Method for synthesizing methyl cyclohexyl dicarbamate through catalytic transfer hydrogenation of nitride-based catalyst

Abstract

The invention relates to a method for synthesizing methyl cyclohexyl dicarbamate through catalytic transfer hydrogenation of a nitride-based catalyst. The method comprises the following steps: adding a nitride-based catalyst, a hydrogen source and toluene dicarbamate into a reaction kettle, and reacting at normal pressure and 40-120 DEG C for 1-10 hours to obtain methyl cyclohexyl dicarbamate, the nitride-based catalyst is a noble metal-auxiliary agent / transition metal nitride, and comprises an active metal, an auxiliary agent and a transition metal nitride. The method has the advantages of mild reaction conditions, low equipment cost, environmental friendliness, high process safety and the like. Meanwhile, the designed and prepared noble metal-assistant / transition metal nitride catalyst has the characteristics of high activity, high stability and high selectivity.

Description

Technical Field

[0001] The invention belongs to the technical field of green chemistry and relates to a process for catalytically synthesizing methylcyclohexyl dicarbamate by using a nitride-based catalyst in the absence of solvent, using biomass oxygen-containing compounds as hydrogen sources and without introducing gas components. Background Art

[0002] Toluene diisocyanate (TDI) is an important basic raw material for the synthesis of polyurethane, and is mainly used in several major fields such as polyurethane foam, polyurethane elastomer, coatings, adhesives, etc. Compared with TDI, methylcyclohexyl diisocyanate (HTDI) does not have unsaturated double bonds in its molecules, so the polyurethane products prepared with it as a raw material have excellent properties such as non-yellowing, good light stability and high mechanical properties. Therefore, HTDI is expected to become another type of isocyanate with a larger demand after TDI.

[0003] The non-phosgene synthesis process of HTDI includes three reaction units: methyloxycarbonylation of toluene diamine to synthesize toluene dicarbamate (TDC), selective hydrogenation of TDC benzene ring to prepare methylcyclohexyl dicarbamate (HTDC), and HTDC cracking to generate HTDI. Among them, the selective hydrogenation of TDC benzene ring is an important intermediate step in the synthesis of HTDI. At present, the process mainly uses high-pressure hydrogen as a hydrogen source. For example, Song et al. used 5wt.% Rh / γ-Al2O3 catalyst at 100°C and 3MPa hydrogen pressure to obtain a nearly 100% HTDC yield (Applied Catalysis A: General, 2023, 651, 119017). However, hydrogen mainly comes from fossil raw materials, which does not meet the requirements of sustainable development; moreover, harsh reaction conditions will not only increase equipment costs, but also pose safety risks.

[0004] Using oxygen-containing compounds derived from biomass (such as isopropanol, isobutanol, formic acid, etc.) as a hydrogen source and utilizing the transfer hydrogenation method to hydrogenate the benzene ring of TDC to produce HTDC can avoid the use of flammable hydrogen from the source, making the reaction process more intrinsically safe. In addition, most of the above oxygen-containing compounds have non-toxicity and excellent solvent properties, and no additional solvent needs to be added during the reaction, making the reaction system simpler. However, in the reaction of synthesizing HTDC by transfer hydrogenation of TDC, the complex process of dehydrogenation of oxygen-containing compounds and selective hydrogenation of the benzene ring of TDC is involved, and the development of an efficient catalytic system is the key to achieving this reaction. Summary of the invention

[0005] The purpose of the present invention is to provide a method for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using a nitride-based catalyst. The method uses a noble metal-auxiliary agent / transition metal nitride multifunctional catalyst, and uses biomass oxygen-containing compounds as a hydrogen source to catalytically synthesize methylcyclohexyl dicarbamate under the conditions of no solvent and no introduction of gas components. The present invention has the advantages of mild reaction conditions, low equipment cost, environmental friendliness, and high process safety. At the same time, the designed and prepared noble metal-auxiliary agent / transition metal nitride catalyst has the characteristics of high activity, high stability and high selectivity.

[0006] The specific technical solutions of the present invention are as follows:

[0007] A method for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using a nitride-based catalyst comprises the following steps:

[0008] Adding a nitride-based catalyst, a hydrogen source and toluene dicarbamate into a reaction kettle, reacting at normal pressure and 40 to 120° C. for 1 to 10 hours to obtain methylcyclohexyl dicarbamate;

[0009] The mass ratio of toluene dicarbamate to the nitride-based catalyst is 1:0.5-3, and the amount of hydrogen source added to each millimole of toluene dicarbamate is 10-50 mL;

[0010] The toluene dicarbamate includes: toluene dicarbamate methyl ester, toluene dicarbamate ethyl ester, toluene dicarbamate n-propyl ester, toluene dicarbamate n-butyl ester or toluene dicarbamate n-pentyl ester.

[0011] The hydrogen source includes isopropanol, isobutanol or formic acid.

[0012] The nitride-based catalyst is a noble metal-promoter / transition metal nitride, which comprises: an active metal, a promoter and a transition metal nitride. The mass fraction of the active metal in the catalyst is 1-20%, the mass fraction of the promoter in the catalyst is 5-30%, and the rest is transition metal nitride;

[0013] The active metal is one or more of rhodium, ruthenium, palladium, platinum and iridium.

[0014] The auxiliary agent in the noble metal-auxiliary agent / transition metal nitride catalyst is one or more of In2O3, SnO2, Ga2O3, and GeO2.

[0015] The transition metal nitride in the noble metal-additive / transition metal nitride catalyst is one or more of TiN, ZrN, W2N, CoN, CrN, Cu3N, Ni3N, Mo2N and NbN.

[0016] The essential features of the present invention are:

[0017] The present invention is to develop a multifunctional catalyst with good stability and high activity, namely a noble metal-auxiliary agent / transition metal nitride catalyst. By relying on the electron transfer and strong interaction between the noble metal, the auxiliary agent and the transition metal nitride, the present invention realizes the efficient synthesis of methylcyclohexyl dicarbamate by transfer hydrogenation using biomass oxygen-containing compounds as a hydrogen source under the conditions of no solvent and without the introduction of gas components (such as hydrogen and inert gases similar to nitrogen).

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The existing process of preparing methylcyclohexyl dicarbamate by hydrogenating the benzene ring of toluene dicarbamate mostly uses hydrogen as the hydrogen source, which has the problems of increased equipment cost and potential safety hazards caused by harsh reaction conditions. The new process provided by the present invention uses precious metal-auxiliary agent / transition metal nitride as a catalyst, biomass oxygen-containing compounds as a hydrogen source, and synthesizes methylcyclohexyl dicarbamate by transfer hydrogenation, which can not only effectively avoid the use of flammable hydrogen, reduce energy consumption and equipment costs from the source, but also avoid the introduction of solvents, thereby simplifying the reaction system and reducing subsequent separation processes.

[0020] 2. The new process for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using precious metal-auxiliary agent / transition metal nitride multifunctional catalyst developed by the present invention further improves the advancedness of process technical indicators and process safety and reliability under the synergistic effect of precious metals, auxiliary agents and transition metal nitrides. The advancedness of technical indicators is reflected in the fact that the conversion rate of toluene dicarbamate and the selectivity of methylcyclohexyl dicarbamate can reach more than 99%; the process safety and reliability is reflected in the fact that the introduction of hydrogen and other inert gases is prevented, and the high-pressure operation of the reaction is completely avoided, which further enhances the intrinsic safety of the methylcyclohexyl dicarbamate synthesis process. DETAILED DESCRIPTION

[0021] Example 1

[0022] The preparation method of the catalyst can be found in the patent (CN116786112A) published by the inventor of this application. Taking Pt-In2O3 / TiN multifunctional catalyst as an example, its preparation process is as follows: (1) Add chloroplatinic acid, In2O3 and TiN in a mass ratio of 1:1:10 to 30 mL of water, add 10 mL of 4-hydroxyethylpiperazinepropanesulfonic acid, and ultrasonicate for 10 min; (2) React the solution obtained in step (1) at 80°C for 1 h, then cool to room temperature, and centrifuge the solution at 6000 rpm for 5 min to obtain solid product A; (3) After centrifugation and washing the solid product A with deionized water, dry it in a vacuum environment at 80°C for 1 h to obtain Pt-In2O3 / TiN catalyst.

[0023] Example 2

[0024] Taking the nitride-supported bimetallic multifunctional catalyst RuPd-GeO2 / ZrN as an example, its preparation process is as follows: (1) ruthenium trichloride, palladium chloride, GeO2 and ZrN are added to 30 mL of water in a mass ratio of 1:2:5:10, 15 mL of 4-hydroxyethylpiperazinepropanesulfonic acid is added, and ultrasonic treatment is performed for 10 min; (2) the solution prepared in step (1) is reacted at 100 °C for 3 h, then cooled to room temperature, and the solution is centrifuged at 6000 rpm for 5 min to obtain a solid product A; (3) the solid product A is centrifuged and washed with deionized water, and then dried in a vacuum environment at 80 °C for 1 h to obtain a RuPd-GeO2 / TiN catalyst.

[0025] The multifunctional catalyst used in the following reaction examples can be prepared by using the catalyst preparation example 1, example 2 or similar methods, but is not limited thereto.

[0026] Example 3

[0027] 0.357 g (1.5 mmol) of toluene dicarbamate, 0.714 g of 10% Rh-5% In2O3 / TiN catalyst (the percentage in the catalyst is the mass percentage of the catalyst occupied by the corresponding substance. The same applies to the following examples) and 15 mL of isopropanol were added to a 50 mL reactor, and stirred at a reaction temperature of 80°C for 10 h. After the reaction was completed, the liquid was subjected to liquid chromatography analysis, and the conversion rate of toluene dicarbamate was 85.3%, and the selectivity of methylcyclohexyl dicarbamate was 97.1%.

[0028] Example 4

[0029] 0.378 g (1.5 mmol) of toluene diurethane, 0.378 g of 10% Ru-5% In2O3 / TiN catalyst and 20 mL of isopropanol were added to a 50 mL reactor and stirred at a reaction temperature of 80°C for 8 h. After the reaction, the liquid product was analyzed by liquid chromatography, and the conversion rate of toluene diurethane was 68.9%, and the selectivity of methylcyclohexyl diurethane was 90.3%.

[0030] Example 5

[0031] 0.42 g of toluene dicarbamic acid n-butyl ester (1.5 mmol), 0.42 g of 15% Ru-10% In2O3 / TiN catalyst and 15 mL of isopropanol were added to a 50 mL reactor and stirred at a reaction temperature of 40°C for 10 h. After the reaction, the liquid product was analyzed by liquid chromatography, and the conversion rate of toluene dicarbamic acid n-butyl ester was 45.1%, and the selectivity of methylcyclohexyl dicarbamic acid n-butyl ester was 89.4%.

[0032] Example 6

[0033] 0.714 g of toluene dicarbamate, 1.428 g of 10% Rh-5% In2O3 / TiN catalyst and 60 mL of isopropanol were added to a 100 mL reactor and stirred at a reaction temperature of 100° C. for 4 h. After the reaction, the liquid product was analyzed by liquid chromatography, and the conversion rate of toluene dicarbamate was 90.8%, and the selectivity of methylcyclohexyl dicarbamate was 96.5%.

[0034] Example 7

[0035] 0.357 g of toluene dicarbamate, 1.071 g of 10% Rh-5% In2O3 / TiN catalyst and 15 mL of formic acid were added to a 50 mL reactor and stirred at a reaction temperature of 120°C for 2 h. After the reaction, the liquid product was analyzed by liquid chromatography, and the conversion rate of toluene dicarbamate was 65.9%, and the selectivity of methylcyclohexyl dicarbamate was 95.7%.

[0036] Example 8

[0037] 0.357 g of toluene dicarbamate, 1.071 g of 10% Rh-5% In2O3 / TiN catalyst and 15 mL of isobutyl alcohol were added to a 50 mL reactor and stirred at a reaction temperature of 120°C for 2 h. After the reaction, the liquid product was analyzed by liquid chromatography, and the conversion rate of toluene dicarbamate was 53.1%, and the selectivity of methylcyclohexyl dicarbamate was 91.3%.

[0038] Examples 9-14 were carried out according to the operating procedures of Reaction Example 6. The reaction conditions and results are shown in the Summary Table.

[0039]

[0040] Embodiment 15

[0041] 0.357g of toluene dicarbamate, 0.714g of 10% Pt10% Rh-5% GeO2 / TiN catalyst and 30mL of isopropanol were added to a 100mL reactor and stirred at a reaction temperature of 100°C for 4h. After the reaction, the liquid was analyzed by liquid chromatography. The conversion rate of toluene dicarbamate was 99%, and the selectivity of methylcyclohexyl dicarbamate was 99%. The catalyst after the reaction was washed with anhydrous ethanol and vacuum dried at 60°C for 5h, and then used for toluene dicarbamate transfer hydrogenation reaction under the same reaction conditions. The results are shown in the table below. The catalyst activity remained basically unchanged after repeated use for 4 times, indicating that the catalyst has good stability and reusability.

[0042] Catalyst reuse times Toluene dicarbamate conversion rate % Methylcyclohexyl dicarbamate selectivity % 1 99.3 99 2 98.9 98.9 3 99.5 99.8 4 99.1 99.2

[0043] From the results of the examples, it can be seen that the precious metal-additive / transition metal nitride multifunctional catalyst developed by the present invention exhibits excellent activity and stability in the process of catalytic transfer hydrogenation to synthesize methylcyclohexyl dicarbamate. Through the synergistic effect between the precious metal, the additive and the transition metal nitride, the advancement of the process technical indicators and the process safety and reliability are further improved.

[0044] The above descriptions are only typical embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0045] Matters not covered by the present invention are known technologies.

Claims

1. A method for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using a nitride-based catalyst, characterized in that: The following steps are involved: Adding a nitride-based catalyst, a hydrogen source and toluene dicarbamate into a reaction kettle, reacting at normal pressure and 40 to 120° C. for 1 to 10 hours to obtain methylcyclohexyl dicarbamate; The mass ratio of toluene dicarbamate to the nitride-based catalyst is 1:0.5-3, and the amount of hydrogen source added to each millimole of toluene dicarbamate is 10-50 mL; The nitride-based catalyst is a noble metal-promoter / transition metal nitride, which comprises: an active metal, a promoter and a transition metal nitride; the mass fraction of the active metal in the catalyst is 1 to 20%, the mass fraction of the promoter in the catalyst is 5 to 30%, and the rest is a transition metal nitride; The active metal is one or more of rhodium, ruthenium, palladium, platinum and iridium.

2. The method for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using a nitride-based catalyst as claimed in claim 1, wherein the toluene dicarbamate is methyl toluene dicarbamate, ethyl toluene dicarbamate, n-propyl toluene dicarbamate, n-butyl toluene dicarbamate or n-pentyl toluene dicarbamate.

3. The method for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using a nitride-based catalyst as claimed in claim 1, characterized in that: The hydrogen source includes isopropanol, isobutanol or formic acid.

4. The method for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using a nitride-based catalyst as claimed in claim 1, characterized in that the auxiliary agent is one or more of In2O3, SnO2, Ga2O3, and GeO2.

5. The method for synthesizing methylcyclohexyl dicarbamate by catalytic transfer hydrogenation using a nitride-based catalyst as claimed in claim 1, characterized in that: The transition metal nitride is one or more of TiN, ZrN, W2N, CoN, CrN, Cu3N, Ni3N, Mo2N and NbN.

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