Preparation method of isocyanate using mesoporous silica as auxiliary agent

Abstract

The present invention belongs to the technical field of organic synthesis, and relates to a method for preparing isocyanate using mesoporous silica as an auxiliary agent. The method introduces mesoporous silica, and utilizes its unique pore structure and large specific surface area to promote the reaction of organic amines and chloroform compounds to generate isocyanates. Mesoporous silica not only acts as an auxiliary agent, but also enhances the adsorption of reactant molecules through its surface action mechanism, thereby improving the efficiency of the entire reaction system. In addition, the preparation method of mesoporous silica is simple and easy to mass produce. Its auxiliary agent effect in the preparation of isocyanate effectively reduces the reaction temperature and time, and has good industrial application prospects. With the help of the effect of the mesoporous silica auxiliary agent, the present invention greatly reduces the dependence of the reaction on the intensity of light, so that the reaction can be carried out at a relatively low light power density, reducing the risks and hazards brought by ultraviolet light.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a method for preparing isocyanate using mesoporous silica as an auxiliary agent. Background Art

[0002] Isocyanate is widely used in the polyurethane industry. It is a key intermediate in the manufacture of foams, elastomers, coatings, adhesives and other products. The traditional isocyanate preparation process is mainly the reaction of amine compounds with phosgene. However, the use of phosgene is not only highly toxic and environmentally harmful, but also requires complex equipment for processing, further increasing production costs and operational risks. Based on this, the development of a more environmentally friendly and efficient isocyanate preparation method has become an important direction in the global scientific research field. Summary of the invention

[0003] In recent years, the application of mesoporous materials in chemical reactions has gradually attracted attention. Mesoporous silica exhibits excellent catalytic performance due to its regular pore structure and large specific surface area. The pore size of mesoporous materials can be adjusted by different templates and reaction conditions, and this characteristic makes its application in catalytic reactions flexible and efficient. In the preparation process of isocyanate, the introduction of mesoporous silica can greatly increase the number of active sites of the reaction, promote the reaction rate, increase the yield, and reduce the generation of by-products. The present invention utilizes mesoporous silica as an auxiliary agent and introduces it into the synthesis system of isocyanate, which not only improves the reaction efficiency, but also reduces environmental pollution, providing a more environmentally friendly and efficient solution for industrial production.

[0004] In order to achieve the above-mentioned invention object, the present invention provides a method for preparing isocyanate using mesoporous silica as an auxiliary agent. The method introduces mesoporous silica and utilizes its unique pore structure and large specific surface area to promote the reaction of organic amines and chloroform compounds to generate isocyanate. Mesoporous silica not only acts as an auxiliary agent, but also enhances the adsorption of reactant molecules through its surface action mechanism, thereby improving the efficiency of the entire reaction system.

[0005] The present invention also relates to a method for preparing mesoporous silica to ensure that it has a suitable pore size and a high specific surface area, thereby exhibiting an excellent auxiliary effect in the preparation process of isocyanate.

[0006] The method for preparing isocyanate using mesoporous silica as an auxiliary agent comprises the following steps:

[0007] (1) Slowly adding tetraethoxysilane (TEOS) dropwise to a hexadecyltrimethylammonium bromide (CTAB) solution, stirring continuously, and controlling the feeding rate to ensure uniform reaction; adding ammonia water to adjust the pH value of the solution to alkaline, stirring, and obtaining a mixture;

[0008] (2) transferring the mixture into a stainless steel autoclave and sealing it for hydrothermal reaction; after the reaction is completed, separating the product by centrifugation and washing the precipitate with ethanol for multiple times;

[0009] (3) drying the washed precipitate and calcining it in an air atmosphere to remove the CTAB template and obtain mesoporous silica with a regular pore structure;

[0010] (4) dissolving the organic amine using chloroform or bromoform to obtain a reaction mixture, and then adding the mesoporous silica described in step (3) to the reaction mixture as an auxiliary agent; controlling the reaction temperature at 20-50° C., stirring the reaction under ultraviolet light, and the reaction is an open reaction; after the reaction is completed, separating the reaction product by distillation or filtration, and purifying it to obtain the target isocyanate.

[0011] In the preparation of mesoporous silica, TEOS is used as a silicon source, CTAB is used as a template, and ammonia water is used as an alkaline catalyst.

[0012] Preferably, in step (1), aqueous ammonia is added to adjust the pH value of the solution to greater than or equal to 10; and the stirring time is 1 hour.

[0013] Preferably, in step (2), the hydrothermal reaction is carried out at 100° C. for 24 hours.

[0014] Preferably, in step (3), drying is performed at 60° C. for 12 hours; and calcination is performed in an air atmosphere at 500° C. for 4 hours.

[0015] Preferably, in step (4), the organic amine is an aliphatic organic amine or an aromatic organic amine.

[0016] More preferably, in step (4), the aliphatic organic amine is butylamine or n-propylamine, and the aromatic organic amine is aniline.

[0017] Preferably, in step (4), the mass volume ratio of the organic amine to bromoform or chloroform is 1 g : (6-10) mL.

[0018] Preferably, the amount of the auxiliary agent in step (4) is 1-5% of the total mass of the organic amine in the reactants.

[0019] Preferably, in step (4), the wavelength range of the ultraviolet lamp is 200-400 nm; and the light power density of the ultraviolet lamp is 0.05 W / cm2.

[0020] Preferably, the reaction time in step (4) is 2-6 hours.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The high specific surface area and regular pore structure of the mesoporous silica of the present invention can significantly increase the contact probability of the reactants in the reaction, increase the reaction rate and improve the yield of isocyanate.

[0023] (2) The preparation method of the mesoporous silica of the present invention is simple and easy to mass produce. Its auxiliary agent function in the preparation of isocyanate effectively reduces the reaction temperature and time, and has good industrial application prospects.

[0024] (3) The present invention uses the effect of mesoporous silica as an auxiliary agent to greatly reduce the dependence of the reaction on light intensity, and can be carried out at a relatively low light power density, thereby reducing the risks and hazards brought by ultraviolet light. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a SEM image of the mesoporous silica in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, the embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0027] Example 1

[0028] The method for preparing phenyl isocyanate using mesoporous silica as an auxiliary agent comprises the following steps:

[0029] (1) Preparation of mesoporous silica: Tetraethoxysilane (TEOS) was used as the silicon source, and hexadecyltrimethylammonium bromide (CTAB) was used as the template, and a hydrothermal reaction was carried out under alkaline conditions.

[0030] At 50°C, 1 g of CTAB was dissolved in 100 mL of deionized water and stirred until completely dissolved to obtain a CTAB solution; 4 mL of TEOS was slowly added dropwise to the CTAB solution and stirred continuously; a 1 M ammonia solution was added to adjust the pH to 10 and stirred for 1 hour to obtain a mixture;

[0031] (2) transferring the mixture to an autoclave and subjecting it to a hydrothermal treatment at 100°C for 24 hours; after the reaction, separating the generated precipitate by centrifugation and washing it with ethanol for multiple times to remove the unreacted template;

[0032] (3) The precipitate was dried at 60°C for 12 hours, and then calcined in an air atmosphere at 500°C for 4 hours to remove the CTAB template and obtain a silica material with a mesoporous structure. The SEM characterization image of the obtained mesoporous silica is shown in Figure 1 shown.

[0033] (4) Mix 10 g of aniline with 60 mL of chloroform, and add 0.1 g of mesoporous silica obtained in step (1) as an auxiliary agent. Stir and react for 6 hours at 30°C under irradiation with a 200 nm ultraviolet lamp (0.05 W / cm2). After the reaction is completed, 11.1 g of phenyl isocyanate is obtained by distillation separation with a yield of 88%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.3, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0034] Example 2

[0035] The method for preparing phenyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0036] Mix 10g of aniline with 60mL of chloroform, and add 0.1g of mesoporous silica as an auxiliary agent. Stir and react for 6 hours at 30°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 11.5g of phenyl isocyanate is obtained by distillation separation with a yield of 91%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.1, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0037] Example 3

[0038] The method for preparing phenyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0039] Mix 10g of aniline with 100mL of chloroform, and add 0.5g of mesoporous silica as an auxiliary agent. Stir and react for 6 hours at 30°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 11.7g of phenyl isocyanate is obtained by distillation separation with a yield of 92%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.1, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0040] Example 4

[0041] The method for preparing butyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0042] Mix 5g of butylamine with 30mL of chloroform, and add 0.25g of mesoporous silica as an auxiliary agent. Stir and react for 6 hours at 30°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 5.8g of butyl isocyanate is obtained by distillation separation with a yield of 87%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 100.5, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0043] Example 5

[0044] The method for preparing butyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0045] Mix 5g of butylamine with 30mL of chloroform, and add 0.25g of mesoporous silica as an auxiliary agent. Stir and react for 2 hours at 30°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 5.5g of butyl isocyanate is obtained by distillation separation with a yield of 81%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 100.2, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0046] Example 6

[0047] The method for preparing phenyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0048] Mix 10g of aniline with 60mL of chloroform, and add 0.1g of mesoporous silica as an auxiliary agent. Stir and react for 6 hours at 20°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 11.1g of phenyl isocyanate is obtained by distillation separation with a yield of 88%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.1, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0049] Example 7

[0050] The method for preparing phenyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0051] Mix 10g of aniline with 60mL of chloroform, and add 0.1g of mesoporous silica as an auxiliary agent. Stir and react for 6 hours at 50°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 11.7g of phenyl isocyanate is obtained by distillation separation with a yield of 92%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.1, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0052] Example 8

[0053] The method for preparing phenyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0054] Mix 10g of aniline with 60mL of chloroform, and add 0.1g of mesoporous silica as an auxiliary agent. Stir and react for 4 hours at 30°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 11.3g of phenyl isocyanate is obtained by distillation separation with a yield of 90%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.1, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0055] Example 9

[0056] The method for preparing phenyl isocyanate using mesoporous silica as an auxiliary agent is different from that of Example 1 in that, in step (1), a 1 M ammonia solution is added to adjust the pH to 11.5.

[0057] Step (4) is: 10 g of aniline is mixed with 60 mL of chloroform, and 0.1 g of mesoporous silica is added as an auxiliary agent. The mixture is stirred and reacted for 6 hours at 30°C under irradiation with a 400 nm ultraviolet lamp (0.05 W / cm2). The reaction is an open reaction. After the reaction is completed, 11.7 g of phenyl isocyanate is obtained by distillation separation, with a yield of 92%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.1, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0058] Example 10

[0059] The method for preparing propyl isocyanate using mesoporous silica as an auxiliary agent, wherein the mesoporous silica is prepared in Example 1, comprises the following steps:

[0060] Mix 10g of n-propylamine with 60mL of chloroform, and add 0.1g of mesoporous silica as an auxiliary agent. Stir and react for 6 hours at 20°C under 400nm ultraviolet light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 12.5g of propyl isocyanate is obtained by distillation separation with a yield of 87%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 86.3, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0061] Comparative Example 1

[0062] A method for preparing phenyl isocyanate comprises the following steps:

[0063] Mix 10g of aniline with 60mL of chloroform. Stir and react for 6 hours at 30°C under 200nm UV light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 2.7g of phenyl isocyanate is obtained by distillation separation with a yield of 21%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.1, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0064] Comparative Example 2

[0065] A method for preparing phenyl isocyanate comprises the following steps:

[0066] Mix 10g of aniline with 60mL of chloroform. Stir and react for 2 hours at 30°C under 200nm UV light (0.05 watts / square centimeter). The reaction is an open reaction. After the reaction is completed, 0.9g of phenyl isocyanate is obtained by distillation separation with a yield of 7%. The molecular weight of the prepared product is verified by GCMS to be [M+H] + : 120.3, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0067] Comparative Example 3

[0068] 10g of aniline was mixed with 60mL of acetonitrile, and 0.1g of mesoporous silica was added as an auxiliary agent. The mixture was stirred and reacted for 6 hours at 30°C under irradiation with a 200nm ultraviolet lamp (0.05 watts / square centimeter). The reaction was an open reaction, and after the reaction was completed, no isocyanate could be obtained by distillation.

Claims

1. A method for preparing isocyanate using mesoporous silica as an auxiliary agent, characterized in that: The following steps are involved: (1) Slowly add tetraethoxysilane to the hexadecyltrimethylammonium bromide solution while stirring continuously; adding aqueous ammonia to adjust the pH value of the solution to alkaline, stirring, and obtaining a mixture; (2) transferring the mixture into a stainless steel autoclave and sealing it for hydrothermal reaction; after the reaction is completed, separating the product by centrifugation and washing the precipitate with ethanol for multiple times; (3) drying the washed precipitate and calcining it in an air atmosphere to remove the CTAB template and obtain mesoporous silica with a regular pore structure; (4) dissolving the organic amine in chloroform or bromoform to obtain a reaction mixture, and then adding the mesoporous silica described in step (3) to the reaction mixture as an auxiliary agent; controlling the reaction temperature to 20-50° C., stirring the reaction under ultraviolet light, and the reaction is an open reaction; after the reaction is completed, separating the reaction product by distillation or filtration, and purifying to obtain the target isocyanate; The organic amine is butylamine, n-propylamine or aniline.

2. The method for preparing isocyanate using mesoporous silica as an auxiliary agent according to claim 1, characterized in that: In step (1), aqueous ammonia is added to adjust the pH value of the solution to greater than or equal to 10; and the stirring time is 1 hour.

3. The method for preparing isocyanate using mesoporous silica as an auxiliary agent according to claim 1, characterized in that: In step (2), a hydrothermal reaction is carried out at 100° C. for 24 hours.

4. The method for preparing isocyanate using mesoporous silica as an auxiliary agent according to claim 1, characterized in that: In step (3), the mixture is dried at 60°C for 12 hours and calcined in an air atmosphere at 500°C for 4 hours.

5. The method for preparing isocyanate using mesoporous silica as an auxiliary agent according to claim 1, characterized in that: In step (4), the mass volume ratio of the organic amine to bromoform or chloroform is 1 g : (6-10) mL.

6. The method for preparing isocyanate using mesoporous silica as an auxiliary agent according to claim 1, characterized in that: The amount of the auxiliary agent used in step (4) is 1-5% of the mass of the organic amine in the reactants.

7. The method for preparing isocyanate using mesoporous silica as an auxiliary agent according to claim 1, characterized in that: The wavelength range of the ultraviolet lamp in step (4) is 200-400 nm; the light power density of the ultraviolet lamp is 0.05 W / cm2.

8. The method for preparing isocyanate using mesoporous silica as an auxiliary agent according to claim 1, characterized in that: The reaction time in step (4) is 2-6 hours.

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