Preparation method of high-purity granular sodium tert-butoxide

Abstract

The invention provides a preparation method of high-purity granular sodium tert-butoxide, which specifically comprises the following steps: S1, placing alkali metal low-carbon alcohol alkoxide and multi-carbon alcohol in a reaction container, adding a molecular sieve catalyst, and heating to reflux for reaction; s2, after the reaction is finished, filtering to remove the molecular sieve catalyst, and distilling to remove impurities to obtain sodium tert-butoxide. And the prepared sodium tert-butoxide is high in purity and good in economical efficiency, and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for preparing high-purity granular sodium tert-butoxide. Background Art

[0002] Sodium tert-butoxide is an important organic base, and its alkalinity is greater than that of sodium hydroxide and potassium hydroxide. Due to its large molecular structure and large steric hindrance, it can show its special advantages in many chiral synthesis reactions. In addition, as a strong base, sodium tert-butoxide is widely used in condensation, rearrangement and ring-opening reactions in organic synthesis such as chemical industry, medicine, pesticide, etc. Therefore, sodium tert-butoxide is increasingly favored by the fine chemical industry, pesticide, and pharmaceutical industry.

[0003] The traditional production technology of sodium tert-butoxide is to first obtain a liquid sodium tert-butoxide product (i.e., its tert-butanol solution), and then evaporate, concentrate, and dry to obtain a powdered solid product. At present, the main methods and research results for the preparation and production of sodium tert-butoxide at home and abroad are as follows:

[0004] 1. Preparation of sodium tert-butoxide by metal method: Sodium metal and tert-butanol are used as raw materials to prepare tert-butanol solution of sodium tert-butoxide. The advantages of this method are thorough reaction, high yield, high product content, and low free alkali. This method can produce sodium tert-butoxide products with better catalytic activity. The disadvantages are: 1. The pre-slicing process of sodium metal needs to be protected by nitrogen all the time; 2. The slicing process of sodium metal increases the contact area between sodium metal and air, and sodium metal is easily oxidized; 3. Sodium flakes will gather together, resulting in an increase in the stirring load of the reactor. The biggest problem is that there are serious drawbacks such as poor safety and easy explosion in production.

[0005] 2. Preparation of sodium tert-butoxide by alkaline method: It is obtained by the reaction of tert-butanol and sodium hydroxide. Compared with the metal method, the ordinary alkaline preparation process is obviously safer, but it has the following four major disadvantages: (1) large steam consumption; (2) tert-butanol is volatile and will cause serious pollution to the atmosphere; (3) the reaction is a balanced reversible reaction, and there will be a high content of water in the liquid phase of sodium tert-butoxide at the bottom of the tower, which does not meet the use requirements of the pharmaceutical industry; (4) the wastewater contains some tert-butanol, which needs to be treated to meet the standards before it can be discharged, increasing the cost of post-treatment.

[0006] 3. Alcohol and alkali metal amide reaction: prepare sodium tert-butoxide with tert-butyl alcohol and alkali metal amide as raw materials. Ammonia will be produced in the reaction process, but no hydrogen will be produced, which greatly improves safety and industrial operability compared with the metal method. In addition, the reaction conditions of this method do not need to be very strict, and the operation is also relatively simple, and the processing process of the product later stage is relatively simple, the drying time of the reaction medium and the reaction product is greatly shortened, and the sodium tert-butoxide product purity and yield obtained are all very ideal. However, due to the expensive price of metal amides, the amide of sodium can also cause environmental pollution, so this type of method is not suitable for large-scale industrial production. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a method for preparing high-purity granular sodium tert-butoxide. The method of the present invention is used to prepare sodium tert-butoxide, and the prepared sodium tert-butoxide has high purity and good economic efficiency.

[0008] The technical solution of the present invention is achieved in this way:

[0009] The present invention provides a method for preparing high-purity granular sodium tert-butoxide, which specifically comprises the following steps:

[0010] S1: placing an alkali metal low-carbon alcohol salt and a polyol in a reaction vessel, adding a molecular sieve catalyst, and heating to reflux for reaction;

[0011] S2: After the reaction is completed, the molecular sieve catalyst is filtered out and impurities are distilled out to obtain the sodium tert-butoxide.

[0012] Potassium tert-butoxide prepared by other methods such as metal method and alkali method contains potassium hydroxide impurities, which often have side effects when participating in pharmaceutical synthesis reactions and decompose lipids in reactants or products. The method of the present invention removes potassium hydroxide impurities that affect product quality and improves product purity.

[0013] Furthermore, the alkali metal low-carbon alcohol alkoxide in step S1 is sodium ethoxide.

[0014] Furthermore, the polyol in step S1 is tert-butanol.

[0015] Sodium ethoxide reacts with tert-butanol to generate sodium tert-butoxide and ethanol. Ethanol is volatile, which reduces the concentration of the product, promotes the reaction equilibrium to move forward, and improves the yield.

[0016] On the other hand, the volatile nature of the alcohol facilitates the purification of the product, and it is clean and pollution-free, environmentally friendly, and can be recycled, which is economical.

[0017] Furthermore, in step S1, the molar ratio of sodium ethoxide to tert-butanol is 1-1.5:1.

[0018] A slight excess of sodium ethoxide ensures that the reactant tert-butyl alcohol reacts fully and prevents harmful substances from remaining.

[0019] Furthermore, the preparation method of the molecular sieve catalyst in step S1 is: calcining the molecular sieve and then immersing it in an organic metal solution, and continuing to calcine after the immersion to obtain the molecular sieve catalyst.

[0020] Further, the organic metal includes organic tin, and the organic tin includes one or more of dibutyltin oxide, butyltin trichloride, tributyltin chloride and dibutyltin maleate.

[0021] In the catalytic process of organotin catalysts, double bonds play an important role, and the electronic effect of the groups contained in the catalyst affects its activity. Compared with titanate, it has better thermal stability and is more stable to water and air.

[0022] Furthermore, the organic-organic metal further includes organic samarium, and the organic samarium includes samarium trifluoromethanesulfonate.

[0023] Samarium fluoromethylsulfonate is relatively stable to air and water, and can maintain stable activity during cyclic use.

[0024] Compared with heterogeneous catalysts, homogeneous catalysts can provide more catalytic active centers, which is the main reason why their catalytic effect is better than that of heterogeneous catalysts. However, homogeneous catalysts make it difficult to separate the catalyst from the product, which affects the purity of the product, and the recovery of the catalyst is more difficult than that of heterogeneous catalysts.

[0025] Immobilized homogeneous catalysts have the advantages of uniform distribution of active centers, high selectivity, easy separation from products and good stability.

[0026] At the same time, the acidic sites on the molecular sieve also have catalytic activity and can cooperate with organic tin to carry out catalytic effects.

[0027] Furthermore, the loading amount of tin on the molecular sieve is 1-5wt%.

[0028] Furthermore, the heating conditions in step S1 are 95-100° C. and normal pressure.

[0029] Furthermore, the distillation conditions in step S2 are 95-100° C. and normal pressure.

[0030] If the temperature is too low, it is not conducive to the reaction and product purification. The boiling point of sodium ethoxide is 91°C under normal pressure. Too high a temperature will cause energy waste.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The boiling points of ethanol and sodium tert-butoxide in the reactants and products are very different, which makes it very convenient to purify the product by distillation to ensure the high purity of the product.

[0033] 2. Sodium ethoxide reacts with tert-butanol to generate sodium tert-butoxide and ethanol. Ethanol is volatile, which reduces the concentration of the product, promotes the reaction equilibrium to move forward, and improves the yield.

[0034] 3. The catalyst is a solid catalyst, insoluble in the reaction system, easy to separate, and useful for increasing product concentration.

[0035] 4. The acidic sites of the molecular sieve carrier itself are catalytic and can work synergistically with organic tin compounds to enhance the catalytic effect. Samarium fluoromethylsulfonate can maintain the stability of the catalyst during recycling. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Reagent Description:

[0038] Tert-butyl alcohol, sodium ethoxide, Hβ molecular sieve, samarium trifluoromethanesulfonate, and dibutyltin oxide were analytically pure and were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0039] Preparation Example 1

[0040] Preparation of molecular sieve catalyst: Hβ molecular sieve was placed in a muffle furnace and calcined at 600℃ for 4h. After calcination, 100g was weighed and immersed in a 2mg·L -1 The solution of dibutyltin oxide was taken out and placed in a muffle furnace again, and calcined at 600°C for 4 hours to prepare a molecular sieve catalyst with a tin loading of 2 wt%. The molecular sieve catalyst loaded with tin was then impregnated with a concentration of 2 mg·L -1 The obtained catalyst was taken out from the samarium trifluoromethanesulfonate solution, placed in the muffle furnace again, and calcined at 600° C. for 4 h to prepare a molecular sieve catalyst with a samarium loading of 2 wt%.

[0041] Example 1

[0042] S1: 85 g of sodium ethoxide and 74 g of tert-butanol were placed in a reaction vessel, 2 g of the molecular sieve catalyst described in Preparation Example 1 was added, and the mixture was heated to 98° C. for reflux reaction;

[0043] S2: After reacting for 2 hours, the temperature is cooled to room temperature and the molecular sieve catalyst is filtered out, and then the temperature is heated to 98° C. to distill out impurities to obtain the sodium tert-butoxide.

[0044] Example 2

[0045] The difference between this embodiment and embodiment 1 is that the amount of sodium ethoxide used is 68 g.

[0046] The other parts are exactly the same as those in Example 1.

[0047] Example 3

[0048] The difference between this embodiment and embodiment 1 is that the amount of sodium ethoxide used is 102 g.

[0049] The other parts are exactly the same as those in Example 1.

[0050] Example 4

[0051] The difference between this example and Example 1 is that the loading amount of tin on the molecular sieve in Preparation Example 1 is 1 wt %.

[0052] The other parts are exactly the same as those in Example 1.

[0053] Example 5

[0054] The difference between this embodiment and embodiment 1 is that the loading amount of tin on the molecular sieve in the preparation example 1 is 5 wt %.

[0055] The other parts are exactly the same as those in Example 1.

[0056] Example 6

[0057] The difference between this embodiment and embodiment 1 is that the distillation temperature is 95°C.

[0058] The other parts are exactly the same as those in Example 1.

[0059] Example 7

[0060] The difference between this embodiment and embodiment 1 is that the distillation temperature is 100°C.

[0061] The other parts are exactly the same as those in Example 1.

[0062] Example 8

[0063] The difference between this embodiment and embodiment 1 is that the catalyst is recycled for the fifth time after filtration.

[0064] The other parts are exactly the same as those in Example 1.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that the loading amount of tin on the molecular sieve in Preparation Example 1 is 10 wt %.

[0067] The other parts are exactly the same as those in Example 1.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that the distillation temperature is 90°C.

[0070] The other parts are exactly the same as those in Example 1.

[0071] Comparative Example 3

[0072] The difference between this comparative example and Example 8 is that the loading amount of samarium trifluoromethanesulfonate in Preparation Example 1 is 0.

[0073] Results and Testing

[0074] The purity of sodium tert-butoxide is shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] It can be seen from Examples 1-3 in Table 1 that the amount of sodium ethoxide used will affect the product yield. When used in an equimolar amount with tert-butyl alcohol, the product yield is reduced to 95%. Increasing the amount can increase the yield, but excessive use will affect the product purity.

[0079] It can be seen from Table 1 Examples 1, 4-5 and Comparative Example 1 that when the loading amount of tin on the medium molecular sieve is 1wt%, the loading amount is low, the catalytic activity is insufficient, and the yield is low. The yield increases with increasing loading amount. When the loading amount is 5wt%, the yield decreases slightly. When the loading amount is 10wt%, tin crystallizes into blocky tin dioxide, the catalytic activity decreases, and the yield is further reduced.

[0080] It can be seen from Table 1 that when the distillation temperature is 98°C, the purity and yield of the product reach the highest value. Lowering the temperature will reduce the purity, while increasing the temperature will affect the yield.

[0081] It can be seen from Examples 1 and 8 and Comparative Example 3 in Table 1 that samarium trifluoromethanesulfonate affects the recycling activity of the molecular sieve catalyst, thereby affecting the product yield and purity.

[0082] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing high-purity granular sodium tert-butoxide, characterized in that: The specific steps include: S1: placing an alkali metal low-carbon alcohol salt and a polyol in a reaction vessel, adding a molecular sieve catalyst, and heating to reflux for reaction; S2: After the reaction is completed, the molecular sieve catalyst is removed by filtering and impurities are removed by distillation to obtain the sodium tert-butoxide.

2. The method for preparing high-purity granular sodium tert-butoxide according to claim 1, characterized in that: In step S1, the alkali metal low-carbon alcohol alkoxide is sodium ethoxide.

3. The method for preparing high-purity granular sodium tert-butoxide according to claim 1, characterized in that: The polyol in step S1 is tert-butyl alcohol.

4. A method for preparing high-purity granular sodium tert-butoxide according to claim 2 or 3, characterized in that: The molar ratio of sodium ethoxide to tert-butanol in step S1 is 1-1.5:

1.

5. The method for preparing high-purity granular sodium tert-butoxide according to claim 1, characterized in that: The preparation method of the molecular sieve catalyst in step S1 is: calcining the molecular sieve and then immersing it in an organic metal solution, and continuing to calcine after the immersion to obtain the molecular sieve catalyst.

6. The method for preparing high-purity granular sodium tert-butoxide according to claim 5, characterized in that: The organic metal comprises organic tin, and the organic tin is one or more of dibutyltin oxide, butyltin trichloride, tributyltin chloride and dibutyltin maleate.

7. The method for preparing high-purity granular sodium tert-butoxide according to claim 5, characterized in that: The organic metal further includes organic samarium, and the organic samarium includes samarium trifluoromethanesulfonate.

8. The method for preparing high-purity granular sodium tert-butoxide according to claim 5, characterized in that: The loading amount of tin on the molecular sieve is 1-5 wt %.

9. The method for preparing high-purity granular sodium tert-butoxide according to claim 1, characterized in that: The heating conditions in step S1 are 95-100° C. and normal pressure.

10. The method for preparing high-purity granular sodium tert-butoxide according to claim 1, characterized in that: The distillation conditions in step S2 are 95-100° C. and normal pressure.

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