Preparation method of high-purity tert-butyl isocyanate

Abstract

The invention discloses a preparation method of high-purity tert-butyl isocyanate. The preparation method is characterized by comprising the following steps: 1) adding an inert solvent into a reactor; 2) adding sodium cyanate, a catalyst and a stabilizer into a reactor, and stirring at room temperature to obtain an initial mixed solution; (3) adding tert-butyl chloride into the step (1); 2) in the initial mixed solution, reacting for 4-6 hours to obtain a reaction mixed solution; and 4) separating and purifying the reaction mixed solution in the step 3) to obtain the high-purity tert-butyl isocyanate. According to the invention, the tert-butyl isocyanate is prevented from polymerization through the synergistic stabilization effect of the catalyst and the stabilizer, and the high-purity tert-butyl isocyanate is obtained after separation and purification.

Description

Technical Field

[0001] The invention relates to a method for preparing high-purity tert-butyl isocyanate (t-BuNCO), which is particularly suitable for application in polyurethane industry, medicine and pesticide synthesis, and material science. Background Art

[0002] Tert-butyl isocyanate is an important organic synthesis intermediate, which is widely used in many fields. In the polyurethane industry, it is used to produce high-performance coatings, adhesives, sealants and elastomers, giving the products excellent chemical resistance and mechanical properties. In the field of medicine and pesticides, tert-butyl isocyanate is a key raw material for the synthesis of certain drugs and agrochemicals. In addition, in materials science, it is used to develop new functional materials, such as optoelectronic materials and polymer composites.

[0003] CN108395383B discloses a method for synthesizing tert-butyl isocyanate, which comprises mixing an inert solvent and p-toluenesulfonamide, introducing phosgene at 100°C-120°C, and introducing an inert gas to drive out the gas after the reaction is completed to prevent phosgene and hydrogen chloride from dissolving in the reaction solution, and reacting with subsequently added tert-butylamine to obtain tert-butyl isocyanate.

[0004] As a highly efficient chemical reagent, phosgene is widely used in industrial production, but its high toxicity and potential lethality make it a highly dangerous substance. The experimental data of sampling and testing show that the yield of tert-butyl isocyanate is high, but it cannot meet the requirements of the industry that requires higher purity tert-butyl isocyanate. Summary of the invention

[0005] Based on this, it is necessary to provide a method for synthesizing tert-butyl isocyanate with safe process and high purity.

[0006] The invention aims to provide a method for synthesizing high-purity tert-butyl isocyanate.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing high-purity tert-butyl isocyanate comprises the following steps:

[0009] 1) adding an inert solvent into a reactor;

[0010] 2) adding sodium cyanate, a catalyst and a stabilizer into a reactor, and stirring at room temperature to obtain an initial mixed solution;

[0011] 3) adding tert-butyl chloride to the initial mixed solution in step 2) and reacting for 4-6 hours to obtain a reaction mixed solution;

[0012] 4) The reaction mixture in step 3) is separated and purified to obtain high-purity tert-butyl isocyanate.

[0013] Furthermore, in the step 1), an inert gas is introduced into the reactor before adding the inert solvent, the inert gas is nitrogen or argon, and the inert solvent is dioxane, tetrahydrofuran, ethyl acetate, xylene or chlorobenzene.

[0014] The introduction of inert gas (such as nitrogen or argon) can effectively remove oxygen and moisture in the reactor, prevent the occurrence of side reactions such as oxidation reaction and hydrolysis, and ensure the stability of the reactants. In particular, when it comes to reactive substances (such as sodium cyanate, tert-butyl chloride, etc.), the oxygen in the air may react undesirably with certain reactants, resulting in the generation of by-products, and even reducing the selectivity and yield of the reaction. Inert solvents (such as dioxane, tetrahydrofuran, ethyl acetate, xylene, chlorobenzene, etc.) are chemically stable in the reaction, which ensures that the solvent will not react undesirably with the active substances (such as tert-butyl chloride, sodium cyanate, etc.) in the reactants, avoiding the generation of unnecessary by-products, thereby improving the selectivity of the reaction and the purity of the product. And inert solvents have relatively high boiling points, which make them stable under high temperature conditions and not easy to volatilize. After the reaction is completed, the solvent can be easily separated from the product by methods such as distillation or rectification, improving the efficiency and purity of the separation.

[0015] Furthermore, in the step 2), the catalyst is at least one of ferric chloride, zinc chloride, ferric bromide and zinc bromide.

[0016] Furthermore, in the step 2), the stabilizer is at least one of sodium lauryl sulfate, sodium cetyl sulfate and sodium stearyl alkyl sulfate.

[0017] During the synthesis of tert-butyl isocyanate, these catalysts promote the nucleophilic reaction between sodium cyanate and tert-butyl chloride through the action of the reactants, reduce the reaction energy barrier between the reactants, speed up the reaction efficiency and avoid the occurrence of side reactions. Stabilizers such as sodium lauryl sulfate, sodium cetyl sulfate and sodium stearyl alkyl sulfate are all surfactants. They inhibit the contact of tert-butyl isocyanate with moisture and impurities in the air by forming a protective film layer in the reaction system, thereby reducing the risk of self-polymerization. Therefore, through the synergistic effect of the catalyst and stabilizer, the self-polymerization reaction can be effectively inhibited while ensuring the efficient reaction, avoiding the formation of by-products, thereby improving the purity of tert-butyl isocyanate.

[0018] Furthermore, in the step 2), the molar ratio of sodium cyanate, catalyst, stabilizer and inert solvent is in the range of (10-15):1:(2-5):(20-30).

[0019] Furthermore, in the step 3), the molar ratio of the catalyst to tert-butyl chloride is in the range of 1:(8-12), and the reaction temperature is controlled at 70-80°C.

[0020] Furthermore, in the step 4), a stabilizer is added to the reaction mixture again and then separated and purified, and the molar ratio of the amount of the stabilizer added to the amount of the stabilizer added in the step 2) is in the range of (2-5):1.

[0021] After the reaction mixture has been tried, the activity of the catalyst decreases, and the catalyst needs more stabilizers to maintain its synergistic stabilization effect. In addition, during the separation and purification stage, the conditions will change. For example, the temperature of the reaction liquid needs to be further increased. At high temperatures, the probability of self-polymerization of tert-butyl isocyanate will increase, resulting in a decrease in purity.

[0022] Furthermore, in the step 4), the separation and purification is a distillation or rectification process.

[0023] Due to the steric hindrance effect of the tert-butyl group, the self-polymerization tendency of tert-butyl isocyanate is much lower than that of other types of isocyanates, but because the isocyanate functional group (-N=C=O) therein has a high reactivity, especially at high temperature or in the presence of trace moisture and impurities, self-polymerization or other side reactions may still occur, affecting the purity of tert-butyl isocyanate, especially the need for high temperature reaction in the preparation process of tert-butyl isocyanate and the need for higher temperature to separate tert-butyl isocyanate during separation and purification, which will affect the purity and yield of tert-butyl isocyanate. Therefore, the present application prevents tert-butyl isocyanate from polymerization by adding stabilizers in batches, and by the synergistic stabilization of catalysts and stabilizers, and obtains high-purity tert-butyl isocyanate after separation and purification. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with embodiments, but the present invention is not limited thereto.

[0025] Example 1

[0026] In a 500mL reactor, nitrogen is introduced to ensure that the reactor is full of inert gas, then 200mL of dioxane is added as an inert solvent, sodium cyanate (2.37g), ferric chloride (0.5g), sodium lauryl sulfate (1.2g) are added to dioxane, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (12.0g) is added at room temperature, the temperature in the reactor is increased and controlled at 75°C, and the reaction is reacted for 4 hours to obtain a reaction mixture. After the reaction is completed, sodium lauryl sulfate (2.4g) is added to the reaction mixture again, and the stirring reaction is continued for 5 minutes, and the following operation is performed to transfer the reaction mixture to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and the temperature section is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low boiling point solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate was collected after distillation, and the purity reached 99%.

[0027] Example 2

[0028] In a 1000 mL reactor, nitrogen was introduced to ensure that the reactor was filled with inert gas, and then 300 mL of tetrahydrofuran was added as an inert solvent, sodium cyanate (4.74 g), zinc chloride (0.6 g), and sodium cetyl sulfate (2.0 g) were added to the tetrahydrofuran, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (15.0 g) was added at room temperature, the temperature in the reactor was increased and controlled at 78° C., and the reaction was carried out for 5 hours to obtain a reaction mixture.

[0029] After the reaction is completed, sodium cetyl sulfate (3.6 g) is added to the reaction mixture again, and the reaction is continued to be stirred for 5 minutes, and the following operations are performed: the reaction mixture is transferred to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and this temperature range is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low-boiling point solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate after distillation is collected, and the purity reaches 99.1%.

[0030] Example 3

[0031] In a 500 mL reactor, nitrogen was introduced to ensure that the reactor was filled with inert gas, and then 250 mL of xylene was added as an inert solvent, sodium cyanate (3.16 g), ferric bromide (0.6 g), and sodium stearyl alkyl sulfate (2.0 g) were added to the xylene, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (13.5 g) was added at room temperature, the temperature in the reactor was increased and controlled at 80° C., and the reaction was carried out for 6 hours to obtain a reaction mixture.

[0032] After the reaction is completed, sodium stearyl alkyl sulfate (3.0 g) is added to the reaction mixture again, and the reaction is continued to be stirred for 5 minutes, and then the following operations are performed: the reaction mixture is transferred to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and the temperature range is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low-boiling solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate after distillation is collected, and the purity reaches 99.5%.

[0033] Example 4

[0034] In a 1000 mL reactor, nitrogen was introduced to ensure that the reactor was filled with inert gas, and then 400 mL of ethyl acetate was added as an inert solvent, sodium cyanate (5.0 g), ferric chloride (0.7 g), and sodium lauryl sulfate (2.5 g) were added to the ethyl acetate, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (20.0 g) was added at room temperature, the temperature in the reactor was increased and controlled at 75° C., and the reaction was carried out for 5 hours to obtain a reaction mixture.

[0035] After the reaction is completed, sodium lauryl sulfate (5.0 g) is added to the reaction mixture again, and the reaction is continued to be stirred for 5 minutes, and then the following operations are performed: the reaction mixture is transferred to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and this temperature range is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low-boiling solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate after distillation is collected, and the purity reaches 99.5%.

[0036] Example 5

[0037] In a 500 mL reactor, nitrogen was introduced to ensure that the reactor was filled with inert gas, and then 250 mL of xylene was added as an inert solvent, sodium cyanate (3.16 g), ferric chloride (0.55 g), and sodium cetyl sulfate (2.2 g) were added to the xylene, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (14.0 g) was added at room temperature, the temperature in the reactor was increased and controlled at 77° C., and the reaction was carried out for 5 hours to obtain a reaction mixture.

[0038] After the reaction is completed, sodium cetyl sulfate (2.8 g) is added to the reaction mixture again, and the reaction is continued to be stirred for 5 minutes, and then the following operations are performed: the reaction mixture is transferred to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and this temperature range is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low-boiling solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate after distillation is collected, and the purity reaches 99.3%.

[0039] Comparative Example 1

[0040] In a 500mL reactor, nitrogen is introduced to ensure that the reactor is full of inert gas, then 200mL of dioxane is added as an inert solvent, sodium cyanate (2.37g) and ferric chloride (0.5g) are added to dioxane, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (12.0g) is added at room temperature, the temperature in the reactor is increased and controlled at 75°C, and the reaction mixture is obtained for 4 hours. After the reaction is completed, the reaction mixture is transferred to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and the temperature section is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low boiling point solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate after distillation is collected, and the purity reaches 97.6%.

[0041] Comparative Example 2

[0042] In a 500mL reactor, nitrogen is introduced to ensure that the reactor is full of inert gas, then 200mL of dioxane is added as an inert solvent, sodium cyanate (2.37g), ferric chloride (0.5g), and sodium lauryl sulfate (1.2g) are added to dioxane, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (12.0g) is added at room temperature, the temperature in the reactor is increased and controlled at 75°C, and the reaction mixture is obtained for 4 hours. After the reaction is completed, the reaction mixture is transferred to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and the temperature section is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low boiling point solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate after distillation is collected, and the purity reaches 98.5%.

[0043] Comparative Example 3

[0044] In a 500mL reactor, nitrogen is introduced to ensure that the reactor is full of inert gas, then 200mL of dioxane is added as an inert solvent, sodium cyanate (2.37g) and ferric chloride (0.5g) are added to dioxane, and stirred evenly at room temperature to obtain an initial mixed solution. Tert-butyl chloride (12.0g) is added at room temperature, the temperature in the reactor is raised and controlled at 75°C, and the reaction is performed for 4 hours to obtain a reaction mixture. After the reaction is completed, sodium lauryl sulfate (2.4g) is added to the reaction mixture, and the stirring reaction is continued for 5 minutes, and the following operations are performed to transfer the reaction mixture to a distillation device, and a condenser is set for separation, and the temperature is gradually raised to 85-90°C, and the temperature section is maintained to ensure that tert-butyl isocyanate is effectively distilled out. Low boiling point solvents and impurities are evaporated in the early stage, and these fractions are collected and discarded for impurity removal. When the temperature reaches 85°C, the main tert-butyl isocyanate is collected. The tert-butyl isocyanate after distillation is collected, and the purity reaches 98%.

[0045] According to the operation of Example 1, sodium lauryl sulfate (stabilizer) was added twice in batches to inhibit the self-polymerization reaction of tert-butyl isocyanate, and impurities were effectively removed by distillation, and the purity of the finally obtained tert-butyl isocyanate reached 99%. In the comparative example, if the stabilizer was added only once or not at all, the purity was low due to the failure to fully inhibit the side reaction and optimize the distillation process. This shows that the batch addition of the stabilizer plays a vital role in ensuring the high purity of the product.

[0046] Those skilled in the art will appreciate that, based on the teachings of this specification, some modifications or adjustments may be made to the present invention, and these modifications or adjustments should also be within the scope defined by the claims of the present invention.

[0047] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the patent and protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing high-purity tert-butyl isocyanate, characterized in that The following steps are involved: 1) adding an inert solvent into a reactor; 2) adding sodium cyanate, a catalyst and a stabilizer into a reactor, and stirring at room temperature to obtain an initial mixed solution; 3) adding tert-butyl chloride to the initial mixed solution in step 2) and reacting for 4-6 hours to obtain a reaction mixed solution; 4) The reaction mixture in step 3) is separated and purified to obtain high-purity tert-butyl isocyanate.

2. The method according to claim 1, characterized in that Before adding the inert solvent, an inert gas is introduced into the reactor, wherein the inert gas is nitrogen or argon.

3. The method according to claim 1, characterized in that The inert solvent is dioxane, tetrahydrofuran, ethyl acetate, xylene or chlorobenzene.

4. The method according to claim 1, characterized in that: The catalyst is at least one of ferric chloride, zinc chloride, ferric bromide and zinc bromide.

5. The method according to claim 1, characterized in that The stabilizer is at least one of sodium lauryl sulfate, sodium cetyl sulfate and sodium stearyl alkyl sulfate.

6. The method according to claim 1, characterized in that The molar ratio of sodium cyanate, catalyst, stabilizer and inert solvent is in the range of (10-15):1:(2-5):(20-30).

7. The method according to claim 1, characterized in that The molar ratio of the catalyst to tert-butyl chloride is in the range of 1:(8-12), and the reaction temperature is controlled at 70-80°C.

8. The method according to claim 1, characterized in that The stabilizer is added to the reaction mixture again for separation and purification.

9. The method according to claim 8, characterized in that The molar ratio of the stabilizer added again to the stabilizer added in step 2) is in the range of (2-5):

1.

10. The method according to claim 1, characterized in that The separation and purification is a distillation or rectification process.