A membrane reactor for producing lithium sulfide and a method for producing lithium sulfide

Abstract

The application relates to a membrane reactor for preparing lithium sulfide and a preparation method of lithium sulfide. The membrane reactor for preparing lithium sulfide comprises a shell, a reaction chamber, a permeation chamber and a membrane assembly located between the reaction chamber and the permeation chamber, wherein the membrane assembly comprises a water separation membrane, and the pressure of the permeation chamber is lower than that of the reaction chamber; the water separation membrane comprises any one or a combination of at least two of a 3A molecular sieve membrane, a 4A molecular sieve membrane, a ZIF-8 membrane or a hydrophilic polymer membrane. The membrane reactor for preparing lithium sulfide is used for the gas-solid reaction of lithium hydroxide and hydrogen sulfide to prepare lithium sulfide, water molecules generated in the reaction can be removed from the reaction system, the contact of water molecules with target product lithium sulfide can be effectively reduced, the occurrence of reverse reaction can be inhibited, and the yield and purity of prepared lithium sulfide can be improved.

Description

Technical Field

[0001] This application relates to the field of lithium sulfide preparation technology, and more particularly to a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. Background Technology

[0002] Lithium sulfide (Li₂S), as a sulfide solid electrolyte and high-capacity cathode material, has significant application prospects in the field of all-solid-state batteries. Currently, the preparation of lithium sulfide via the gas-solid reaction of lithium hydroxide (LiOH) and hydrogen sulfide (H₂S) is a highly industrially valuable route, with the main reaction formula being: 2LiOH + H₂S → Li₂S + 2H₂O. However, this reaction faces a fundamental challenge: the water generated in the reaction immediately undergoes a strong reverse reaction with the target product, lithium sulfide, regenerating lithium hydroxide and hydrogen sulfide, with the reaction formula being: Li₂S + 2H₂O → 2LiOH + H₂S. This reverse reaction results in extremely low single-pass yield and low product purity of lithium sulfide, severely restricting the industrial application of this process.

[0003] To address this issue, existing technologies have primarily explored the following solutions: 1. High-temperature vacuum dehydration: Water generated during or after the reaction is removed under high temperature and vacuum conditions. This method improves product purity through post-reaction dehydration, but high-temperature processing consumes significant energy, and since dehydration occurs after the reaction, reverse reactions are difficult to completely avoid. 2. Inert gas purging: Inert gas is continuously introduced during the reaction to carry away the generated water vapor. This method is simple to operate, but its purging efficiency is limited, requiring a large gas volume to effectively reduce the water vapor partial pressure, thus its economic viability needs improvement. 3. Organic solvent dehydration: The reaction is carried out in an organic solvent, which removes water. This method can yield a high-purity product, but it introduces an organic solvent recovery process, increasing process complexity. 4. Physically mixed desiccant method: A desiccant (such as a molecular sieve) is mixed into the reaction system to capture the generated water. This method can suppress reverse reactions to some extent, but the diffusion path of water molecules from the lithium hydroxide particle surface to the desiccant particle surface is long, and reverse reactions may still occur during diffusion. V. Core-shell structured particle method: Using lithium hydroxide as the core and molecular sieve as the outer shell to prepare core-shell structured particles can shorten the diffusion path of water, so that the generated water is adsorbed by the outer shell before leaving the core region. This method improves the reverse reaction inhibition effect to a new level, but still faces problems such as the relatively complex preparation process of core-shell particles and the need for regeneration treatment after water absorption saturation.

[0004] In summary, existing technologies have made some progress in suppressing the reverse reaction of lithium hydroxide and hydrogen sulfide to prepare lithium sulfide, but further exploration and development of simpler devices and preparation methods that can effectively suppress the reverse reaction are still needed. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. Using the membrane reactor described above for preparing lithium sulfide via a gas-solid reaction of lithium hydroxide and hydrogen sulfide allows for the removal of water molecules generated during the reaction process from the reaction system. This effectively reduces the contact between water molecules and the target product, lithium sulfide, inhibits the occurrence of reverse reactions, and improves the yield and purity of the obtained lithium sulfide.

[0006] To achieve this objective, the following technical solution is adopted in this application: In a first aspect, this application provides a membrane reactor for preparing lithium sulfide, the membrane reactor for preparing lithium sulfide comprising a shell, a reaction chamber, a permeation chamber and a membrane module, the membrane module being located between the reaction chamber and the permeation chamber, the membrane module comprising a water separation membrane, the pressure of the permeation chamber being lower than the pressure of the reaction chamber; the water separation membrane comprising any one or a combination of at least two of 3A molecular sieve membrane, 4A molecular sieve membrane, ZIF-8 membrane or hydrophilic polymer membrane.

[0007] In this application, the outer shell refers to the outermost shell of a membrane reactor used to prepare lithium sulfide, wherein the reaction chamber, the permeation chamber, and the membrane module are all located within the space enclosed by the outer shell.

[0008] Preferably, the 3A molecular sieve membrane comprises a porous stainless steel support 3A molecular sieve composite membrane, wherein the porous stainless steel support 3A molecular sieve composite membrane comprises a porous stainless steel support and a 3A molecular sieve layer loaded on the surface of the porous stainless steel support.

[0009] Preferably, the 4A molecular sieve membrane comprises a porous stainless steel support 4A molecular sieve composite membrane, wherein the porous stainless steel support 4A molecular sieve composite membrane comprises a porous stainless steel support and a 4A molecular sieve layer loaded on the surface of the porous stainless steel support.

[0010] Preferably, the ZIF-8 membrane comprises a porous stainless steel support ZIF-8 composite membrane, wherein the porous stainless steel support ZIF-8 composite membrane comprises a porous stainless steel support and a ZIF-8 layer loaded on the surface of the porous stainless steel support.

[0011] Preferably, the hydrophilic polymer membrane includes a Nafion membrane and / or a cross-linked polyvinyl alcohol membrane.

[0012] For example, the Nafion membrane includes DuPont Nafion 117 membrane; the polyvinyl alcohol membrane includes glutaraldehyde cross-linked polyvinyl alcohol membrane or heat-treated cross-linked polyvinyl alcohol membrane.

[0013] Preferably, the membrane module includes at least one tubular membrane module.

[0014] Preferably, the membrane module includes at least one flat sheet membrane module.

[0015] In this application, the tubular membrane module means that the water separation membrane is in a tubular shape; the flat sheet membrane module means that the water separation membrane is in a flat sheet shape.

[0016] Preferably, the reaction chamber is provided with a gas inlet, a solid raw material inlet, a gas outlet, and a solid product outlet.

[0017] In a second aspect, this application provides a membrane reaction system for preparing lithium sulfide, the membrane reaction system for preparing lithium sulfide comprising at least one membrane reactor as described in the first aspect for preparing lithium sulfide.

[0018] Preferably, when the membrane reaction system for preparing lithium sulfide includes at least two membrane reactors for preparing lithium sulfide as described in the first aspect, the membrane reactors for preparing lithium sulfide are connected in series or in parallel.

[0019] Thirdly, this application provides a method for preparing lithium sulfide, the method comprising placing solid lithium hydroxide in the reaction chamber of a membrane reactor for preparing lithium sulfide as described in the first aspect or a membrane reaction system for preparing lithium sulfide as described in the second aspect, introducing a gas containing hydrogen sulfide into the reaction chamber to react and prepare lithium sulfide, while simultaneously performing vacuum treatment in the permeation chamber to make the pressure in the permeation chamber lower than the pressure in the reaction chamber, so that water vapor in the reaction chamber enters the permeation chamber through a water separation membrane driven by the pressure difference; the reaction temperature is ≥200℃ and the reaction time is ≥1 h.

[0020] Preferably, the solid lithium hydroxide has a particle size ≤1000 μm, and more preferably 50~300 μm.

[0021] Preferably, the reaction temperature is 200~400℃, more preferably 280~350℃.

[0022] Preferably, the reaction time is 1 to 8 hours, more preferably 3 to 8 hours.

[0023] Preferably, the hydrogen sulfide-containing gas also includes an inert gas.

[0024] Preferably, the volume fraction of hydrogen sulfide in the hydrogen sulfide-containing gas is ≥5%, more preferably 15~50%.

[0025] Preferably, the pressure in the permeation chamber is ≤1000 Pa, and more preferably 100~500 Pa.

[0026] Preferably, the pressure in the reaction chamber is 0.1~0.5 MPa.

[0027] Preferably, the pressure difference between the reaction chamber and the permeation chamber is ≥0.1 MPa.

[0028] Preferably, the flow rate of the hydrogen sulfide-containing gas introduced into the reaction chamber is 50~1000 mL / min.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects: The membrane reactor provided in this application for preparing lithium sulfide, used in the gas-solid reaction of lithium hydroxide and hydrogen sulfide, effectively reduces the contact between the byproduct water and the target product lithium sulfide, suppresses the occurrence of reverse reactions, and achieves a separation factor of H2O / H2S ≥60, preferably ≥800. The lithium sulfide prepared by the method described in this application has a yield ≥70% and a purity ≥73%, preferably ≥85% and a purity ≥90%. The lithium sulfide preparation method provided in this application is feasible for continuous industrial production. The lithium sulfide preparation method provided in this application results in extremely low levels of impurities such as lithium hydroxide and lithium oxide in the lithium sulfide product due to the suppression of the reverse reaction. This characteristic improves the air stability of the lithium sulfide product, which is crucial for the subsequent preparation of sulfide solid electrolytes. It can avoid the influence of oxygen impurities introduced by lithium sulfide hydrolysis on the electrolyte performance. The prepared lithium sulfide is tested for air stability, and the hydrogen sulfide generation is ≤1245 ppm / g. In preferred cases, the hydrogen sulfide generation is ≤500 ppm / g. Attached Figure Description

[0030] Figure 1 A schematic diagram of a membrane reactor for preparing lithium sulfide provided in an embodiment of this application; Wherein, 1-outer shell; 2-membrane module; 3-permeation chamber upper cover; 4-permeation chamber lower cover; 5-gas inlet; 6-solid raw material inlet; 7-gas outlet; 8-solid product outlet; 9-vacuum connection port; 10-reaction chamber; 11-permeation chamber; 12-solid material support structure; 13-solid lithium hydroxide; Figure 2 Another schematic diagram of the structure of a membrane reactor for preparing lithium sulfide provided in the embodiments of this application; Wherein, 1-shell; 2-membrane module; 5-gas inlet; 6-solid raw material inlet; 7-gas outlet; 8-solid product outlet; 9-vacuum connection port; 10-reaction chamber; 11-permeation chamber; 12-solid material support structure; 13-solid lithium hydroxide. Detailed Implementation

[0031] To enable those skilled in the art to better understand the solutions of this application, a further detailed description of this application is provided below. The specific embodiments listed below are merely descriptions of the principles and features of this application; the examples are only for explaining this application and are not intended to limit its scope. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0032] The preparation of lithium sulfide by reacting lithium hydroxide with hydrogen sulfide in a gas-solid reaction results in water that immediately undergoes a strong reverse reaction with the target product, lithium sulfide, leading to extremely low single-pass yield and low product purity.

[0033] To address the aforementioned problems, this application provides a membrane reactor for preparing lithium sulfide, such as... Figure 1 and Figure 2 As shown, the membrane reactor for preparing lithium sulfide includes a shell 1, a reaction chamber 10, a permeation chamber 11, and a membrane module 2. The membrane module 2 is located between the reaction chamber 10 and the permeation chamber 11. The membrane module 2 includes a water separation membrane. The pressure in the permeation chamber 11 is lower than the pressure in the reaction chamber 10. The water separation membrane includes any one or a combination of at least two of 3A molecular sieve membrane, 4A molecular sieve membrane, ZIF-8 membrane, or hydrophilic polymer membrane.

[0034] In this application, the membrane reactor used for preparing lithium sulfide is used to carry out the gas-solid reaction of lithium hydroxide and hydrogen sulfide to prepare lithium sulfide, which can achieve spatial coupling of the reaction process and the product separation process at the reactor scale. The pressure in the permeation chamber is lower than that in the reaction chamber, and the dynamic diameter of water molecules (approximately 0.26 nm) is smaller than that of hydrogen sulfide molecules (approximately 0.36 nm). With the same pore size, the smaller water molecule diameter makes it easier for water molecules to pass through the water separation membrane. Utilizing this characteristic, when hydrogen sulfide reacts with lithium hydroxide in the reaction chamber to generate water molecules, the water molecules, driven by the concentration and pressure differences, immediately permeate through the water separation membrane into the permeation chamber and are continuously removed. The diffusion path of water molecules from generation to removal can be compressed to the distance from the surface of the water separation membrane to the membrane pores (reaching micrometer or even submicrometer levels), which is much shorter than the shell diffusion path in the core-shell structure of core-shell particle methods (approximately tens of micrometers). This design of the present application results in a short removal path and fast removal speed for the water molecules generated in the reaction, achieving "zero path" and "zero residence" for water from generation to removal. This effectively reduces the contact between water molecules and the target product, lithium sulfide, and inhibits the occurrence of reverse reactions. In this application, the outer shell 1 refers to the outermost shell of the membrane reactor used to prepare lithium sulfide, and the reaction chamber 10, the permeation chamber 11 and the membrane module 2 are all located within the space enclosed by the outer shell.

[0035] In some embodiments, the 3A molecular sieve membrane includes a porous stainless steel support 3A molecular sieve composite membrane, wherein the porous stainless steel support 3A molecular sieve composite membrane includes a porous stainless steel support and a 3A molecular sieve layer loaded on the surface of the porous stainless steel support.

[0036] In some embodiments, the 4A molecular sieve membrane includes a porous stainless steel support 4A molecular sieve composite membrane, wherein the porous stainless steel support 4A molecular sieve composite membrane includes a porous stainless steel support and a 4A molecular sieve layer loaded on the surface of the porous stainless steel support.

[0037] In some embodiments, the ZIF-8 membrane comprises a porous stainless steel support ZIF-8 composite membrane, wherein the porous stainless steel support ZIF-8 composite membrane comprises a porous stainless steel support and a ZIF-8 layer loaded on the surface of the porous stainless steel support.

[0038] In some embodiments, the thickness of the porous stainless steel support in the porous stainless steel support 3A molecular sieve composite membrane, the porous stainless steel support 4A molecular sieve composite membrane, and the porous stainless steel support ZIF-8 composite membrane is independently 1~2 mm, for example 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, or 1.9 mm.

[0039] In some embodiments, the thicknesses of the 3A molecular sieve layer, 4A molecular sieve layer, and ZIF-8 layer in the porous stainless steel support 3A molecular sieve composite membrane, porous stainless steel support 4A molecular sieve composite membrane, and porous stainless steel support ZIF-8 composite membrane are each independently 5~15 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, or 14 μm, etc.

[0040] In this application, the porous stainless steel support exhibits high mechanical strength and thermal shock resistance. The water separation membrane formed by the 3A molecular sieve layer, 4A molecular sieve layer, or ZIF-8 layer loaded on the porous stainless steel support can withstand a reaction chamber pressure of ≥0.5 MPa and a reaction temperature of ≥300℃, demonstrating long-term mechanical stability. The porous stainless steel support 3A molecular sieve composite membrane, porous stainless steel support 4A molecular sieve composite membrane, and porous stainless steel support ZIF-8 composite membrane can be selected from commercially available products or prepared using existing technologies.

[0041] In some embodiments, the hydrophilic polymer membrane includes a Nafion membrane and / or a cross-linked polyvinyl alcohol membrane; exemplaryly, the Nafion membrane includes a DuPont Nafion 117 membrane; the polyvinyl alcohol membrane includes a glutaraldehyde cross-linked polyvinyl alcohol membrane or a heat-treated cross-linked polyvinyl alcohol membrane.

[0042] In some embodiments, a solid material support structure 12 is provided inside the reaction chamber 10.

[0043] In some embodiments, the solid material support structure 12 includes any one or a combination of at least two of a sieve plate, a porous tray, or a fluidized bed distribution plate. In this application, the solid material support structure 12 is used to support particles or powder of solid lithium hydroxide.

[0044] In some embodiments, the reaction chamber 10 is a fixed-bed reactor or a fluidized-bed reactor.

[0045] In this application, the solid material support structure 12 is preferably a fluidized bed distribution plate, and the reaction chamber 10 is a fluidized bed reactor. Hydrogen sulfide-containing gas is used as the fluidizing medium to keep the solid lithium hydroxide in a fluidized state, thereby enhancing gas-solid contact and mass transfer. When the solid material support structure 12 is a sieve plate or a porous tray, the solid lithium hydroxide 13 is filled in the reaction chamber 10 in a fixed bed form, and the reaction chamber 10 is a fixed bed reactor.

[0046] like Figure 1 As shown, in some embodiments, the membrane module 2 includes at least one tubular membrane module that divides the internal space enclosed by the housing 1 into a permeation chamber 11 and a reaction chamber 10.

[0047] like Figure 1 As shown, in some embodiments, the space inside the tubular membrane module is the permeation chamber 11, and the space between the tubular membrane module and the housing 1 is the reaction chamber 10.

[0048] In some embodiments, the space inside the tubular membrane module is a reaction chamber, and the space between the tubular membrane module and the housing is a permeation chamber.

[0049] like Figure 1 As shown, in some embodiments, the membrane module 2 includes a tubular membrane module, which comprises a tubular porous stainless steel support 3A molecular sieve composite membrane. The tubular porous stainless steel support 3A molecular sieve composite membrane is installed in the inner space enclosed by the outer shell 1 after a permeation chamber upper cover 3 and a permeation chamber lower cover 4 are installed on both sides. The space inside the tubular membrane module is the permeation chamber 11, and the space between the tubular membrane module and the outer shell is the reaction chamber 10. The outer shell 1 is provided with a gas inlet 5, a solid feed inlet 6, a gas outlet 7, and a solid product outlet 8. The permeation chamber lower cover 4 is provided with a vacuum connection port 9. Multiple tubular membrane modules can also be connected in parallel to form a membrane bundle.

[0050] like Figure 2As shown, in some embodiments, the membrane module 2 includes at least one flat sheet membrane module, which divides the inner space enclosed by the outer shell into a stacked permeation chamber 11 and a reaction chamber 10. In this application, the flat sheet membrane module is a flat water separation membrane, which is placed in the inner space enclosed by the outer shell 1 and connected and fixed using graphite gaskets and flanges (not shown in the figure), which can divide the inner space into two parts, serving as the permeation chamber 11 and the reaction chamber 10 respectively.

[0051] In some embodiments, the reaction chamber is provided with a gas inlet 5, a solid raw material inlet 6, a gas outlet 7, and a solid product outlet 8.

[0052] In some embodiments, the gas inlet 5 is connected to a gas preheating device (not shown in the figure).

[0053] In some embodiments, the permeation chamber 11 is provided with a vacuum connection port 9.

[0054] In some embodiments, the vacuum connection port 9 is connected to a condensation device and a vacuum system (not shown in the figure).

[0055] In a second aspect, this application provides a membrane reaction system for preparing lithium sulfide, the membrane reaction system for preparing lithium sulfide comprising at least one membrane reactor as described in the first aspect for preparing lithium sulfide.

[0056] In some embodiments, when the membrane reaction system for preparing lithium sulfide includes at least two membrane reactors for preparing lithium sulfide as described in the first aspect, the membrane reactors for preparing lithium sulfide are connected in series or in parallel.

[0057] In this application, the term "connecting in series" means connecting the gas outlet of a previous membrane reactor used for preparing lithium sulfide to the gas inlet of a subsequent membrane reactor used for preparing lithium sulfide, which helps to improve the utilization rate of hydrogen sulfide and the total yield of lithium sulfide.

[0058] In this application, the parallel connection refers to connecting the gas inlets of each membrane reactor used for lithium sulfide preparation in parallel to the same hydrogen sulfide-containing gas supply pipeline, and connecting the gas outlets of each membrane reactor in parallel to the same tail gas treatment or circulation system; the vacuum connection ports of the permeate chambers of each membrane reactor used for lithium sulfide preparation are respectively connected to the same vacuum system via valves; and each membrane reactor used for lithium sulfide preparation has an independent sealing switch device for both the solid raw material inlet and the solid product outlet. Through the switching control of the pipeline valve group, at least one membrane reactor used for lithium sulfide preparation is in a reaction state (introducing hydrogen sulfide-containing gas, evacuating the permeate chamber, and maintaining the reaction temperature in the reaction chamber), while simultaneously at least one other membrane reactor used for lithium sulfide preparation is in a discharging and loading state (stopping gas supply, closing the vacuum, discharging the product, and loading fresh solid lithium hydroxide). This alternating operation enables continuous production of the entire membrane reactor system for lithium sulfide preparation: after one or more membrane reactors complete their reaction cycle, the system switches to another batch of reactors to begin the reaction. Meanwhile, the reactors that have completed their reaction are unloaded and loaded, and then remain in standby for the next switchover. Through a well-planned sequence, uninterrupted lithium sulfide production can be achieved.

[0059] In some embodiments, the membrane reaction system for preparing lithium sulfide further includes a solid lithium hydroxide supply device, a product collection device, a vacuum system, and a control system.

[0060] In this application, the solid lithium hydroxide supply device is connected to the solid feed inlet of the membrane reactor used to prepare lithium sulfide, for continuously or intermittently replenishing the reaction chamber with solid lithium hydroxide. The product collection device is connected to the solid product outlet, for continuously or intermittently discharging the reaction product, lithium sulfide. The vacuum system is connected to the vacuum connection port provided on the lower cover of the permeation chamber, for maintaining the vacuum level of the permeation chamber and extracting water vapor separated by the water separation membrane. The control system is used to control the reaction temperature, pressure, gas flow rate, and vacuum level, etc.

[0061] In some embodiments, the membrane reaction system for preparing lithium sulfide further includes a gas separation and circulation device.

[0062] In this application, a gas circulation device is used to separate unreacted hydrogen sulfide from the gas outlet and recirculate it back to the gas outlet, thereby improving the utilization rate of hydrogen sulfide.

[0063] Thirdly, this application provides a method for preparing lithium sulfide, the method comprising placing solid lithium hydroxide in the reaction chamber of a membrane reactor for preparing lithium sulfide as described in the first aspect or a membrane reaction system for preparing lithium sulfide as described in the second aspect, introducing a gas containing hydrogen sulfide into the reaction chamber to react and prepare lithium sulfide, while simultaneously performing a vacuum treatment in the permeation chamber to make the pressure in the permeation chamber lower than the pressure in the reaction chamber, so that water vapor in the reaction chamber enters the permeation chamber through a water separation membrane driven by the pressure difference; the reaction temperature is ≥200℃ (e.g., 250℃, 300℃, 350℃, 400℃, 450℃ or 500℃, etc.), and the reaction time is ≥1 h (e.g., 5 h, 10 h, 15 h, 20 h or 25 h, etc.).

[0064] In this application, the preparation method involves introducing a hydrogen sulfide-containing gas into the reaction chamber, controlling the reaction temperature, and allowing the hydrogen sulfide to react with solid lithium hydroxide to generate lithium sulfide and water vapor. By evacuating the permeation chamber to reduce its pressure to that of the reaction chamber, a pressure difference is created across the water separation membrane. Driven by this pressure difference, the water vapor generated in the reaction chamber permeates through the water separation membrane into the permeation chamber, thereby achieving the separation of lithium sulfide and water vapor and suppressing the reverse reaction.

[0065] In this application, the preparation method does not require pretreatment such as coating of solid lithium hydroxide, which simplifies the process flow. Unlike the core-shell structure particle method, which requires complex rolling granulation or fluidized bed coating of solid lithium hydroxide, this application can directly use commercially available lithium hydroxide particles or powder, which greatly shortens the process flow and reduces production costs.

[0066] In this application, the preparation method enables continuous production, overcoming the bottleneck of intermittent operation. Compared to the core-shell particle method, where the core-shell particles must be replaced or regenerated after saturation with water, leading to forced interruptions in the production process, the preparation method described in this application continuously removes water vapor from the permeation chamber (and can also recover it through condensation in a cold trap). The membrane module itself does not adsorb water, and theoretically, it can operate continuously indefinitely.

[0067] In this application, the preparation method has a short process flow, compact equipment, and small footprint: compared with the traditional process that requires multiple sets of equipment such as reactors, dehydration towers, and solvent recovery devices, this application integrates the reaction and separation into a single membrane reactor, which can reduce the equipment footprint by about 60% and shorten the process flow by more than 50%.

[0068] In some embodiments, the particle size of the solid lithium hydroxide is ≤1000 μm (e.g., 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm or 900 μm, etc.), and more preferably 50~300 μm.

[0069] In this application, the solid lithium hydroxide is preferably 50-300 μm in size for better results. If the particle size of the solid lithium hydroxide is too small, the bed pressure drop in the reaction chamber will be large due to the excessively fine particles, resulting in uneven gas distribution in the reaction chamber, local channeling or short circuits, reduced gas-solid contact efficiency, and uneven reaction. At the same time, the excessive bed pressure drop weakens the effective pressure difference between the reaction chamber and the permeation chamber, reduces the membrane permeation flux of water vapor, and weakens the effect of suppressing the reverse reaction. If the particle size of the solid lithium hydroxide is too large, the specific surface area will be reduced, the gas-solid contact area will be reduced, the reaction rate will be reduced, and the conversion rate will decrease in the same reaction time.

[0070] In some embodiments, the reaction temperature is 200~400℃ (e.g., 220℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃ or 380℃, etc.), more preferably 280~350℃; the reaction time is 1~8 h (e.g., 2 h, 3 h, 4 h, 5 h, 6 h or 7 h, etc.), more preferably 3~8 h.

[0071] In this application, the reaction temperature is preferably 200~400℃. If the temperature is too low, the reaction rate will be slow, and if the temperature is too high, lithium sulfide may sinter or decompose.

[0072] In some embodiments, the hydrogen sulfide-containing gas also includes an inert gas.

[0073] In some embodiments, the volume fraction of hydrogen sulfide in the hydrogen sulfide-containing gas is ≥5% (e.g., 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc.), and more preferably 15-50%.

[0074] In some embodiments, the pressure of the permeation chamber is ≤1000 Pa (e.g., 100 Pa, 200 Pa, 300 Pa, 400 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa or 900 Pa, etc.), and more preferably 100~500 Pa.

[0075] In this application, the pressure in the permeation chamber is preferably ≤1000 Pa to ensure sufficient driving force for water vapor mass transfer.

[0076] In some embodiments, the pressure in the reaction chamber is 0.1 to 0.5 MPa (e.g., 0.15 MPa, 0.20 MPa, 0.25 MPa, 0.30 MPa, 0.35 MPa, 0.40 MPa, or 0.45 MPa, etc.).

[0077] In this application, the pressure in the reaction chamber is preferably 0.1~0.5 MPa to promote the diffusion of hydrogen sulfide to the surface of solid lithium hydroxide.

[0078] In some embodiments, the pressure difference between the reaction chamber and the permeation chamber is ≥0.1 MPa (e.g., 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, or 1.0 MPa, etc.).

[0079] In some embodiments, the flow rate of the hydrogen sulfide-containing gas introduced into the reaction chamber is 50~1000 mL / min, such as 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min, 500 mL / min, 600 mL / min, 700 mL / min, 800 mL / min or 900 mL / min.

[0080] In some embodiments, the reaction further includes the steps of stopping the flow of hydrogen sulfide-containing gas, purging the reaction chamber with inert gas, and collecting the solid products from the reaction chamber.

[0081] In this application, water vapor discharged from the vacuum connection port at the outlet of the permeation chamber is condensed and recovered to obtain high-purity water, realizing the recovery of by-product water resources in a green and environmentally friendly manner. Water vapor entering the permeation chamber through the water separation membrane is condensed in a cold trap to obtain high-purity water (tested to have a conductivity of <1 μS / cm and an organic carbon content of <0.5 ppm), which can be reused as industrial pure water. Based on an annual production of 1000 tons of lithium sulfide, theoretically, approximately 450 tons of high-purity water can be recovered, reducing wastewater discharge and achieving resource recycling.

[0082] In this application, by controlling parameters such as the pressure difference between the reaction chamber and the permeation chamber, as well as the reaction temperature and time, the reaction can be promoted, achieving continuous and efficient removal of water vapor, and further improving the yield and purity of the lithium sulfide product. In the preparation method described, the reaction parameters and separation parameters can be independently adjusted, offering high operational flexibility. Reaction parameters such as the temperature, pressure, and hydrogen sulfide concentration in the reaction chamber, and separation parameters such as the pressure in the permeation chamber and the condensation temperature of the gas discharged from the permeation chamber, can be independently optimized and controlled.

[0083] In this application, the sampling and storage of the solid products after the reaction are carried out in a glove box (H2O<0.1 ppm, O2<0.1 ppm) to avoid contact with air.

[0084] To facilitate understanding of this application, the technical solutions of this application will be clearly and completely described below with reference to specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this application and should not be construed as specific limitations upon it.

[0085] Unless otherwise specified, the materials and equipment involved in the following detailed embodiments are all conventional materials and equipment in the art and will not affect the technical effect of this application.

[0086] Example 1 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide, such as... Figure 1 The membrane reactor for preparing lithium sulfide includes a shell 1, a membrane module 2, a permeate chamber upper cover 3, a permeate chamber lower cover 4, a gas inlet 5, a solid raw material inlet 6, a gas outlet 7, a solid product outlet 8, a vacuum connection port 9, a reaction chamber 10, a permeate chamber 11, and a solid material support structure 12.

[0087] The outer shell 1 is a stainless steel shell (material is 304 stainless steel); the gas inlet 5 and the solid raw material inlet 6 are located at the upper part of the stainless steel shell; the gas outlet 7 and the solid product outlet 8 are located at the lower part of the stainless steel shell, and are all connected to the reaction chamber.

[0088] The membrane module 2 is a single tubular membrane module, which is a tubular porous stainless steel support 3A molecular sieve composite membrane. The porous stainless steel support 3A molecular sieve composite membrane consists of a porous stainless steel support and a 3A molecular sieve layer loaded on the surface of the porous stainless steel support. The tubular porous stainless steel support 3A molecular sieve composite membrane has an outer diameter of 12 mm, an inner diameter of 8 mm, a length of 300 mm, and an average thickness of 10 μm for the 3A molecular sieve layer. After installing the upper cover 4 (made of 304 stainless steel) and the lower cover 3 (made of 304 stainless steel) of the permeation chamber at both ends of the tubular porous stainless steel support 3A molecular sieve composite membrane, the entire assembly is installed in the inner space enclosed by the outer shell 1. The tubular porous stainless steel support 3A molecular sieve composite membrane is connected and fixed to the upper and lower covers of the permeation chamber using graphite gaskets and flanges (not shown in the figure). A vacuum connection port 9 is provided on the lower cover 4 of the permeation chamber.

[0089] The reaction chamber 10 has a volume of 50 mL and a solid material support structure 12 is provided at its bottom. The solid material support structure is a quartz sand core sieve plate (average pore size of 20 μm) used to support solid lithium hydroxide 13. The reaction chamber is a fixed bed reactor.

[0090] The vacuum connection port 9 of the permeation chamber 11 is connected to a vacuum pump and a cold trap for vacuuming and collecting water vapor.

[0091] The membrane reactor used to prepare lithium sulfide is also equipped with an electric heating mantle and a thermocouple temperature control device to control the reaction temperature.

[0092] The method for preparing the lithium sulfide includes the following steps: Solid lithium hydroxide (particle size ranging from 100 to 200 μm, with an average particle size of 150 μm) was dried at 200°C under a nitrogen atmosphere for 2 hours to remove free water. Then, 50 g of the dried lithium hydroxide was placed on the solid material support structure of the reaction chamber in the membrane reactor used for lithium sulfide preparation. The vacuum pump was turned on, and the pressure in the permeate chamber was maintained at 500 Pa (absolute pressure) by adjusting the valve of the vacuum pump. The membrane reactor for lithium sulfide preparation was heated to 300°C while purging with nitrogen (N2) at a flow rate of 100 mL / min through the gas inlet. After the temperature stabilized, the gas was switched to a hydrogen sulfide-containing gas (composed of nitrogen and hydrogen sulfide, with a hydrogen sulfide volume fraction of 20%), and the flow rate of the hydrogen sulfide-containing gas into the reaction chamber was 200 mL / min. At this time, the pressure in reaction chamber 10 was 0.12 MPa. The reaction proceeded as follows: h; During the reaction, the composition (water vapor content) of the gas discharged from the vacuum connection port can be monitored by online gas chromatography; After the reaction is completed, switch back to nitrogen purging for 30 minutes, cool to room temperature, and take out the solid product from the reaction chamber in a glove box (H2O<0.1 ppm, O2<0.1 ppm) to obtain lithium sulfide.

[0093] Example 2 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide, such as... Figure 2 The membrane reactor for preparing lithium sulfide includes a shell 1, a membrane module 2, a gas inlet 5, a solid raw material inlet 6, a gas outlet 7, a solid product outlet 8, a vacuum connection 9, a reaction chamber 10, a permeation chamber 11, and a solid material support structure 12.

[0094] The outer shell 1 is a stainless steel shell (made of 316L stainless steel), consisting of an upper part and a lower part.

[0095] The membrane module 2 is a flat sheet membrane module, specifically a Nafion membrane (DuPont Nafion 117 membrane, with an effective area of ​​100 cm²). 2 The membrane assembly 2 (with an average thickness of 180 μm) is located between the upper and lower parts of the stainless steel shell. The membrane assembly is connected and fixed to the upper and lower parts of the stainless steel shell by graphite gaskets and flanges. The membrane assembly divides the inner space enclosed by the shell into a reaction chamber 10 (with a volume of 60 mL) and a permeation chamber 11.

[0096] The bottom of the reaction chamber 10 is provided with a solid material support structure 12, which is a quartz sand core sieve plate (average pore size of 20μm) used to support solid lithium hydroxide 13. The reaction chamber is a fixed bed reactor.

[0097] The vacuum connection port 9 of the permeation chamber 11 is connected to a vacuum pump and a cold trap for vacuuming and collecting water vapor.

[0098] The membrane reactor used to prepare lithium sulfide is also equipped with an electric heating mantle and a thermocouple temperature control device to control the reaction temperature.

[0099] The method for preparing the lithium sulfide includes the following steps: Solid lithium hydroxide (particle size ranging from 100 to 200 μm, with an average particle size of 150 μm) was dried at 200 °C under a nitrogen atmosphere for 2 hours to remove free water. Then, 50 g of this dried lithium hydroxide was placed on the solid material support structure of the reaction chamber in the membrane reactor used for lithium sulfide preparation. The vacuum pump was turned on, and the pressure in the permeate chamber was maintained at 500 Pa (absolute pressure) by adjusting the vacuum pump valve. The membrane reactor for lithium sulfide preparation was heated to 200 °C while purging with nitrogen (N2) at a flow rate of 100 mL / min through the gas inlet. After the temperature stabilized, the gas was switched to a hydrogen sulfide-containing gas (composed of nitrogen and hydrogen sulfide, with a hydrogen sulfide volume fraction of 20%), and the flow rate of the hydrogen sulfide-containing gas into the reaction chamber was 200 mL / min. At this point, the pressure in the reaction chamber was approximately 0.12. The reaction was carried out at MPa (absolute pressure) for 4 hours. During the reaction, the composition of the gas discharged from the vacuum connection port (water vapor content) could be monitored by online gas chromatography. After the reaction was completed, nitrogen was switched back for 30 minutes, and the mixture was cooled to room temperature. The solid product in the reaction chamber was taken out in a glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) to obtain lithium sulfide.

[0100] Example 3 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the tubular porous stainless steel support 3A molecular sieve composite membrane is replaced with a tubular porous stainless steel support 4A molecular sieve composite membrane. The 4A molecular sieve composite membrane consists of a tubular porous stainless steel support and a 4A molecular sieve layer loaded on the inner surface of the tubular porous stainless steel support. The tubular porous stainless steel support 4A molecular sieve composite membrane has an outer diameter of 12 mm, an inner diameter of 8 mm, and a length of 300 mm. The average thickness of the 4A molecular sieve layer is 10 μm. Other conditions are the same as in Embodiment 1.

[0101] Example 4 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the tubular porous stainless steel support 3A molecular sieve composite membrane is replaced with a tubular porous stainless steel support ZIF-8 composite membrane. The ZIF-8 composite membrane consists of a tubular porous stainless steel support and a ZIF-8 layer loaded on the inner surface of the tubular porous stainless steel support. The tubular porous stainless steel support ZIF-8 composite membrane has an outer diameter of 12 mm, an inner diameter of 8 mm, and a length of 300 mm. The average thickness of the ZIF-8 layer is 10 μm. Other conditions are the same as in Embodiment 1.

[0102] Example 5 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the membrane reactor for preparing lithium sulfide is heated to 250°C in the method for preparing lithium sulfide, while other conditions are the same as in Embodiment 1.

[0103] Example 6 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the membrane reactor for preparing lithium sulfide is heated to 400°C in the method for preparing lithium sulfide, while other conditions are the same as in Embodiment 1.

[0104] Example 7 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the membrane reactor for preparing lithium sulfide is heated to 500°C in the method for preparing lithium sulfide, while other conditions are the same as in Embodiment 1.

[0105] Example 8 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that in the method for preparing lithium sulfide, the pressure in the permeation chamber is maintained at 2000 Pa (absolute pressure) by adjusting the valve of the vacuum pump. Other conditions are the same as in Embodiment 1.

[0106] Example 9 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the method for preparing lithium sulfide uses a vacuum pump with a higher vacuum level to maintain the pressure in the permeation chamber at 100 Pa (absolute pressure). Other conditions are the same as in Embodiment 1.

[0107] Example 10 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the method for preparing lithium sulfide uses a vacuum pump with a higher vacuum level to maintain the pressure in the permeation chamber at 10 Pa (absolute pressure). Under the same flow rate of hydrogen sulfide-containing gas, the pressure in the reaction chamber is reduced to 0.09 MPa (absolute pressure). Other conditions are the same as in Embodiment 1.

[0108] Example 11 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that a back pressure valve is installed at the gas outlet of the reaction chamber in the method for preparing lithium sulfide, so that the pressure of the reaction chamber is 0.3 MPa (absolute pressure). Other conditions are the same as in Embodiment 1.

[0109] Example 12 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that a back pressure valve is installed at the gas outlet of the reaction chamber in the method for preparing lithium sulfide, so that the pressure of the reaction chamber is 0.6 MPa (absolute pressure). Other conditions are the same as in Embodiment 1.

[0110] Example 13 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the hydrogen sulfide-containing gas introduced into the reaction chamber in the method for preparing lithium sulfide is composed of nitrogen and hydrogen sulfide, wherein the volume fraction of hydrogen sulfide is 5%, and other conditions are the same as in Embodiment 1.

[0111] Example 14 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the hydrogen sulfide-containing gas introduced into the reaction chamber in the method for preparing lithium sulfide is composed of nitrogen and hydrogen sulfide, wherein the volume fraction of hydrogen sulfide is 10%, and other conditions are the same as in Embodiment 1.

[0112] Example 15 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the hydrogen sulfide-containing gas introduced into the reaction chamber in the method for preparing lithium sulfide is composed of nitrogen and hydrogen sulfide, wherein the volume fraction of hydrogen sulfide is 50%, and other conditions are the same as in Embodiment 1.

[0113] Example 16 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the method for preparing lithium sulfide introduces a hydrogen sulfide-containing gas into the reaction chamber, wherein the volume fraction of hydrogen sulfide is 100%, and other conditions are the same as in Embodiment 1.

[0114] Example 17 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the reaction time in the method for preparing lithium sulfide is adjusted to 2 hours, while other conditions are the same as in Embodiment 1.

[0115] Example 18 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the reaction time in the method for preparing lithium sulfide is adjusted to 8 hours, while other conditions are the same as in Embodiment 1.

[0116] Example 19 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the reaction time in the method for preparing lithium sulfide is adjusted to 24 h, while other conditions are the same as in Embodiment 1.

[0117] Example 20 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the quartz sand core sieve plate (average pore size of 20 μm) is replaced with a microporous quartz sand core sieve plate (average pore size of 3 μm) in the membrane reactor for preparing lithium sulfide. In the method for preparing lithium sulfide, the particle size of solid lithium hydroxide is <10 μm (obtained by grinding and sieving the solid lithium hydroxide in Example 1), and the average particle size is 5 μm. Other conditions are the same as in Example 1.

[0118] Example 21 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the particle size of the solid lithium hydroxide in the method for preparing lithium sulfide is in the range of 30~70 μm (obtained by grinding and sieving solid lithium hydroxide in Embodiment 1), and the average particle size is 50 μm. Other conditions are the same as in Embodiment 1.

[0119] Example 22 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the particle size of the solid lithium hydroxide in the method for preparing lithium sulfide is in the range of 450~550 μm (obtained by pressing, crushing and sieving the solid lithium hydroxide in Embodiment 1), and the average particle size is 500 μm. Other conditions are the same as in Embodiment 1.

[0120] Example 23 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this embodiment and Embodiment 1 is that the solid lithium hydroxide in the method for preparing lithium sulfide has a particle size >1000 μm (obtained by pressing, crushing and sieving the solid lithium hydroxide in Embodiment 1), and an average particle size of 1200 μm. Other conditions are the same as in Embodiment 1.

[0121] Example 24 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The membrane reactor for preparing lithium sulfide replaces the outer shell with a stainless steel shell with a larger volume, so that the reaction chamber volume is 200 mL. The quartz sand core sieve plate at the bottom of the reaction chamber is replaced with a fluidized bed distribution plate (sintered metal plate with an average pore size of 10 μm). The reaction chamber is a fluidized bed reactor.

[0122] The method for preparing the lithium sulfide includes the following steps: Solid lithium hydroxide (particle size ranging from 50 to 150 μm, with an average particle size of 100 μm) was dried at 200°C under a nitrogen atmosphere for 2 hours to remove free water. Then, 100 g of the dried lithium hydroxide was placed on the gas distribution plate of the reaction chamber in a membrane reactor used for lithium sulfide preparation. The vacuum pump was turned on, and the pressure in the permeate chamber was maintained at 500 Pa (absolute pressure) by adjusting the valve of the vacuum pump. The membrane reactor for lithium sulfide preparation was heated to 300°C by purging with nitrogen gas at a flow rate of 800 mL / min through the gas inlet at the lower part of the stainless steel shell. The gas introduced through the gas inlet was a fluidizing medium to fluidize the solid lithium hydroxide (fluidization number approximately 3). After the temperature stabilized, the gas was switched to a hydrogen sulfide-containing gas (composed of nitrogen and hydrogen sulfide, with a hydrogen sulfide volume fraction of 20%), and the flow rate of the hydrogen sulfide-containing gas into the reaction chamber was 800 mL / min. At this time, the pressure in the reaction chamber was 0.12 MPa (absolute pressure). The reaction proceeded for 4 hours. h; During the reaction, the composition (water vapor content) of the gas discharged from the vacuum connection port can be monitored by online gas chromatography; After the reaction, switch back to nitrogen purging for 30 minutes, cool to room temperature, and remove the solid product from the reaction chamber in a glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) to obtain lithium sulfide. Other conditions are the same as in Example 1.

[0123] Example 25 This embodiment provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference from Embodiment 1 is that the preparation of lithium sulfide is carried out in two membrane reactors for preparing lithium sulfide as described in Embodiment 1, connected in series. The gas outlet of the first membrane reactor for preparing lithium sulfide is adjacent to the gas inlet of the second membrane reactor for preparing lithium sulfide, allowing unreacted hydrogen sulfide in the first membrane reactor to enter the second membrane reactor for further reaction. Each membrane reactor for preparing lithium sulfide contains 50g of solid lithium hydroxide after removing free water. After the reaction, the solid products from the two membrane reactors are collected separately, combined, and lithium sulfide is obtained. Other conditions are the same as in Embodiment 1.

[0124] Comparative Example 1 This comparative example provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference from Example 1 is that the tubular porous stainless steel support 3A molecular sieve composite membrane is replaced with a tubular porous stainless steel support 5A molecular sieve composite membrane. The 5A molecular sieve composite membrane consists of a tubular porous stainless steel support and a 5A molecular sieve layer loaded on the inner surface of the tubular porous stainless steel support. The tubular porous stainless steel support 5A molecular sieve composite membrane has an outer diameter of 12 mm, an inner diameter of 8 mm, and a length of 300 mm. The average thickness of the 5A molecular sieve layer is 10 μm. Other conditions are the same as in Example 1.

[0125] Comparative Example 2 This comparative example provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this example and Example 2 is that the Nafion membrane is replaced with a polytetrafluoroethylene microfiltration membrane (effective area 100 cm²). 2 (The pore size is 0.22 μm and the thickness is 60 μm); in the method for preparing lithium sulfide, the membrane reactor used to prepare lithium sulfide is heated to 300°C, and other conditions are the same as in Example 2.

[0126] Comparative Example 3 This comparative example provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this and Example 1 is that the membrane reactor for preparing lithium sulfide is heated to 150°C in the method of preparing lithium sulfide, while other conditions are the same as in Example 1.

[0127] Comparative Example 4 This comparative example provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this method and Example 1 is that the method for preparing lithium sulfide does not use a vacuum pump, and the vacuum connection port is open to the atmosphere, so that the pressure in the permeation chamber is 0.1 Pa (absolute pressure). Other conditions are the same as in Example 1.

[0128] Comparative Example 5 This comparative example provides a membrane reactor for preparing lithium sulfide and a method for preparing lithium sulfide. The difference between this method and Example 1 is that the reaction time in the lithium sulfide preparation method is adjusted to 0.5 h, while other conditions are the same as in Example 1.

[0129] Comparative Example 6 This comparative example provides a method for preparing lithium sulfide, the method comprising the following steps: Solid lithium hydroxide (particle size in the range of 100~200 μm, average particle size of 150 μm) was dried at 200℃ under a nitrogen atmosphere for 2 hours to remove free water. Then, 50 g of the product was weighed and placed in a conventional fixed-bed reactor (quartz tube, inner diameter 20 mm, without membrane module). Under the purging of nitrogen (N2) at a flow rate of 100 mL / min, the temperature was raised to 300℃. After the temperature stabilized, the gas was switched to a hydrogen sulfide gas (composed of nitrogen and hydrogen sulfide, with a volume fraction of 20% hydrogen sulfide) at a flow rate of 200 mL / min. The reaction was carried out for 4 hours. After the reaction was completed, the gas was switched back to nitrogen for purging for 30 minutes. The mixture was cooled to room temperature, and the solid product in the fixed-bed reactor was removed in a glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) to obtain lithium sulfide.

[0130] Performance testing (1) The H2O / H2S separation factor of the membrane reactors used for preparing lithium sulfide provided in Examples 1-25 and Comparative Examples 1-5 was tested. The test method was as follows: In the lithium sulfide preparation methods provided in Examples 1-25 and Comparative Examples 1-5, the start time of the reaction was taken as the introduction of gas containing hydrogen sulfide. The gas discharged from the gas outlet of the reaction chamber during the process from the start to the end of the reaction was collected and its gas composition was tested; the gas discharged from the vacuum connection port of the permeation chamber during the process from the start to the end of the reaction was collected and its gas composition was tested. The average mole fraction of water vapor in the gas discharged from the gas outlet is denoted as Y. H2O The average mole fraction of hydrogen sulfide is denoted as Y. H2S The average mole fraction of water vapor in the gas discharged from the vacuum connection port is denoted as X. H2O The average mole fraction of hydrogen sulfide is denoted as X. H2S ; Calculate the H2O / H2S separation factor according to the following formula: (Y H2O / Y H2S ) / (X H2O / X H2S When the calculated value exceeds 1000, it is recorded as >1000.

[0131] (2) The lithium sulfide prepared by the methods provided in Examples 1-25 and Comparative Examples 1-6 was subjected to the following performance tests.

[0132] Lithium sulfide yield determination: The total mass of the solid product after the reaction is weighed, and the lithium sulfide content is determined by chemical titration (iodometric titration). Specifically, the sample to be tested is dissolved in water under an inert atmosphere. Lithium sulfide hydrolyzes, releasing hydrogen sulfide. The hydrogen sulfide is absorbed by zinc acetate solution to form zinc sulfide precipitate, and then the lithium sulfide content is indirectly calculated by iodometric titration. The formula for calculating the lithium sulfide yield is: Yield (%) = (Actual lithium sulfide yield / Theoretical lithium sulfide yield) × 100%, where the theoretical lithium sulfide yield is calculated based on the complete initial conversion of lithium hydroxide.

[0133] Lithium sulfide purity determination: X-ray diffraction (XRD) was used to analyze the phase composition of the solid product using a Bruker D8 Advance diffractometer (Cu Kα radiation, λ = 1.5406 Å, scanning range 10–80°). The content of lithium sulfide and impurity phases (such as LiOH, Li₂O, Li₂CO₃, etc.) was quantitatively calculated using Rietveld full-spectrum fitting. Lithium sulfide purity is defined as the mass fraction of lithium sulfide in the solid product.

[0134] Air stability test: 100 mg of the solid product was exposed to a constant temperature and humidity chamber at 25°C and 30% relative humidity for 2 hours. Subsequently, it was transferred to a sealed test bottle and placed for 24 hours. The concentration of hydrogen sulfide gas accumulated in the bottle was measured using a GASTEC gas detection tube (model 4H). The result is expressed as the volume of hydrogen sulfide produced per gram of solid product (ppm / g). This indicator directly reflects the solid product's resistance to hydrolysis in air. The solid product's resistance to hydrolysis in air is related to the purity of lithium sulfide and the content of the impurity lithium hydroxide.

[0135] When lithium hydroxide impurities are present, its strong hygroscopic properties allow it to rapidly absorb moisture from the air, even deliquescing, forming a strongly alkaline liquid film on the particle surface. This film violently absorbs CO2 from the air, resulting in the reaction: 2LiOH + CO2 → Li2CO3 + H2O, consuming OH-. - At the same time, more water is generated, further wetting the surface and triggering the reaction between lithium sulfide and water to produce hydrogen sulfide. Lithium hydroxide accelerates the deterioration of lithium sulfide through a chain reaction of "hygroscopic-neutralization-hydrolysis". When the purity of lithium sulfide is high and the content of impurity lithium hydroxide is low, its surface absorbs moisture slowly and hydrolyzes slowly, and it is relatively stable in dry air.

[0136] The test results are shown in Table 1 below.

[0137] Table 1 In the table, " / " indicates that the test was not performed.

[0138] According to the test results in Table 1, the membrane reactors provided in Examples 1-25 for preparing lithium sulfide have a separation factor of ≥60 for H2O / H2S. The lithium sulfide prepared by the methods provided in Examples 1-25 has a yield ≥70% and a purity ≥73%. The prepared lithium sulfide was tested for air stability, and the hydrogen sulfide production was ≤…ppm / g.

[0139] Compared to Example 1, the Nafion membrane used in Example 2 showed a decreased separation effect of hydrogen sulfide and water vapor, and its temperature resistance was lower, requiring the reaction temperature to be controlled at a lower level. In Example 3, the pore size of the 4A molecular sieve layer was slightly larger (approximately 0.4 nm), increasing the permeability of hydrogen sulfide and resulting in a decrease in the separation factor for preparing H2O / H2S. In Example 4, the pore size of the ZIF-8 layer (approximately 0.34 nm) was slightly larger, resulting in a relatively poor separation effect of hydrogen sulfide and water vapor. Furthermore, compared to Example 4, although the pore size of the ZIF-8 layer was slightly smaller than that of the 4A molecular sieve layer, the actual measured separation factor for H2O / H2S was lower, and the effect of preparing lithium sulfide was even worse. Compared to Example 1, the pore size of the 5A molecular sieve layer (approximately 0.5 nm) in Comparative Example 1 was larger, allowing a large amount of hydrogen sulfide to pass through along with water vapor. The hydrophobic polytetrafluoroethylene microfiltration membrane (approximately 0.22 μm) in Comparative Example 2 had almost no gas separation properties. As can be seen from the comparison of Examples 1-4 and Comparative Examples 1-2, the pore size of the 3A molecular sieve layer is approximately 0.3 nm, which is between the dynamic diameter of water molecules (0.26 nm) and the dynamic diameter of hydrogen sulfide molecules (0.36 nm). This allows for highly selective permeation of water molecules using the molecular sieving effect, while simultaneously forming an effective barrier against hydrogen sulfide molecules, resulting in a more ideal separation effect. This reduces the water vapor concentration in the reaction chamber and inhibits the occurrence of reverse reactions.

[0140] Compared with Example 1, if the reaction temperature in the lithium sulfide preparation method is lower (Example 5), the reaction rate is slower and the reaction is incomplete at the end of the reaction, resulting in a decrease in the purity, yield and air stability of lithium sulfide.

[0141] Compared with Example 1, if the reaction temperature in the lithium sulfide preparation method is increased (Example 6), the long-term reaction is prone to damage to the 3A molecular sieve membrane, and the H2O / H2S separation factor decreases.

[0142] Compared with Example 1, if the reaction temperature in the preparation method of lithium sulfide is too high (Example 7), lithium sulfide is prone to decomposition and sintering, damage to the 3A molecular sieve membrane, decrease in the H2O / H2S separation factor, and decrease in the purity, yield and air stability of lithium sulfide.

[0143] Compared to Example 1, if the pressure in the permeation chamber is too high (Example 8), the pressure difference is low, the mass transfer driving force is insufficient, and the effect of suppressing the reverse reaction decreases.

[0144] Compared to Example 1, if the pressure in the permeation chamber is too low (Example 10), it will cause the pressure in the reaction chamber to drop, affecting the reaction.

[0145] Compared with Example 1, if the pressure in the reaction chamber is increased (Example 11), while the pressure in the permeation chamber is kept at 500 Pa, the pressure difference is increased to 0.2995 MPa, mass transfer is enhanced, the water vapor permeation flux is increased by about 30%, the reverse reaction can be effectively suppressed, and the reaction rate is also increased. This ability to decouple and independently control parameters is something that traditional physical mixed water absorbent methods or core-shell structure particle methods cannot achieve.

[0146] Compared to Example 1, if the pressure in the reaction chamber is too high (Example 12), the excessive pressure in the reaction chamber will lead to an excessive partial pressure of hydrogen sulfide, which may trigger side reactions and increase the sealing requirements of the membrane reactor used to prepare lithium sulfide.

[0147] Compared with Example 1, the volume fraction of hydrogen sulfide in the hydrogen sulfide-containing gas in Examples 13 and 14 is lower, which leads to a slower reaction rate and a lower yield.

[0148] Compared with Examples 1 and 15, the volume fraction of hydrogen sulfide in the hydrogen sulfide-containing gas in Example 16 is higher. The yield, purity and air stability of the prepared lithium sulfide are not significantly improved, but more hydrogen sulfide is wasted.

[0149] Compared to Example 1, if the reaction time is too short (Example 17), the reaction is incomplete.

[0150] Compared to Example 1, if the reaction time is longer (Example 19), the yield, purity, and air stability of the prepared lithium sulfide decrease, possibly due to side reactions.

[0151] Compared with Example 1, if the particle size of solid lithium hydroxide is too small (Example 20), the bed pressure drop in the reaction chamber will be large due to the excessively fine particles, resulting in uneven gas distribution in the reaction chamber, local channeling or short circuits, reduced gas-solid contact efficiency, and uneven reaction. At the same time, the excessive bed pressure drop weakens the effective pressure difference between the reaction chamber and the permeation chamber, reduces the membrane permeation flux of water vapor, and weakens the effect of suppressing the reverse reaction.

[0152] Compared to Example 1, if the particle size of solid lithium hydroxide is larger (Example 22), the diffusion path of water vapor from the larger particles to the outer surface is longer, the residence time of water vapor inside the particles is longer, and the probability of reverse reaction with the already generated lithium sulfide increases, resulting in a decrease in the purity of the lithium sulfide product. At the same time, the specific surface area of ​​the larger particles is reduced, the gas-solid contact area is reduced, the reaction rate is reduced, and the conversion rate is reduced within the same reaction time. Therefore, the lithium sulfide yield (90.5%) and purity (92.0%) obtained in Example 22 are both lower than those in Example 1 (yield 96.8%, purity 97.5%), and the hydrogen sulfide production in the air stability test (102 ppm / g) is also higher than that in Example 1 (16 ppm / g). If the particle size of solid lithium hydroxide is too large (Example 23), the diffusion of water vapor from the large particles to the outer surface is severely restricted, and the water vapor generated inside the particles cannot escape quickly, forming a local high water vapor partial pressure zone inside the particles. This leads to a violent reverse reaction, severely reducing the purity and yield of lithium sulfide. At the same time, the excessively large particle size results in a significant reduction in the gas-solid contact area, which also restricts the diffusion of hydrogen sulfide into the particle interior, resulting in a less complete reaction. Therefore, the lithium sulfide yield (78.2%) and purity (80.5%) obtained in Example 23 are significantly reduced, and the hydrogen sulfide generation in the air stability test is as high as 815 ppm / g, which is far worse than that in Example 1 (16 ppm / g).

[0153] Compared to Example 1, if the reaction chamber is a fluidized bed reactor (Example 24), the fluidization state results in higher gas-solid contact efficiency, leading to better lithium sulfide yield and purity. The purity of lithium sulfide can reach 98.5%, and the hydrogen sulfide production in the air stability test is less than 5 ppm / g, which is more than two orders of magnitude higher than commercially available lithium sulfide products (typically >1000 ppm / g). Furthermore, after a 72-hour operation test, it can operate continuously and stably, with the yield consistently remaining above 97% without any decline, confirming its continuous operation capability.

[0154] Compared to Example 1, Example 25 uses two identical membrane reactors for lithium sulfide preparation connected in series. Unreacted hydrogen sulfide in the gas discharged from the first lithium sulfide membrane reactor enters the second lithium sulfide membrane reactor to continue reacting with fresh solid lithium hydroxide, achieving a cascade utilization of hydrogen sulfide. In cases where the conversion rate at the outlet of a single lithium sulfide membrane reactor is low due to the decay of hydrogen sulfide concentration along the bed, the series operation effectively recovers residual hydrogen sulfide in the tail gas, ensuring sufficient conversion of solid lithium hydroxide in the second lithium sulfide membrane reactor, increasing the overall system yield to 98.5%. Simultaneously, the pre-separation of water vapor by the membrane module in the first lithium sulfide membrane reactor reduces the moisture pressure in the gas entering the second lithium sulfide membrane reactor, further suppressing the reverse reaction and slightly improving product purity.

[0155] In this application, the reaction temperature is 280~400℃, the reaction time is 3~8 h, the pressure in the permeation chamber is ≤1000 Pa, the pressure in the reaction chamber is 0.1~0.5 MPa, the volume fraction of hydrogen sulfide in the hydrogen sulfide-containing gas is 10%~100%, the particle size of solid lithium hydroxide is ≤500 μm, and the water separation membrane in the membrane reactor used to prepare lithium sulfide is any one of 3A molecular sieve membrane, 4A molecular sieve membrane or Nafion membrane, which can stably obtain technical effects that are significantly better than the prior art (yield >85%, purity >90%, H2S generation <500 ppm / g).

[0156] Compared to Example 1, if the reaction temperature is too low (Comparative Example 3), the reaction hardly occurs and the yield is extremely low.

[0157] Compared to Example 1, if the permeation chamber is not evacuated (Comparative Example 4), the pressure difference is low, there is almost no driving force, the diffusion of water vapor is extremely slow, and it is difficult to effectively suppress the occurrence of the reverse reaction.

[0158] Compared to Example 1, if the reaction time is too short (Comparative Example 5), the reaction is incomplete.

[0159] Compared with Example 1, if a conventional fixed-bed reactor (Comparative Example 6) is used, water vapor cannot be separated and it is difficult to suppress the occurrence of reverse reaction. This shows that the presence of a reactor alone is not enough. A water separation membrane is the key to achieving in-situ dehydration and efficient suppression of reverse reaction.

[0160] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A membrane reactor for preparing lithium sulfide, characterized in that, The membrane reactor for preparing lithium sulfide includes a shell, a reaction chamber, a permeation chamber, and a membrane module located between the reaction chamber and the permeation chamber. The membrane module includes a water separation membrane, and the pressure in the permeation chamber is lower than the pressure in the reaction chamber. The water separation membrane includes any one or a combination of at least two of the following: 3A molecular sieve membrane, 4A molecular sieve membrane, ZIF-8 membrane, or hydrophilic polymer membrane.

2. The membrane reactor for preparing lithium sulfide according to claim 1, characterized in that, The 3A molecular sieve membrane includes a porous stainless steel support 3A molecular sieve composite membrane, which includes a porous stainless steel support and a 3A molecular sieve layer loaded on the surface of the porous stainless steel support. Preferably, the 4A molecular sieve membrane comprises a porous stainless steel support 4A molecular sieve composite membrane, wherein the porous stainless steel support 4A molecular sieve composite membrane comprises a porous stainless steel support and a 4A molecular sieve layer loaded on the surface of the porous stainless steel support. Preferably, the ZIF-8 membrane comprises a porous stainless steel support ZIF-8 composite membrane, wherein the porous stainless steel support ZIF-8 composite membrane comprises a porous stainless steel support and a ZIF-8 layer loaded on the surface of the porous stainless steel support. Preferably, the hydrophilic polymer membrane includes a Nafion membrane and / or a cross-linked polyvinyl alcohol membrane.

3. The membrane reactor for preparing lithium sulfide according to claim 1 or 2, characterized in that, The membrane module includes at least one tubular membrane module; Preferably, the membrane module includes at least one flat sheet membrane module.

4. The membrane reactor for preparing lithium sulfide according to claim 1 or 2, characterized in that, The reaction chamber is equipped with a gas inlet, a solid raw material inlet, a gas outlet, and a solid product outlet.

5. A membrane reaction system for preparing lithium sulfide, characterized in that, The membrane reaction system for preparing lithium sulfide includes at least one membrane reactor for preparing lithium sulfide as described in any one of claims 1 to 4.

6. The membrane reaction system for preparing lithium sulfide according to claim 5, characterized in that, When the membrane reaction system for preparing lithium sulfide includes at least two membrane reactors for preparing lithium sulfide as described in any one of claims 1 to 4, the membrane reactors for preparing lithium sulfide are connected in series or in parallel.

7. A method for preparing lithium sulfide, characterized in that, The preparation method includes placing solid lithium hydroxide in the reaction chamber of a membrane reactor for preparing lithium sulfide as described in any one of claims 1 to 4 or a membrane reaction system for preparing lithium sulfide as described in claim 5 or 6, introducing a gas containing hydrogen sulfide into the reaction chamber to react and prepare lithium sulfide, while simultaneously performing vacuum treatment in the permeation chamber to make the pressure in the permeation chamber lower than the pressure in the reaction chamber, so that water vapor in the reaction chamber enters the permeation chamber through a water separation membrane under the pressure difference. The reaction temperature is ≥200℃ and the reaction time is ≥1 h.

8. The preparation method according to claim 7, characterized in that, The particle size of the solid lithium hydroxide is ≤1000 μm, and more preferably 50~500 μm; Preferably, the reaction temperature is 200~400℃ and the reaction time is 1~8 h.

9. The preparation method according to claim 7 or 8, characterized in that, The hydrogen sulfide-containing gas also includes an inert gas; Preferably, the volume fraction of hydrogen sulfide in the hydrogen sulfide-containing gas is ≥5%, more preferably 15%~50%.

10. The preparation method according to any one of claims 7 to 9, characterized in that, The pressure in the permeation chamber is ≤1000 Pa, more preferably 100~500 Pa; Preferably, the pressure in the reaction chamber is 0.1~0.5 MPa; Preferably, the pressure difference between the reaction chamber and the permeation chamber is ≥0.1 MPa; Preferably, the flow rate of the hydrogen sulfide-containing gas introduced into the reaction chamber is 50~1000 mL / min.

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