A three-step continuous synthesis method for alkali metal salts of alcohols

Abstract

This invention provides a three-step continuous synthesis method for alkali metal salts of alcohols, comprising: First, using tetrahydrofuran as a solvent, synthesizing an alkali metal naphthalene salt from naphthalene and a liquid alkali metal; Second, using the tetrahydrofuran solution of the alkali metal naphthalene salt obtained in the first step as a raw material, preparing a tetrahydrofuran solution of an alkali metal hydride by introducing hydrogen gas; Third, adding a tetrahydrofuran solution of an alcohol to a mixed solution of the tetrahydrofuran solution of the alkali metal hydride obtained in the second step and the byproduct naphthalene to synthesize the alkali metal salt and release hydrogen gas, which can be treated and recycled for use in the second step reaction; After the reaction is complete, tetrahydrofuran and naphthalene are collected by fractional distillation and recycled for use in the first step synthesis. The reaction is continuous, safe to produce, has a short reaction time, is thorough, leaves no alkali metal residue, is low in cost, and the byproducts and solvent can be repeatedly recycled, resulting in high atom economy, low energy consumption, and requiring only a small heat source, all at atmospheric pressure.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical intermediate synthesis technology, and relates to alcohol-alkali metal salts, specifically a three-step continuous synthesis method for alcohol-alkali metal salts. Background Technology

[0002] Alcohol-alkali metal salts are a category of organometallic compounds in a broad sense. Their general molecular formula is ROM, where R is an alkyl group and M is an alkali metal. Due to the strong electronegativity of oxygen atoms, alcohol-alkali metal salts often exhibit a certain degree of polarity and possess some solubility in organic solvents, especially alcohols. They also possess some characteristics of covalent compounds. They are frequently used as intermediates in organic synthesis and pharmaceuticals; or as strong bases in chemical, pharmaceutical, and pesticide applications, particularly in condensation, rearrangement, and ring-opening reactions in organic synthesis. Therefore, they are increasingly favored by the fine chemical, pesticide, and pharmaceutical industries.

[0003] Traditional methods for synthesizing alkali metal alcohols mainly include the metal method, the alkaline method, the alkali metal amine method, and the alcohol exchange method. The metal method involves a direct reaction between the alcohol and the metal; a modification involves adding a high-boiling-point inert solvent such as toluene to raise the reaction temperature above the metal's melting point. The alkaline method involves the reaction of the alcohol with sodium hydroxide or potassium hydroxide while continuously distilling off the water produced in the reaction; a modification involves adding an azeotropic agent. The alkali metal amine method uses inert solvents such as toluene or heptane as the solvent in the reaction system, where the alcohol reacts with an alkali metal amine to prepare the alkali metal alcohol salt. There is also an improved method of alcohol exchange reaction, where a lower-carbon alkali metal alkoxide reacts with a higher-carbon alcohol to produce an alkali metal alkoxide of the higher-carbon alcohol, used to prepare alkali metal alkali ...

[0004] Sun Xiangdong et al., in their paper "Production Process of Sodium Methylmethoxide Using Metallic Sodium," described a metal method using tert-butanol as the solvent, with pre-cut sodium or potassium metal slowly added to the tert-butanol. After the reaction was complete, the tert-butanol was distilled off to obtain the tert-butanol alkali metal salt. In 2002, Liu Yu, in his paper "Synthesis of Sodium Tert-Butoxide," proposed a new metal method for synthesizing sodium tert-butoxide, using o-xylene as the solvent in the reaction system. US Patent Application No. US2002 / 0062050A1 proposed a method for preparing alkali metal potassium alkoxide by reacting an alkali metal (alkaline earth metal) with an alcohol. This method utilizes the difference in solubility of alkali metal alkoxides and alkaline earth metal alkoxides in alcohol to purify the product. The alkali method involves reacting tert-butanol with sodium hydroxide or potassium hydroxide. Wang Huachun, Guo Guangyuan, et al. proposed a method for preparing potassium tert-butoxide using azeotropic reactive distillation, using an azeotropic agent (such as cyclohexane) to remove water generated in the reaction, thus shifting the equilibrium to the right. In their 2004 paper, "A New Process for the Synthesis of Sodium Tert-Butoxide," Tang Shucheng and Duan Zhengkang proposed a method for preparing alkali metal alkoxides by reacting alcohols with alkali metal amines using toluene or heptane as the solvent in the reaction system. This method uses alkali metal amines instead of the alkali metals themselves as reactants, resulting in the release of ammonia gas instead of hydrogen gas. US Patent 3418383 proposes an improved method for preparing alkali metal alkoxides of multicarbon alcohols by reacting alkali metal lower-carbon alcohol alkoxides with multicarbon alcohols.

[0005] Among these methods, the metal method is unsafe and costly, with high steam consumption; the alkali method has low content, high free alkali, and low yield; the alkali metal amination method uses expensive raw materials; and the alcohol exchange method has high equipment and maintenance investment costs. Other methods either have imperfect processes, complex processes, or high costs. The synthesis of alkali metal salts via alkali metal hydrides is problematic because the alkali metal hydrides themselves are highly reactive and cannot be transported over long distances. They are often protected with solid oils, which brings many inconveniences to the reaction and post-processing. Currently, there are no reports of industrial production using this method. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a three-step continuous synthesis method for alkali metal salts, thereby solving the technical problem that the methods disclosed in the prior art are difficult to achieve large-scale industrial production.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A three-step continuous synthesis method for alkali metal salts, comprising the following steps:

[0009] The first step involves synthesizing alkali metal naphthalene salts from naphthalene and liquid alkali metals using tetrahydrofuran as a solvent.

[0010] The second step involves using the tetrahydrofuran solution of the alkali metal naphthalene salt obtained in the first step as a raw material, and then introducing hydrogen gas to prepare a tetrahydrofuran solution of the alkali metal hydride.

[0011] In the third step, a tetrahydrofuran solution of the alkali metal hydride obtained in the second step and a mixed solution of the byproduct naphthalene are added dropwise to a tetrahydrofuran solution of alcohol to synthesize an alkali metal alcohol salt and release hydrogen gas. The released hydrogen gas can be recycled and reused in the second step reaction after treatment. After the reaction is completed, tetrahydrofuran and naphthalene are collected by fractional distillation and recycled for the first step synthesis.

[0012] The present invention also has the following technical features:

[0013] This method employs a three-step continuous synthesis apparatus for alkali-metal salts. The apparatus includes a reaction vessel, inside which is installed a stirring paddle. The stirring paddle is mounted at the bottom end of a stirring shaft, and the top end of the stirring shaft extends beyond the top of the reaction vessel and is connected to a stirring motor.

[0014] It also includes an alcohol high-level storage tank, which is connected to a dropwise liquid high-level preparation storage tank via a pipeline, and the dropwise liquid high-level preparation storage tank is connected to the top of the reactor via a pipeline.

[0015] It also includes a tetrahydrofuran high-level storage tank, which is connected to the high-level dispensing tank of the dropping liquid via a pipeline, and the tetrahydrofuran high-level storage tank is also directly connected to the top of the reactor via a pipeline.

[0016] It also includes a high-level naphthalene storage tank, which is connected to the top of the reactor via a pipeline.

[0017] It also includes alkali metal storage tanks, which are connected to the top of the reactor via pipes equipped with alkali metal flow indicator regulators.

[0018] It also includes a hydrogen storage tank, which is connected to the top of the reactor via a pipe equipped with a first hydrogen flow meter.

[0019] The top of the reactor is connected to the first condenser via a pipe, the first condenser is connected to the tetrahydrofuran recovery storage tank, and the tetrahydrofuran recovery storage tank is connected to the tetrahydrofuran high-level storage tank via a pipe.

[0020] The top of the reactor is connected to the second condenser via a pipe, the second condenser is connected to the naphthalene recovery storage tank, and the naphthalene recovery storage tank is connected to the naphthalene high-level storage tank via a pipe.

[0021] The top of the reactor is connected to a gas compressor via a pipe equipped with a second hydrogen flow meter, and the gas compressor is connected to a hydrogen storage tank.

[0022] The pipeline equipped with the first hydrogen flow meter is connected to the main vent pipe inside the reactor, and the main vent pipe is connected to the branch vent pipes located inside the reactor.

[0023] The stirring paddle and stirring shaft have hollow internal structures that allow air to pass through, and ventilation holes are provided on the ventilation branch pipe, stirring paddle and stirring shaft.

[0024] The reactor is equipped with a nitrogen purging inlet pipe on its side wall, and a gas flow meter is installed on the nitrogen purging inlet pipe. The reactor is also equipped with air and nitrogen outlet pipes at its top.

[0025] In this invention, each pipeline is equipped with a valve and / or an electric pump.

[0026] In this invention, a discharge port is provided at the bottom of the reactor, and a temperature control jacket is installed at the bottom of the reactor.

[0027] In this invention, a thermometer is installed on the top of the reaction vessel.

[0028] Preferably, the alkali metal hydride includes sodium hydride or potassium hydride; the alcohol is a low-carbon alcohol with 1 to 8 carbon atoms; and the alcohol-alkali metal salt is a salt formed by an alcohol with 1 to 8 carbon atoms and an alkali metal.

[0029] Preferably, the alkali metal hydride includes sodium hydride; the alcohol is a low-carbon alcohol with 3 to 5 carbon atoms; and the alkali metal salt is a salt formed by an alcohol with 3 to 5 carbon atoms and an alkali metal.

[0030] Most preferably, the alcohol includes isopropanol, n-butanol, tert-butanol, isobutanol, isoamyl alcohol, or tert-amyl alcohol; the alkali metal salt includes sodium isopropoxide, potassium isopropoxide, sodium n-butoxide, potassium n-butoxide, sodium tert-butoxide, potassium tert-butoxide, sodium isobutoxide, potassium isobutoxide, sodium isoamyl alcohol, potassium isoamyl alcohol, sodium tert-amyl alcohol, or potassium tert-amyl alcohol.

[0031] Preferably, the reaction temperature of the first step is 10-50℃; the reaction temperature of the second step is 10-50℃; and the reaction temperature of the third step is 10-60℃.

[0032] More preferably, the reaction temperature of the first step is 20-30°C; the reaction temperature of the second step is 25-40°C; and the reaction temperature of the third step is 20-50°C.

[0033] Preferably, the mass ratio of the solvent tetrahydrofuran to the raw material alkali metal is (10-50):1; the molar ratio between naphthalene and alkali metal is (1.00-1.20):1; and the molar ratio between alcohol and alkali metal hydride is (1.00-1.10):1.

[0034] More preferably, the mass ratio of the solvent tetrahydrofuran to the raw material alkali metal is (10-20):1; the molar ratio between naphthalene and alkali metal is (1.00-1.10):1; and the molar ratio between alcohol and alkali metal hydride is (1.00-1.05):1.

[0035] Preferably, the reaction time in the first step is 0.5 to 2 hours, and the reaction is complete when the color of the reaction solution no longer changes and is maintained for 10 to 30 minutes; the hydrogen gas flow rate in the second step is 0.5 to 3.0 L / min; after the gas flow rates of the first and second hydrogen flow meters are consistent, the gas flow continues for another 30 to 60 minutes to complete the reaction; in the third step, the tetrahydrofuran solution of alcohol is added dropwise over 1 to 2 hours; after the addition is complete, the reaction continues until the reading of the second hydrogen flow meter is "0" and remains so for 30 to 90 minutes to complete the reaction.

[0036] In this invention, the system is purged with nitrogen gas both before and after the reaction.

[0037] In this invention, the hydrogen generated in the third step reaction and the residual hydrogen from the second step reaction are transported through a pipeline to the alkali metal hydride synthesis section for the synthesis of alkali metal hydrides.

[0038] In this invention, tetrahydrofuran and naphthalene are recovered by fractional distillation after the reaction is complete, and can be reused after drying and peroxide removal. The remaining solids in the reactor are discharged and dried using a dryer.

[0039] Compared with the prior art, the present invention has the following technical effects:

[0040] (I) The reaction of the method of the present invention is continuous, safe to produce, short reaction time, complete reaction, no alkali metal residue, low cost, by-products can be recycled, solvent can be recycled, high atom economy, low energy consumption, only a small amount of heat source is needed, and it can be completed at atmospheric pressure.

[0041] (II) The method of the present invention has high product content and yield, and the intermediate alkali metal hydride can be used without solid oil treatment, which reduces the cost of raw material transportation and processing, and is a green and environmentally friendly production method. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the apparatus for the three-step continuous synthesis of alkali-metal salts.

[0043] Figure 2 This is a schematic diagram of a three-step continuous synthesis method for alkali metal salts.

[0044] The labels in the diagram represent the following: 1-Reaction vessel, 2-Agitator, 3-Agitator shaft, 4-Agitator motor, 5-High-level alcohol storage tank, 6-High-level dispensing solution storage tank, 7-Tetrahydrofuran high-level storage tank, 8-Naphthalene high-level storage tank, 9-Alkali metal storage tank, 10-Alkali metal flow indicator and regulator, 11-Hydrogen storage tank, 12-First hydrogen flow meter, 13-First condenser, 14-Tetrahydrofuran recovery storage tank, 15-Second condenser, 16-Naphthalene recovery storage tank, 17-Second hydrogen flow meter, 18-Gas compressor, 19-Main vent pipe, 20-Branch vent pipe, 21-Ventilation port, 22-Nitrogen purging inlet pipe, 23-Gas flow meter, 24-Air and nitrogen outlet pipes, 25-Valve, 26-Electric pump, 27-Discharge port, 28-Temperature control jacket, 29-Thermometer.

[0045] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0046] It should be noted that, unless otherwise specified, all raw materials, equipment and components used in this invention are those known in the prior art.

[0047] A schematic diagram of the reaction of a three-step continuous synthesis method for alkali metal salts according to the present invention is shown below. Figure 2 As shown, the method includes the following steps:

[0048] The first step involves synthesizing alkali metal naphthalene salts from naphthalene and liquid alkali metals using tetrahydrofuran as a solvent.

[0049] The second step involves using the tetrahydrofuran solution of the alkali metal naphthalene salt obtained in the first step as a raw material, and then introducing hydrogen gas to prepare a tetrahydrofuran solution of the alkali metal hydride.

[0050] In the third step, a tetrahydrofuran solution of the alkali metal hydride obtained in the second step and a mixed solution of the byproduct naphthalene are added dropwise to a tetrahydrofuran solution of alcohol to synthesize an alkali metal alcohol salt and release hydrogen gas. The released hydrogen gas can be recycled and reused in the second step reaction after treatment. After the reaction is completed, tetrahydrofuran and naphthalene are collected by fractional distillation and recycled for the first step synthesis.

[0051] The chemical reaction equation for this method is as follows:

[0052]

[0053] Wherein, R is an alkyl group from C1 to C8, and M is an alkali metal Na / K.

[0054] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0055] Example 1:

[0056] This embodiment provides an apparatus for the three-step continuous synthesis of alkali metal salts, such as... Figure 1 As shown, the device includes a reaction vessel 1, a stirring paddle 2 is installed inside the reaction vessel 1, the stirring paddle 2 is installed at the bottom end of a stirring shaft 3, and the top end of the stirring shaft 3 extends to the top of the reaction vessel 1 and is connected to a stirring motor 4.

[0057] It also includes an alcohol high-level storage tank 5, which is connected to a dropwise liquid high-level mixing and storage tank 6 via a pipeline, and the dropwise liquid high-level mixing and storage tank 6 is connected to the top of the reactor 1 via a pipeline.

[0058] It also includes a tetrahydrofuran high-level storage tank 7, which is connected to the high-level dispensing liquid storage tank 6 via a pipeline. The tetrahydrofuran high-level storage tank 7 is also directly connected to the top of the reactor 1 via a pipeline.

[0059] It also includes a high-level naphthalene storage tank 8, which is connected to the top of the reactor 1 via a pipeline.

[0060] It also includes an alkali metal storage tank 9, which is connected to the top of the reactor 1 via a pipe with an alkali metal flow indicator regulator 10.

[0061] It also includes a hydrogen storage tank 11, which is connected to the top of the reactor 1 via a pipe with a first hydrogen flow meter 12.

[0062] The top of the reactor 1 is connected to the first condenser 13 via a pipe. The first condenser 13 is connected to the tetrahydrofuran recovery storage tank 14. The tetrahydrofuran recovery storage tank 14 is connected to the tetrahydrofuran high-level storage tank 7 via a pipe.

[0063] The top of the reactor 1 is connected to the second condenser 15 via a pipe. The second condenser 15 is connected to the naphthalene recovery storage tank 16, which is connected to the naphthalene high-level storage tank via a pipe.

[0064] The top of the reactor 1 is connected to the gas compressor 18 via a pipe with a second hydrogen flow meter 17, and the gas compressor 18 is connected to the hydrogen storage tank 11.

[0065] As a preferred embodiment, the pipe with the first hydrogen flow meter 12 is connected to the main vent pipe 19 in the reactor 1, and the main vent pipe 19 is connected to the branch vent pipe 20 provided in the reactor 1.

[0066] As a preferred embodiment, the stirring paddle 2 and stirring shaft 3 are hollow structures that allow air to pass through, and ventilation holes 21 are provided on the ventilation branch pipe 20, the stirring paddle 2 and the stirring shaft 3.

[0067] As a preferred embodiment, the side wall of the reactor 1 is provided with a nitrogen purging inlet pipe 22, the nitrogen purging inlet pipe 22 is equipped with a gas flow meter 23, and the top of the reactor 1 is provided with an air and nitrogen outlet pipe 24.

[0068] In this invention, each pipeline is equipped with a valve 25 and / or an electric pump 26. The number of valves 25 and electric pumps 26 and their installation positions on the pipeline are determined according to process requirements.

[0069] In this invention, a discharge port 27 is provided at the bottom of the reactor 1, and a temperature control jacket 28 is installed at the lower part of the reactor 1.

[0070] In this invention, a thermometer 29 is installed on the top of the reaction vessel 1.

[0071] In this invention, the alcohol high-level storage tank 5 is equipped with a known flow indication and regulating device, the dropwise liquid high-level mixing storage tank 6 is equipped with a known flow indication and regulating device, the tetrahydrofuran high-level storage tank 7 is equipped with a known flow indication and regulating device, the naphthalene high-level storage tank 8 is equipped with a known high-frequency electric heating system and a flow indication and regulating device, the alkali metal storage tank 9 is equipped with a known high-frequency electric heating system, and the naphthalene recovery storage tank 16 is equipped with a known high-frequency electric heating system.

[0072] Example 2:

[0073] This embodiment provides a three-step continuous synthesis method for alcohol-alkali metal salts, which uses the apparatus for the three-step continuous synthesis of alcohol-alkali metal salts given in Example 1.

[0074] The method includes the following steps:

[0075] First, the valve on the nitrogen purging inlet pipe 22 of reactor 1 is opened to purge with nitrogen and maintain a nitrogen environment. The exhaust gas is discharged through the air and nitrogen outlet pipes 24, with the valves on these pipes kept open. The naphthalene high-level storage tank 8 is heated to liquefy the naphthalene. 141 kg of sublimed naphthalene is added to reactor 1. 500 L of freshly distilled tetrahydrofuran is added directly to reactor 1 from the tetrahydrofuran high-level storage tank 14. Stirring is started, and the stirring shaft 3 drives the stirring paddle 4 to rotate slowly. The alkali metal storage tank 9 is heated to liquefy the alkali metal sodium. 23 kg of sodium is added, and the dropping rate is adjusted using the alkali metal flow indicator regulator 10. After dropping, the temperature is adjusted to around 20°C to 25°C using the sleeve in the temperature control jacket 28. The temperature is measured and displayed using the thermometer 29. The reaction system is maintained at 20°C to 25°C for 1.5 hours to obtain a dark brown sodium naphthalene solution.

[0076] The second step, at 20°C, is to close the valves on the nitrogen purging inlet pipe 22 and the air and nitrogen outlet pipes 24, and open the valves on the hydrogen inlet and outlet pipes.

[0077] Hydrogen gas enters the reaction system successively through the main vent pipe 19, the branch vent pipes 20 distributed on the inner wall of the reactor 1, and the vent holes 21 with a diameter of approximately 2 to 5 mm on the stirring shaft 3 and the stirring paddle 2. Hydrogen gas is introduced into the sodium naphthalene solution obtained in the first step, and the hydrogen flow rate is adjusted to 1.0 L / min by the first hydrogen flow meter 12. Once the hydrogen flow rates at the inlet and outlet of the device are consistent with those at the second hydrogen flow meter 17, the gas flow continues for another 30 minutes to complete the reaction. The reaction produces a tetrahydrofuran solution containing sodium hydride as a byproduct of naphthalene. The hydrogen gas at the outlet of the device is compressed by the gas compressor 18 and then enters the hydrogen storage tank 11, where it can be recycled after further treatment.

[0078] Third, close the valves on the hydrogen inlet and outlet pipelines, and purge reactor 1 with nitrogen. Add 100 kg of tetrahydrofuran from the tetrahydrofuran high-level storage tank 7 to the high-level liquid preparation tank 6. Then, add 74.5 kg of tert-butanol from the high-level alcohol storage tank 5 to the high-level liquid preparation tank 6. The tetrahydrofuran and tert-butanol will mix in the high-level liquid preparation tank 6 to form a tetrahydrofuran-tert-butanol mixed solution. Then, stop the nitrogen purging.

[0079] Open the valve on the hydrogen outlet pipe. Adjust the temperature of the reaction liquid in reactor 1 to around 25°C using the sleeve inside the temperature control jacket 28. The temperature of the reaction liquid is measured and displayed by thermometer 29. Open the valve and slowly add a tetrahydrofuran mixture of tert-butanol to reactor 1. The hydrogen gas generated during the addition process is displayed in real-time by the second hydrogen flow meter 17. After comprehensive compression by gas compressor 18, it enters hydrogen storage tank 11. After treatment, it can be controlled by the valve for recycling. During the addition process, the temperature rises, but is controlled not to exceed 60°C. The addition is completed after 2 hours. After the second hydrogen flow meter 17 at the hydrogen outlet displays 0, continue the reaction for another 60 minutes.

[0080] Post-processing:

[0081] After the third synthesis step is completed, close the valve on the hydrogen pipeline, start nitrogen purging to remove residual hydrogen from the reaction system, and regulate the flow rate using gas flow meter 23. After shutting off the nitrogen purging, heat the system to approximately 80°C under normal pressure using temperature control jacket 28, collecting the fraction between 60°C and 80°C. The resulting tetrahydrofuran solvent is condensed by the first condenser 13 and then enters the tetrahydrofuran recovery storage tank 14. After collection, close the valve on the corresponding pipeline. The recovered tetrahydrofuran, after passing quality control, is recycled. For recycling, it is transported via pipeline to the tetrahydrofuran high-level storage tank 7 for later use. After the tetrahydrofuran fraction is evaporated to dryness, the temperature is further increased and vacuum distilled. The resulting recovered liquid naphthalene is condensed by the second condenser 15 and then enters the naphthalene recovery storage tank 16. After passing quality control, it is recycled. For recycling, the electric heating system of the naphthalene recovery storage tank 8 is activated to ensure the naphthalene is in a liquid state, and it is transported via pipeline to the naphthalene high-level storage tank 8. The pipeline needs to be insulated or heated to ensure it remains liquid during transport. The recovered tetrahydrofuran and naphthalene must have a water content of less than 0.1%. Tetrahydrofuran is tested for the presence of peroxides using starch-potassium iodide test paper. If peroxides are present, they need to be removed with sodium hydroxide (2 wt%), etc. Then, reflux drying is performed using sodium with benzophenone as an indicator.

[0082] After all the solvent in reactor 1 is evaporated, the resulting white solid is discharged through outlet 27. The opening and closing of outlet 27 is controlled by a valve. After discharge, the solid enters a rake dryer for drying and is packaged to obtain the target product.

[0083] The target product obtained was 95.1 kg of white granular sodium tert-butoxide solid, with a m.p. of 179.9℃, a purity of 99.6%, a free alkali of 0.3%, and a yield of 98.6%.

[0084] Testing method: (Q-LH004-2021 Enterprise Testing Standard)

[0085] (1) Determination of total alkali: Weigh approximately 0.5 g of the sample (accurate to 0.0002 g) and place it in a dry 100 ml iodine flask. Add approximately 20 ml of distilled water (boiled and cooled) to dissolve the sample, shake well, and let stand for 5 min. Add 3 drops of 1% phenolphthalein indicator and titrate with 0.5 mol / L hydrochloric acid standard solution until the endpoint is reached (colorless). The total alkali content of sodium tert-butoxide is expressed as a mass fraction and calculated using the following formula: X1 = C * V * 0.09610 / m * 100%, where: C represents the concentration of hydrochloric acid standard solution (mol / L); V represents the volume of hydrochloric acid standard solution consumed (ml); and m represents the mass of the sample (g).

[0086] (2) Determination of free base:

[0087] Add 5 ml of benzoic acid-methanol solution and 15-20 ml of methanol as the stock solution to the reaction flask, ensuring the electrodes are submerged. Titrate with Karl Fischer reagent until the galvanometer pointer shows a significant deflection that remains constant for 30 seconds; this is the endpoint, and the amount consumed is negligible. Then weigh approximately 0.5 g of the sample (accurate to 0.0002 g) and quickly add it to the reaction flask. Titrate with Karl Fischer reagent until the galvanometer pointer shows the same significant deflection as in the blank experiment and remains constant for 30 seconds; this is the endpoint, and the volume of Karl Fischer reagent consumed is recorded. The water content by mass percentage is calculated using the following formula: X2 = T * V / m * 100%. Where T represents the Karl Fischer reagent titer for water (g / ml); V represents the volume of Karl Fischer reagent consumed in titrating the sample (ml); and m represents the sample mass (g). The arithmetic mean of two parallel determinations is taken as the final result, and the difference between the two parallel determinations should not exceed 0.1%. Then, calculate the free alkali content using the formula X3 = 2.222X2, where 2.222 is the conversion factor for water to sodium hydroxide.

[0088] Example 3:

[0089] This embodiment provides a three-step continuous synthesis method for alcohol-alkali metal salts, which uses the apparatus for the three-step continuous synthesis of alcohol-alkali metal salts given in Example 1.

[0090] The method includes the following steps:

[0091] Step 1: Pretreatment is the same as in Example 2. 135 kg of sublimed naphthalene is added to the reactor. 500 L of freshly distilled tetrahydrofuran is added to the reactor through a tetrahydrofuran high-level storage tank. The temperature of the mixture in the reactor is maintained at 25 °C. The alkali metal storage tank is heated to make the alkali metal potassium liquid. 39 kg of liquid potassium is slowly added dropwise. After the addition is completed, the mixture is kept at 25-30 °C for 2 hours to obtain a dark brown potassium naphthalene solution.

[0092] In the second step, at 25°C, close the nitrogen inlet and outlet valves, open the hydrogen inlet valve, and introduce hydrogen gas into the potassium naphthalene solution from the first step. Adjust the hydrogen flow rate to 1.5 L / min using a hydrogen gas flow meter. Once the gas flow rates at the inlet and outlet of the device are consistent, continue introducing gas for another 45 minutes to complete the reaction. The reaction produces a tetrahydrofuran solution containing potassium hydride as a byproduct of naphthalene. The hydrogen gas at the outlet of the device is processed by a gas compressor and other components before entering a hydrogen storage tank, where it can be recycled after further treatment.

[0093] Step 3: Close the hydrogen inlet and outlet valves, open the nitrogen inlet and outlet valves, purge the reactor with nitrogen, and add 100 kg of tetrahydrofuran from the tetrahydrofuran high-level storage tank and 74.5 kg of tert-butanol from the alcohol high-level storage tank to form a tetrahydrofuran mixed solution of tert-butanol. Close the nitrogen inlet and outlet valves. Open the hydrogen outlet valve. Slowly add the tetrahydrofuran mixed solution of tert-butanol to the reactor at 25°C. The hydrogen generated during the adding process is processed by a gas compressor and then enters the hydrogen storage tank for recycling. During the adding process, the temperature rises, but is controlled not to exceed 50°C. The adding process is completed in 2 hours. After the gas flow meter at the hydrogen outlet shows 0, continue the reaction for another 75 minutes.

[0094] Post-processing: Same as in Example 2.

[0095] The target product was obtained as 109.9 kg of white potassium tert-butoxide solid granules, with a m.p. of 257.4℃, a content of 99.8%, free alkali of 0.2%, and a yield of 97.7%.

[0096] Testing method: (Q-LH003-2021 Enterprise Testing Standard)

[0097] (1) Determination of total alkali: Weigh approximately 0.5 g of the sample (accurate to 0.0002 g) and place it in a dry 100 ml iodine flask. Add approximately 20 ml of distilled water (boiled and cooled) to dissolve the sample, shake well, and let stand for 5 min. Add 3 drops of 1% phenolphthalein indicator and titrate with 0.5 mol / L hydrochloric acid standard solution until the solution becomes colorless. The total alkali content of potassium tert-butoxide is expressed as a mass fraction and calculated using the following formula: X1 = C * V * 0.11221 / m * 100%, where: C represents the concentration of hydrochloric acid standard solution (mol / L); V represents the volume of hydrochloric acid standard solution consumed (ml); and m represents the mass of the sample (g).

[0098] (2) Determination of free base:

[0099] Add 5 ml of benzoic acid-methanol solution and 15-20 ml of methanol as the stock solution to the reaction flask, ensuring the electrodes are submerged. Titrate with Karl Fischer reagent until the galvanometer pointer shows a significant deflection that remains constant for 30 seconds; this is the endpoint, and the amount consumed is negligible. Then weigh approximately 0.5 g of the sample (accurate to 0.0002 g) and quickly add it to the reaction flask. Titrate with Karl Fischer reagent until the galvanometer pointer shows the same significant deflection as in the blank experiment and remains constant for 30 seconds; this is the endpoint, and the volume of Karl Fischer reagent consumed is recorded. The water content by mass percentage is calculated using the following formula: X2 = T * V / m * 100%. Where T represents the Karl Fischer reagent titer for water (g / ml); V represents the volume of Karl Fischer reagent consumed in titrating the sample (ml); and m represents the sample mass (g). The arithmetic mean of two parallel determinations is taken as the final result, and the difference between the two parallel determinations should not exceed 0.1%. Then, calculate the free alkali content according to the formula X3 = 3.111X2, where 3.111 is the conversion factor for water to potassium hydroxide.

[0100] Example 4:

[0101] This embodiment provides a three-step continuous synthesis method for alcohol-alkali metal salts, which uses the apparatus for the three-step continuous synthesis of alcohol-alkali metal salts given in Example 1.

[0102] The method includes the following steps:

[0103] Step 1: Pretreatment is the same as in Example 2. 138 kg of sublimed naphthalene is added to the reactor. 500 L of freshly distilled tetrahydrofuran is added through a tetrahydrofuran high-level storage tank. The temperature of the mixture in the reactor is maintained at 30 °C. The alkali metal storage tank is heated to make the alkali metal sodium liquid. 23 kg of sodium is slowly added dropwise. After the addition is completed, the solution is maintained at 30-35 °C for 2 hours to obtain a dark brown sodium naphthalene solution.

[0104] In the second step, at 30°C, close the nitrogen inlet and outlet valves, open the hydrogen inlet valve, and introduce hydrogen gas into the sodium naphthalene solution from the first step. Adjust the hydrogen flow rate to 2.0 L / min using a hydrogen gas flow meter. Once the gas flow rates at the inlet and outlet of the device are consistent, continue introducing gas for another 60 minutes to complete the reaction. The reaction produces a tetrahydrofuran solution containing sodium hydride as a byproduct of naphthalene. The hydrogen gas at the outlet of the device is processed by a gas compressor and other components before entering a hydrogen storage tank, where it can be recycled after further treatment.

[0105] Step 3: Close the hydrogen inlet and outlet valves, open the nitrogen inlet and outlet valves, purge the reactor with nitrogen, and add 100 kg of tetrahydrofuran from the tetrahydrofuran high-level tank and 88.2 kg of tert-amyl alcohol from the alcohol high-level storage tank to the high-level storage tank to form a tetrahydrofuran mixed solution of tert-amyl alcohol. Close the nitrogen inlet and outlet valves. Open the hydrogen outlet valve. Slowly add the tetrahydrofuran mixed solution of tert-amyl alcohol to the reactor at 30°C. The hydrogen generated during the adding process is processed by a gas compressor and then enters the hydrogen storage tank for recycling. During the adding process, the temperature rises, but is controlled not to exceed 55°C. The adding process is completed in 2 hours. After the gas flow meter at the hydrogen outlet shows 0, continue the reaction for another 90 minutes.

[0106] Post-processing: Same as in Example 2.

[0107] The target product obtained was 109.5 kg of white granular sodium tert-amyl alcohol solid, with a m.p. 200.2℃, a content of 99.6%, free alkali of 0.3%, and a yield of 97.3%.

[0108] Test method: (Q-320411ATU 002-2017)

[0109] (1) Determination of total alkali: Weigh approximately 1-2 g of sample (accurate to 0.0002 g) and place it in a dry 250 ml iodine flask. Add approximately 50 ml of distilled water (boiled and cooled) to dissolve the sample, shake well, and let stand for 5 min. Add 3 drops of 1% phenolphthalein indicator and titrate with 0.5 mol / L hydrochloric acid standard solution until the endpoint is reached (colorless). The total alkali content of potassium tert-butoxide is expressed as a mass fraction and calculated using the following formula: X1 = C * V * 0.11013 / m * 100%, where: C represents the concentration of hydrochloric acid standard solution (mol / L); V represents the volume of hydrochloric acid standard solution consumed (ml); and m represents the mass of the sample (g).

[0110] (2) Determination of free base:

[0111] Add 4 ml of glacial acetic acid and 20 ml of anhydrous methanol to the reaction flask as the mother liquor, just enough to cover the electrodes. Titrate with Karl Fischer reagent to the endpoint. Then weigh approximately 1-2 g of the sample (accurate to 0.0002 g) and quickly add it to the reaction flask. Titrate with Karl Fischer reagent to the endpoint and record the volume of Karl Fischer reagent consumed. The percentage of free base mass is calculated using the following formula: X2 = 2.22T*V / m*100%. Where, T represents the titer of Karl Fischer reagent against water (g / ml); V represents the volume of Karl Fischer reagent consumed in titrating the sample (ml); m represents the sample mass (g); and 2.22 is the molar mass ratio of sodium hydroxide to water. The arithmetic mean of two parallel determinations is taken as the final result, and the difference between the two parallel determinations should not exceed 0.2%.

[0112] Comparative Example 1: (Amino Alkali Metal Method)

[0113] This comparative example provides a method for synthesizing alkali metal salts via the amino-alkali metal method. The method includes the following steps: In a 500L reactor equipped with a stirrer, reflux condenser, and thermometer, 240L of dry toluene, 9.8kg of sodium amide, and 19.0g of tert-butanol are added. The mixture is stirred thoroughly until completely dissolved. The temperature is raised to 70℃ to initiate the reaction. The released ammonia gas is absorbed by water or alkaline solution. The reaction temperature is raised to 100–110℃ and held for 1.5 hours to stop the reaction. After the reaction is complete, the reactants are cooled. Most of the reaction medium and a slight excess of tert-butanol are distilled off under normal pressure. The remaining small amount of reaction medium is then distilled off under reduced pressure. Low-temperature nitrogen gas (-20℃) is blown into the reactor through the bottom valve to cool the mixture to below 40℃. Vacuum discharge yields 23.2kg of white sodium tert-butoxide solid particles with a purity of 99% and a yield of 95.1%.

[0114] Comparative Example 2: (Metal Method)

[0115] This comparative example provides a method for synthesizing alkali-alkali metal salts using a metal method. The method includes the following steps: In a 2000L reactor equipped with a mechanical stirrer, thermometer, and reflux condenser, 320kg of tert-amyl alcohol, 1000kg of dried toluene, and 53kg of small pieces of metallic sodium are added. Under nitrogen protection, the mixture is refluxed at 100-110℃ for 10 hours until the metallic sodium is completely eliminated. Excess residual tert-amyl alcohol and toluene mother liquor are distilled off under normal pressure. The remaining small amount of reaction medium is then distilled off under reduced pressure to obtain off-white potassium tert-butoxide solid. Low-temperature nitrogen gas (-20℃) is blown into the reactor through the bottom valve to cool it to below 40℃. Vacuum discharge yields the desired off-white granular sodium tert-amyl alcohol, with a purity of 99% and a yield of 93.9%.

[0116] Comparative Example 3: (Azeotropic Distillation)

[0117] This comparative example presents a method for synthesizing alkali metal salts via azeotropic distillation. The method includes the following steps: 105.6 kg of tert-butanol and 10.8 kg of potassium hydroxide aqueous solution (50% purity, containing 10.8 kg of water) are weighed and fed into a static mixer via metering pumps from storage tanks, then enter the top of a distillation column; the top vapor is cooled by a condenser and then enters a phase separator for separation. The lower aqueous phase leaves the system, while the upper oil phase, containing tert-butanol and the azeotropic agent cyclohexane, is refluxed into the column for azeotropic distillation and dehydration; the tert-butanol solution of the product potassium tert-butoxide is collected from the bottom of the column, which is heated by steam. The azeotropic agent cyclohexane is added at the phase separator. The top temperature is controlled at approximately 70°C, and the bottom temperature at approximately 87°C. An azeotrope of tert-butanol, water, and cyclohexane was distilled off from the top of the column. After reacting for 300 minutes, 100.8 kg of the condensate was obtained from the top of the column and entered into a phase separator. 166.2 kg of potassium tert-butoxide in tert-butanol was obtained from the bottom of the column and placed in a desiccator. The solution was then distilled until complete crystallization, yielding 12.1 kg of granular potassium tert-butoxide with a purity of 98.1%, with a yield of 54.9%.

Claims

1. A method for the three-step continuous synthesis of alkali-alkali metal salts, the method employing an apparatus for the three-step continuous synthesis of alkali-alkali metal salts, the apparatus comprising a reaction vessel (1), a stirring paddle (2) disposed within the reaction vessel (1), the stirring paddle (2) being mounted at the bottom end of a stirring shaft (3), the top end of the stirring shaft (3) extending beyond the top of the reaction vessel (1) and connected to a stirring motor (4); characterized in that: It also includes an alcohol high-level storage tank (5), which is connected to a dropwise liquid high-level preparation storage tank (6) via a pipeline, and the dropwise liquid high-level preparation storage tank (6) is connected to the top of the reactor (1) via a pipeline; It also includes a tetrahydrofuran high-level storage tank (7), which is connected to the high-level liquid preparation tank (6) of the dripping liquid via a pipeline. The tetrahydrofuran high-level storage tank (7) is also directly connected to the top of the reactor (1) via a pipeline. It also includes a high-level naphthalene storage tank (8), which is connected to the top of the reactor (1) via a pipeline; It also includes an alkali metal storage tank (9), which is connected to the top of the reactor (1) via a pipe with an alkali metal flow indicator regulator (10); It also includes a hydrogen storage tank (11), which is connected to the top of the reactor (1) via a pipe with a first hydrogen flow meter (12); The top of the reactor (1) is connected to the first condenser (13) via a pipe. The first condenser (13) is connected to the tetrahydrofuran recovery storage tank (14). The tetrahydrofuran recovery storage tank (14) is connected to the tetrahydrofuran high-level storage tank (7) via a pipe. The top of the reactor (1) is connected to the second condenser (15) via a pipe. The second condenser (15) is connected to the naphthalene recovery storage tank (16). The naphthalene recovery storage tank is connected to the naphthalene high-level storage tank via a pipe. The top of the reactor (1) is connected to the gas compressor (18) via a pipe with a second hydrogen flow meter (17), and the gas compressor (18) is connected to the hydrogen storage tank (11). The method includes the following steps: The first step involves synthesizing alkali metal naphthalene salts from naphthalene and liquid alkali metals using tetrahydrofuran as a solvent. The reaction temperature for the first step is 10–50℃; the reaction time for the first step is 0.5–2 hours, and the reaction is complete when the color of the reaction solution no longer changes and remains unchanged for 10–30 minutes. The second step involves using the tetrahydrofuran solution of alkali metal naphthalene salt obtained in the first step as raw material, and passing hydrogen gas through it to prepare a tetrahydrofuran solution of alkali metal hydride. The alkali metal hydrides include sodium hydride or potassium hydride; The reaction temperature in the second step is 10–50°C; the hydrogen flow rate in the second step is 0.5–3.0 L / min; once the gas flow rates of the first and second hydrogen flow meters are consistent, continue to flow for another 30–60 minutes to complete the reaction. In the third step, a tetrahydrofuran solution of alkali metal hydride obtained in the second step and a mixed solution of naphthalene by-product are added dropwise to a tetrahydrofuran solution of alcohol to synthesize an alkali metal salt and release hydrogen gas. The released hydrogen gas can be recycled and reused in the second step reaction after treatment. After the reaction is completed, tetrahydrofuran and naphthalene are collected by fractional distillation and recycled for the first step synthesis. The alcohol is a low-carbon alcohol with 1 to 8 carbon atoms; The alcohol-alkali metal salts mentioned are salts formed by alcohols with 1 to 8 carbon atoms and alkali metals; The reaction temperature in the third step is 10–60°C; the tetrahydrofuran solution of alcohol is added dropwise over 1–2 hours during the third step reaction; after the addition is complete, the reaction continues until the reading of the second hydrogen flow meter shows "0" and remains so for 30–90 minutes, at which point the reaction is complete.

2. The method for the three-step continuous synthesis of alkali metal salts as described in claim 1, characterized in that, The pipeline with the first hydrogen flow meter (12) is connected to the main vent pipe (19) inside the reactor (1), and the main vent pipe (19) is connected to the branch vent pipe (20) inside the reactor (1). The stirring paddle (2) and stirring shaft (3) are hollow structures that allow air to pass through. The ventilation branch pipe (20), stirring paddle (2) and stirring shaft (3) are all provided with ventilation holes (21).

3. The method for the three-step continuous synthesis of alkali metal salts as described in claim 1, characterized in that, The side wall of the reactor (1) is provided with a nitrogen purge inlet pipe (22), and the nitrogen purge inlet pipe (22) is equipped with a gas flow meter (23). The top of the reactor (1) is provided with an air and nitrogen outlet pipe (24).

4. The method for the three-step continuous synthesis of alkali metal salts as described in claim 1, characterized in that, The alkali metal hydride includes sodium hydride; the alcohol is a low-carbon alcohol with 3 to 5 carbon atoms; the alcohol-alkali metal salt is a salt formed by an alcohol with 3 to 5 carbon atoms and an alkali metal.

5. The method for the three-step continuous synthesis of alkali metal salts as described in claim 1, characterized in that, The reaction temperature for the first step is 20–30℃; the reaction temperature for the second step is 25–40℃; and the reaction temperature for the third step is 20–50℃.

6. The method for the three-step continuous synthesis of alkali metal salts as described in claim 1, characterized in that, The mass ratio of the solvent tetrahydrofuran to the raw material alkali metal is (10-50):1; the molar ratio between naphthalene and alkali metal is (1.00-1.20):1; and the molar ratio between alcohol and alkali metal hydride is (1.00-1.10):1.

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