A sulfur-modified heterogeneous catalyst, a preparation method and application thereof, and a preparation method of N-methyl secondary amine compounds

Abstract

The application belongs to the technical field of organic synthesis, and particularly relates to a sulfur-modified heterogeneous catalyst, a preparation method and application thereof, and a preparation method of N-methyl secondary amine compounds. The application provides a sulfur-modified heterogeneous catalyst, which comprises a sulfur-modified carrier and an active component loaded on the sulfur-modified carrier; and the active component comprises palladium and / or nickel. The sulfur-modified heterogeneous catalyst provided by the application improves the selectivity and yield of N-methyl secondary amine compounds. The preparation method of N-methyl secondary amine compounds provided by the application uses organic amine as a solvent, which can effectively improve the selectivity and yield of N-methyl secondary amine compounds. Moreover, the sulfur-modified heterogeneous catalyst provided by the above technical solution has good stability in the reaction system and is easy to separate after catalysis, and can still maintain high reaction activity and product selectivity after multiple cycles.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a sulfur-modified heterogeneous catalyst, its preparation method and application, and a method for preparing N-methyl secondary amine compounds. Background Technology

[0002] N-methyl secondary amines are a diverse and widely used class of chemicals. For example, N-methylaniline is an important raw material for the synthesis of dyes and can also be used as an antiknock agent and antioxidant in the gasoline industry; N-methylethylamine is a key intermediate in the preparation of rivastigmine, a drug for treating Alzheimer's disease; N-methylpentylamine is an important intermediate in the preparation of the bisphosphate drug sodium ebum phosphate; N-methylcyclohexylamine is a key intermediate in the preparation of the drug bromhexine hydrochloride; and N-methylo-fluoroaniline is an important intermediate raw material for the novel, safe, and broad-spectrum herbicide Hanqiuhao. With the continuous development of pesticides, pharmaceuticals, and dyes, N-methyl secondary amines have a very broad market application prospect, therefore, research on their efficient synthesis methods has attracted much attention.

[0003] Currently, the synthesis of N-methyl secondary amines mainly uses primary amines as raw materials and halomethane as a methylating agent. A mixture of monomethylated secondary amines and dimethylated tertiary amines is generated under the action of acid-binding agents such as NaOH, and then separated to obtain the final product. However, the N-methyl secondary amines formed by the monomethylation of primary amines have higher reactivity than primary amines, and are therefore more easily converted into N,N-dimethylated tertiary amines. This leads to a decrease in the selectivity of N-methyl secondary amines, and the yield of the product is generally below 60%, resulting in a low yield. Summary of the Invention

[0004] In view of this, the present invention aims to provide a sulfur-modified heterogeneous catalyst, its preparation method and application, and a method for preparing N-methyl secondary amine compounds. When using the sulfur-modified heterogeneous catalyst provided by the present invention to catalyze the synthesis of N-methyl secondary amine compounds from primary amine compounds, the selectivity and yield of N-methyl secondary amine compounds are high.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a sulfur-modified heterogeneous catalyst, comprising a sulfur-modified support and an active component supported on the sulfur-modified support;

[0007] The active components include palladium and / or nickel.

[0008] Preferably, the carrier in the sulfur-modified carrier includes one or more of activated carbon, alumina, titanium dioxide, and silicon dioxide.

[0009] Preferably, when the active component is palladium, the palladium loading is ≤2%; when the active component is nickel, the nickel loading is ≤10%.

[0010] This invention provides a method for preparing the sulfur-modified heterogeneous catalyst described above, comprising the following steps:

[0011] Thiosulfate and a carrier are mixed and thermally modified to obtain a sulfur-modified carrier;

[0012] The sulfur-modified support and metal source solution were mixed, the pH value was adjusted to 9-11, and formaldehyde aqueous solution was added for loading to obtain a sulfur-modified heterogeneous catalyst.

[0013] The metal source solution includes a palladium source solution and / or a nickel source solution.

[0014] Preferably, the palladium source solution comprises a chloropalladium acid solution; the nickel source solution comprises one or more of nickel nitrate solution, nickel chloride solution, and nickel acetate solution.

[0015] The mass ratio of the thiosulfate to the carrier is 1:100 to 1000;

[0016] The molar ratio of sulfur in the sulfur-modified carrier to metal in the metal source solution is 0.006–15:1.

[0017] This invention provides the application of the sulfur-modified heterogeneous catalyst described in the above-described technical solution or the sulfur-modified heterogeneous catalyst prepared by the above-described technical solution in the catalytic synthesis of N-methyl secondary amine compounds from primary amine compounds.

[0018] This invention provides a method for preparing N-methyl secondary amine compounds, comprising the following steps:

[0019] Primary amine compounds, paraformaldehyde, reducing agent, catalyst and organic amine are mixed and subjected to reduction-amination reaction to obtain N-methyl secondary amine compounds;

[0020] The catalyst is the sulfur-modified heterogeneous catalyst described in the above technical solution or the sulfur-modified heterogeneous catalyst prepared by the preparation method described in the above technical solution.

[0021] Preferably, the primary amine compounds include one or more of aliphatic primary amine compounds, aromatic primary amine compounds, and heterocyclic primary amine compounds;

[0022] The mass of the catalyst is less than 10% of the mass of the primary amine compound.

[0023] Preferably, the organic amine comprises a tertiary amine with the structural formula shown in Formula I:

[0024]

[0025] Wherein, R1, R2 and R3 are independently alkyl or alcohol groups;

[0026] The organic amine accounts for less than 85% of the total mass of organic amines and primary amine compounds.

[0027] Preferably, the molar ratio of the primary amine compound to paraformaldehyde is 1:0.9 to 1.5.

[0028] This invention provides a sulfur-modified heterogeneous catalyst, comprising a sulfur-modified support and an active component supported on the sulfur-modified support; the active component includes palladium and / or nickel. This invention utilizes a sulfur-modified support, modifying the metal active sites with sulfur to induce interactions between sulfur and the support, and between sulfur and the active component, thereby altering the coordination environment of the active sites in the active component. This changes the electronic properties of the metal atoms and improves the selectivity of N-methyl secondary amine compounds; the active component (palladium and / or nickel) enhances the activity of hydrogenation reduction. The sulfur-modified heterogeneous catalyst provided by this invention is used for the catalytic reduction of primary amine compounds, significantly improving the selectivity and yield of N-methyl secondary amine compounds.

[0029] This invention provides a method for preparing the sulfur-modified heterogeneous catalyst described in the above technical solution. The preparation method provided by this invention is simple, low-cost, and has minimal environmental pollution, making it suitable for industrial production.

[0030] This invention provides a method for preparing N-methyl secondary amine compounds, comprising the following steps: mixing a primary amine compound, paraformaldehyde, a reducing agent, a catalyst, and an organic amine, and carrying out a reduction-amination reaction to obtain N-methyl secondary amine compounds. This invention uses an organic amine as a solvent, which can effectively improve the selectivity of N-methyl secondary amine compounds (monomethylated products), limit their over-reaction to dimethylated products, and improve the yield of N-methyl secondary amine compounds. Furthermore, this invention uses the sulfur-modified heterogeneous catalyst described in the above technical solution as a catalyst, resulting in high selectivity and yield of N-methyl secondary amine compounds. The catalyst also exhibits good stability in the reaction system, is easily separated after catalysis, and maintains high reactivity and product selectivity even after multiple cycles. In addition, the paraformaldehyde used in this invention is inexpensive and readily available, easy to transport and store, and the reaction process is simple and easy to operate, making it suitable for the industrial preparation of N-methyl secondary amine compounds. Detailed Implementation

[0031] This invention provides a sulfur-modified heterogeneous catalyst, comprising a sulfur-modified support and an active component supported on the sulfur-modified support;

[0032] The active components include palladium and / or nickel.

[0033] Unless otherwise specified, all reagents used in this invention are commercially available products well known to those skilled in the art.

[0034] In this invention, the carrier in the sulfur-modified carrier (abbreviated as carrier-S) preferably includes one or more of activated carbon, alumina, titanium dioxide and silicon dioxide.

[0035] In this invention, the sulfur-modified heterogeneous catalyst preferably includes Pd / CS, Pd / SiO2-S, Pd / Al2O3-S, Pd / TiO2-S, Ni / CS, Ni / SiO2-S, Ni / Al2O3-S, or Ni / TiO2-S.

[0036] In this invention, the palladium loading is preferably ≤2%, more preferably 0.1-2%, further preferably 0.5-2%, and most preferably 1-1.5%, and the nickel loading is preferably ≤10%, more preferably 1-10%, further preferably 2-8%, and most preferably 4-6%.

[0037] This invention provides a method for preparing the sulfur-modified heterogeneous catalyst described in the above technical solution, comprising the following steps:

[0038] Thiosulfate and a carrier are mixed and thermally modified to obtain a sulfur-modified carrier;

[0039] The sulfur-modified support and metal source solution were mixed, the pH value was adjusted to 9-11, and formaldehyde aqueous solution was added for loading to obtain a sulfur-modified heterogeneous catalyst.

[0040] The metal source solution includes a palladium source solution and / or a nickel source solution.

[0041] This invention involves mixing thiosulfate and a carrier, followed by thermal modification to obtain a sulfur-modified carrier.

[0042] In this invention, the thiosulfate preferably includes one or more of sodium thiosulfate, ammonium thiosulfate, and potassium thiosulfate; the support preferably includes one or more of activated carbon, alumina, titanium dioxide, and silicon dioxide; the mass ratio of the thiosulfate to the support is preferably 1:100-1000, more preferably 1:200-800, and even more preferably 1:400-600.

[0043] In this invention, the temperature for thermal modification is preferably 500–700°C, more preferably 550–650°C, and most preferably 600–620°C; the time for thermal modification is preferably 1–3 h, more preferably 1.5–2.5 h, and most preferably 2–2.3 h; the heating rate to the temperature for thermal modification is preferably 1–5°C / min, more preferably 2–4°C / min, and most preferably 3–3.5°C / min; the thermal modification is preferably carried out in an inert gas atmosphere; the inert gas atmosphere is preferably N2; the flow rate of the inert gas is preferably 5–20 mL / min, more preferably 8–15 mL / min, and most preferably 10–12 mL / min.

[0044] After obtaining the sulfur-modified support, the present invention mixes the sulfur-modified support with a metal source solution, adjusts the pH value to 9-11, adds formaldehyde aqueous solution, and loads the solution to obtain a sulfur-modified heterogeneous catalyst.

[0045] In this invention, the palladium source solution preferably includes a chloropalladium acid solution; the mass concentration of palladium in the palladium source solution is preferably 0.02-0.4 mg / mL, more preferably 0.05-0.3 mg / mL, and most preferably 0.1-0.2 mg / mL.

[0046] In this invention, the nickel source solution preferably includes one or more of nickel nitrate solution, nickel chloride solution and nickel acetate solution; the mass concentration of nickel element in the nickel source solution is preferably 0.2-5 mg / mL, more preferably 1-4 mg / mL, and most preferably 1.5-2.5 mg / mL.

[0047] In this invention, the molar ratio of sulfur element in the sulfur-modified carrier to metal element in the metal source solution is preferably 0.006 to 15:1, more preferably 0.03 to 10:1, and most preferably 1 to 5:1.

[0048] In this invention, the alkali used to adjust the pH value preferably includes an alkali metal hydroxide, more preferably sodium hydroxide and / or potassium hydroxide; the alkali is preferably used as a solid alkali or an aqueous solution of alkali; the concentration of the aqueous solution of alkali is preferably 1 to 2 mol / L, more preferably 1.2 to 1.8 mol / L, and most preferably 1.4 to 1.6 mol / L.

[0049] In this invention, the mass concentration of the formaldehyde aqueous solution is preferably 30-40%, more preferably 35-38%, and specifically preferably 37%; the volume ratio of the metal source solution to the formaldehyde aqueous solution is preferably 2-5:1, more preferably 3-5:1, and most preferably 4-5:1.

[0050] In this invention, the temperature of the load is preferably 60-100°C, more preferably 70-90°C, and most preferably 75-80°C; the duration of the load is preferably 2-5 hours, more preferably 2-4 hours, and most preferably 2-3 hours.

[0051] After the loading is completed, the present invention preferably further includes washing the crude catalyst obtained by the loading until neutral and then drying it. In the present invention, the washing preferably includes water washing; the present invention does not have special limitations on the washing conditions, as long as the crude catalyst is washed until neutral. In the present invention, the drying temperature is preferably 80-100°C; more preferably 85-95°C, and most preferably 90-93°C; the drying time is preferably 6-12 hours, more preferably 8-12 hours, and most preferably 10-12 hours.

[0052] This invention provides the application of the sulfur-modified heterogeneous catalyst described in the above-described technical solutions, or the sulfur-modified heterogeneous catalyst prepared by the above-described technical solutions, in the catalytic synthesis of N-methyl secondary amine compounds from primary amine compounds. The sulfur-modified heterogeneous catalyst provided by this invention, when used for the catalytic reduction of primary amine compounds, can significantly improve the selectivity and yield of N-methyl secondary amine compounds. Furthermore, the catalyst exhibits good stability in the reaction system, is easily separated after catalysis, and maintains high reactivity and product selectivity even after multiple cycles of use.

[0053] This invention provides a method for preparing N-methyl secondary amine compounds, comprising the following steps:

[0054] Primary amine compounds, paraformaldehyde, reducing agent, catalyst and organic amine are mixed and subjected to reduction-amination reaction to obtain N-methyl secondary amine compounds;

[0055] The catalyst is the sulfur-modified heterogeneous catalyst described in the above technical solution or the sulfur-modified heterogeneous catalyst prepared by the preparation method described in the above technical solution.

[0056] In this invention, the primary amine compounds preferably include one or more of aliphatic primary amine compounds, aromatic primary amine compounds, and heterocyclic primary amine compounds, more preferably one or more of aniline, p-methoxyaniline, o-fluoroaniline, 2-pyridinemethylamine, cyclohexylamine, octylamine, pentylamine, and ethanolamine; the heteroatoms in the heterocyclic primary amine compounds preferably include one or more of N, O, and S.

[0057] In this invention, the mass of the catalyst is preferably less than 10% of the mass of the primary amine compound, more preferably 2 to 10%, further preferably 3 to 9%, and most preferably 4 to 8%.

[0058] In this invention, the organic amine preferably comprises a tertiary amine; its structural formula is preferably as shown in Formula I:

[0059]

[0060] Wherein, R1, R2, and R3 are independently preferably alkyl or hydroxyl groups; the number of carbon atoms in the alkyl and hydroxyl groups is independently preferably 1 to 12, specifically preferably 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12. In this invention, the organic amine is specifically preferably one or more of N-methyldiethanolamine (MDEA), triethanolamine (TEA), triethylamine, and tripropylamine. In this invention, the mass of the organic amine is preferably less than 85% of the total mass of the organic amine and primary amine compounds, more preferably 20 to 85%, and most preferably 40 to 80%.

[0061] In this invention, the molar ratio of the primary amine compound to paraformaldehyde is preferably 1:0.9 to 1.5, more preferably 1:1 to 1.4, and most preferably 1:1.1 to 1.3.

[0062] In this invention, the reducing agent is preferably hydrogen; the pressure of the hydrogen is preferably 0.5-5 MPa, more preferably 1-4 MPa, and most preferably 2-3 MPa.

[0063] Before the reduction-amination reaction, the present invention preferably includes a displacement reaction using hydrogen gas; the displacement reaction is preferably performed 3 to 5 times, more preferably 3 to 4 times.

[0064] In this invention, the temperature of the reduction-amination reaction is preferably 30-150°C, more preferably 50-120°C, and most preferably 80-100°C; the time of the reduction-amination reaction is preferably 1-24 h, more preferably 3-12 h, and most preferably 6-10 h.

[0065] After completing the reduction-amination reaction, the present invention preferably further includes distilling the obtained reaction solution to recover the catalyst, thereby obtaining an N-methyl secondary amine compound. In the present invention, the distillation preferably includes atmospheric distillation or vacuum distillation.

[0066] To further illustrate the present invention, the following detailed descriptions, in conjunction with embodiments, provide a sulfur-modified heterogeneous catalyst, its preparation method and application, and a method for preparing N-methyl secondary amine compounds. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0067] In all embodiments of the present invention, qualitative analysis was performed using an Agilent 5977A / 7890B GC-MS gas chromatograph to determine the product structure; quantitative analysis was performed using an Agilent 7890A gas chromatograph (capillary column specifications 30m×0.25mm×0.33μm, detector is flame ionization detector) gas chromatograph.

[0068] The gas chromatography-mass spectrometry (GC-MS) detection conditions for qualitative analysis were as follows: HP-5 column, detector temperature 260℃, column temperature increased from 80℃ to 260℃ and held for 5 min, with a heating rate of 10℃ / min.

[0069] Example 1

[0070] 5 mg of sodium thiosulfate and 1 g of activated carbon were mixed evenly and placed in a tube furnace. The mixture was heated to 500 °C at a rate of 5 °C / min under a nitrogen atmosphere and held at that temperature for 1 hour. The mixture was then cooled to room temperature to obtain the sulfur-modified support (abbreviated as CS). 0.005 ), where the flow rate of N2 is 10 mL / min.

[0071] Add 1g of the obtained CS to 50mL of chloropalladium acid solution (palladium concentration is 0.2mg / mL). 0.005 The mixture was stirred until homogeneous. The pH of the chloropalladium acid solution was adjusted to 11 using a 2 mol / L NaOH solution. 10 mL of a 37% formaldehyde aqueous solution was added. The mixture was heated to 80°C and stirred for 2 hours. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. The product was then dried at 80°C for 12 hours to obtain the sulfur-modified heterogeneous catalyst (abbreviated as Pd1 / CS). 0.005 The Pd content is 1 wt%, and the mass ratio of sodium thiosulfate to activated carbon carrier is 0.005:1.

[0072] Example 2

[0073] 1 mg of sodium thiosulfate and 1 g of titanium dioxide were mixed evenly and placed in a tube furnace. The mixture was heated to 500 °C under a nitrogen atmosphere and held at that temperature for 1 hour. Then, the mixture was cooled to room temperature to obtain TiO2-S. 0.001 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0074] Prepare 50 mL of nickel nitrate solution (containing 50 mg of nickel), and add 1 g of the obtained TiO2-S. 0.001 The support was stirred until homogeneous. The pH of the nickel nitrate solution was adjusted to 11 with 1 mol / L NaOH solution. 10 mL of 37% formaldehyde aqueous solution was added. The mixture was heated to 80℃ and stirred for 2 h. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80℃ for 12 h to obtain the catalyst Ni5 / TiO2-S. 0.001 (Ni content is 5wt%, and the mass ratio of sodium thiosulfate to TiO2 support is 0.001:1).

[0075] Example 3

[0076] 10 mg of ammonium thiosulfate and 1 g of titanium dioxide were mixed evenly and placed in a tube furnace. The mixture was heated to 500 °C under a nitrogen atmosphere and held at that temperature for 1 hour. Then, the mixture was cooled to room temperature to obtain TiO2-S. 0.01 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0077] Prepare 50 mL of chloropalladium acid solution (palladium content 10 mg), add 1 g of the obtained TiO2-S 0.01 The support was stirred until homogeneous. The pH of the chloropalladium acid solution was adjusted to 10 with 1.5 mol / L NaOH solution. 10 mL of 37% formaldehyde aqueous solution was added. The mixture was heated to 80°C and stirred for 2 h. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80°C for 12 h to obtain the catalyst Pd1 / TiO2-S. 0.01 (Pd content is 1wt%, and the mass ratio of ammonium thiosulfate to TiO2 support is 0.01:1).

[0078] Example 4

[0079] 5 mg of potassium thiosulfate and 1 g of activated carbon were mixed evenly and placed in a tube furnace. The mixture was heated to 500 °C under a N2 atmosphere and held at that temperature for 1 hour. Then, the mixture was cooled to room temperature to obtain CS. 0.005 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0080] Prepare 50 mL of chloropalladium acid solution (palladium content 5 mg), add 1 g of the obtained CS 0.005 The support was stirred until homogeneous. The pH of the chloropalladium acid solution was adjusted to 11 with 2 mol / L NaOH solution. 10 mL of 37% formaldehyde aqueous solution was added. The mixture was heated to 80℃ and stirred for 2 h. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80℃ for 12 h to obtain the catalyst Pd. 0.5 / CS 0.005 (Pd content is 0.5wt%, and the mass ratio of potassium thiosulfate to activated carbon C carrier is 0.005:1).

[0081] Example 5

[0082] 6 mg of sodium thiosulfate and 1 g of silicon dioxide were mixed evenly and placed in a tube furnace. The mixture was heated to 500 °C under a nitrogen atmosphere and held at that temperature for 1 hour. Then, the mixture was cooled to room temperature to obtain SiO2-S. 0.006 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0083] Prepare 50 mL of nickel chloride solution (containing 50 mg of nickel), and add 1 g of the obtained SiO2-S0.006 The support was stirred until homogeneous. The pH of the nickel chloride solution was adjusted to 11 with a 2 mol / L NaOH solution. 10 mL of a 37% formaldehyde aqueous solution was added. The mixture was heated to 80°C and stirred for 2 hours. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80°C for 12 hours to obtain the catalyst Ni5 / SiO2-S. 0.006 (Ni content is 5wt%, and the mass ratio of sodium thiosulfate to silica carrier is 0.006:1).

[0084] Example 6

[0085] 2 mg of potassium thiosulfate and 1 g of alumina were mixed thoroughly and placed in a tube furnace. The mixture was heated to 500 °C under a nitrogen atmosphere and held at that temperature for 1 hour. Then, the mixture was cooled to room temperature to obtain Al2O3-S. 0.002 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0086] Prepare 50 mL of nickel acetate solution (containing 100 mg of nickel), and add 1 g of the obtained Al2O3-S. 0.002 The support was stirred until homogeneous. The pH of the nickel acetate solution was adjusted to 10 with 2 mol / L NaOH solution. 10 mL of 37% formaldehyde aqueous solution was added. The mixture was heated to 80°C and stirred for 2 h. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80°C for 12 h to obtain the Ni catalyst. 10 / Al2O3-S 0.002 (Ni content is 10wt%, and the mass ratio of potassium thiosulfate to alumina carrier is 0.002:1).

[0087] Example 7

[0088] 1 mg of sodium thiosulfate and 1 g of alumina were mixed thoroughly and placed in a tube furnace. The mixture was heated to 500 °C under a nitrogen atmosphere and held at that temperature for 1 hour. After cooling to room temperature, Al2O3-S was obtained. 0.001 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0089] Prepare 50 mL of nickel nitrate solution (containing 100 mg of nickel), and add 1 g of the obtained Al₂O₃-S. 0.001 The support was stirred until homogeneous. The pH of the nickel nitrate solution was adjusted to 11 with 2 mol / L NaOH solution. 10 mL of 37% formaldehyde aqueous solution was added. The mixture was heated to 80℃ and stirred for 2 h. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80℃ for 12 h to obtain the Ni catalyst. 10 / Al2O3-S0.001 (Ni content is 10wt%, and the mass ratio of sodium thiosulfate to alumina carrier is 0.001:1).

[0090] Example 8

[0091] 10 mg of sodium thiosulfate and 1 g of activated carbon were mixed evenly and placed in a tube furnace. The mixture was heated to 500 °C under a N2 atmosphere and held at that temperature for 1 hour. Then, the mixture was cooled to room temperature to obtain CS. 0.01 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0092] Prepare 50 mL of chloropalladium acid solution (palladium content 2 mg), add 1 g of the obtained CS 0.01 The support was stirred until homogeneous. The pH of the chloropalladium acid solution was adjusted to 11 with 1.5 mol / L NaOH solution. 10 mL of 37% formaldehyde aqueous solution was added. The mixture was heated to 80°C and stirred for 2 h. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80°C for 12 h to obtain the catalyst Pd. 0.2 / CS 0.01 (Pd content is 0.2wt%, and the mass ratio of sodium thiosulfate to activated carbon carrier is 0.01:1).

[0093] Example 9

[0094] 5 mg of sodium thiosulfate and 1 g of alumina were mixed thoroughly and placed in a tube furnace. The mixture was heated to 500 °C under a nitrogen atmosphere and held at that temperature for 1 hour. After cooling to room temperature, Al2O3-S was obtained. 0.005 The carrier, wherein the N2 flow rate is 10 mL / min and the heating rate is 5 °C / min.

[0095] Prepare 50 mL of chloropalladium acid solution (palladium content 15 mg), add 1 g of the obtained Al2O3-S 0.005 The support was stirred until homogeneous. The pH of the chloropalladium acid solution was adjusted to 11 with 2 mol / L NaOH solution. 10 mL of 37% formaldehyde aqueous solution was added. The mixture was heated to 80℃ and stirred for 2 h. After cooling to room temperature, the resulting solid product was washed with water until the pH reached 7. It was then dried at 80℃ for 12 h to obtain the catalyst Pd. 1.5 / Al2O3-S 0.005 (Pd content is 1.5wt%, and the mass ratio of sodium thiosulfate to alumina carrier is 0.005:1).

[0096] Example 10

[0097] The Pd1 / CS prepared in Example 1 was made by mixing 9.3 g aniline, 3.5 g paraformaldehyde, 40 g triethylamine, and 500 mg of...0.005 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 90 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 5 MPa. The reduction-amination reaction was carried out for 12 h. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methylaniline. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0098] Example 11

[0099] The Ni5 / TiO2-S prepared in Example 2 was prepared using 9.3g aniline, 3g paraformaldehyde, 40g triethanolamine, and 500mg of... 0.001 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 120 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 5 MPa. The reduction-amination reaction was carried out for 15 h. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methylaniline. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0100] Example 12

[0101] 12.3 g of p-methoxyaniline, 4 g of paraformaldehyde, 40 g of N-methyldiethanolamine, and 100 mg of Pd1 / TiO2-S prepared in Example 3 were mixed. 0.01 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 80 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 2 MPa. The reduction-amination reaction was carried out for 5 h. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methyl-p-methoxyaniline. The reaction product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry.

[0102] Example 13

[0103] 11.1 g of o-fluoroaniline, 3 g of paraformaldehyde, 50 g of triethylamine, and 50 mg of Pd prepared in Example 4 were mixed. 0.5 / CS 0.005 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 110 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 4 MPa. The reduction-amination reaction was carried out for 18 h. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methyl-o-fluoroaniline. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0104] Example 14

[0105] 10.8 g of 2-pyridinemethylamine, 4.5 g of paraformaldehyde, 50 g of tripropylamine, and 100 mg of Ni5 / SiO2-S prepared in Example 5 were mixed. 0.006The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 60 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 3 MPa. The reduction-amination reaction was carried out for 10 h. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methyl-2-pyridinemethylamine. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0106] Example 15

[0107] The Ni prepared in Example 6 was composed of 9.9 g cyclohexylamine, 2.8 g paraformaldehyde, 50 g tripropylamine, and 200 mg. 10 / Al2O3-S 0.002 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 50 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 2 MPa. The reduction-amination reaction was carried out for 6 hours. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methylcyclohexylamine. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0108] Example 16

[0109] The Ni prepared in Example 7 was made by mixing 12.9 g of octylamine, 3.5 g of paraformaldehyde, 50 g of triethylamine, and 500 mg of sodium chloride. 10 / Al2O3-S 0.001 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 60 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 1 MPa. The reduction-amination reaction was carried out for 10 h. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methyloctylamine. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0110] Example 17

[0111] The Pd prepared in Example 8 was composed of 8.7 g pentylamine, 2.8 g paraformaldehyde, 45 g triethylamine, and 500 mg of... 0.2 / CS 0.01 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 100 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 0.5 MPa. The reduction-amination reaction was carried out for 5 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product N-methylpentane. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0112] Example 18

[0113] 6.1 g ethanolamine, 4 g paraformaldehyde, 34 g tripropylamine, and 50 mg of Pd prepared in Example 9 were mixed. 1.5 / Al2O3-S0.005 The catalyst was added to a 150 mL reactor, sealed, and purged four times with hydrogen. The temperature was raised to 80 °C under stirring, and then hydrogen was introduced to bring the reactor pressure to 5 MPa. The reduction-amination reaction was carried out for 12 h. After the reaction was completed, the temperature was lowered to room temperature to obtain the reaction product N-methylmonoethanolamine. Gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of the reaction product.

[0114] The structural formulas, primary amine conversion rates, and product selectivity of the reaction products prepared in Examples 10-18 are shown in Table 1.

[0115] Table 1. Structural formulas, primary amine conversion rates, and selectivity of the reaction products prepared in Examples 10-18

[0116]

[0117]

[0118] As shown in Table 1, the sulfur-modified heterogeneous catalyst provided by this invention can be used to synthesize N-methyl secondary amine compounds from primary amine compounds, resulting in high selectivity and yield of N-methyl secondary amine compounds.

[0119] Example 19

[0120] The reaction solution obtained after the reaction in Example 11 was filtered to obtain Ni5 / TiO2-S. 0.001 The catalyst was reused repeatedly under the same reaction conditions as in Example 11. After each reaction, the Ni5 / TiO2-S obtained by filtering the reaction solution was... 0.001 The catalyst was reused in the next reaction, and the aniline conversion and N-methylaniline selectivity are shown in Table 2.

[0121] Table 2. Statistical table of aniline conversion rate and N-methylaniline selectivity.

[0122] 1st time 95.3 96.8 2nd time 95.0 96.7 3rd time 94.8 96.5 4th 94.6 96.8 5th 93.9 96.4

[0123] As shown in Table 2, the sulfur-modified heterogeneous catalyst provided by the present invention has good stability in the reaction system, is easy to separate after catalysis, and can still maintain high reactivity and product selectivity after multiple cycles.

[0124] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an N-methyl secondary amine compound, characterized in that, Includes the following steps: Primary amine compounds, paraformaldehyde, reducing agent, catalyst and organic amine are mixed and subjected to reduction-amination reaction to obtain N-methyl secondary amine compounds; The catalyst is a sulfur-modified heterogeneous catalyst; The sulfur-modified heterogeneous catalyst includes a sulfur-modified support and an active component supported on the sulfur-modified support; The active component includes palladium and / or nickel; The carrier in the sulfur-modified carrier includes one or more of alumina, titanium dioxide, and silicon dioxide; The preparation method of the sulfur-modified heterogeneous catalyst includes the following steps: Thiosulfate and a carrier are mixed and thermally modified to obtain a sulfur-modified carrier; The sulfur-modified support and metal source solution were mixed, the pH value was adjusted to 9-11, and formaldehyde aqueous solution was added for loading to obtain a sulfur-modified heterogeneous catalyst. The metal source solution includes a palladium source solution and / or a nickel source solution; The temperature for thermal modification is 500~700℃; The organic amine is a tertiary amine, and its structural formula is shown in Formula I: Equation I; R1, R2 and R3 are independently alkyl groups.

2. The preparation method according to claim 1, characterized in that, The palladium source solution includes a chloropalladium acid solution; the nickel source solution includes one or more of nickel nitrate solution, nickel chloride solution, and nickel acetate solution. The mass ratio of the thiosulfate to the carrier is 1:100~1000.

3. The preparation method according to claim 1, characterized in that, The primary amine compounds include one or more of aliphatic primary amine compounds, aromatic primary amine compounds, and heterocyclic primary amine compounds; The mass of the catalyst is 2 to 10% of the mass of the primary amine compound.

4. The preparation method according to claim 1, characterized in that, The mass of the organic amine is 20-85% of the total mass of the organic amine and primary amine compounds.

5. The preparation method according to claim 1 or 4, characterized in that, The molar ratio of the primary amine compound to paraformaldehyde is 1:0.9~1.5.

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