A method for preparing sodium alcoholate using sodium slag

Abstract

The invention discloses a method for preparing sodium alcoholate using sodium slag, and the technical field of sodium slag recycling. The method comprises the following steps: placing the sodium slag in an inert solvent at a certain temperature, filtering, obtaining a mixed solution of metallic sodium and the inert solvent, and a filter residue; dropping the mixed solution into an alcohol solvent, distilling and separating after the reaction is completed, obtaining solid sodium alcoholate; adding the filter residue into an alcohol solvent, pressing and separating after the reaction is completed, obtaining a filtrate containing calcium alcoholate; adding sodium peroxide to the filtrate containing calcium alcoholate, filtering after the reaction is completed, obtaining a sodium alcoholate solution and insoluble calcium oxide, distilling and separating, and obtaining solid sodium alcoholate. The technical solution of the invention has mild reaction conditions, safe operation, and low energy consumption. By using sodium peroxide for decalcification, the conversion rate of sodium alcoholate is further improved, the recovery rate of metallic sodium in the sodium slag reaches more than 98%, and the influence of impurities in the sodium slag on the quality of solid sodium alcoholate is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of recycling sodium slag, and in particular to a method for preparing sodium alcoholate by using sodium slag. Background Art

[0002] Sodium metal is a common alkali metal. At present, the mainstream method for preparing sodium metal is to use a ternary electrolyte of sodium chloride, calcium chloride, and barium chloride to lower the melting point of the mixed salt and then electrolyze it to generate sodium metal and chlorine. After the above steps, a certain amount of electrolytic slag, that is, sodium slag, will remain after the electrolytic cell separates the sodium metal. At present, the amount of sodium slag generated is 1.5~3% of the sodium metal output. The sodium slag contains up to 60~85% sodium metal and 15~40% calcium metal. Sodium slag is cheap and difficult to store. Because sodium metal and calcium metal are very easy to react chemically in air or water, the sodium slag treatment is difficult and there are safety hazards. Therefore, how to safely dispose of and recycle sodium slag is a long-standing technical problem for sodium metal production companies.

[0003] The existing sodium slag treatment methods mainly include alcoholysis, vacuum distillation, melt filter press and other methods. However, these methods are difficult to use in production due to technical difficulties or safety issues. At present, factories producing sodium metal still sell sodium slag at a low price. Developing a process for safe disposal of sodium slag and recovery of sodium resources has become a problem that needs to be solved urgently in the sodium metal industry. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for preparing sodium alcoholate using sodium slag, which is used to overcome the problems of low sodium recovery rate and high energy consumption in the existing sodium slag treatment process.

[0005] In a first aspect, the present invention provides a method for preparing sodium alkoxide using sodium slag, comprising the following steps:

[0006] The sodium slag is placed in an inert solvent, wherein the temperature of the inert solvent is higher than the melting point of metallic sodium and lower than the melting points of other metal impurities in the sodium slag, and filtered to obtain a mixed solution of metallic sodium and the inert solvent, and a filter residue.

[0007] The mixed solution is added dropwise to an alcohol solvent under stirring. After the reaction is completed, distillation separation is performed at a temperature not higher than the decomposition temperature of the sodium alcoholate to obtain solid sodium alcoholate.

[0008] The filter residue is added into an alcohol solvent under stirring, and after the reaction is completed, the filter is pressed and separated to obtain a filtrate containing calcium alcoholate.

[0009] Sodium peroxide is added to the filtrate containing calcium alkoxide, and after the reaction is completed, the filtrate is filtered to obtain a sodium alkoxide solution and insoluble calcium oxide, and the sodium alkoxide solution is distilled and separated at a temperature not higher than the decomposition temperature of the sodium alkoxide to obtain solid sodium alkoxide.

[0010] Compared with the prior art, the invention firstly utilizes the characteristic of low melting point of metallic sodium to purify metallic sodium in sodium slag by using an inert solvent at a specific temperature, filters to obtain a filtrate, i.e., a mixed solution of metallic sodium and the inert solvent, and drops the filtrate into an alcohol solvent for reaction to obtain a sodium alcoholate solution. This step can separate 90% of metallic sodium in the sodium slag and convert it into sodium alcoholate. Then, the filter residue is added into an alcohol solvent for reaction, metallic calcium in the filter residue and residual metallic sodium are further reacted with the alcohol solvent to generate calcium alcoholate and sodium alcoholate dissolved in the alcohol solvent. Through filter pressing separation, the calcium alcoholate and sodium alcoholate mixed solution can be further separated from insoluble impurities. Sodium peroxide is added into the mixed solution, and the sodium peroxide and the calcium alcoholate undergo a substitution reaction to further obtain a sodium alcoholate solution. The sodium alcoholate solutions obtained in two ways are subjected to distillation separation to obtain solid sodium alcoholate with a purity of ≥99%, thereby achieving full recovery and utilization of the sodium in the sodium slag. The technical solution of the present invention has mild reaction conditions, safe operation and low energy consumption, and effectively reduces the influence of impurities in the sodium slag on the quality of solid sodium alcoholate. In addition, the present invention further recovers the sodium in the filter residue on the basis of purifying the sodium slag by using an inert solvent, and decalcifies the filter residue by using sodium peroxide, thereby improving the conversion rate of the sodium alcoholate, and making the recovery rate of the sodium in the sodium slag reach more than 98%.

[0011] Furthermore, the amount of sodium slag added is 15% to 25% of the mass of the inert solvent.

[0012] Furthermore, the dropping rate of the mixed solution is: 5-10 kg / h of the mixed solution is added to every 10 L of alcohol solvent; or, the mass ratio of the filter residue to the alcohol solvent is (120-200): (1000-3000).

[0013] The above technical solution defines the dripping rate of the mixed solution, which can make the metallic sodium in the mixed solution fully react with the alcohol solvent to generate sodium alcoholate. In addition, the above technical solution also defines the mass ratio of the filter residue to the alcohol solvent, which can make the metallic calcium and the residual metallic sodium in the filter residue fully react with the alcohol solvent to generate calcium alcoholate and sodium alcoholate.

[0014] Furthermore, during the distillation separation, fractions at different temperatures are collected and the inert solvent and / or alcohol solvent are recovered.

[0015] Furthermore, during the filter press separation, multi-stage filtration is performed using filter screens with pore sizes of 8-12 mm, 4-6 mm, and 1.5-2.5 mm in sequence, with a pressure of 0.05-0.5 MPa.

[0016] The above technical scheme stipulates that filter screens with different pore sizes are used for multi-stage filtration during pressure filtration separation, and also stipulates the pressure during pressure filtration separation, which can effectively remove impurities in the filter residue that do not react with and are insoluble in alcohol solvents, thereby avoiding these impurities from affecting the purity of the solid sodium alcohol obtained by the final distillation.

[0017] Furthermore, the molar ratio of the amount of sodium peroxide added to the content of calcium alkoxide in the filtrate containing calcium alkoxide is 1:1.

[0018] The above technical solution limits the amount of sodium peroxide added. The sodium peroxide can undergo a replacement reaction with calcium alcoholate in the filtrate to generate sodium alcoholate and insoluble calcium oxide. The insoluble calcium oxide can be removed by filtration, thereby achieving the purpose of removing metallic calcium impurities in the filter residue.

[0019] Furthermore, placing the sodium slag in an inert solvent includes: heating the sodium slag to 100-120° C., fully melting the metallic sodium in the sodium slag under stirring to obtain a solid-liquid mixture, and dripping the solid-liquid mixture into the inert solvent, wherein the amount of the solid-liquid mixture dripped into the inert solvent per hour is 10%-30% of the mass of the inert solvent.

[0020] In the above technical solution, the sodium slag is first heated to 100-120°C to fully melt the metallic sodium, and then the obtained solid-liquid mixture is added dropwise to an inert solvent, so that the molten metallic sodium can be more evenly dispersed in the inert solvent, which is convenient for subsequent filtration and separation.

[0021] Furthermore, before the sodium alcoholate solution is distilled and separated, a dehydrating agent is added to the sodium alcoholate solution to react the sodium hydroxide in the sodium alcoholate solution with the alcohol solvent to generate sodium alcoholate; the dehydrating agent is any one or more of molecular sieves, sodium carbonate or resins.

[0022] The above technical solution adds a dehydrating agent to the sodium alcoholate solution before distillation separation, which can promote the reaction of sodium hydroxide and alcohol solvent in the sodium alcoholate solution to proceed in a positive direction, generate the target product sodium alcoholate, and improve the conversion rate of the sodium alcoholate.

[0023] Furthermore, the amount of water removal reagent added is 0.1% to 1% of the mass of the sodium alcoholate solution.

[0024] Furthermore, the temperature of the inert solvent is 100-130° C., the stirring rate is 40 r / min-120 r / min, the inert solvent is a hydrocarbon solvent and / or an ether solvent, and the alcohol solvent includes any one or more of methanol, ethanol, isopropanol, n-butanol, tert-butanol, pentanol or fluoroalcohol. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] In a first aspect, an embodiment of the present invention provides a method for preparing sodium alkoxide using sodium slag, comprising the following steps:

[0027] S1. placing the sodium slag in an inert solvent, wherein the temperature of the inert solvent is higher than the melting point of metallic sodium and lower than the melting points of other metal impurities in the sodium slag, filtering to obtain a mixed solution of metallic sodium and the inert solvent, and filter residue.

[0028] The amount of sodium slag added is 15% to 25% of the mass of the inert solvent. For example, the amount of sodium slag added can be 15%, 20% or 25% of the mass of the inert solvent, depending on whether the metallic sodium in the sodium slag can be fully dispersed in the inert solvent after melting.

[0029] Furthermore, the above-mentioned placing of the sodium slag in an inert solvent may also include the following steps:

[0030] The sodium slag is heated to 100-120°C and slowly stirred at a speed of 10-20 r / min to fully melt the metallic sodium in the sodium slag and form a solid-liquid mixture with other unmelted components. Under stirring at 40-120 r / min, the obtained solid-liquid mixture is dripped into an inert solvent, and the hourly dripping amount of the solid-liquid mixture is 10%-30% of the mass of the inert solvent.

[0031] The sodium slag in the above step can be selected from the electrolytic sodium slag remaining after the electrolytic cell separates the metallic sodium when the ternary electrolyte of sodium chloride, calcium chloride and barium chloride is used to reduce the melting point of the mixed salt and then electrolyze to prepare metallic sodium. In addition to metallic sodium, the sodium slag also contains impurities such as metallic calcium, sodium chloride, calcium chloride, barium chloride, graphite, calcium oxide, and sodium oxide.

[0032] Furthermore, in the above steps, the temperature of the inert solvent is 100-130° C., and the type of the inert solvent is a hydrocarbon solvent and / or an ether solvent. For example, the inert solvent can be selected from any one or more of ethylene glycol dimethyl ether, butyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, trioxymethylene, anisole, or 1,4-dioxane, and the inert solvent does not react with the sodium slag and the alcohol solvent, so that the molten metallic sodium can be dispersed in the inert solvent, and separated from the non-molten solid impurities with a higher melting point in the sodium slag by filtering to obtain a mixed solution of metallic sodium and the inert solvent, and a filter residue.

[0033] Furthermore, in the above step, a filter with a pore size of 2 mm can be selected for filtration. Preferably, in order to prevent clogging of the filter and improve the filtration efficiency, multi-stage filtration can be performed in sequence with filter screens with pore sizes of 10 mm, 5 mm, and 2 mm. That is, according to the particle size of the solid impurities, first use filter screens with pore sizes of 10 mm and 5 mm to separate solid impurities with larger particle sizes, and then use a filter screen with a pore size of 2 mm to separate solid impurities with smaller particle sizes, collect the filtrate, and mix the filter residues obtained at each stage for standby use.

[0034] The above technical solution uses an inert solvent to preferentially purify more than 90% of the metallic sodium in the sodium slag. The purified metallic sodium has a smooth surface and no voids, and can react smoothly with alcohol solvents at room temperature in subsequent steps, reducing the risk of reaction. At the same time, since 90% of the metallic sodium has been separated out, the overall activity of the filter residue is reduced, and when reacting with alcohol solvents, there will be no rushing or deflagration due to rapid heat release.

[0035] S2. Under stirring, the mixed solution is added dropwise to an alcohol solvent. After the reaction is completed, distillation is performed at a temperature not higher than the decomposition temperature of the sodium alcoholate to obtain solid sodium alcoholate.

[0036] Furthermore, the alcohol solvent in the above steps can be selected from any one or more of methanol, ethanol, isopropanol, n-butanol, tert-butanol, amyl alcohol or fluoroalcohol at room temperature.

[0037] Wherein, the stirring rate is 40-120r / min; the dripping rate of the mixed solution is: 5-10kg / h of the mixed solution is dripped into every 10L of alcohol solvent. For example, 5kg / h, 6kg / h, 7kg / h, 8kg / h, 9kg / h or 10kg / h of the mixed solution can be dripped into every 10L of alcohol solvent. It should be understood that different dripping rates are selected according to different types of alcohol solvents, so that the metallic sodium in the mixed solution can fully react with the alcohol solvent to generate sodium alcoholate, and the generated sodium alcoholate is dissolved in the alcohol solvent.

[0038] The reaction in the above steps is that the metallic sodium in the mixed solution reacts with the alcohol solvent to generate sodium alcoholate and hydrogen, so after the dropwise addition is completed, the room temperature is maintained for 1 to 3 hours until no bubbles emerge on the surface of the solution, indicating that the reaction has ended. After the reaction is completed, a mixed solution containing sodium alcoholate, alcohol solvent and inert solvent is obtained.

[0039] When the above steps are distilled to separate and obtain solid sodium alcoholate, in order to prevent the sodium alcoholate from decomposing at high temperature, it should be noted that the distillation temperature cannot be higher than the decomposition temperature of the sodium alcoholate, and the temperature is generally controlled not to exceed 100° C. As the distillation proceeds, the solvent gradually decreases, and the sodium alcoholate gradually precipitates until the solvent is evaporated and the sodium alcoholate is completely precipitated to obtain solid sodium alcoholate. It should be understood that different distillation temperatures need to be selected according to the boiling points of the selected alcohol solvents and inert solvents during distillation.

[0040] For example, when the alcohol solvent is methanol and the inert solvent is ethylene glycol dimethyl ether, the boiling point of methanol is 64.7° C., the boiling point of ethylene glycol dimethyl ether is 85° C., and the decomposition temperature of sodium methoxide is 127° C. During distillation, the temperature can be first raised to 70° C. to 80° C. to evaporate the methanol, and then the temperature can be raised to 90° C. to 110° C. to evaporate the inert solvent, and after the solvent is completely evaporated, solid sodium methoxide is obtained.

[0041] It should be noted that if the boiling point of the selected alcohol solvent or inert solvent is greater than the decomposition temperature of the sodium alkoxide, reduced pressure distillation can be selected to ensure that the sodium alkoxide does not decompose at high temperature. Preferably, in order to save resources, the alcohol solvent and the inert solvent can be recovered by condensation during distillation, and the obtained alcohol solvent can be used in step S3, and the obtained inert solvent can be reused in step S1.

[0042] In the prior art, when a solvent method is used to purify metallic sodium, a small amount of inert solvent cannot be completely separated and remains in the metallic sodium. The inventors directly use a mixed solution of metallic sodium and an inert solvent to produce solid sodium alcohol, thereby completely removing the inert solvent without increasing the processing cost.

[0043] S3. Add the filter residue into an alcohol solvent under stirring, and separate by filter pressing after the reaction is completed to obtain a filtrate containing calcium alcoholate.

[0044] In the above steps, the stirring rate is 40-120 r / min, and the mass ratio of the filter residue to the alcohol solvent is (120-200): (1000-3000). The alcohol solvent used is the same as the alcohol solvent used in step S2.

[0045] Furthermore, in the above steps, during the filter press separation, filter screens with apertures of 8 to 12 mm, 4 to 6 mm, and 1.5 to 2.5 mm are sequentially used for multi-stage filtration, and the pressure is 0.05 to 0.5 MPa, and a filtrate containing calcium alcohol is obtained after multi-stage filtration. Multi-stage filtration is performed step by step according to the particle size of solid impurities in the solution. A filter screen with an aperture of 8 to 12 mm is first used to remove large particles of impurities in the solution, and then filter screens with apertures of 4 to 6 mm and 1.5 to 2.5 mm are used in sequence to remove medium and small particles of impurities, which can prevent the filter screen from being blocked and improve the filtration efficiency.

[0046] The filter used in filter press separation can be a two-in-one filter, a box filter, a bag filter, a push filter or a cartridge filter.

[0047] The components of the filter residue in the above steps are residual metallic sodium, and impurities such as metallic calcium, sodium chloride, calcium chloride, barium chloride, graphite, calcium oxide, and sodium oxide. When the filter residue is added with an alcohol solvent, the metallic sodium remaining in the filter residue reacts with the alcohol solvent to form sodium alcoholate, and the metallic calcium reacts with the alcohol solvent to form calcium alcoholate, and the sodium alcoholate and calcium alcoholate are dissolved in the alcohol solvent, while other solid impurities that do not react with or dissolve in the alcohol solvent are separated and removed by filter pressing.

[0048] S4. Add sodium peroxide to the filtrate containing calcium alkoxide, filter after the reaction is completed to obtain a sodium alkoxide solution and insoluble calcium oxide, and distill and separate the sodium alkoxide solution at a decomposition temperature not higher than that of the sodium alkoxide to obtain solid sodium alkoxide.

[0049] Furthermore, the molar ratio of the amount of sodium peroxide added in the above step to the content of calcium alkoxide in the filtrate containing calcium alkoxide is 1:1. After adding an appropriate amount of sodium peroxide, sodium peroxide undergoes a replacement reaction with the calcium alkoxide in the filtrate to generate sodium alkoxide and insoluble calcium oxide. The insoluble calcium oxide is removed by a subsequent filtration step, and the filtration pore size is 0.05-5 mm.

[0050] Furthermore, before distilling and separating the sodium alcoholate solution, the above step further includes adding a dehydrating agent to the sodium alcoholate solution, wherein the dehydrating agent is any one or more of a molecular sieve, sodium carbonate or a resin. For example, the molecular sieve can be 4A molecular sieve or 5A molecular sieve; the resin can be ion exchange resin or chelating resin.

[0051] The amount of the dehydrating agent added is 0.1% to 1% of the mass of the sodium alcoholate solution. For example, the amount of the dehydrating agent added can be 0.1%, 0.3%, 0.5%, 0.8% or 1% of the mass of the sodium alcoholate solution.

[0052] It should be understood that the sodium alcoholate solution obtained after filtering in the above steps will contain a small amount of water, mainly a small amount of water in the alcohol solvent and a small amount of water entering from the environment. When these waters encounter the impurity sodium oxide in the filter residue in step S3, they will react with it to generate sodium hydroxide, so that the sodium alcoholate solution contains a small amount of sodium hydroxide. Sodium hydroxide reacts with the alcohol solvent to generate sodium alcoholate and water. This reaction is a reversible reaction. Therefore, before the sodium alcoholate solution is distilled and separated, the inventor adds a dehydrating agent to the sodium alcoholate solution to remove the water generated by the reversible reaction, so that the reaction is forward to generate sodium alcoholate, thereby further improving the conversion rate of sodium alcoholate and the recovery rate of metallic sodium.

[0053] The sodium alcoholate solution obtained after filtration in the above step contains sodium alcoholate and alcohol solvent. During distillation separation, in order to prevent the sodium alcoholate from decomposing at high temperature, the distillation temperature should be greater than the boiling point of the alcohol solvent and less than the decomposition temperature of the sodium alcoholate. The above method can be used for details. Preferably, in order to save resources, the evaporated alcohol solvent can be recovered by condensation, and the obtained alcohol solvent can be reused in step S3.

[0054] In order to better illustrate the technical solution of the present invention, the present invention also provides the following specific examples. It should be understood that the raw materials used in the following examples are all commercially available raw materials unless otherwise specified. Example 1

[0055] This embodiment provides a method for preparing sodium alkoxide using sodium slag, comprising the following steps:

[0056] S1. Heat 15g of sodium slag, wherein the percentage of metallic sodium in the sodium slag is 82%, to 110°C and slowly stir at a rate of 15r / min until all the metallic sodium in the sodium slag is melted and forms a solid-liquid mixture with other unmelted components.

[0057] 100 g of dibutyl ether was heated to 110° C. and the solid-liquid mixture was added dropwise to the dibutyl ether under stirring at 80 r / min. The amount added per hour was 20% of the mass of the dibutyl ether.

[0058] After the dropwise addition was completed, multi-stage filtration was performed using filter screens with pore sizes of 10 mm, 5 mm, and 2 mm in sequence to obtain 110 g of a mixed solution of metallic sodium and butyl ether and 5 g of filter residue.

[0059] S2. Add the mixed solution of sodium metal and butyl ether to 45g of methanol at 25°C under stirring at 80r / min. Add 7.5kg / h of the mixed solution to every 10L of methanol. After the addition is completed, keep the room temperature for 2h until no bubbles emerge on the surface.

[0060] The solution after the reaction was completed was placed in a distillation flask, heated to 80°C, and the fraction 1 methanol condensed through the condenser was collected; after the methanol was collected, the vacuum pump was turned on, the pressure in the distillation flask was reduced to -0.083MPa, the temperature was raised to 96°C, and the fraction 2 butyl ether condensed through the condenser was collected until the solution was completely evaporated to obtain 26.43g of solid sodium methoxide.

[0061] The collected methanol is used in step S3, and the collected butyl ether is reused in step S1.

[0062] S3. Under stirring at 80 r / min, add 5 g of the filter residue obtained after filtering in step S1 into 80 g of methanol to react until no bubbles appear on the surface of the solution.

[0063] After the reaction was completed, the solution was filtered in multiple stages using filter screens with pore sizes of 10 mm, 5 mm, and 2 mm, respectively, with the pressure controlled at 0.3 MPa to obtain 84.09 g of filtrate containing calcium methoxide.

[0064] S4, detect the content of calcium methoxide in the filtrate containing calcium methoxide as 0.05mol, add 0.05mol sodium peroxide thereto, sodium peroxide reacts with calcium methoxide to generate sodium methoxide and insoluble calcium oxide, filter the reacted solution using a filter with an aperture of 1mm, remove insoluble calcium oxide 4.33g, and obtain sodium methoxide solution. 0.5g of 4A molecular sieve is added to the sodium methoxide solution as a water-removing agent, so that the sodium hydroxide in the sodium methoxide solution reacts with methanol to generate sodium methoxide. Filter the 4A molecular sieve using a filter with an aperture of 1mm to remove.

[0065] The sodium methoxide solution was placed in a distillation flask, heated to 80° C., and the methanol fraction condensed by the condenser was collected until the solution was completely evaporated to dryness, thereby obtaining 2.21 g of solid sodium methoxide. The collected methanol was reused in step S3. Example 2

[0066] This embodiment provides a method for preparing sodium alkoxide using sodium slag, comprising the following steps:

[0067] S1, 2000g of diethylene glycol dimethyl ether is warming up to 100 DEG C, 400g of sodium slag, wherein the percentage of metallic sodium in the sodium slag is 81.84%, is placed in the diethylene glycol dimethyl ether after heating up, and the metallic sodium in the sodium slag is all melted. After melting, the filter screen with an aperture of 10mm, 5mm, and 2mm is used to carry out multi-stage filtration successively, and a mixed solution of metallic sodium and diethylene glycol dimethyl ether 2300g, and filter residue 100g are obtained.

[0068] S2. Add the mixed solution of sodium metal and diethylene glycol dimethyl ether to 2500g of ethanol at 25°C under stirring at 40r / min, adding 5kg / h of the mixed solution to every 10L of ethanol. After the addition is completed, keep the room temperature for 3h until no bubbles emerge on the surface.

[0069] The solution after the reaction was completed was placed in a distillation flask, heated to 80°C, and the fraction 1 ethanol condensed through the condenser was collected; after the ethanol was collected, the vacuum pump was turned on, the pressure in the distillation flask was reduced to -0.085MPa, the temperature was raised to 90°C, and the fraction 2 diethylene glycol dimethyl ether condensed through the condenser was collected until the solution was completely evaporated to obtain 907g of solid sodium ethoxide.

[0070] The collected ethanol is used in step S3, and the collected diethylene glycol dimethyl ether is reused in step S1.

[0071] S3. Under stirring at 40 r / min, add 100 g of the filter residue obtained after filtering in step S1 to 1200 g of ethanol to react until no bubbles appear on the surface of the solution.

[0072] After the reaction was completed, the solution was filtered in multiple stages using filter screens with pore sizes of 10 mm, 5 mm, and 2 mm, respectively, with the pressure controlled at 0.05 MPa to obtain 1288.16 g of filtrate containing calcium ethoxide.

[0073] S4, detecting the content of calcium ethoxide in the above-mentioned filtrate containing calcium ethoxide is 2 mol, 2 mol of sodium peroxide is added thereto, sodium peroxide reacts with calcium ethoxide to generate sodium ethoxide and insoluble calcium oxide, and the reacted solution is filtered using a filter with a pore size of 0.8 mm to remove 213 g of insoluble calcium oxide to obtain a sodium ethoxide solution.

[0074] The sodium ethoxide solution was placed in a distillation flask, heated to 80°C, and the ethanol fraction condensed by the condenser was collected until the solution was completely evaporated to dryness, thereby obtaining 51.87 g of solid sodium ethoxide. The collected ethanol was reused in step S3. Example 3

[0075] This embodiment provides a method for preparing sodium alkoxide using sodium slag, comprising the following steps:

[0076] S1. 150 g of ethylene glycol diethyl ether was heated to 110°C, and 25 g of sodium slag, wherein the percentage of metallic sodium in the sodium slag was 78%, was placed in an inert solvent after heating to melt all the metallic sodium in the sodium slag. After melting, multi-stage filtration was performed with filter screens having apertures of 10 mm, 5 mm, and 2 mm in sequence to obtain 167 g of a mixed solution of metallic sodium and ethylene glycol diethyl ether, and 8 g of filter residue.

[0077] S2. Add the mixed solution of sodium metal and ethylene glycol diethyl ether to 250 g of tert-butyl alcohol at 25°C under stirring at 120 r / min. Add 10 kg / h of the mixed solution to every 10 L of tert-butyl alcohol. After the addition is completed, keep the room temperature for 1 hour until no bubbles emerge on the surface.

[0078] The solution after the reaction was completed was placed in a distillation flask, heated to 88°C, and the fraction 1 tert-butanol condensed through the condenser was collected; after the tert-butanol was collected, the vacuum pump was turned on, the pressure in the distillation flask was reduced to -0.8MPa, the temperature was raised to 90°C, and the fraction 2 ethylene glycol diethyl ether condensed through the condenser was collected until the solution was completely evaporated to obtain 69.4g of solid sodium tert-butoxide.

[0079] S3. Under stirring at 120 r / min, add 8 g of the filter residue obtained after filtering in step S1 to 80 g of tert-butyl alcohol to react until no bubbles appear on the surface of the solution.

[0080] After the reaction was completed, the solution was filtered in multiple stages using filter screens with pore sizes of 10 mm, 5 mm, and 2 mm, respectively, with the pressure controlled at 0.5 MPa to obtain 84.1 g of a filtrate containing calcium tert-butoxide.

[0081] S4, detect the content of calcium tert-butoxide in the filtrate containing calcium tert-butoxide for 0.06mol, add 0.06mol sodium peroxide thereto, sodium peroxide reacts with calcium tert-butoxide to generate sodium tert-butoxide and insoluble calcium oxide, filter the reacted solution using a filter with an aperture of 1mm, remove insoluble calcium oxide 5.3g, and obtain sodium tert-butoxide solution. Add 0.5g of water-removing reagent sodium carbonate to the sodium tert-butoxide solution, react the sodium hydroxide in the sodium tert-butoxide solution with the tert-butanol to generate sodium tert-butoxide. Filter and remove sodium carbonate using a filter with an aperture of 2mm.

[0082] The sodium tert-butoxide solution was placed in a distillation flask, heated to 88°C, and the tert-butanol fraction condensed through a condenser was collected until the solution was completely evaporated to dryness, thereby obtaining 11.42 g of solid sodium tert-butoxide. Comparative Example 1

[0083] Sodium alkoxide is prepared using sodium slag according to the method of Example 3, except that, in step S1, after all the metallic sodium in the sodium slag is melted, no filtering is performed, and in step S2, the obtained solid-liquid mixture is directly added dropwise to tert-butyl alcohol. Comparative Example 2

[0084] Sodium alkoxide is prepared using sodium slag according to the method of Example 1, except that, in step S1, after heating the sodium slag to melt all the metallic sodium in the sodium slag to obtain a solid-liquid mixture, the metallic sodium in the sodium slag is not purified using an inert solvent, but butyl ether, and the solid-liquid mixture is directly subjected to multi-stage filtration to obtain liquid metallic sodium and filter residue. Next, in step S2, the obtained liquid metallic sodium is added dropwise to methanol.

[0085] Test Example 1

[0086] The recovery rate of metallic sodium and the purity of solid sodium alcoholate in the sodium slag of Examples 1 to 3 and Comparative Examples 1 to 2 were calculated using the following calculation formulas. The calculation results are shown in Table 1.

[0087] Purity of solid sodium alkoxide:

[0088] ;

[0089] The calculation formula of sodium metal yield is as follows:

[0090] ;

[0091] in: represents the yield of metallic sodium; represents the theoretical mass of sodium alkoxide, represents the sum of the mass of the solid sodium alkoxide collected for the first time in step S2 and the mass of the solid sodium alkoxide collected for the second time in step S4, Represents the quality of sodium slag, Represents the purity of solid sodium alkoxide, Represents the percentage of metallic sodium in sodium slag. represents the molar mass of metallic sodium, represents the molar mass of sodium alkoxide.

[0092] Table 1

[0093]

[0094] It can be seen from the above test results that: in Comparative Example 1, after all the metallic sodium in the sodium slag in step S1 of Example 3 is melted, no filtering is performed, and the obtained solid-liquid mixture is directly added dropwise to tert-butanol in step S2, the recovery rate of metallic sodium in the sodium slag and the purity of solid sodium alcohol are reduced, indicating that after filtering to obtain a mixed solution of metallic sodium and ethylene glycol diethyl ether, and a filter residue, respectively recovering metallic sodium from the mixed solution and the filter residue can further improve the recovery rate of metallic sodium in the sodium slag and the purity of solid sodium alcohol.

[0095] Compared to Example 1, in step S1 of Comparative Example 2, after heating the sodium slag to melt all the metallic sodium in the sodium slag to obtain a solid-liquid mixture, the metallic sodium in the sodium slag is purified without using an inert solvent, butyrate, and the solid-liquid mixture is directly subjected to multi-stage filtration to obtain liquid metallic sodium and filter residue. Then, in step S2, the obtained liquid metallic sodium is added dropwise to methanol. The recovery rate of metallic sodium and the purity of solid sodium alcoholate in the sodium slag of Comparative Example 2 are both reduced, indicating that after the metallic sodium in the sodium slag is purified using an inert solvent, the molten metallic sodium can be uniformly dispersed in the inert solvent, and more fully reacted with an alcohol solvent in a subsequent step, thereby improving the recovery rate of metallic sodium in the sodium slag and the purity of solid sodium alcoholate.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing sodium alkoxide using sodium slag, characterized in that: The following steps are involved: placing the sodium slag in an inert solvent, wherein the temperature of the inert solvent is higher than the melting point of metallic sodium and lower than the melting points of other metal impurities in the sodium slag, filtering to obtain a mixed solution of metallic sodium and the inert solvent, and a filter residue; Under stirring, the mixed solution is added dropwise to an alcohol solvent, and after the reaction is completed, distillation is performed at a temperature not higher than the decomposition temperature of the sodium alkoxide to obtain solid sodium alkoxide; Under stirring, adding the filter residue into an alcohol solvent, and after the reaction is completed, filtering and separating by pressure to obtain a filtrate containing calcium alcoholate; Sodium peroxide is added to the filtrate containing calcium alkoxide, and after the reaction is completed, the filtrate is filtered to obtain a sodium alkoxide solution and insoluble calcium oxide, and the sodium alkoxide solution is distilled and separated at a temperature not higher than the decomposition temperature of the sodium alkoxide to obtain solid sodium alkoxide.

2. The method for preparing sodium alkoxide using sodium slag according to claim 1, wherein: The amount of sodium slag added is 15%~25% of the mass of the inert solvent.

3. The method for preparing sodium alkoxide using sodium slag according to claim 1, wherein: The dropping rate of the mixed solution is: adding 5-10 kg / h of the mixed solution to every 10 L of alcohol solvent; or The mass ratio of the filter residue to the alcohol solvent is (120-200): (1000-3000).

4. The method for preparing sodium alkoxide using sodium slag according to claim 1, wherein: During distillation separation, fractions at different temperatures are collected and the inert solvent and / or alcohol solvent are recovered.

5. The method for preparing sodium alkoxide using sodium slag according to claim 1, characterized in that: During the pressure filtration separation, filter screens with pore sizes of 8-12 mm, 4-6 mm, and 1.5-2.5 mm are used in sequence for multi-stage filtration at a pressure of 0.05-0.5 MPa.

6. The method for preparing sodium alkoxide using sodium slag according to claim 1, characterized in that: The molar ratio of the amount of sodium peroxide added to the content of calcium alkoxide in the filtrate containing calcium alkoxide is 1:

1.

7. The method for preparing sodium alkoxide using sodium slag according to any one of claims 1, 3 to 6, characterized in that: The step of placing the sodium slag in an inert solvent comprises: heating the sodium slag to 100-120° C., fully melting the metallic sodium in the sodium slag under stirring to obtain a solid-liquid mixture, and dripping the solid-liquid mixture into the inert solvent, wherein the amount of the solid-liquid mixture dripped into the inert solvent per hour is 10%-30% of the mass of the inert solvent.

8. The method for preparing sodium alkoxide using sodium slag according to claim 1, characterized in that: Before distilling and separating the sodium alcoholate solution, a dehydrating agent is added to the sodium alcoholate solution to react the sodium hydroxide in the sodium alcoholate solution with an alcohol solvent to generate sodium alcoholate; the dehydrating agent is any one or more of molecular sieves, sodium carbonate or resins.

9. The method for preparing sodium alkoxide using sodium slag according to claim 8, characterized in that: The amount of the dehydrating agent added is 0.1% to 1% of the mass of the sodium alcoholate solution.

10. The method for preparing sodium alkoxide using sodium slag according to claim 1, characterized in that: The temperature of the inert solvent is 100-130° C., the stirring rate is 40 r / min-120 r / min, the inert solvent is a hydrocarbon solvent and / or an ether solvent, and the alcohol solvent includes any one or more of methanol, ethanol, isopropanol, n-butanol, tert-butanol, amyl alcohol or fluoroalcohol.

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