Method for preparing furfuryl amine through reductive amination of biomass-based furfural

Abstract

The invention discloses a method for preparing furfuryl amine by reductive amination of biomass-based furfural, which comprises the following steps: adding furfural, a catalyst, ammonia water and a solvent into a closed reaction kettle in proportion, replacing air in the reaction kettle with high-purity hydrogen, and reacting in an oil bath pan for a period of time to obtain a target product furfuryl amine, the nano-catalyst provided by the invention is a nitrogen-doped porous hollow carbon sphere loaded nano bimetallic catalyst, takes noble metal and non-noble metal as a metal active center together, and has adjustability of macroscopic size and microstructure at the same time; the method has the advantages of simple reaction system, mild conditions, no pollution to the environment, high efficiency, energy conservation, low cost, few byproducts, high yield, high selectivity and the like, the furfural is efficiently converted into furfuryl amine at low temperature and low pressure within a short time, the used heterogeneous catalyst is stable and easy to recover, a new thought and direction are provided for enterprise production and scientific research, and the method is suitable for industrial production. The method has great significance on development and utilization of biomass-based furfural.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a method for preparing furfural amine, and specifically relates to a method for preparing furfural amine through reductive amination of biomass-based furfural. Background Art

[0002] As environmental problems caused by traditional petrochemical industry become increasingly prominent, the use of renewable biomass to prepare a variety of high-value-added nitrogen-containing compounds is a feasible solution. Among them, primary amines with higher value are the most prolific organic chemical raw materials and are widely used in the fields of medicine, agricultural chemicals, polymer materials, coatings and surfactants, and have attracted much attention. At present, among the many synthesis methods of primary amines, the catalytic reductive amination of carbonyl compounds with hydrogen (H2) as a reducing agent and ammonia (NH3) as a nitrogen source is the most cost-effective and atom-efficient method. It can be carried out under relatively mild conditions, and water is the main by-product, which greatly reduces the undesirable products. However, due to the strong nucleophilicity of the initially generated amines, it is difficult to directly produce primary amines, and it is difficult to avoid the formation of by-products such as secondary amines and tertiary amines. The development of efficient catalysts for the reductive amination of carbonyl compounds to prepare primary amines with high activity and high selectivity remains a challenging goal.

[0003] Furfural (FUR) is one of the important compounds obtained from biomass and is a typical representative of furan compounds. Furfuralamine (FUA), as its nitrogen derivative, can be prepared through the reductive amination reaction of furfural. It is an important organic synthesis intermediate and chemical product, and is also an emerging molecule with far-reaching application prospects.

[0004] The prior art has the following defects in the process of furfural reductive amination to prepare furfuralamine, such as harsh reaction conditions, long reaction time, low selectivity, high cost of precious metal catalysts, poor stability and low activity of non-precious metal catalysts, etc. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing furfurylamine by reductive amination of biomass-based furfural, using ammonia water and hydrogen as nitrogen sources and reducing agents, with a simple reaction system, mild conditions, no pollution to the environment, high efficiency and energy saving, low cost, few by-products, high yield and selectivity.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing furfurfural by reductive amination of biomass-based furfural, comprising the following steps:

[0008] Step 1, using an autoclave as a container, adding furfural, a catalyst and aqueous ammonia in an organic solvent, wherein the mass ratio of furfural to the catalyst is (5-50):1, and the molar ratio of ammonia ions to furfural in the aqueous ammonia is (5-45):1, and sealing the autoclave;

[0009] Step 2: Place the sealed high-pressure reactor in an oil bath, fill it with hydrogen to a pressure of 0.1-2 MPa, stir and react at 50-150° C. for 0.1-6 h. After the reaction time is reached, place the reactor in ice water and quickly cool it to room temperature. Filter out the precipitate, wash and dry it to obtain furfural amine.

[0010] The present invention also has the following technical features:

[0011] Preferably, the organic solvent includes any one of methanol, ethanol, n-propanol, isopropanol, dioxane, tetrahydrofuran, cyclohexane, toluene and n-hexane.

[0012] Preferably, the catalyst is M1M2@NHCS-T, wherein M1M2 is a bimetallic active component, NHCS is a nitrogen-doped porous hollow carbon sphere carrier, and T is the pyrolysis temperature;

[0013] The bimetallic active component includes a noble metal M1 and a base metal M2, and the mass ratio of the noble metal to the base metal is (0.02-6):1;

[0014] The precious metal includes any one of ruthenium, platinum, palladium, rhodium and gold, and the base metal includes any one of cobalt, nickel and copper;

[0015] The pyrolysis temperature is 600-1000°C.

[0016] Preferably, in the step 2, high-purity hydrogen is introduced into the sealed high-pressure reactor to replace the air in the reactor 3 to 6 times and then filled with hydrogen.

[0017] Preferably, the stirring rotor speed in step 2 is 300-800 rpm.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] The method for preparing furfural amine based on furfural reductive amination is characterized in that ammonia water and hydrogen are used as nitrogen source and reducing agent, and under the action of temperature and ammonia water, the C=O bond of furfural is attacked by NH3 and converted into an imine intermediate, and under the action of a catalyst and H2, the C=N bond of the imine is activated and then hydrogenated into furfural amine; at the same time, the imine can also generate a Schiff base under the action of the catalyst and then be converted into furfural amine by the Schiff base; the method has the advantages of simple reaction system, mild conditions, no pollution to the environment, high efficiency and energy saving, low cost, few by-products, high yield and selectivity, and is suitable for the industrial production of furfural amine;

[0020] The present invention realizes the efficient conversion of furfural into furfuralamine in a relatively short time under low temperature and low pressure conditions. The multiphase catalyst used is stable and easy to recover, which provides new ideas and directions for enterprise production and scientific research and is of great significance to the utilization and development of furfural. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The reaction pathway diagram for the reductive amination of furfural to furfurfurylamine;

[0022] Figure 2 The gas chromatogram of the product of Example 1 is shown in FIG. DETAILED DESCRIPTION

[0023] The specific contents of the present invention are further explained in detail below in conjunction with embodiments.

[0024] The catalyst is M1M2@NHCS-T prepared by a one-pot synthesis method. The specific preparation method includes: taking polystyrene nanospheres (with a size of 200-350 nm), dopamine hydrochloride, Tris and a metal precursor in a mass ratio of 10:(5-32):(14-89.6):(1-5), ultrasonically dispersing the polystyrene nanospheres in deionized water for 1-1.5 hours, transferring the polystyrene nanospheres to an oil bath pot and stirring at room temperature for 30-60 minutes, slowly adding dopamine hydrochloride and the metal precursor, stirring for 30-60 minutes, adding Tris, adding hydrochloric acid to adjust the pH to 8.0-10.0, slowly stirring and polymerizing at room temperature for 20-36 hours, then centrifuging the suspension to obtain a precipitate, washing and drying to obtain a catalyst precursor, placing the catalyst precursor in a tubular furnace, and calcining at 600-1000° C. for 3-6 hours in a nitrogen-hydrogen mixed atmosphere to obtain a M1M2@NHCS-T catalyst.

[0025] M1M2 is a bimetallic active component, the precious metal M1 includes any one of ruthenium, platinum, palladium, rhodium, and gold, the base metal M2 includes any one of cobalt, nickel, and copper, and the mass ratio of the precious metal to the base metal is (0.02-6):1.

[0026] The metal precursors include two of the chlorides, nitrates or sulfates of ruthenium, platinum, palladium, rhodium, gold, cobalt, nickel and copper.

[0027] Example 1

[0028] This embodiment provides a method for preparing furfural amine by reductive amination of biomass-based furfural. There are two specific implementation paths, such as Figure 1 As shown: under the action of ammonia water, the C=O bond of furfural is replaced and converted into imine, and the imine is directly catalytically hydrogenated by the catalyst in a H2 environment to produce the product furfural amine; at the same time, the imine can also generate Schiff base under the action of the catalyst, and then the Schiff base is further converted into furfural amine; the specific steps are as follows:

[0029] Step 1: Using a high pressure reactor as a container, add furfural and catalyst Ru2Co to methanol. 1.5 @NHCS-600 and ammonia water, wherein the mass ratio of furfural to catalyst is 10:1, the molar ratio of ammonia ions to furfural in ammonia water is 10:1, and the autoclave is sealed;

[0030] Step 2: Place the sealed high-pressure reactor in an oil bath, replace the air in the reactor with 0.3MPa high-purity H2 for 5 times, fill with hydrogen to a pressure of 0.1MPa, stir the reaction at 110°C for 1.5h, and the stirring rotor speed is 500rpm. After the reaction time is reached, place the reactor in ice water and quickly cool it to room temperature. Filter out the precipitate, wash it alternately with ethanol and deionized water for 3 times, and obtain furfural amine after vacuum drying at 60°C for 12h.

[0031] Catalyst Ru2Co 1.5 The preparation method of @NHCS-600 includes: taking polystyrene nanospheres (size of 200-350nm), dopamine hydrochloride, Tris and metal precursors RuCl3·3H2O and Co(NO3)2·6H2O in a mass ratio of 10:10:30.3:5, ultrasonically dispersing the polystyrene nanospheres in deionized water for 1.5h, transferring them to an oil bath pot and stirring at room temperature for 60min, slowly adding dopamine hydrochloride and metal precursors, stirring for 60min, adding Tris, adding hydrochloric acid to adjust the pH to 8.5, slowly stirring and polymerizing at room temperature for 36h, then centrifuging the suspension to obtain a precipitate, washing and drying to obtain a catalyst precursor, placing the catalyst precursor in a tubular furnace, and calcining it at 600℃ for 6h in a nitrogen-hydrogen mixed atmosphere to obtain Ru2Co 1.5 @NHCS-600 catalyst.

[0032] The reaction products were quantitatively analyzed by gas chromatograph (GC9720Plus, Zhejiang Fuli Analytical Instruments). The front-end injection port temperature was 260°C; the separation column used a KB-1 capillary column (specifications were 60m×0.32mm×0.5μm), and the working process used a programmed temperature rise method: 100°C for 5 min, then heated to 150°C at a rate of 20°C / min, then kept at 150°C for 4 min, then heated to 260°C at a rate of 30°C / min, and kept warm for 6 min. The back end used a FID hydrogen flame ionization detector, and the working temperature was 260°C.

[0033] The gas chromatogram of the product of Example 1 is as follows Figure 2As shown, a certain amount of furfural, catalyst and ammonia water are added to an organic solvent, heated and stirred in an oil bath under a hydrogen atmosphere for a certain period of time, and the solution after the reaction is analyzed by gas chromatography, wherein the main substance is the product furfural amine, accompanied by trace amounts of furfuryl alcohol and Schiff base, indicating that the method of efficiently converting furfural into furfural amine in a relatively short time under low temperature and low pressure conditions is feasible.

[0034] Example 2

[0035] This embodiment provides a method for preparing furfurfural by reductive amination of biomass-based furfural, comprising the following steps:

[0036] Step 1: Using a high-pressure reactor as a container, add furfural and catalyst Ru2Co to ethanol. 1.5 @NHCS-600 and ammonia water, wherein the mass ratio of furfural to catalyst is 5:1, the molar ratio of ammonia ions to furfural in ammonia water is 5:1, and the high-pressure reactor is sealed;

[0037] Step 2: Place the sealed high-pressure reactor in an oil bath, replace the air in the reactor with 0.3MPa high-purity H2 for 5 times, fill with hydrogen to a pressure of 0.5MPa, stir the reaction at 50°C for 6 hours, and the stirring rotor speed is 300rpm. After the reaction time is reached, place the reactor in ice water and quickly cool it to room temperature. Filter out the precipitate, wash it alternately with ethanol and deionized water for 3 times, and obtain furfural amine after vacuum drying at 60°C for 12 hours.

[0038] Catalyst Ru2Co 1.5 The preparation method of @NHCS-600 includes: taking polystyrene nanospheres (size of 200-350nm), dopamine hydrochloride, Tris and metal precursors RuCl3·3H2O and Co(NO3)2·6H2O in a mass ratio of 10:5:14:1, ultrasonically dispersing the polystyrene nanospheres in deionized water for 1 hour, transferring them to an oil bath pot and stirring at room temperature for 30 minutes, slowly adding dopamine hydrochloride and metal precursors, stirring for 30 minutes, adding Tris, adding hydrochloric acid to adjust the pH to 8.0, slowly stirring and polymerizing at room temperature for 20 hours, then centrifuging the suspension to obtain a precipitate, washing and drying to obtain a catalyst precursor, placing the catalyst precursor in a tubular furnace, and calcining it at 600°C for 3 hours in a nitrogen-hydrogen mixed atmosphere to obtain Ru2Co 1.5 @NHCS-600 catalyst.

[0039] Example 3

[0040] This embodiment provides a method for preparing furfurfural by reductive amination of biomass-based furfural, comprising the following steps:

[0041] Step 1: Using a high pressure reactor as a container, add furfural and catalyst Ru2Co to isopropanol. 1.5@NHCS-600 and ammonia water, wherein the mass ratio of furfural to catalyst is 50:1, the molar ratio of ammonia ion to furfural in ammonia water is 45:1, and the autoclave is sealed;

[0042] Step 2: Place the sealed high-pressure reactor in an oil bath, replace the air in the reactor with 0.3MPa high-purity H2 for 5 times, fill with hydrogen to a pressure of 2MPa, stir the reaction at 150°C for 0.1h, and the stirring rotor speed is 800rpm. After the reaction time is reached, place the reactor in ice water and quickly cool it to room temperature, filter out the precipitate, wash it alternately with ethanol and deionized water for 3 times, and obtain furfural amine after vacuum drying at 60°C for 12h.

[0043] Catalyst Ru2Co 1.5 The preparation method of @NHCS-600 includes: taking polystyrene nanospheres (size of 200-350nm), dopamine hydrochloride, Tris and metal precursors RuCl3·3H2O and Co(NO3)2·6H2O in a mass ratio of 10:32:89.6:3, ultrasonically dispersing the polystyrene nanospheres in deionized water for 1.2h, transferring them to an oil bath pot and stirring at room temperature for 40min, slowly adding dopamine hydrochloride and metal precursors, stirring for 40min, adding Tris, adding hydrochloric acid to adjust the pH to 10.0, slowly stirring and polymerizing at room temperature for 24h, then centrifuging the suspension to obtain a precipitate, washing and drying to obtain a catalyst precursor, placing the catalyst precursor in a tubular furnace, and calcining it at 600℃ for 4h in a nitrogen-hydrogen mixed atmosphere to obtain Ru2Co 1.5 @NHCS-600 catalyst.

[0044] Example 4

[0045] Example 4 is basically the same as Example 1, except that the catalyst is Ru1Co2@NHCS-600.

[0046] Example 5

[0047] Example 5 is substantially the same as Example 1, except that the catalyst is Ru1Co1@NHCS-600.

[0048] Example 6

[0049] Example 6 is basically the same as Example 1, except that the catalyst is Ru2Co 1.5 @NHCS-700.

[0050] Example 7

[0051] Example 7 is basically the same as Example 1, except that the catalyst is Ru2Co 1.5 @NHCS-800.

[0052] Example 8

[0053] Example 8 is basically the same as Example 1, except that the catalyst is Ru2Co 1.5 @NHCS-900.

[0054] Example 9

[0055] Example 9 is basically the same as Example 1, except that the catalyst is Ru3Ni1@NHCS-1000.

[0056] Example 10

[0057] Example 10 is substantially the same as Example 1, except that the catalyst is Ru2Cu1@NHCS-900.

[0058] Embodiment 11

[0059] Example 11 is basically the same as Example 1, except that the catalyst is Rh2Cu 1.5 @NHCS-600.

[0060] Example 12

[0061] Example 12 is basically the same as Example 1, except that the catalyst is Pd2Cu 1.5 @NHCS-600.

[0062] Example 13

[0063] Example 13 is basically the same as Example 1, except that the catalyst is Ru2Ni 1.5 @NHCS-600.

[0064] Embodiment 14

[0065] Example 14 is basically the same as Example 1, except that the catalyst is Ru 3.5 Ni1@NHCS-600.

[0066] Embodiment 15

[0067] Example 15 is basically the same as Example 1, except that the catalyst is Ru 0.1 Ni9@NHCS-600.

[0068] The preparation methods of the catalysts in Examples 4 to 15 are substantially the same as those in Example 1, with the only difference being the type, proportion or pyrolysis temperature of the metal precursors.

[0069] Example 16

[0070] Example 16 is basically the same as Example 1, except that the ratio of ammonia to water is 5:1.

[0071] Embodiment 17

[0072] Example 17 is basically the same as Example 1, except that the ratio of ammonia to water is 45:1.

[0073] The furfural conversion rate and furfural amine yield were calculated according to the following formula, and the results are shown in Table 1;

[0074]

[0075]

[0076]

[0077] Table 1 Reductive amination performance of different catalysts

[0078] Example catalyst Conversion rate / % Furfurylamine yield / % 1 <![CDATA[Ru2Co 1.5 @NHCS-600]]> 100 96 5 <![CDATA[Ru1Co1@NHCS-600]]> 100 84 6 <![CDATA[Ru2Co 1.5 @NHCS-700]]> 100 74 7 <![CDATA[Ru2Co 1.5 @NHCS-800]]> 97 30 13 <![CDATA[Ru2Ni 1.5 @NHCS-600]]> 100 87 14 <![CDATA[Ru 3.5 Co1@NHCS-600]]> 100 71 15 <![CDATA[Ru 0.1 Co9@NHCS-600]]> 100 52

[0079] The furfural conversion rate and furfural amine yield of Examples 1, 16 and 17 were calculated, and the results are shown in Table 2:

[0080] Table 2 Effect of different ammonia dosage on the reaction system

[0081]

[0082] It can be seen from Table 2 that the yield of furfural is highest when the molar ratio of ammonia water to furfural is 10:1.

[0083] The method for preparing furfuralamine by reductive amination of biomass-based furfural has the advantages of simple reaction system, mild conditions, no pollution to the environment, high efficiency and energy saving, low cost, few by-products, high yield and selectivity, etc., and is suitable for the industrial production of furfuralamine. The method realizes efficient conversion of furfural into furfuralamine in a short time under low temperature and low pressure conditions, and the multiphase catalyst used is stable and easy to recover, which provides new ideas and directions for enterprise production and scientific research, and is of great significance to the utilization and development of furfural.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The solvent used in the present invention may also be other solvents given in the technical solution, and the catalyst may also be other catalysts within the scope of the technical solution. Among them, the bimetallic material may also be other combinations of ruthenium, platinum, palladium, rhodium, gold, cobalt, nickel and copper other than those listed in the embodiments, which are not listed here one by one. 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.

Claims

1. A method for preparing furfurfural by reductive amination of biomass-based furfural, characterized in that: The following steps are involved: Step 1, using an autoclave as a container, adding furfural, a catalyst and aqueous ammonia in an organic solvent, wherein the mass ratio of furfural to the catalyst is (5-50):1, and the molar ratio of ammonia ions to furfural in the aqueous ammonia is (5-45):1, and sealing the autoclave; Step 2: Place the sealed high-pressure reactor in an oil bath, fill it with hydrogen to a pressure of 0.1-2 MPa, stir and react at 50-150° C. for 0.1-6 h. After the reaction time is reached, place the reactor in ice water and quickly cool it to room temperature. Filter out the precipitate, wash and dry it to obtain furfural amine.

2. The method for preparing furfurfurylamine by reductive amination of biomass-based furfural according to claim 1, characterized in that: The organic solvent includes any one of methanol, ethanol, n-propanol, isopropanol, dioxane, tetrahydrofuran, cyclohexane, toluene and n-hexane.

3. The method for preparing furfurfurylamine by reductive amination of biomass-based furfural according to claim 1, characterized in that: The catalyst is M1M2@NHCS-T, wherein M1M2 is a bimetallic active component, NHCS is a nitrogen-doped porous hollow carbon sphere carrier, and T is the pyrolysis temperature; The bimetallic active component includes a noble metal M1 and a base metal M2, and the mass ratio of the noble metal to the base metal is (0.02-6):1; The precious metal includes any one of ruthenium, platinum, palladium, rhodium and gold, and the base metal includes any one of cobalt, nickel and copper; The pyrolysis temperature is 600-1000°C.

4. The method for preparing furfurfurylamine by reductive amination of biomass-based furfural according to claim 1, characterized in that: In the step 2, high-purity hydrogen is introduced into the sealed high-pressure reactor to replace the air in the reactor 3 to 6 times and then filled with hydrogen.

5. The method for preparing furfurfurylamine by reductive amination of biomass-based furfural according to claim 1, characterized in that: The stirring rotor speed in step 2 is 300-800 rpm.

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