vacuum degree ≤ -0.095MPa to obtain a light yellow or grayish-yellow phosphorus pentasulfide solid product.

[0062] Preferably, the filtrate is distilled in a distillation kettle to recover the organic solvent. A small amount of low-boiling impurities and dissolved gases are carried out at the top, and a small amount of inorganic salts remain in the distillation kettle and can be centrally treated. The purity of the recovered o-dichlorobenzene can be restored to ≥99wt%, and after drying, it can be reused in the next batch of reaction, realizing solvent recycling.

[0063] Figure 1 This is a schematic diagram of the process flow of the present invention, wherein: Sulfur source supply device 1: Used to provide the sulfur source gas required for the reaction.

[0064] Gas buffer / drying device 2: Used to buffer and pretreat the sulfur source, prevent gas backflow, and improve the stability of the introduced gas.

[0065] Reactor 3: Contains an inert high-boiling-point solvent containing dissolved phosphorus pentachloride. A sulfur source is bubbled into the solution through a gas inlet pipe and reacts with phosphorus pentachloride to produce solid phosphorus pentasulfide.

[0066] Exhaust gas treatment system 4: Used to absorb unreacted hydrogen sulfide gas and generated acidic gases during the reaction process, ensuring the safety and environmental friendliness of the reaction process.

[0067] This invention prepares high-purity phosphorus pentasulfide by reacting phosphorus pentachloride and hydrogen sulfide gas in an inert, high-boiling-point organic solvent. The method involves dissolving phosphorus pentachloride in a halogenated aromatic hydrocarbon inert solvent with a boiling point not lower than 150°C under a closed, inert atmosphere. Hydrogen sulfide gas is then introduced to initiate the sulfidation reaction. During the reaction, the resulting phosphorus pentasulfide precipitates out in solid form, thus achieving simultaneous reaction and product separation. By controlling the reaction temperature, hydrogen sulfide gas introduction rate, and system pressure, side reactions are effectively suppressed, avoiding the formation of low-sulfur phosphides or oxidized impurities. The resulting phosphorus pentasulfide exhibits high purity, stable crystal phase, and uniform particle morphology. Compared with existing technologies, this invention offers milder reaction conditions, a simplified process flow, high safety, and recyclable solvents, making it suitable for continuous and large-scale production. The obtained phosphorus pentasulfide can serve as an important precursor for sulfide solid electrolytes and related functional materials, showing promising industrial application prospects.

[0068] Example 2: This example provides a method for preparing high-purity phosphorus pentasulfide using a low-temperature liquid phase method. The method involves reacting phosphorus pentachloride with hydrogen sulfide gas under controlled temperature and atmosphere via a liquid phase approach to ultimately generate high-purity phosphorus pentasulfide. The process steps are as follows: Step 1: Raw material preparation and pretreatment Take 50g of high-purity phosphorus pentachloride (purity ≥99wt%), dry it at 100℃ and vacuum degree -0.08MPa for 5h, and immediately transfer it to a glove box under argon protection for later use after cooling.

[0069] Preferably, in this embodiment, o-dibromobenzene (moisture content ≤ 50 ppm) is used as a solvent, added to 150 mL of the reaction vessel, and stirred and degassed under argon atmosphere for 30 min to remove dissolved oxygen and trace amounts of moisture.

[0070] Step 2: Charging and Atmosphere Control The dried phosphorus pentachloride was added to the degassed o-dibromobenzene solvent to form a near-saturated phosphorus pentachloride-solvent system. Subsequently, the internal pressure of the reactor was adjusted to atmospheric pressure (0.1 MPa), and stirring was started (350 rpm) to reduce local concentration deviations.

[0071] Step 3: Low-temperature preliminary sulfidation (generating sulfur-chlorine-phosphorus intermediates) Start at 75℃ with a flow rate of 0.1 L·min -1 Dry hydrogen sulfide gas is introduced at a certain flow rate to fully dissolve it in the phosphorus pentachloride-solvent system and react with phosphorus pentachloride to undergo a sulfochlorination reaction.

[0072] The total ventilation time was 1.5 hours, so that the total molar ratio of n (hydrogen sulfide gas):n (phosphorus pentachloride) reached approximately 3.5:1.

[0073] During the reaction, the system color gradually changes from colorless to pale yellow. The tail gas mainly contains hydrogen chloride gas, which is absorbed by a 10wt% NaOH alkaline scrubbing tower. The side reactions are as follows: HCl + NaOH = NaCl + H₂O Step 4: Deep sulfurization reaction by heating (to produce phosphorus pentasulfide) After the initial sulfidation is completed, the hydrogen sulfide gas supply is stopped, and the gas is discharged at 2°C / min. -1 The heating rate is adjusted to bring the reaction temperature to 150°C and the reaction is kept at a constant temperature. After the temperature is raised to the set temperature, hydrogen sulfide gas is introduced again to maintain a deep sulfidation reaction, so that the trichlorophosphorus intermediate is further sulfidated and polymerized to generate phosphorus pentasulfide. The molar ratio of the added hydrogen sulfide gas to phosphorus pentachloride is 1:(1.3~1.8), preferably 1:(1.4~1.6).

[0074] The exhaust gas generated during this process enters a two-stage absorption system. The first stage involves alkaline scrubbing to remove hydrogen chloride gas, while the second stage involves an oxidation absorption tower to capture trace amounts of hydrogen sulfide gas to meet emission standards.

[0075] Step 5: Cooling, solid-liquid separation and product purification After stopping ventilation, use nitrogen (100 mL / min) -1 The system was purged for 30 minutes to completely replace the residual hydrogen sulfide and hydrogen chloride gases. The system was then cooled to 50°C under argon protection. The filter residue was dried under vacuum at 80°C and -0.09 MPa for 6 hours to obtain a light yellow phosphorus pentasulfide powder. The chemical equation is as follows: 2PCl5 + 5H2S = P2S5 + 10HCl Example 3: This example proposes a method for preparing high-purity phosphorus pentasulfide using a low-temperature liquid phase. In a non-polar chlorinated solvent, by controlling the carbon disulfide gas introduction rate and temperature program, efficient conversion of phosphorus pentachloride to phosphorus pentasulfide with low chlorine residue is achieved. The specific steps are as follows: Step 1: Raw material preparation and pretreatment Weigh 50g of high-purity phosphorus pentachloride (purity ≥99wt%), dry it at 100℃ and vacuum degree -0.09MPa for 5h, and then transfer it to the reaction vessel under argon protection.

[0076] N-methylpyrrolidone (water content ≤30ppm) was selected as the reaction medium and added to the reaction vessel in 120mL. The mixture was stirred and degassed for 15min to reduce the oxygen and water content in the solvent.

[0077] Step 2: Charging and Atmosphere Control After sealing the pretreated phosphorus pentachloride-solvent system, the reactor was purged with high-purity nitrogen (250 sccm) for 10 minutes, and then three cycles of "pressurization (0.15 MPa) - vacuuming (-0.09 MPa)" were performed.

[0078] Step 3: Low-temperature preliminary sulfidation (generating sulfur-chlorine-phosphorus intermediates) Carbon disulfide gas was introduced at 50°C, with a flow rate controlled at 0.3 L / min. -1 Carbon disulfide gas gradually reacts with phosphorus pentachloride to form thiophosgene and thiophosphoric chloride. The thiophosphoric chloride is mainly composed of trichlorophosphorus and part of the PS-Cl network structure.

[0079] The reaction lasted for 1 hour, resulting in an overall molar ratio of n(carbon disulfide gas):n(phosphorus pentachloride) ≈ 3:1.

[0080] The hydrogen chloride gas in the tail gas is absorbed by a 10wt% NaOH alkaline scrubbing tower. The absorption reaction is as follows: HCl + NaOH → NaCl + H₂O As the rate of hydrogen chloride gas release decreases, it indicates that phosphorus pentachloride has essentially completed the initial sulfur chlorination stage.

[0081] Step 4: Deep sulfurization reaction by heating (to produce phosphorus pentasulfide) After the initial sulfidation is completed, the carbon disulfide gas flow is stopped, and the system is cooled at 3°C / min. -1 The temperature was increased to 140°C at a rate of 0.2 L / min, and then restarted at a rate of 0.2 L / min. -1 Hydrogen sulfide gas is introduced at a certain flow rate to carry out deep sulfidation, causing the condensation and further substitution reactions of the phosphorus pentachloride intermediate. The phosphorus trichloride intermediate is further sulfidated and polymerized to generate phosphorus pentasulfide, wherein the molar ratio of the added sulfur source to phosphorus pentachloride is 1:(1.3~1.8), preferably 1:(1.4~1.6).

[0082] Maintain the reaction at a constant temperature for 2.5 hours. During this stage, yellow solid suspended particles gradually form in the system, and the particle size increases as the reaction proceeds.

[0083] The exhaust gas enters a two-stage treatment system to absorb and oxidize hydrogen chloride gas and residual hydrogen sulfide gas.

[0084] Step 5: Cooling, solid-liquid separation and product purification After stopping the aeration, nitrogen was introduced to purge the system for 20 minutes to remove any remaining hydrogen sulfide gas. After the reaction system was cooled to 40°C, the solid-liquid mixture was filtered under argon protection and dried at 110°C and -0.09 MPa for 6 hours to obtain a light yellow phosphorus pentasulfide powder.

[0085] CS2 + PCl5 = CSCl2 + PSCl3 The trichlorophosphorus generated in step 3 is further sulfided by heating and introducing H2S to produce phosphorus pentasulfide: 2PSCl3 + 3H2S = P2S5 + 6HCl Example 4: This example provides a method for preparing high-purity phosphorus pentasulfide using a low-temperature liquid phase method. By adjusting the solvent polarity, increasing the partial pressure of the sulfur source, and employing a two-stage heating program, phosphorus pentachloride is converted to phosphorus pentasulfide more efficiently. This method further verifies the applicability and reproducibility of the invention under different reaction conditions. The method includes the following steps: Step 1: Raw material preparation and pretreatment Weigh 40g of high-purity phosphorus pentachloride (purity ≥99wt%) and dry it at 115℃ and -0.08MPa for 4h. Immediately after drying, transfer it to a glove box.

[0086] Dichlorobenzene (o-DCB, moisture ≤30ppm), which has a high boiling point and strong chemical stability, was selected as the solvent, with a mass ratio of 2:1.

[0087] Step 2: Charging and Atmosphere Control The dried phosphorus pentachloride is added to a solvent to form a homogeneous mixture. Preferably, the resulting mixture is transferred to a closed corrosion-resistant reactor equipped with a mechanical stirrer, a temperature probe, a pressure gauge, a gas inlet pipe, and a tail gas outlet pipe. The mixture is stirred under nitrogen or argon protection and the system is evacuated and purged with inert gas 2 to 3 times to remove air and moisture.

[0088] Step 3: Low-temperature preliminary sulfidation (generating sulfur-chlorine-phosphorus intermediates) Start at 75℃ with a flow rate of 0.4 L·min -1 A mixture of hydrogen sulfide and carbon disulfide gases is introduced at a flow rate of approximately 1.2 hours, resulting in an overall molar ratio of n(hydrogen sulfide + carbon disulfide):n(phosphorus pentachloride) ≈ 3.8:1. Preferably, the molar ratio of hydrogen sulfide to carbon disulfide in the mixed gas is (0.5~2):1, more preferably (0.8~1.2):1. During this stage, phosphorus pentachloride and hydrogen sulfide undergo a preliminary sulfidation reaction, generating a phosphorus-sulfide intermediate primarily composed of trichlorophosphorus. Simultaneously, carbon disulfide can participate in intermediate regulation or form volatile sulfur- and chlorine-containing byproducts. The main reaction can be represented as follows: PCl5 + H2S = PSCl3 + 2HCl PCl5 + CS2 = PSCl3 + CSCl2 The exhaust gas generated in step 3 enters the exhaust gas treatment system. Preferably, it first passes through a primary alkaline scrubbing tower to absorb hydrogen chloride gas, and then passes through a secondary alkaline absorption tower or oxidation absorption tower to absorb residual hydrogen sulfide gas. Unreacted carbon disulfide gas is then condensed, recovered, adsorbed, or incinerated.

[0089] The absorption reaction of hydrogen chloride gas is as follows: HCl + NaOH → NaCl + H₂O When the concentration of hydrogen chloride gas in the exhaust gas decreases significantly and tends to stabilize, it can be considered that phosphorus pentachloride has basically completed the initial sulfidation stage.

[0090] Step 4: Deep sulfurization reaction by heating (to produce phosphorus pentasulfide) After stopping the flow of the mixed gas, the system was refluxed at 3℃·min -1 The temperature rises to 160°C at a rate of [missing information].

[0091] After heating to the set temperature, hydrogen sulfide gas is introduced again, with the flow rate adjusted to 120 mL / min. -1 The deep sulfidation reaction is maintained for 2 hours to ensure that sulfur elements fully enter the sulfur-chlorine-phosphorus structure and promote the final formation of phosphorus pentasulfide. Preferably, the molar ratio of hydrogen sulfide gas and phosphorus pentachloride added in step 4 is 1.3~1.8:1, more preferably 1.4~1.6:1, and the theoretical value is about 1.5:1.

[0092] In this stage, the trichlorophosphorus intermediate undergoes a deep sulfidation reaction with hydrogen sulfide gas to generate phosphorus pentasulfide. The main reaction can be represented as follows: 2PSCl3 + 3H2S → P2S5 + 6HCl The exhaust gas produced in step 4 continues to enter the exhaust gas treatment system, where hydrogen chloride gas is absorbed in the first stage and residual hydrogen sulfide gas is absorbed in the second stage to ensure emission safety and reduce environmental pollution. If the main reaction pathway is represented by phosphorus pentachloride ultimately forming phosphorus pentasulfide via the phosphorus trichloride intermediate, then its overall main reaction can be expressed as: 2PCl5 + 5H2S → P2S5 + 10HCl However, since carbon disulfide gas is introduced in step 3, sulfur- and chlorine-containing carbon byproducts may also exist in the actual system. Therefore, this embodiment is more suitable for characterizing the reaction process using the above stepwise reaction formula.

[0093] Step 5: Cooling, solid-liquid separation and product purification Nitrogen gas was introduced into the purging system for 20 minutes to completely replace the residual hydrogen sulfide gas. After natural cooling to 45°C, solid-liquid separation was performed under argon protection. Finally, the product was dried at 85°C and -0.09 MPa for 8 hours to obtain a light yellow powdery phosphorus pentasulfide product. Preferably, after solid-liquid separation, the filter cake can be washed 1-2 times with a small amount of dry dichlorobenzene or other anhydrous organic solvent that does not react with the product to remove residual solvent and trace soluble impurities on the surface. The obtained filtrate can be used to recover the solvent by distillation and recycled.

[0094] This invention addresses the technical bottlenecks of existing phosphorus pentasulfide preparation processes, which involve high temperatures, high energy consumption, numerous impurity phases, and difficulties in handling byproduct gases, making it challenging to meet the high-purity raw material requirements of solid-state electrolytes. It proposes a novel preparation route based on the reaction of phosphorus pentachloride with a sulfur source (hydrogen sulfide gas, carbon disulfide gas, or a mixture of both). This system achieves a continuous and uniform gas-liquid sulfidation process at lower temperatures, avoiding the formation of polysulfide impurity phases that easily occur in solid-phase sulfidation. Furthermore, the byproducts are singular and easily captured, resulting in a high overall process safety and controllability. It is particularly suitable for preparing high-purity, low-chlorine, and structurally stable phosphorus pentasulfide under anhydrous conditions. This method not only significantly improves product quality and preparation efficiency but also highly matches the large-scale preparation requirements of solid-state electrolyte materials, demonstrating significant innovation and urgent research necessity.

[0095] Example 5: This example provides an application of phosphorus pentasulfide prepared by any one of the low-temperature liquid phase preparation methods of Examples 1-4 in the preparation of lubricating oil additives, solid electrolyte materials, organophosphorus compounds, pesticide intermediates or high-performance sulfide functional materials.

Claims

1. A method for preparing high-purity phosphorus pentasulfide using low-temperature liquid phase, characterized in that, Includes the following steps: Step 1: Select phosphorus pentachloride with a purity ≥ 99.0 wt%, and dry it to ensure that its moisture content does not exceed 50 ppm; place the treated phosphorus pentachloride in an organic solvent to form a suspension or slurry system, with the mass fraction of phosphorus pentachloride in the solvent being 10~60 wt%; Step 2: Place the suspended phase or slurry system from Step 1 into a closed reactor (3); Step 3: Introduce a sulfur source into reactor (3) to allow phosphorus pentachloride to undergo a preliminary sulfidation reaction with the sulfur source, converting phosphorus pentachloride into a phosphorus sulfide intermediate mainly composed of phosphorus trichloride intermediate, while releasing hydrogen chloride gas; monitor the volume fraction of hydrogen chloride gas in the tail gas online, and when the concentration of hydrogen chloride gas decreases significantly and approaches stability, it is considered that the preliminary sulfidation of phosphorus pentachloride is basically completed, wherein the molar ratio of sulfur source to phosphorus pentachloride is controlled at 3:1~6:1; Step 4: After the initial vulcanization is completed, the temperature is slowly increased to 100℃~200℃. After the temperature is raised to the set temperature, a sulfur source is introduced to maintain the deep vulcanization reaction, so that the trichlorophosphorus intermediate is further vulcanized and polymerized to generate phosphorus pentasulfide. The hydrogen chloride gas and unreacted sulfur source generated during the reaction are continuously removed through the tail gas absorption system. Step 5: After the reaction is complete, the product is cooled and separated into solid and liquid phases to remove the solvent. After drying, solid phosphorus pentasulfide is obtained.

2. The method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase according to claim 1, characterized in that, The organic solvent in step 1 is at least one of N-methylpyrrolidone, chlorobenzene, dichlorobenzene, trichlorobenzene, o-dichlorobenzene, bromochlorobenzene, dichlorobromobenzene, dibromobenzene, tribromobenzene, chloronaphthalene, bromonaphthalene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene, tribromobenzene and their isomers, or other organic solvents that do not react with phosphorus pentachloride and have a boiling point of not less than 150°C.

3. The method for preparing high-purity phosphorus pentasulfide using low-temperature liquid phase according to claim 1, characterized in that, The drying process for phosphorus pentachloride in step 1 is as follows: phosphorus pentachloride is vacuum dried at 50℃~140℃ for 2~6 hours.

4. The method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase according to claim 1, characterized in that, The sulfur source in step 3 is hydrogen sulfide gas, carbon disulfide gas, or a mixture of hydrogen sulfide gas and carbon disulfide gas.

5. The method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase according to claim 1, characterized in that, The flow rate of the sulfur source in step 3 is 0.05~0.5 L·min. -1 .

6. The method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase according to claim 1, characterized in that, The reaction temperature for steps 3 and 4 is 50℃~200℃.

7. The method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase according to claim 1, characterized in that, The reactor (3) is made of corrosion-resistant metal, enamel or halide-resistant glass lining and is equipped with a tail gas extraction system and a reflux condenser.

8. The method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase according to claim 1, characterized in that, The exhaust gas in step 4 undergoes a two-stage absorption process: the first stage uses an alkaline solution to absorb hydrogen chloride gas, and the second stage uses a strong alkali or amine absorbent to absorb unreacted sulfur sources.

9. The method for preparing high-purity phosphorus pentasulfide in a low-temperature liquid phase according to claim 1, characterized in that, In step 5, the obtained phosphorus pentasulfide is separated into solid and liquid phases and then dried at 50℃~140℃ under vacuum for 4~12 hours to obtain phosphorus pentasulfide powder with a purity ≥99wt%.

10. The application of phosphorus pentasulfide prepared by the low-temperature liquid phase preparation method of claim 1 in the preparation of lubricating oil additives, solid electrolyte materials, organophosphorus compounds, pesticide intermediates or high-performance sulfide functional materials.

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