A method for one-step synthesis of methyl methylcyclohexanedicarbamate from toluene diamine

Abstract

This invention discloses a one-step method for synthesizing methyl methylcyclohexanedicarbamate from toluenediamine. The method includes the following steps: adding a supported composite metal oxide catalyst, toluenediamine, and dimethyl carbonate to a high-pressure reactor; sealing the reactor and reacting it at 120–200°C and 1.5–6 MPa hydrogen pressure for 5–15 h; and separating the methyl methylcyclohexanedicarbamate after the reaction. The supported composite metal oxide catalyst comprises a composite metal oxide and a support, wherein the composite metal oxide in the catalyst is two or three of CuO, Co3O4, PtO2, PdO, NiO, RuO2, Rh2O3, and Fe2O3. The catalyst of this invention exhibits high activity, high selectivity, and good stability; the conversion rate of toluenediamine can reach 100%, and the yield of methyl methylcyclohexanedicarbamate can reach over 80%.

Description

Technical Field

[0001] This invention relates to the field of green chemistry technology, specifically to a method for one-step synthesis of methyl methylcyclohexanedicarbamate from toluenediamine catalyzed by a supported composite metal oxide catalyst. Background Technology

[0002] Methylcyclohexane diisocyanate (also known as hydrogenated TDI) is an upgraded chemical of toluene diisocyanate (TDI), and is a non-yellowing alicyclic diisocyanate. Because the benzene ring in the TDI molecule is replaced by a six-membered alicyclic ring, there are no unsaturated double bonds. Polyurethane products prepared from it possess excellent properties such as non-yellowing, light stability, weather resistance, and high mechanical properties, making it a core raw material for the production of high-grade polyurethane.

[0003] Currently, the production process of methylcyclohexane diisocyanate (HTDI) uses the phosgene process (CN109748822A). This process consists of two steps: hydrogenation of toluene diamine (TDA) to prepare methylcyclohexane diamine, and then phosgenation of methylcyclohexane diamine to obtain HTDI. Phosgene, the raw material used in the reaction of methylcyclohexane diamine with phosgene to produce HTDI, is a highly toxic chemical, posing serious safety hazards in production, storage, transportation, and use. Furthermore, the byproduct hydrogen chloride corrodes equipment and pollutes the environment.

[0004] Given the serious environmental and safety issues associated with the phosgene-based HTDI production process, Wang Yanji et al. (Applied Catalysis A:General, 2022, 651:119017) proposed a green route for HTDI synthesis without phosgene (see formula below). This route includes: methoxycarbonylation of TDA with dimethyl carbonate to synthesize methyl toluene dicarboxylate (TDC) (step 1); hydrogenation of the benzene ring of TDC to generate methyl methylcyclohexanedicarboxylate (HTDC) (step 2); and catalytic cracking of HTDC to HTDI (step 3). This process route has advantages such as not using phosgene, being environmentally friendly, and having high atom utilization, aligning with the concept of green development. However, this method also suffers from problems such as a long process flow and high equipment and operating costs.

[0005]

[0006] The process of integrating multi-step reactions into one step, also known as reaction process integration, can simplify the process flow, reduce equipment and operating costs, and meet the requirements of green chemistry and green chemical engineering.

[0007] This invention integrates the methoxycarbonylation reaction of toluene diamine and the selective hydrogenation reaction of the benzene ring of methyl toluene dicarboxylate to achieve a one-step synthesis of methyl methylcyclohexanedicarboxylate from toluene diamine. This simplifies the process, reduces equipment and operating costs, and improves process economy. The supported composite metal oxide catalyst used has advantages such as high activity and selectivity, and easy catalyst recovery and reuse. Summary of the Invention

[0008] The purpose of this invention is to address the limitations of current technologies by providing a one-step synthesis method for methyl methylcyclohexanedicarbamate from toluenediamine. This method uses a supported composite metal oxide as a catalyst to achieve the one-step synthesis of the target product, methyl methylcyclohexanedicarbamate, from toluenediamine, dimethyl carbonate, and hydrogen. This invention eliminates the need for catalyst pre-reduction steps, and the catalyst possesses high activity, high selectivity, and good stability. As a green new process, it offers advantages such as a short process flow, low equipment and operating costs, and environmental friendliness.

[0009] The specific technical solution of this invention is as follows:

[0010] A method for one-step synthesis of methyl methylcyclohexanedicarbamate from toluene diamine, the method comprising the following steps:

[0011] A supported composite metal oxide catalyst, toluene diamine, and dimethyl carbonate were added to a high-pressure reactor. After sealing, the reactor was reacted at 120–200 °C and 1.5–6 MPa hydrogen pressure for 5–15 h. After the reaction was completed, methyl methylcyclohexanedicarbamate was separated.

[0012] The mass ratio of toluene diamine to catalyst is 1:0.5–3; the mass ratio of toluene diamine to dimethyl carbonate is 1:10–30.

[0013] The supported composite metal oxide catalyst comprises a composite metal oxide and a support, wherein the composite metal oxide accounts for 2-20% of the mass fraction of the catalyst, and the remainder is the support.

[0014] The composite metal oxide in the supported composite metal oxide catalyst is two or three of the following metal oxides: CuO, Co3O4, PtO2, PdO, NiO, RuO2, Rh2O3 or Fe2O3; preferably, the mass fraction of each metal oxide in the catalyst is at least 0.5%;

[0015] The support in the supported composite metal oxide catalyst is specifically one or more of Al2O3, CeO2, TiO2, ZrO2, and ZnO.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. The green new process for one-step synthesis of methyl methylcyclohexanedicarbamate using a supported composite metal oxide catalyst provided by this invention not only shortens the process flow for synthesizing methyl methylcyclohexanedicarbamate and reduces equipment and operating costs, but also eliminates the intermediate product separation step.

[0018] 2. The supported composite metal oxide catalyst for the one-step synthesis of methyl methylcyclohexanedicarbamate from toluene diamine provided by this invention eliminates the pre-reduction step of the catalyst, simplifies the catalyst preparation process, and reduces operating costs.

[0019] 3. A supported composite metal oxide catalyst is used to synthesize methyl methylcyclohexanedicarbamate from toluenediamine in one step. The conversion rate of toluenediamine can reach 100%, and the yield of methyl methylcyclohexanedicarbamate can reach more than 80%. Detailed Implementation

[0020] The supported composite metal oxide catalyst used in this invention is a known material and can be prepared using conventional impregnation methods, but is not limited thereto:

[0021] Taking the NiO-RuO2 / CeO2 catalyst as an example, its preparation process is as follows: First, weigh 2.908g Ni(NO3)2·6H2O and 0.261g RuCl3·3H2O and add them to 50mL of distilled water respectively. Then, put 10g CeO2 into a rotary evaporating flask and pour the dissolved mixed solution into the rotary evaporating flask. After soaking for 12h, rotary evaporate at 70℃ for 3h to remove water. Place the rotary evaporated solid sample in a drying oven and dry at 100℃ for 12h. Finally, calcine it in a muffle furnace at 450℃ for 2h to obtain the NiO-RuO2 / CeO2 catalyst (wherein, the loading of metal oxide is 8.80%).

[0022] Example 1

[0023] 1.0 g of toluenediamine, 1.0 g of NiO-RuO2 / CeO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 190 °C, and then 4.0 MPa of H2 was introduced. The mixture was magnetically stirred for 9 h. After the reaction was complete, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 100%, and the yield of methyl methylcyclohexanedicarbamate was 78.5%.

[0024] Example 2

[0025] 0.5 g of toluenediamine, 1.0 g of NiO-Rh2O3 / ZrO2 catalyst, and 15 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 170 °C, and then 4.0 MPa of H2 was introduced. The mixture was magnetically stirred for 10 h. After the reaction, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 100%, and the yield of methyl methylcyclohexanedicarbamate was 81.2%.

[0026] Example 3

[0027] 1.0 g of toluenediamine, 1.0 g of NiO-Co3O4 / TiO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 170 °C, and then 3.0 MPa of H2 was introduced. The mixture was magnetically stirred for 10 h. After the reaction was complete, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 95.6%, and the yield of methyl methylcyclohexanedicarbamate was 72.5%.

[0028] Example 4

[0029] 1.5 g of toluenediamine, 2.0 g of PtO2-Co3O4-NiO / Al2O3 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 180 °C, and then H2 was introduced at 6.0 MPa. The mixture was magnetically stirred for 10 h. After the reaction, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 92.8%, and the yield of methyl methylcyclohexanedicarbamate was 73.1%.

[0030] Example 5

[0031] 1.0 g of toluenediamine, 1.0 g of NiO-Co3O4 / ZnO-ZrO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 200 °C, and then 5.0 MPa of H2 was introduced. The mixture was magnetically stirred for 8 h. After the reaction was complete, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 100%, and the yield of methyl methylcyclohexanedicarbamate was 76.8%.

[0032] Example 6

[0033] 1.0 g of toluenediamine, 2.0 g of NiO-RuO2 / CeO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 160 °C, and then 5.0 MPa of H2 was introduced. The mixture was magnetically stirred for 8 h. After the reaction was complete, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 100%, and the yield of methyl methylcyclohexanedicarbamate was 82.1%.

[0034] Example 7

[0035] 1.5 g of toluenediamine, 3.0 g of NiO-PdO / CeO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 160 °C, and then 3.0 MPa of H2 was introduced. The mixture was magnetically stirred for 15 h. After the reaction was complete, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 98.7%, and the yield of methyl methylcyclohexanedicarbamate was 79.3%.

[0036] Example 8

[0037] 1.0 g of toluenediamine, 2.0 g of NiO-RuO2 / CeO2-TiO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 160 °C, and then 5.0 MPa of H2 was introduced. The mixture was magnetically stirred for 8 h. After the reaction was complete, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 100%, and the yield of methyl methylcyclohexanedicarbamate was 82.1%.

[0038] Example 9

[0039] 2.0 g of toluenediamine, 1.0 g of NiO-RuO2 / CeO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 150 °C, and then 5.0 MPa of H2 was introduced. The mixture was magnetically stirred for 15 h. After the reaction was complete, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 100%, and the yield of methyl methylcyclohexanedicarbamate was 78.3%.

[0040] Example 10

[0041] 1.0 g of toluenediamine, 1.5 g of NiO-RuO2 / CeO2-ZrO2 catalyst, and 20 g of dimethyl carbonate were added sequentially to a 50 mL autoclave. Air was first replaced with N2, followed by N2 replacement with H2. The reaction temperature was raised to 170 °C, and then 3.0 MPa of H2 was introduced. The mixture was magnetically stirred for 12 h. After the reaction, the product was analyzed by liquid chromatography. The conversion rate of toluenediamine was 100%, and the yield of methyl methylcyclohexanedicarbamate was 80.6%. The catalyst was washed with anhydrous ethanol, dried at 110 °C for 6 h, and calcined in a muffle furnace at 450 °C for 2 h. Under the same reaction conditions, it was used to catalyze the one-step synthesis of methyl methylcyclohexanedicarbamate from toluenediamine. The results are shown in the table below. It can be seen that the catalytic activity remained essentially unchanged after five repetitions, indicating that the catalyst has good reusability.

[0042]

[0043] Matters not covered in this invention are common knowledge.

Claims

1. A method for one-step synthesis of methyl methylcyclohexanedicarbamate from toluene diamine, characterized in that the method comprises the following steps: A supported composite metal oxide catalyst, toluene diamine, and dimethyl carbonate were added to a high-pressure reactor. After sealing, the reactor was reacted at 120-200 °C and 1.5-6 MPa hydrogen pressure for 5-15 h. After the reaction was completed, methyl methylcyclohexanedicarbamate was separated. The mass ratio of toluene diamine to catalyst is 1:0.5~3; the mass ratio of toluene diamine to dimethyl carbonate is 1:10~30. The supported composite metal oxide catalyst is composed of composite metal oxide and support, wherein the mass fraction of composite metal oxide in the catalyst is 2-20%, and the remainder is support. The composite metal oxide in the supported composite metal oxide catalyst is a composite of two or three of the following: Co3O4, PtO2, PdO, NiO, RuO2, and Rh2O3. The carrier is one or more of Al2O3, CeO2, TiO2, ZrO2 and ZnO.

2. The method for one-step synthesis of methyl methylcyclohexanedicarbamate from toluene diamine as described in claim 1, characterized in that the mass fraction of each metal oxide in the catalyst is at least 0.5%.

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