System and method for regenerating metal sodium and elemental sulfur by electrolyzing Na2SX

Abstract

The invention discloses a system and a method for regenerating metal sodium and elemental sulfur by electrolyzing Na2SX. The system comprises a power supply and a double-chamber Na2SX electrolysis device for separating an anode region from a cathode region through a solid sodium ion membrane. Na2SX is used as a raw material and dissolved in a strong-polarity organic aprotic solvent, liquid metal sodium is generated in a cathode area under the action of an electric field, and the liquid metal sodium is protected by protective gas and is led to a metal sodium storage tank at proper time to be stored; and elemental sulfur is generated in the anode region, led out, cooled and separated. The tin-sodium alloy is introduced, so that the wettability of metal sodium and a solid sodium ion membrane is enhanced, and dendritic crystals are prevented from being formed; the carbon nanotubes are introduced into the anode region, the resistance of the anode region is reduced, the interface resistance of micropores of the diaphragm is reduced, the current efficiency is improved, the process energy consumption is low, metal sodium and elemental sulfur can be efficiently regenerated, and the problems of high energy consumption, high risk and the like caused by an ultrahigh-temperature molten state are avoided.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemistry, and specifically relates to an electrolytic Na2S X System and method for regenerating metallic sodium and elemental sulfur. Background Art

[0002] Sodium will oxidize rapidly in the air and react violently with water, so it can only exist in organic compounds. Because of its active chemical properties, it can react with organic sulfides in heavy oils such as residual oil to increase the API of the crude oil and reduce the sulfur content of the crude oil. This process is called the sodium desulfurization process. Because the sodium desulfurization process has low energy consumption and hydrogen consumption, it is favored by domestic and foreign researchers. People are trying to use the sodium desulfurization process to replace the traditional hydrodesulfurization process. However, the sodium desulfurization process will produce a large amount of by-product Na2S X For heavy oil with a sulfur content of 5% to 8% by mass, if the sodium desulfurization process is used, 7 to 12 tons of metallic sodium will be consumed for every 100 tons of crude oil, producing 12 to 20 tons of Na2S X How to take effective measures to convert Na2S X The regeneration and conversion into metallic sodium and elemental sulfur can not only solve the source problem of metallic sodium in the sodium desulfurization process, but also produce elemental sulfur as a by-product, further reducing the cost of the sodium desulfurization process. Therefore, it is imperative to provide a method for regenerating and reducing metallic sodium.

[0003] Take Na2S as an example. Its melting point is as high as 950℃. If Na2S is electrolyzed in a molten state, it will require a lot of energy consumption and have high risks. How to generate electrolysis reaction under low temperature conditions and obtain metallic sodium quickly and conveniently is an urgent problem to be solved by researchers in the field of electrochemistry.

[0004] Patent CN102719857A discloses a method and an electrolytic cell for producing titanium metal by direct electrolysis of titanium dioxide, wherein the electrolytic cell includes anode and cathode interfaces, a thermocouple interface, a cooling water system, etc., and uses 40.8%-47.0% KCl-LiCl binary mixed molten salt as a molten salt electrolyte in the anode area and liquid metallic sodium as a reducing medium in the cathode area, which can reduce powdered TiO2 to titanium metal. However, the operating temperature of the electrolytic cell is relatively high (reaching 450°C), and on the other hand, the electrolysis process is an intermittent process and cannot achieve continuous operation.

[0005] Patent CN1748047A discloses an electrochemical reduction of metal oxides, a method for reducing solid metal oxides in an electrochemical cell, first applying a cell potential to the electrolytic cell so that it can electrochemically reduce the metal oxides supplied to the molten electrolyte, and then delivering powdered or pelletized metal oxides to the molten electrolyte bath, which can achieve continuous or semi-continuous reduction of metal oxides from the molten electrolyte. However, the method involved in the patent requires the use of a molten electrolyte, which has high temperature and high energy consumption, and cannot be used to reduce metal sulfides. Summary of the invention

[0006] The present invention provides a method for electrolyzing Na2S X System and method for regenerating metallic Na and elemental sulfur. The method can efficiently regenerate metallic sodium and elemental sulfur, has low energy consumption, can be produced continuously, and is suitable for Na2S produced by residual oil desulfurization. X Electrolysis produces metallic sodium and elemental sulfur.

[0007] One of the purposes of the present invention is to provide a method for electrolyzing Na2S X A system for regenerating metallic sodium and elemental sulfur, comprising: a power supply, a double-chamber electrolytic Na2S with anode and cathode separated by a solid sodium ion membrane X The device comprises a tin-sodium alloy attached to the inner side of the solid sodium ion membrane.

[0008] According to the present invention, the electrolytic Na2S X In the system of regenerating metallic sodium and elemental sulfur:

[0009] The anode area is equipped with a graphite crucible tube, the side line of the tube wall is provided with an electrolyte solution outlet and a carbon nanotube filter at the outlet, which is used to intercept the carbon nanotubes in the electrolyte solution, the bottom of the tube is provided with a raw material inlet, a raw material filter at the inlet, and a heater, the top of the tube is provided with an anode sealing cover, and the anode thermocouple insertion port is provided on the anode sealing cover;

[0010] A solid sodium ion membrane, wherein the axial height of the solid sodium ion membrane is higher than the axial height of the anode graphite layer crucible tube, and a cathode sealing cover is arranged on the top of the solid sodium ion membrane;

[0011] The cathode area includes a liquid metal sodium bath, a platinum wire or platinum sheet or platinum rod. A protective gas inlet pipeline and a liquid metal sodium outlet pipeline are arranged on the cathode sealing cover; the tin-sodium alloy attached to the inner side of the solid sodium ion membrane is in contact with the liquid metal sodium bath.

[0012] According to the present invention, in the anode region:

[0013] The graphite layer crucible tube includes a graphite layer, a heat-insulating layer, and a stainless steel tank body from the inside to the outside; preferably, the graphite layer is connected to the positive electrode of the power supply; the graphite layer is in close contact with the anode electrolyte solution;

[0014] The anode region has a built-in heater, preferably, a heater is arranged at the bottom of the anode region;

[0015] The anode region is equipped with a built-in thermocouple for monitoring and controlling the temperature of the anode region, and the anode thermocouple is vertically inserted into the anode electrolyte solution;

[0016] The anode region is also provided with a liquid level meter for monitoring the liquid level of the solution in the anode region. The liquid level meter is not particularly limited and a commonly used liquid level meter can be used.

[0017] According to the present invention, the solid sodium ion membrane is Na + An organic or inorganic film that is a good conductor or electronic insulator; preferably, the organic film is selected from at least one of a polyolefin composite sodium ion membrane and a sodium fluorosulfonate resin membrane, and is a diaphragm material with thermal stability, chemical stability, and mechanical strength; the inorganic film is selected from at least one of a β-Al2O3 membrane and a NZSP membrane, and is a sodium ion conductor membrane material;

[0018] The solid sodium ion membrane is a cylindrical structure, a square cylindrical structure, a star-shaped structure, a stacked structure or a sea urchin-shaped structure, preferably a cylindrical structure;

[0019] The solid sodium ion membrane selectively passes Na + The membrane has an increase in admittance as the temperature increases, specifically Na + The organic or inorganic film is a good conductor or electronic insulator, the thickness of the film is 0.1mm to 1mm, the conductivity is 100μS / cm to 10000μS / cm, and the conductivity of the solid sodium ion film increases with the increase of temperature;

[0020] The thickness of the tin-sodium alloy attached to the inner side of the solid sodium ion membrane is 10 μm to 100 μm;

[0021] In the solid sodium ion membrane, the pore diameter of the micropores is 1 mm to 2 mm.

[0022] According to the present invention, in the cathode region:

[0023] The tin-sodium alloy coating is attached to the inner surface of the solid sodium ion membrane to form a Schottky junction for supporting a liquid metal sodium bath; the Schottky junction is electroplated with sodium stannate in an inert gas atmosphere to uniformly deposit metal sodium and metal tin on the surface of the solid sodium ion membrane in the cathode region to form a surface contact Schottky junction;

[0024] The platinum wire or platinum sheet or platinum rod is placed in a liquid sodium metal bath and connected to the negative electrode of a power source;

[0025] The lower end of the protective gas inlet pipeline is arranged above the liquid level of the liquid metal sodium bath;

[0026] The lower end of the liquid metal sodium outlet pipeline is arranged below the liquid level of the liquid metal sodium bath;

[0027] The cathode region is equipped with a built-in thermocouple for monitoring and controlling the temperature of the cathode region;

[0028] The cathode region is also provided with a liquid level meter for monitoring the liquid level of the liquid metal sodium bath in the cathode region. The liquid level meter is not particularly limited and a commonly used liquid level meter can be used.

[0029] According to the present invention, the device further comprises a raw material area and a product area, wherein the raw material area comprises Na2S X dissolving, stirring and feeding equipment; the product area includes a liquid metal sodium storage tank and an elemental sulfur crystallization separation device, the liquid metal sodium storage tank is connected to the cathode area, and the inlet of the elemental sulfur crystallization separation device is connected to the anode electrolyte solution outlet of the anode area, wherein the elemental sulfur crystallization separation equipment includes an electrolyte solution inlet, a desulfurization solvent outlet, a rotating shaft and a filter.

[0030] The second object of the present invention is to provide an electrolytic Na2S X The method for regenerating metallic sodium and elemental sulfur comprises the following steps: X The system for regenerating metallic sodium and elemental sulfur converts Na2S X The step of electrolyzing to generate metallic sodium and elemental sulfur, preferably, the method comprises the following steps:

[0031] (1) Raw material preparation: sodium sulfide and / or sodium polysulfide is subjected to low temperature drying treatment, and then dissolved in an aprotic solvent to obtain an anode electrolyte solution;

[0032] (2) Preheating and electrolysis of Na2S X Device: In electrolysis of Na2S X A protective gas is introduced into the anode and cathode regions of the device, an anolyte solution is added to the anode region and heating begins, and liquid metal sodium is added to the cathode region;

[0033] (3) Electrolysis: Turn on the power supply to perform electrolysis. Under the action of the potential of the external power supply, the Na + Passing through the solid sodium ion membrane, it enters the cathode region and obtains electrons to be reduced to metallic sodium. At the same time, the sulfur anions lose electrons in the anode region to generate elemental sulfur.

[0034] (4) Product separation: For the metallic sodium in the cathode area, the liquid metallic sodium is sent to the metallic sodium storage tank under the pressure of the protective gas. For the elemental sulfur in the anode area, the anode electrolyte solution containing elemental sulfur in the anode area is led out to the elemental sulfur crystallization separation equipment for separation.

[0035] According to the present invention, in step (1):

[0036] The Na2S X is sodium sulfide or sodium polysulfide, wherein X It can be 1, 2, 3, 4, 5, 6;

[0037] The purity of the sodium sulfide and sodium polysulfide is not less than 95%;

[0038] The aprotic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone and N-methylpyrrolidone;

[0039] The low temperature drying treatment condition is 100°C to 300°C for dehydration for 3h to 5h;

[0040] The anode electrolyte solution is a saturated solution of sodium sulfide or sodium polysulfide at the dissolution temperature;

[0041] The electrolyte solution contains carbon nanotubes. Preferably, the amount of the carbon nanotubes is 1wt% to 5wt% of the electrolyte solution. The radial size of the carbon nanotubes is 10nm to 20nm, and the axial size is 10μm to 100μm.

[0042] The dissolution temperature is not particularly limited as long as sodium sulfide and / or sodium polysulfide can be dissolved. For example, the dissolution temperature is 20°C to 60°C.

[0043] According to the present invention, in step (2):

[0044] The feeding equipment injects the anolyte solution into the electrolytic Na2S at a rate of 100g / h to 300g / h. X The device anode region;

[0045] Electrolysis of Na2S X The device is heated to above 98°C and liquid metallic sodium is added to the cathode region.

[0046] According to the present invention, in step (3):

[0047] The electrolysis temperature is 100℃~160℃;

[0048] External power is applied to the electrolytic Na2S X The DC constant voltage potential of the device is between 1.7V and 2.0V;

[0049] When the concentration of elemental sulfur in the electrolyte solution in the anode region reaches 10wt% to 30wt%, it is introduced into an elemental sulfur crystallization separation device;

[0050] During the electrolysis process, the liquid level in the anode region is maintained by pumping the anode electrolyte solution in the raw material region into the anode region, and the liquid level in the cathode region is maintained by introducing a protective gas to drive the liquid metal sodium to the cathode region under pressure;

[0051] The separation operation of elemental sulfur includes: the elemental sulfur produced in the electrolysis process in the anode area is dissolved in the anode electrolyte solution, and then electrolyzed into Na2S X The outlet of the anode electrolyte solution in the anode area of ​​the device is led to the elemental sulfur crystallization separation equipment, cooled to 65°C ~ 75°C to reduce the solubility of elemental sulfur. After reaching supersaturation, sulfur crystals are generated and sink to the bottom. The desulfurized solution can be pumped away from the bottom of the elemental sulfur crystallization separation equipment and returned to the raw material area.

[0052] The electrolysis process of the present invention is that under the action of the potential of an external power source, S 2- 、S2 2- 、S3 2- 、S4 2- , S5 2- 、S6 2- The plasma loses electrons to produce elemental sulfur, while reducing the Na2S in the electrolyte solution. X concentration; driven by external potential, Na + Through the solid sodium ion membrane to the cathode area, high-purity metallic sodium can be obtained at the cathode. The temperature in the cathode area is higher than the melting point of metallic sodium, and the metallic sodium is in liquid state. The separation process includes, under the condition of controlling the liquid level, relying on the protective gas pressure in the cathode area to lead the metallic sodium to the metallic sodium storage tank and store it in an inert environment, and leading the electrolyte solution (containing elemental sulfur) in the anode area to the elemental sulfur crystallization separation equipment in the anode area, and reducing the solubility of elemental sulfur by lowering the temperature, thereby generating sulfur crystals, sinking to the bottom of the filter screen under the centrifugal effect, and the desulfurization solvent passes through the filter screen and returns to the non-proton solvent inlet of the raw material area.

[0053] The present invention has the following advantages:

[0054] (1) The present invention uses a polar organic aprotic solvent to dissolve Na2S X , which can significantly reduce the electrolysis temperature, thereby reducing energy consumption and ensuring the safety of the electrolysis reaction;

[0055] (2) The present invention adopts a tin-sodium alloy to enhance the wettability of metallic sodium and the solid sodium ion membrane, while preventing the formation of dendrites;

[0056] (3) The raw materials of the present invention are dried before use, thereby ensuring the selectivity of the electrolysis product and the safety of the electrolysis;

[0057] (4) The microporous structure of the solid sodium ion membrane in the present invention reduces the interface resistance and improves the current efficiency;

[0058] (5) The present invention adopts a temperature control method to change the solubility of elemental sulfur in aprotic solvents, thereby forming sulfur crystals, thereby effectively achieving the separation of elemental sulfur.

[0059] The electrolytic Na2S provided by the present invention X The process of regenerating metallic sodium and elemental sulfur has low energy consumption and can efficiently regenerate metallic sodium and elemental sulfur, avoiding the problems of high energy consumption and high risk caused by ultra-high temperature molten state. It can be used for the sodium desulfurization product Na2S of heavy oil such as residual oil and asphalt. X of electrolytic reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 The electrolytic Na2S used in Examples 1 to 4 of the present invention X System diagram.

[0061] Among them, A is the anode region, C is the cathode region and B is the solid sodium ion membrane;

[0062] A anode region includes 8 an anode electrolyte solution (containing elemental sulfur) outlet, 9 a raw material inlet, 10 a graphite layer crucible (from inside to outside, 11 a graphite layer, 12 a heat preservation and insulation layer, 13 a stainless steel tank body), 14 an anode region sealing cover, 15 an anode region thermocouple, 16 a heater, 17 an anode electrolyte solution, 18 a carbon nanotube filter, 19 a raw material filter, and 20 an electrolyte level gauge;

[0063] C cathode area includes 1 protective gas inlet, 2 liquid sodium outlet, 3 metal sodium bath, 4 cathode area sealing cover, 5 cathode area thermocouple, 6 platinum wire / platinum sheet / platinum rod, 7 sodium bath liquid level gauge.

[0064] Figure 2 The electrolytic Na2S used in Examples 1 to 4 of the present invention X Schematic diagram of the raw material area in the system, where 21Na2S X inlet, 22 aprotic solvent inlet, 23 raw material agitator, 24 raw material heater, 25 raw material outlet, 26 raw material metering pump.

[0065] Figure 3 The electrolytic Na2S used in Examples 1 to 4 of the present invention X Schematic diagram of the elemental sulfur crystallization separation equipment in the system, wherein 27 is an electrolyte solution (containing elemental sulfur) inlet, 28 is a desulfurization solvent outlet, 29 is a desulfurization solvent, 30 is a rotating shaft, 31 is a filter, and 32 is elemental sulfur. DETAILED DESCRIPTION

[0066] In order to make the purpose and advantages of the present invention more clearly understood, the implementation steps of the present invention are described in detail below in conjunction with examples. The DC power supply, electric constant temperature blast drying oven (including protective gas system), precision metering pump, liquid level meter, controller, separation equipment and other related terms involved in the experiment do not limit the present invention, but are only for the purpose of describing specific embodiments, and are not intended to limit the present invention, and should not be understood as being limited to the embodiments described herein.

[0067] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0068] Example 1

[0069] Combine the following Figure 1 The present invention describes the electrolysis of Na2S X Systems and methods for regenerating metallic sodium and elemental sulfur.

[0070] like Figure 1 As mentioned above, electrolysis of Na2S X The system includes a power supply and a double-chamber electrolytic Na2S system in which the anode region A and the cathode region C are separated by a solid sodium ion membrane B. X device.

[0071] The anode region A is provided with a graphite layer crucible 10, and the side line of the tube wall is provided with an anode electrolyte solution outlet 8 and a carbon nanotube filter 18 at the outlet, a raw material inlet 9 and a raw material filter 19 are provided at the bottom of the tube, and an anode sealing cover 14 is provided at the top of the tube, and an anode thermocouple insertion port 15 is provided on the anode sealing cover 14. The graphite layer crucible 10 includes a graphite layer 11, a heat preservation and insulation layer 12, and a stainless steel tank body 13 from the inside to the outside. The graphite layer 11 is connected to the positive pole of the power supply, and the graphite layer 11 is in close contact with the anode electrolyte solution 17. A heater 16 is provided at the bottom of the anode region A, and a thermocouple 15 is built into the anode region A for monitoring and controlling the temperature of the anode region A. The anode thermocouple 15 is vertically inserted into the anode electrolyte solution 17; the anode region A is also provided with an electrolyte level meter 20 for monitoring the liquid level of the solution in the anode region A. The solid sodium ion membrane B adopts NZSP solid sodium ion membrane, preferably with a cylindrical structure. The axial height of the solid sodium ion membrane B is higher than the axial height of the anode graphite layer crucible 10, and a cathode region sealing cover 4 is arranged on the top of the solid sodium ion membrane B; a tin-sodium alloy is attached to the inner side of the solid sodium ion membrane B; the thickness of the inner tin-sodium alloy is 10 μm, the thickness of the solid sodium ion membrane B is 1 mm, the pore diameter of the micropore is 1 mm, and the conductivity of the solid sodium ion membrane B is 8600 μS / cm, which increases with the increase of temperature.

[0072] In cathode region C, the tin-sodium alloy coating contacts the liquid metal sodium bath 3 and the platinum wire / platinum sheet / platinum rod 6, and a protective gas inlet pipeline 1 and a liquid metal sodium outlet pipeline 2 are provided on the cathode region sealing cover 4. The tin-sodium alloy coating is attached to the inner surface of the solid sodium ion membrane B to form a Schottky junction and support the liquid metal sodium bath 3. The platinum wire / platinum sheet / platinum rod 6 is placed in the liquid metal sodium bath 3 and connected to the negative pole of the power supply; the lower end of the protective gas inlet pipeline 1 is above the liquid level of the liquid metal sodium bath 3; the lower end of the liquid metal sodium outlet pipeline 2 is below the liquid level of the liquid metal sodium bath 3. The cathode region C has a built-in thermocouple 5 for monitoring and controlling the temperature of the cathode region C; the cathode region C is also provided with a sodium bath level gauge 7 for monitoring the liquid level of the liquid metal sodium bath 3 in the cathode region C.

[0073] Figure 2 For electrolysis of Na2S X Schematic diagram of the raw material area in the system, which includes Na2S X Dissolution, stirring and feeding equipment, including Na2S X Inlet 21 , aprotic solvent inlet 22 , raw material stirrer 23 , raw material heater 24 , raw material outlet 25 , raw material metering pump 26 .

[0074] Figure 3 For electrolysis of Na2S X The schematic diagram of the elemental sulfur crystallization separation equipment in the system includes a liquid metal sodium storage tank and an elemental sulfur crystallization separation equipment. The liquid metal sodium storage tank is connected to the cathode region. There is no special requirement for the liquid metal sodium storage tank. The liquid metal sodium storage tank commonly used in the art can be used, which is not shown in the figure. The inlet of the elemental sulfur crystallization separation equipment is connected to the anode electrolyte solution outlet of the anode region. The elemental sulfur crystallization separation equipment includes an electrolyte solution (containing elemental sulfur) inlet 27, a desulfurization solvent outlet 28, a rotating shaft 30 and a filter 31. The rotating shaft 30 is vertically arranged at the center of the separation equipment. The filter 31 is used to filter the electrolyte solution to obtain elemental sulfur 32 on the filter and the desulfurization solvent 29 at the bottom of the equipment. The desulfurization solvent 29 is discharged through the desulfurization solvent outlet 28.

[0075] use Figures 1 to 3 The device uses Na2S (purity ≮95%) as an example to electrolyze and regenerate metallic sodium and elemental sulfur. The specific method includes:

[0076] Step 1: Dissolve the raw materials: Place Na2S (purity ≮95%) in a drying oven, set the temperature to 100°C, and dehydrate for 5 hours. X In the raw material area of ​​the device, the dried Na2S is dissolved in the DMF aprotic solvent at room temperature to obtain a DMF solution of Na2S (the dissolution process is sealed and nitrogen protected) to obtain an anode electrolyte solution.

[0077] Step 2 Preheating the electrolytic Na2SX Device: In electrolysis of Na2S X Nitrogen was introduced into the anode and cathode regions of the device, 500 g of anode electrolyte solution was added to the anode region, 5 g of carbon nanotubes with a radial dimension of 20 nm and an axial dimension of 100 μm were added, heating was turned on and the temperature was raised to 100°C, and 50 g of liquid metal sodium was injected into the cathode.

[0078] Step 3 Electrolysis: Turn on the power supply at 100°C to electrolyze Na2S X The device applies a voltage of 1.7V; at the same time, a precision metering pump is used to pump the anolyte solution into the electrolytic Na2S X In the anode area of ​​the device, the raw material metering pump rate was adjusted to 100 g / h to maintain the liquid level of the electrolyte in the anode area and the liquid level of the liquid sodium in the cathode area.

[0079] Step 4 Product separation: Metallic sodium is generated in the cathode area and leaves the electrolytic Na2S through the liquid sodium outlet under the pressure of nitrogen. X The device enters the sodium storage tank; elemental sulfur is generated in the anode area and dissolved in the electrolyte solution. When the content of elemental sulfur in the electrolyte solution reaches 10wt%, the electrolyte solution (containing elemental sulfur) is led out through the anode area to the elemental sulfur crystallization separation equipment, the temperature is reduced to 65°C, sulfur crystals appear, and are deposited at the bottom of the filter under the action of centrifugal force. The desulfurization solvent passes through the filter and returns to the non-protonic solvent inlet of the raw material area. The purity of sulfur is analyzed, the electrolysis potential and current density are recorded, and the energy consumption is calculated. The results are shown in Table 1.

[0080] Example 2

[0081] The electrolysis process is the same as in Example 1, except that:

[0082] In step 1, Na2S (purity ≮ 95%) is placed in a drying oven protected by nitrogen, the temperature is set at 150°C, and the constant temperature dehydration is performed for 4 hours. X In the raw material area of ​​the device, the dried Na2S is dissolved in the DMSO aprotic solvent at a dissolution temperature of 40°C to obtain a DMSO solution of Na2S (the dissolution process is sealed and protected by nitrogen).

[0083] In step 2, the amount of carbon nanotubes was changed to 10 g, and the remaining steps were the same as in Example 1.

[0084] In step 3, when the temperature rises to 120°C, turn on the power supply to electrolyze Na2S X The device applies a voltage of 1.8V; at the same time, a precision metering pump is used to pump the anode electrolyte solution into the electrolytic Na2S X In the anode area of ​​the device, the raw material metering pump rate was adjusted to 150 g / h to maintain the liquid level of the electrolyte in the anode area and the liquid level of the liquid sodium in the cathode area.

[0085] In step 4, metallic sodium is generated in the cathode region and leaves the electrolytic Na2S through the liquid sodium outlet under the pressure of nitrogen. X The device enters the sodium storage tank; elemental sulfur is generated in the anode area and dissolved in the electrolyte solution. When the content of elemental sulfur in the electrolyte solution reaches 20wt%, the electrolyte solution (containing elemental sulfur) is led out through the anode area to the elemental sulfur crystallization separation equipment, the temperature is reduced to 70°C, sulfur crystals appear, and are deposited at the bottom of the filter under the action of centrifugal force. The desulfurization solvent passes through the filter and returns to the non-protonic solvent inlet of the raw material area. The purity of sulfur is analyzed, the electrolysis potential and current density are recorded, and the energy consumption is calculated. The results are shown in Table 1.

[0086] Example 3

[0087] The electrolysis process is the same as in Example 1, except that:

[0088] In step 1, Na2S (purity ≮ 95%) is placed in a drying oven protected by nitrogen, the temperature is set to 300°C, and the constant temperature is used for dehydration for 3 hours. X In the raw material area of ​​the device, the dried Na2S is dissolved in the DMI aprotic solvent at a dissolution temperature of 60°C to obtain a Na2S DMI solution (the dissolution process is sealed and protected by nitrogen).

[0089] In step 2, the amount of carbon nanotubes was changed to 20 g, and the remaining steps were the same as in Example 1.

[0090] In step 3, when the temperature rises to 140°C, turn on the power supply to electrolyze Na2S X The device applies a voltage of 1.9V; at the same time, a precision metering pump is used to pump the anolyte solution into the electrolytic Na2S X In the anode area of ​​the device, the raw material metering pump rate was adjusted to 200 g / h to maintain the liquid level of the electrolyte in the anode area and the liquid level of the liquid sodium in the cathode area.

[0091] In step 4, metallic sodium is generated in the cathode region and leaves the electrolytic Na2S through the liquid sodium outlet under the pressure of nitrogen. X The device enters the sodium storage tank; elemental sulfur is generated in the anode area and dissolved in the electrolyte solution. When the content of elemental sulfur in the electrolyte solution reaches 25wt%, the electrolyte solution (containing elemental sulfur) is led out through the anode area to the elemental sulfur crystallization separation equipment, the temperature is reduced to 75°C, sulfur crystals appear, and are deposited at the bottom of the filter under the action of centrifugal force. The desulfurization solvent passes through the filter and returns to the non-protonic solvent inlet of the raw material area. The purity of sulfur is analyzed, the electrolysis potential and current density are recorded, and the energy consumption is calculated. The results are shown in Table 1.

[0092] Example 4

[0093] The electrolysis process is the same as in Example 1, except that:

[0094] In step 1, Na2S (purity ≮ 95%) is placed in a drying oven protected by nitrogen, the temperature is set to 300°C, and the constant temperature is used for dehydration for 3 hours. X In the raw material area of ​​the device, the dried Na2S is dissolved in the aprotic solvent N-methylpyrrolidone at a dissolution temperature of 60°C to obtain an N-methylpyrrolidone solution of Na2S (the dissolution process is sealed and protected by nitrogen).

[0095] In step 2, the amount of carbon nanotubes was changed to 25 g, and the remaining steps were the same as in Example 1.

[0096] In step 3, when the temperature rises to 160°C, turn on the power supply to electrolyze Na2S X The device applies a voltage of 2.0V; at the same time, a precision metering pump is used to pump the anolyte solution into the electrolytic Na2S X In the anode area of ​​the device, the raw material metering pump rate was adjusted to 300 g / h to maintain the liquid level of the electrolyte in the anode area and the liquid level of the liquid sodium in the cathode area.

[0097] In step 4, metallic sodium is generated in the cathode region and leaves the electrolytic Na2S through the liquid sodium outlet under the pressure of nitrogen. X The device enters the sodium storage tank; elemental sulfur is generated in the anode area and dissolved in the electrolyte solution. When the content of elemental sulfur in the electrolyte solution reaches 30wt%, the electrolyte solution (containing elemental sulfur) is led out through the anode area to the elemental sulfur crystallization separation equipment, the temperature is reduced to 65°C, sulfur crystals appear, and are deposited at the bottom of the filter under the action of centrifugal force. The desulfurization solvent passes through the filter and returns to the non-protonic solvent inlet of the raw material area. The purity of sulfur is analyzed, the electrolysis potential and current density are recorded, and the energy consumption is calculated. The results are shown in Table 1.

[0098] Example 5

[0099] use Figures 1 to 3 The device is used to electrolyze and regenerate metallic sodium and elemental sulfur using sodium disulfide Na2S (x=2) (purity≮95%) as an example. The specific method is the same as that in Example 1. The purity of sulfur is analyzed, the electrolysis potential and current density are recorded, and the energy consumption is calculated. The results are shown in Table 1.

[0100] Example 6

[0101] use Figures 1 to 3 The device is used to electrolyze and regenerate metallic sodium and elemental sulfur using sodium hexasulfide Na2S (x=6) (purity≮95%) as an example. The specific method is the same as that in Example 1. The purity of sulfur is analyzed, the electrolysis potential and current density are recorded, and the energy consumption is calculated. The results are shown in Table 1.

[0102] Comparative Example 1

[0103] The method for recovering alkali metal and sulfur from alkali metal sulfides and polysulfides mentioned in patent CN 106757146B is used to electrolyze Na2S (purity ≮ 95%). 2 The NaSICON membrane (conductivity of 6200μS / cm) was sealed to a bracket made of non-conductive material, aluminum was used as the anode and aluminum was used as the cathode. At a temperature of 150°C, a voltage of 2.2V was applied to electrolyze the tetraethylene glycol dimethyl ether solution of Na2S with a processing capacity of 9.60g / h, producing metallic sodium and sulfur, and then continuously removing liquid metallic sodium and liquid sulfur. The purity of sulfur was analyzed, the electrolysis potential and current density were recorded, and the energy consumption was calculated. The results are shown in Table 1.

[0104] Comparative Example 2

[0105] There is no tin-sodium alloy attached to the inner side of the solid sodium ion membrane B, and the rest is the same as in Example 4. The purity of sulfur was analyzed, the electrolysis potential and current density were recorded, and the energy consumption was calculated. The results are shown in Table 1.

[0106] Comparative Example 3

[0107] No carbon nanotubes were added to the electrolyte solution in the anode region, and the rest was the same as in Example 4. The purity of sulfur was analyzed, the electrolysis potential and current density were recorded, and the energy consumption was calculated. The results are shown in Table 1.

[0108] Table 1 shows the results of using Na2S in Examples 1 to 6 and Comparative Examples 1 to 3. X Technical parameters and energy consumption indicators for electrolytic regeneration of metallic sodium and elemental sulfur.

[0109] Table 1. Na2S X Technical parameters and energy consumption indicators for electrolytic regeneration of metallic sodium and elemental sulfur

[0110]

[0111] It can be seen from Table 1 that for the electrolysis of Na2S X There is a linear relationship between current density and processing capacity. Under the same current density, the voltage used in the electrolysis device and electrolysis method used in Examples 1 to 6 of the present invention is lower, which can be as low as 1.7V, and the energy consumption can be as low as 8.73MJ / kg sodium. The purity of the obtained elemental sulfur is higher, reaching 99.9%; and it is safe and reliable during operation, which is significantly better than Comparative Example 1. In addition, it can be seen from Example 4 and Comparative Example 2 that the tin-sodium alloy technology used in the cathode region of the present invention has a significant effect on the electrolysis of Na2S XThe energy consumption of the electrolysis system plays a key role. Under the condition of electrolyzing Na2S at the same current density, Example 2 of the present invention uses the tin-sodium alloy technology to reduce the resistance of the electrolysis system, thereby reducing the electrolysis potential, and avoiding the dendrite phenomenon of the sodium ion conductor membrane, thereby improving the safety of the electrolysis system. In addition, compared with Comparative Example 3, the carbon nanotube technology used in the anode area of ​​Example 2 and Example 4 enhances the conductivity of the anode electrolyte, improves the current efficiency of the electrolysis system, and achieves the purpose of reducing the energy consumption of electrolysis.

Claims

1. Electrolysis of Na2S X A system for regenerating metallic sodium and elemental sulfur, comprising: Power supply, double-chamber electrolysis of Na2S with anode and cathode separated by a solid sodium ion membrane X The device comprises a tin-sodium alloy attached to the inner side of the solid sodium ion membrane.

2. The system according to claim 1, characterized in that In the system: The anode area is equipped with a graphite crucible tube, the side line of the tube wall is provided with an electrolyte solution outlet and a carbon nanotube filter at the outlet, the bottom of the tube is provided with a raw material inlet, a raw material filter at the inlet, and a heater, the top of the tube is provided with an anode sealing cover, and the anode thermocouple insertion port is provided on the anode sealing cover; A solid sodium ion membrane, wherein the axial height of the solid sodium ion membrane is higher than the axial height of the anode graphite layer crucible tube, and a cathode sealing cover is arranged on the top of the solid sodium ion membrane; The cathode area includes a liquid metal sodium bath, a platinum wire or platinum sheet or platinum rod. A protective gas inlet pipeline and a liquid metal sodium outlet pipeline are arranged on the cathode sealing cover; the tin-sodium alloy attached to the inner side of the solid sodium ion membrane is in contact with the liquid metal sodium bath.

3. The system according to claim 2, characterized in that In the anode region: The graphite layer crucible tube includes a graphite layer, a heat-insulating layer, and a stainless steel tank body from the inside to the outside; preferably, the graphite layer is connected to the positive electrode of the power supply; and / or, the graphite layer is in close contact with the anode electrolyte solution; and / or, The anode region has a built-in heater; and / or, The anode region has a built-in thermocouple for monitoring and controlling the temperature of the anode region; and / or, The anode region is also provided with a liquid level meter for monitoring the liquid level of the solution in the anode region.

4. The system according to claim 1 or 2, characterized in that: The solid sodium ion membrane is Na + An organic or inorganic film that is a good conductor or electronic insulator; preferably, the organic film is selected from at least one of a polyolefin composite sodium ion membrane and a sodium fluorosulfonate resin membrane; and / or, the inorganic film is selected from at least one of a β-Al2O3 membrane and a NZSP membrane; and / or, The solid sodium ion membrane is a cylindrical structure, a square cylindrical structure, a star-shaped structure, a stacked structure or a sea urchin-shaped structure, preferably a cylindrical structure; and / or, The solid sodium ion membrane has a thickness of 0.1 mm to 1 mm and a conductivity of 100 μS / cm to 10000 μS / cm; and / or, The thickness of the tin-sodium alloy attached to the inner side of the solid sodium ion membrane is 10 μm to 100 μm; and / or, In the solid sodium ion membrane, the pore diameter of the micropores is 1 mm to 2 mm.

5. The system according to claim 2, characterized in that The platinum wire or platinum sheet or platinum rod is placed in a liquid sodium metal bath and connected to the negative electrode of a power source; and / or, The lower end of the protective gas inlet pipeline is arranged above the liquid level of the liquid metal sodium bath; and / or, The lower end of the liquid metal sodium outlet pipeline is arranged below the liquid level of the liquid metal sodium bath; and / or, The cathode region has a built-in thermocouple for monitoring and controlling the temperature of the cathode region; and / or, The cathode region is also provided with a liquid level meter for monitoring the liquid level of the liquid metal sodium bath in the cathode region; and / or, The system also includes a raw material area and a product area. The raw material area includes Na2S X dissolving, stirring and feeding equipment; the product area includes a liquid metal sodium storage tank and an elemental sulfur crystallization separation device, the liquid metal sodium storage tank is connected to the cathode area, and the inlet of the elemental sulfur crystallization separation device is connected to the anode electrolyte solution outlet of the anode area, wherein the elemental sulfur crystallization separation equipment includes an electrolyte solution inlet, a desulfurization solvent outlet, a rotating shaft and a filter.

6. Electrolysis of Na2S X A method for regenerating metallic sodium and elemental sulfur, comprising electrolyzing Na2S according to any one of claims 1 to 5 X The system for regenerating metallic sodium and elemental sulfur converts Na2S X The step of electrolyzing to generate metallic sodium and elemental sulfur, preferably, the method comprises the following steps: (1) Raw material preparation: sodium sulfide and / or sodium polysulfide is subjected to low temperature drying treatment, and then dissolved in an aprotic solvent to obtain an anode electrolyte solution; (2) Preheating and electrolysis of Na2S X Device: In electrolysis of Na2S X A protective gas is introduced into the anode and cathode regions of the device, an anolyte solution is added to the anode region and heating begins, and liquid metal sodium is added to the cathode region; (3) Electrolysis: Turn on the power supply to perform electrolysis. Under the action of the potential of the external power supply, the Na + Passing through the solid sodium ion membrane, it enters the cathode region and obtains electrons to be reduced to metallic sodium. At the same time, the sulfur anions lose electrons in the anode region to generate elemental sulfur. (4) Product separation: For the metallic sodium in the cathode area, the liquid metallic sodium is sent to the metallic sodium storage tank under the pressure of the protective gas. For the elemental sulfur in the anode area, the anode electrolyte solution containing elemental sulfur in the anode area is led out to the elemental sulfur crystallization separation equipment for separation.

7. The method according to claim 6, characterized in that In the step (1): The aprotic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone and N-methylpyrrolidone; and / or, The purity of the sodium sulfide and sodium polysulfide is not less than 95%; and / or, The low temperature drying treatment condition is 100°C to 300°C for dehydration for 3h to 5h; and / or, The anolyte solution is a saturated solution of sodium sulfide and / or sodium polysulfide; The electrolyte solution contains carbon nanotubes. Preferably, the amount of the carbon nanotubes is 1wt% to 5wt% of the electrolyte solution. The radial size of the carbon nanotubes is 10nm to 20nm, and the axial size is 10μm to 100μm. And / or, The dissolving temperature is 20°C to 60°C.

8. The method according to claim 6, characterized in that In the step (2): The feeding equipment injects the anolyte solution into the electrolytic Na2S at a rate of 100g / h to 300g / h. X anode region of the device; and / or, Electrolysis of Na2S X The device is heated to above 98°C and liquid metallic sodium is added to the cathode region.

9. The method according to claim 6, characterized in that In the step (3): The electrolysis temperature is 100°C to 160°C; and / or, External power is applied to the electrolytic Na2S X The DC constant voltage potential of the device is between 1.7V and 2.0V; and / or, When the concentration of elemental sulfur in the electrolyte solution of the anode region reaches 10wt% to 30wt%, it is introduced to the elemental sulfur crystallization separation equipment.

10. The method according to claim 6, characterized in that During the electrolysis process, the liquid level in the anode region is maintained by pumping the anode electrolyte solution in the raw material region into the anode region, and the liquid level in the cathode region is maintained by introducing a protective gas to drive the liquid metal sodium to the cathode region under pressure; and / or, The separation operation of elemental sulfur includes: the elemental sulfur produced in the electrolysis process in the anode area is dissolved in the anode electrolyte solution, and then electrolyzed into Na2S X The outlet of the anode electrolyte solution in the anode area of ​​the device is led to the elemental sulfur crystallization separation equipment, cooled to 65°C ~ 75°C to reduce the solubility of elemental sulfur. After reaching supersaturation, sulfur crystals are generated and sink to the bottom. The desulfurized solution can be pumped away from the bottom of the elemental sulfur crystallization separation equipment and returned to the raw material area.

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