Process for the synthesis of methylcyclohexyldiaminocarbamate by catalytic transfer hydrogenation using a nitride-based catalyst

Abstract

The application discloses a method for synthesizing methylcyclohexyl diurethane by catalytic transfer hydrogenation of a nitride-based catalyst. The method comprises the following steps: adding a nitride-based catalyst, a hydrogen source and toluene diurethane into a reaction kettle, and reacting at normal pressure and at 40-120 DEG C for 1-10 hours to obtain methylcyclohexyl diurethane; the nitride-based catalyst is a noble metal-supporting / transition metal nitride, and the composition comprises an active metal, a support and a transition metal nitride. The application 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-supporting / transition metal nitride catalyst has the characteristics of high activity, high stability and high selectivity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of green chemistry, and relates to a process for synthesizing methylcyclohexyl diurethane using a nitride-based catalyst under the conditions of no solvent, using biomass oxygen-containing compounds as a hydrogen source, and without introducing gas components. BACKGROUND

[0002] Toluene diisocyanate (TDI) is an important basic raw material for synthesizing polyurethane, and is mainly used in the fields of polyurethane foam, polyurethane elastomer, paint, adhesive, etc. Compared with TDI, methylcyclohexyl diisocyanate (HTDI) has no unsaturated double bond in the molecule, and the polyurethane products prepared by using HTDI 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 isocyanate with a larger demand after TDI.

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

[0004] Using oxygen-containing compounds derived from biomass (such as isopropyl alcohol, isobutyl alcohol, formic acid, etc.) as a hydrogen source, and using a transfer hydrogenation method to realize the hydrogenation of the benzene ring of TDC to HTDC, can avoid the use of flammable hydrogen gas from the source, making the reaction process more inherently safe. Moreover, most of the above-mentioned oxygen-containing compounds have non-toxic and excellent solvent properties themselves, and no additional solvent needs to be added in the reaction process, making the reaction system more simple. However, in the reaction of synthesizing HTDC from TDC by transfer hydrogenation, a complex process involving the dehydrogenation of oxygen-containing compounds and the selective hydrogenation of the benzene ring of TDC is involved, and the development of a high-efficiency catalytic system is the key to realizing this reaction. SUMMARY

[0005] The application aims to provide a method for synthesizing methylcyclohexyl dicarbamic acid ester by using a nitride-based catalyst for catalytic transfer hydrogenation.

[0006] The specific technical scheme of the application is as follows:

[0007] The method for synthesizing methylcyclohexyl dicarbamic acid ester by using a nitride-based catalyst for catalytic transfer hydrogenation comprises the following steps:

[0008] The nitride-based catalyst, hydrogen source and toluene dicarbamic acid ester are added into a reaction kettle, and then the reaction is carried out under normal pressure and at 40-120 DEG C for 1-10 hours to obtain methylcyclohexyl dicarbamic acid ester.

[0009] The mass ratio of toluene dicarbamic acid ester to the nitride-based catalyst is 1:0.5-3, and the hydrogen source is added in an amount of 10-50 mL per millimole of toluene dicarbamic acid ester.

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

[0011] The hydrogen source includes isopropyl alcohol, isobutyl alcohol or formic acid.

[0012] The nitride-based catalyst is a noble metal-supporting / transition metal nitride, and its composition includes active metal, support and transition metal nitride.

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

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

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

[0016] The substantial feature of the present application is:

[0017] The present application develops a multifunctional catalyst with good stability and high activity, namely, noble metal-supporting transition metal nitride catalyst, which realizes the efficient transfer hydrogenation synthesis of methylcyclohexyl dicarbamic acid ester by relying on the electron transfer and strong interaction among the noble metal, the supporting agent and the transition metal nitride under the conditions of no solvent and no introduction of gas components (such as hydrogen and inert gases like nitrogen).

[0018] The present application has the following beneficial effects:

[0019] 1. The existing process for preparing methylcyclohexyl dicarbamic acid ester by hydrogenation of the benzene ring of toluene diamino carbamic acid ester mostly uses hydrogen as the hydrogen source, which brings about the increase of equipment cost and safety hazards due to harsh reaction conditions. The new process for transfer hydrogenation synthesis of methylcyclohexyl dicarbamic acid ester provided by the present application uses the noble metal-supporting transition metal nitride as the catalyst and biomass oxygen-containing compounds as the hydrogen source, which can not only effectively avoid the use of flammable hydrogen, thereby reducing the energy consumption and equipment cost from the source, but also avoid the introduction of solvent, thereby simplifying the reaction system and reducing the subsequent separation process.

[0020] 2. The noble metal-supporting transition metal nitride multifunctional catalyst developed in the present application further improves the advanced nature of the technical index and the safety and reliability of the process in the synergistic action of the noble metal, the supporting agent and the transition metal nitride. The advanced nature of the technical index is reflected in that the conversion rate of toluene diamino carbamic acid ester and the selectivity of methylcyclohexyl dicarbamic acid ester can both reach more than 99%; the safety and reliability of the process is reflected in that the introduction of hydrogen and other inert gases is prevented, the high-pressure operation of the reaction is completely avoided, and the intrinsic safety of the methylcyclohexyl dicarbamic acid ester synthesis process is further enhanced. DETAILED DESCRIPTION

[0021] Example 1

[0022] The preparation method of the catalyst can refer to the patent (CN116786112A) disclosed by the present inventor. Taking the Pt-In2O3 / TiN multifunctional catalyst as an example, the preparation process is as follows: (1) chloroplatinic acid, In2O3 and TiN are added to 30 mL of water in a mass ratio of 1:1:10, 10 mL of 4-hydroxyethylpiperazine propyl sulfonic acid is added, and ultrasonic is performed for 10 min; (2) the solution prepared in step (1) is reacted at 80℃ for 1h, and then cooled to room temperature, the solution is centrifuged at a speed of 6000 rpm for 5 min to obtain a solid product A; (3) the solid product A is washed by centrifugation with deionized water, and then dried at 80℃ under vacuum for 1h to obtain the Pt-In2O3 / TiN catalyst.

[0023] Example 2

[0024] For example, the multifunctional catalyst RuPd-GeO2 / ZrN is prepared as follows: (1) 0.357 g (1.5 mmol) of methyl toluene diaminoformate, 0.714 g of 10% Rh-5% In2O3 / TiN catalyst (the percentage in the catalyst refers to the mass percentage of the corresponding substance in the catalyst. The same below) and 15 mL of isopropyl alcohol are added into a 50 mL reaction kettle, and stirred at a reaction temperature of 80°C for 10 h. After the reaction, the product liquid is analyzed by liquid chromatography. The conversion rate of methyl toluene diaminoformate is 85.3%, and the selectivity of methyl cyclohexyl diaminoformate is 97.1%.

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

[0026] Example 3

[0027] Into a 50 mL reaction kettle, 0.357 g (1.5 mmol) of methyl toluene diaminoformate, 0.714 g of 10% Rh-5% In2O3 / TiN catalyst (the percentage in the catalyst refers to the mass percentage of the corresponding substance in the catalyst. The same below) and 15 mL of isopropyl alcohol are added, and stirred at a reaction temperature of 80°C for 10 h. After the reaction, the product liquid is analyzed by liquid chromatography. The conversion rate of methyl toluene diaminoformate is 85.3%, and the selectivity of methyl cyclohexyl diaminoformate is 97.1%.

[0028] Example 4

[0029] Into a 50 mL reaction kettle, 0.378 g (1.5 mmol) of ethyl toluene diaminoformate, 0.378 g of 10% Ru-5% In2O3 / TiN catalyst and 20 mL of isopropyl alcohol are added, and stirred at a reaction temperature of 80°C for 8 h. After the reaction, the product liquid is analyzed by liquid chromatography. The conversion rate of ethyl toluene diaminoformate is 68.9%, and the selectivity of ethyl cyclohexyl diaminoformate is 90.3%.

[0030] Example 5

[0031] Into a 50 mL reaction kettle, 0.42 g of n-butyl toluene diaminoformate (1.5 mmol), 0.42 g of 15% Ru-10% In2O3 / TiN catalyst and 15 mL of isopropyl alcohol are added, and stirred at a reaction temperature of 40°C for 10 h. After the reaction, the product liquid is analyzed by liquid chromatography. The conversion rate of n-butyl toluene diaminoformate is 45.1%, and the selectivity of n-butyl cyclohexyl diaminoformate is 89.4%.

[0032] Example 6

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

[0034] Example 7

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

[0036] Example 8

[0037] Into a 50 mL autoclave, 0.357 g of methyl toluene diamino formate, 1.071 g of 10% Rh-5% In2O3 / TiN catalyst and 15 mL of isobutanol were added, and stirred at a reaction temperature of 120°C for 2 h. After the reaction was completed, the product liquid was analyzed by liquid chromatography, and the conversion of methyl toluene diamino formate was 53.1%, and the selectivity of methyl cyclohexyl diamino formate was 91.3%.

[0038] Examples 9-14 were carried out according to the procedure of reaction example 6, and the reaction conditions and results are summarized in the table.

[0039]

[0040] Example 15

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

[0042] Number of times the catalyst was reused Conversion % of methyl toluene diaminoformate Selectivity % of methyl methylcyclohexyl diaminoformate 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 noble metal-promoter / transition metal nitride multifunctional catalyst developed by the present application exhibits excellent activity and stability in the catalytic transfer hydrogenation synthesis of methylcyclohexyl diaminoformate process.

[0044] The above only describes typical embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0045] The details of the present application are known technologies.

Claims

1. A process for the catalytic transfer hydrogenation synthesis of methylcyclohexyldiaminocarbonates from a nitride-based catalyst characterized by, The method comprises the following steps: The nitride-based catalyst, hydrogen source and toluene dicarbamic acid ester are added into a reaction kettle, and reacted at normal pressure and 40-120 DEG C for 1-10 hours to obtain methylcyclohexyl dicarbamic acid ester; The mass ratio of toluene dicarbamic acid ester to the nitride-based catalyst is 1:0.5-3, and the hydrogen source is added in an amount of 10-50 mL per mmol of toluene dicarbamic acid ester; The nitride-based catalyst is a noble metal-supporting / transition metal nitride, which comprises active metal, support and transition metal nitride; the mass fraction of the active metal in the catalyst is 1-20%, the mass fraction of the support in the catalyst is 5-30%, and the rest is transition metal nitride; The active metal is one or more of rhodium, ruthenium, palladium, platinum and iridium; The toluene dicarbamic acid ester is methyl toluene dicarbamic acid ester, ethyl toluene dicarbamic acid ester, n-propyl toluene dicarbamic acid ester, n-butyl toluene dicarbamic acid ester or n-pentyl toluene dicarbamic acid ester; The hydrogen source is isopropyl alcohol, isobutyl alcohol or formic acid; The support is one or more of In2O3, SnO2, Ga2O3 and GeO2; The transition metal nitride is one or more of TiN, ZrN, W2N and Mo2N.

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