A preparation method of isocyanate based on rare earth upconversion materials

Abstract

The present invention belongs to the technical field of the preparation of isocyanates, and specifically discloses a method for preparing isocyanates based on rare earth upconversion materials, which comprises the following steps: mixing a rare earth metal salt and a ligand and dissolving them in absolute ethanol or anhydrous ethylene glycol, and carrying out a solvothermal reaction to obtain rare earth nanoparticles; calcining the obtained rare earth nanoparticles at 450-550 °C to obtain rare earth upconversion materials; adding the rare earth upconversion materials to a solution of an organic amine compound, wherein the mass percentage of the rare earth upconversion materials in the organic amine compound is 1%-10%, and carrying out a photocatalytic oxidation reaction under near-infrared light irradiation to prepare isocyanates. Due to the light conversion characteristics of the rare earth upconversion materials, the isocyanate reaction of the present invention can proceed smoothly under the excitation of low-energy near-infrared light, and has the advantages of mild reaction, low equipment requirements and high efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of isocyanate preparation, and particularly relates to a method for preparing isocyanate based on rare earth upconversion materials. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Isocyanate is an important organic intermediate and is widely used in multiple industries such as polyurethane materials, coatings, adhesives, etc. The preparation of isocyanate mainly relies on phosgenation reactions, mainly including direct phosgenation of amines, phosgenation of amine hydrochlorides, phosgenation of carbamic acids, and gas-phase phosgenation methods, etc. Among them, phosgene, also known as carbonyl chloride, is a very reactive electrophilic reagent, is easy to hydrolyze, is a highly toxic asphyxiating gas, and high-concentration inhalation can cause pulmonary edema. Therefore, the traditional method for preparing isocyanate relying on phosgene has toxicity, corrosiveness, and high operational risk. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for preparing isocyanate based on rare earth upconversion materials. This method generates high-energy visible light or ultraviolet light under the irradiation of low-energy near-infrared light by introducing the prepared rare earth upconversion materials, thereby exciting the reactants to generate free radicals and promoting the reaction between organic amines and chloroform compounds, and finally generating isocyanate.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0006] A method for preparing isocyanate based on rare earth upconversion materials, comprising the following steps:

[0007] Mix and dissolve rare earth metal salts and ligands in absolute ethanol or anhydrous ethylene glycol, and perform a solvothermal reaction to obtain rare earth nanoparticles;

[0008] After calcining the obtained rare earth nanoparticles at 450 - 550 °C, rare earth upconversion materials are obtained;

[0009] Add the rare earth upconversion materials to a solution of organic amine compounds, where the mass percentage of the rare earth upconversion materials in the organic amine compounds is 1% - 10%, and perform a photocatalytic oxidation reaction under the irradiation of near-infrared light in an oxygen-containing environment to prepare isocyanate.

[0010] When using rare earth nanoparticles as a catalyst, the yield of isocyanate is relatively high and the experimental reproducibility is good.

[0011] In some embodiments, the organic amine compounds are aniline, butylamine, ethylamine, propylamine, or phenethylamine.

[0012] In some embodiments, the rare earth metal salt is a mixture of yttrium chloride, ytterbium chloride and europium chloride.

[0013] Preferably, in the rare earth metal salt, the mass ratio of yttrium chloride, ytterbium chloride and europium chloride is 10-15:10-15:1.

[0014] In some embodiments, the ligand is citric acid or acetic acid.

[0015] In some embodiments, the temperature of the solvothermal reaction is 160-200 °C, and the reaction time is 8-12 hours. During the solvothermal process, rare earth ions interact with the ligand to form rare earth nanoparticles.

[0016] In some embodiments, before calcination, it further includes the steps of washing and drying the prepared rare earth nanoparticles. Washing is used to remove impurities and improve the purity of the rare earth upconversion material. Calcination is used to remove the organic matter on the surface of the rare earth nanoparticles to obtain a rare earth upconversion material with good upconversion performance.

[0017] In some embodiments, the wavelength of the near-infrared light is 808 nm or 980 nm.

[0018] Preferably, the optical power of the near-infrared light is 0.1-5 watts per square centimeter.

[0019] Preferably, the time of the photocatalytic oxidation reaction is 1-12 hours.

[0020] In some embodiments, the organic solvent in the solution of the organic amine compound is chloroform or bromoform. These two types of solvents can generate free radicals under ultraviolet light, and then attack the organic amine to generate isocyanate, which cannot be achieved by other solvents.

[0021] In some embodiments, it further includes the step of purifying the prepared isocyanate, and the purification method is solvent evaporation, extraction or recrystallization.

[0022] The beneficial effects obtained by one or more of the above embodiments of the present invention are as follows:

[0023] 1) The prepared rare earth upconversion material has excellent optical properties. It can convert low-energy light into high-energy ultraviolet light or visible light under near-infrared light irradiation, which enables it to effectively generate free radicals in the photocatalytic reaction, and then oxidize the organic amine to generate isocyanate.

[0024] 2) By introducing rare earth upconversion materials, this method can effectively achieve the efficient preparation of isocyanates under mild conditions, reduce the use of phosgene, and solve the problems of equipment loss and complex operation caused by the use of high-energy ultraviolet light in traditional methods. Through the light conversion characteristics of rare earth upconversion materials, the isocyanate reaction in this invention proceeds smoothly under the excitation of low-energy near-infrared light, with the advantages of mild reaction, low equipment requirements, and high efficiency. It avoids the high requirements for equipment and operation of traditional ultraviolet light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0026] Figure 1 It is the TEM image of the rare earth upconversion material prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0028] The present invention will be further described below in conjunction with embodiments.

[0029] Example 1

[0030] Weigh 0.781 g (2 mmol) of yttrium chloride (YCl3·6H2O), 0.274 g (0.75 mmol) of ytterbium chloride (YbCl3·6H2O), and 0.061 g (0.15 mmol) of europium chloride (EuCl3·6H2O), and dissolve them in 20 mL of absolute ethanol. Add 0.640 g of citric acid (2 mmol) to the solution as a ligand, and stir until completely dissolved.

[0031] Transfer the above solution to a 300 mL autoclave, and ensure that the reactor body is well sealed. Place the autoclave in an oven, set the temperature to 180 °C, and carry out a solvothermal reaction for 12 hours.

[0032] After the reaction is completed, take out the autoclave and let it cool naturally to room temperature.

[0033] Transfer the reaction solution to a 50 mL centrifuge tube, centrifuge at a speed of 8000 rpm for 10 minutes to separate the precipitate. Wash the precipitate 3 times with deionized water, adding 30 mL of deionized water each time, and keep the centrifugation conditions unchanged. Wash it 2 times with absolute ethanol, adding 30 mL of absolute ethanol each time, and keep the centrifugation conditions unchanged.

[0034] The washed precipitate was dried in an oven at 60 °C for 12 hours to obtain dry rare earth nanoparticles. The dried nanoparticles were transferred to a muffle furnace and calcined in an air atmosphere at 500 °C for 4 hours to remove surface organic matter, obtaining a rare earth upconversion material with good upconversion performance. The SEM images of the obtained material are as shown in Figure 1 shown.

[0035] Example 2

[0036] 10 g of aniline was mixed with 50 mL of chloroform, and 1 g of the rare earth upconversion material (Yb 3 + / Er 3+ -doped NaYF4 nanoparticles) prepared in Example 1 was added. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), the reaction was carried out for 1 hour in an open state. After the reaction was completed, 11.3 g of phenyl isocyanate was obtained by distillation separation, and the yield was 89%. The molecular weight of the product was verified by GCMS to be [M+H] + : 120.1, which was consistent with the theoretical molecular weight, proving that the obtained product was the target product.

[0037] Example 3

[0038] 10 g of aniline was mixed with 50 mL of chloroform, and 0.1 g of the rare earth upconversion material (Yb 3 + / Er 3+ -doped NaYF4 nanoparticles) prepared in Example 1 was added. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), the reaction was carried out for 12 hours in an open state. After the reaction was completed, 10.1 g of phenyl isocyanate was obtained by distillation separation, and the yield was 79%. The molecular weight of the product was verified by GCMS to be [M+H] + : 120.3, which was consistent with the theoretical molecular weight, proving that the obtained product was the target product.

[0039] Example 4

[0040] 10 g of aniline was mixed with 50 mL of chloroform, and 1 g of the rare earth upconversion material (Yb 3 + / Er 3+ -doped NaYF4 nanoparticles) prepared in Example 1 was added. Under irradiation with 808 nm near-infrared light (light power density 5 W / cm²), the reaction was carried out for 4 hours in an open state. After the reaction was completed, 10.7 of phenyl isocyanate was obtained by distillation separation, and the yield was 84%. The molecular weight of the product was verified by GCMS to be [M+H] + : 120.3, which was consistent with the theoretical molecular weight, proving that the obtained product was the target product.

[0041] Example 5

[0042] Mix 10 g of aniline with 50 mL of chloroform, and add 0.1 g of the rare-earth upconversion material (Yb 3 + / Er 3+ -doped NaYF4 nanoparticles) prepared in Example 1. Under irradiation with 980 nm near-infrared light (light power density 0.1 W / cm²), react for 12 hours in an open state. After the reaction is completed, 10.5 g of phenyl isocyanate is obtained by distillation separation, and the yield is 83%. The molecular weight of the product is verified by GCMS to be [M+H] + : 120.2, which is consistent with the theoretical molecular weight, proving that the obtained product is the target product.

[0043] Example 6

[0044] Mix 5 g of butylamine with 30 mL of chloroform, and add 0.8 g of the rare-earth upconversion material prepared in Example 1. Under irradiation with 980 nm near-infrared light in an open state, react for 3 hours. After the reaction is completed, 5.9 g of butyl isocyanate is obtained by filtration separation, and the yield is 88%. The molecular weight of the 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.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that europium chloride is replaced by ytterbium chloride, that is, when preparing the rare-earth upconversion material, the rare-earth metal salts used are: 0.781 g of yttrium chloride (YCl3·6H2O) and 0.335 g of ytterbium chloride (YbCl3·6H2O), and the others are the same as in Example 1.

[0047] Mix 10 g of aniline with 50 mL of chloroform, and add 1 g of the rare-earth upconversion material prepared in Example 7. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), react for 1 hour in an open state. After the reaction is completed, an oily product is obtained by distillation separation, and no target product is obtained as verified by GCMS.

[0048] Comparative Example 2

[0049] The difference from Example 1 is that europium chloride is replaced by yttrium chloride, that is, when preparing the rare-earth upconversion material, the rare-earth metal salts used are: 0.842 g of yttrium chloride (YCl3·6H2O) and 0.274 g of ytterbium chloride (YbCl3·6H2O), and the others are the same as in Example 1.

[0050] Mix 10 g of aniline with 50 mL of chloroform, and add 1 g of the rare earth upconversion material prepared in Example 8. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), react for 1 hour in an open state. After the reaction is completed, an oily product is obtained by distillation separation, and the product is verified by GCMS and no target product is obtained.

[0051] Comparative Example 3

[0052] The difference from Example 1 is that only yttrium chloride is used, that is, when preparing the rare earth upconversion material, the rare earth metal salt used is: 1.116 g of yttrium chloride (YCl₃·6H₂O), and the others are the same as in Example 1.

[0053] Mix 10 g of aniline with 50 mL of chloroform, and add 1 g of the rare earth upconversion material prepared in Example 9. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), react for 1 hour in an open state. After the reaction is completed, an oily product is obtained by distillation separation, and the product is verified by GCMS and no target product is obtained.

[0054] Comparative Example 4

[0055] The difference from Example 1 is that only ytterbium chloride is used, that is, when preparing the rare earth upconversion material, the rare earth metal salt used is: 1.116 g of ytterbium chloride (YbCl₃·6H₂O), and the others are the same as in Example 1.

[0056] Mix 10 g of aniline with 50 mL of chloroform, and add 1 g of the rare earth upconversion material prepared in Example 10. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), react for 1 hour in an open state. After the reaction is completed, an oily product is obtained by distillation separation, and the product is verified by GCMS and no target product is obtained.

[0057] Comparative Example 5

[0058] Mix 10 g of aniline with 50 mL of chloroform, and under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), react for 1 hour. After the reaction is completed, an oily product is obtained by distillation separation, and the product is verified by GCMS and no target product is obtained.

[0059] Comparative Example 6

[0060] Mix 10 g of aniline with 50 mL of chloroform, and under irradiation with 980 nm near-infrared light (light power density 0.1 W / cm²), react for 12 hours. After the reaction is completed, an oily product is obtained by distillation separation, and the product is verified by GCMS and no target product is obtained.

[0061] Comparative Example 7

[0062] 5 g of butylamine was mixed with 30 mL of chloroform and reacted under 980 nm near-infrared light irradiation for 3 hours. After the reaction was completed, the oily product was obtained by distillation separation. The product was verified by GCMS and the target product was not obtained.

[0063] Comparative Example 8

[0064] 10 g of aniline was mixed with 50 mL of chloroform, and 1 g of the rare earth upconversion material (Yb 3 + / Er 3+ doped NaYF4 nanoparticles) prepared in Example 1 was added. Under 500 nm light irradiation (light power density 0.1 W / cm2), in the open state, the reaction was carried out for 1 hour. After the reaction was completed, 1.4 g of phenyl isocyanate was obtained by distillation separation, and the yield was 11%. The product was verified by GCMS and the molecular weight was [M+H] + : 120.2, which was consistent with the theoretical molecular weight, proving that the obtained product was the target product.

[0065] The yield of phenyl isocyanate in this comparative example was very low, indicating that it was difficult to obtain the corresponding isocyanate under 500 nm light irradiation, and the wavelength of light irradiation was a crucial factor.

[0066] Comparative Example 9

[0067] 10 g of aniline was mixed with 50 mL of acetonitrile, and 1 g of the rare earth upconversion material (Yb 3 + / Er 3+ doped NaYF4 nanoparticles) prepared in Example 1 was added. Under 808 nm near-infrared light irradiation (light power density 0.1 W / cm2), in the open state, the reaction was carried out for 1 hour. After the reaction was completed, the target product was not obtained by distillation. It shows that when the solvent is acetonitrile, the corresponding isocyanate cannot be obtained, and the selection of the solvent in the reaction system is a crucial factor.

[0068] Comparative Example 10

[0069] The difference from Example 1 was that the ligand used was porphyrin, and the others were the same as in Example 1.

[0070] 10 g of aniline was mixed with 50 mL of chloroform, and 1 g of the rare earth upconversion material prepared in Comparative Example 6 was added. Under 808 nm near-infrared light irradiation (light power density 0.1 W / cm2), in the open state, the reaction was carried out for 1 hour. After the reaction was completed, the oily product was obtained by distillation separation. The product was verified by GCMS and the target product was not obtained.

[0071] Comparative Example 11

[0072] The difference from Example 1 was that the rare earth metal salt used was erbium chloride, and the others were the same as in Example 1.

[0073] 10 g of aniline was mixed with 50 mL of chloroform, and 1 g of the rare earth upconversion material prepared in Comparative Example 7 was added. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), the reaction was carried out for 1 hour in an open state. After the reaction was completed, an oily product was obtained by distillation separation, and the product was verified by GCMS and the target product was not obtained.

[0074] Comparative Example 12

[0075] The difference from Example 1 was that the rare earth metal salt used was thulium chloride, and the others were the same as in Example 1.

[0076] 10 g of aniline was mixed with 50 mL of chloroform, and 1 g of the rare earth upconversion material prepared in Comparative Example 8 was added. Under irradiation with 808 nm near-infrared light (light power density 0.1 W / cm²), the reaction was carried out for 1 hour in an open state. After the reaction was completed, an oily product was obtained by distillation separation, and the product was verified by GCMS and the target product was not obtained.

[0077] The present invention realizes a preparation method for catalytic oxidation of organic amines to generate isocyanates by a near-infrared light source under mild conditions by introducing a rare earth upconversion material. Compared with the traditional method, the preparation process of the present invention is more environmentally friendly and green, the reaction conditions are mild, and the rare earth upconversion material has good photocatalytic performance, effectively improving the reaction efficiency and yield.

[0078] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of isocyanate based on rare earth upconversion materials, characterized in that: It includes the following steps: Mix a rare earth metal salt and a ligand and dissolve them in absolute ethanol or absolute ethylene glycol, and carry out a solvothermal reaction to obtain rare earth nanoparticles; After calcining the obtained rare earth nanoparticles at 450 - 550 °C, a rare earth upconversion material is obtained; Add the rare earth upconversion material to a solution of an organic amine compound, and the mass percentage of the rare earth upconversion material in the organic amine compound is 1% - 10%. Carry out a photocatalytic oxidation reaction under near-infrared light irradiation in an oxygen-containing environment to prepare isocyanate; The rare earth metal salt is a mixture of yttrium chloride, ytterbium chloride and europium chloride; The ligand is citric acid; The organic amine compound is aniline, butylamine, ethylamine or propylamine; The temperature of the solvothermal reaction is 160 - 200 °C, and the reaction time is 8 - 12 hours; The wavelength of the near-infrared light is 808 nm or 980 nm; The light power of the near-infrared light is 0.1 - 5 W / cm²; the photocatalytic oxidation reaction time is 1 - 12 hours; The organic solvent in the solution of the organic amine compound is chloroform.

2. The method for preparing isocyanate based on rare earth upconversion material according to claim 1, wherein: The organic amine compound is aniline or butylamine.

3. The method for preparing isocyanate based on rare earth upconversion material according to claim 1, wherein: In the rare earth metal salt, the mass ratio of yttrium chloride, ytterbium chloride and europium chloride is 10 - 15:10 - 15:

1.

4. The method for preparing isocyanate based on rare earth upconversion materials according to claim 1, characterized in that: The temperature of the solvothermal reaction is 180 °C; the reaction time is 12 hours.

5. The method for preparing isocyanate based on rare earth upconversion materials according to claim 1, wherein: Before calcining, it also includes the steps of washing and drying the prepared rare earth nanoparticles.

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