A method for preparing 2,5-furandimethylamine

Abstract

This invention discloses a method for preparing 2,5-furandimethylamine, comprising the following steps: 1) preparing a 2,5-diformylfuran solution for later use; 2) taking the 2,5-diformylfuran solution prepared in step 1) into a reaction vessel, adding an inorganic amine source, an organic amine stabilizer, and a catalyst, reacting under a hydrogen atmosphere, and after the reaction is completed, cooling the reaction solution to room temperature, and slowly discharging the remaining hydrogen gas to obtain 2,5-furandimethylamine. The 2,5-furandimethylamine prepared by this method uses an inorganic ammonium salt as the amine source, which gradually decomposes to produce ammonia as the reaction temperature increases. At this temperature, the imine generated can be reduced in situ to a primary amine, avoiding the accumulation and aggregation of the imine intermediate, thereby avoiding the occurrence of side reactions. On the other hand, the use of a small amount of organic amine as a stabilizer further inhibits the occurrence of side reactions, increasing the yield of 2,5-furandimethylamine to 95%.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing 2,5-furandimethylamine. Background Technology

[0002] Primary amines are a class of multifunctional platform compounds used to prepare polymers, dyes, pharmaceutical intermediates, etc. Primary diamines, as important polymer monomers, are widely used in the production of polyamides and polyureas in industries such as automotive, aerospace, electronics, construction, and biomedicine. Industrially, primary diamines (such as ethylenediamine, 1,3-propanediamine, and hexamethylenediamine) are mainly derived from petrochemicals. With the increasing depletion of petrochemical resources and the environmental problems caused by their use, the search for renewable resources to replace petrochemical resources in the preparation of primary diamines has attracted increasing attention from researchers. Biomass is the only renewable organic carbon resource in nature and can replace petrochemical energy for the synthesis of chemicals and fuels. Fully utilizing biological resources to prepare bio-based primary diamines is an important way to achieve green and sustainable development of the chemical industry.

[0003] 5-Hydroxymethylfurfural is a platform molecule derived from biomass hexoses or their polymers, and a series of furanyl high-value-added derivatives can be prepared through hydrogenation, oxidation, and reductive amination. Among them, 2,5-furandimethylamine (BAMF) can be used as an ideal substitute for p-phenylenediamine or m-phenylenediamine in the preparation of epoxy resins, photosensitive nylon, polyurethane coatings, etc.

[0004] Currently, the main methods for preparing 2,5-furandimethylamine include the direct catalytic amination of 5-hydroxymethylfurfural, the reductive amination of 2,5-dicarboxyfuran, and other indirect catalytic methods. For example, Chinese Patent Publication No. CN113976131A discloses a method for preparing 2,5-furandimethylamine from 5-hydroxymethylfurfural. This invention uses 5-hydroxymethylfurfural as a raw material and tetrahydrofuran as a solvent. In the presence of the aforementioned heterogeneous catalyst, the reaction proceeds in a hydrogen and ammonia atmosphere to generate 2,5-furandimethylamine, with a yield of over 97%. Another example is Patent Publication No. CN1042... Chinese Patent 77017B discloses the preparation of 2,5-dimethylaminofuran from 2,5-dihydroxymethylfuran. This method uses ammonia as the amine source, in-situ generated active hydrogen as the hydrogen source, and a supported metal as the catalyst. At 30-220°C, 2,5-dihydroxymethylfuran is selectively reduced and aminationed to 2,5-dimethylaminofuran. This method features mild reaction conditions, high product yield, easily separable and recyclable catalyst, and readily separable and purified products with a purity exceeding 99%. For example, Yuan et al. used a bifunctional CuNiAlOx catalyst, reacting for 18 hours after a two-step heating to 210°C. The yield of 2,5-furandimethylamine reached 85.9% (RSC Adv., 2019, 9, 38877); for example, Kita et al. prepared a Ru–MgO / TiO2 catalyst to achieve the direct reductive amination of furandimethylethanol to 2,5-furandimethylamine with a yield of approximately 86% (Chem. Sci., 2020, 11, 9884-9890). These methods mainly use ammonia and suffer from problems such as high reaction temperatures and complex and expensive catalyst preparation processes. The use of ammonia or ammonia water as the nitrogen source easily leads to side reactions.

[0005] This invention proposes a novel method for preparing 2,5-furandimethylamine, which achieves efficient reductive amination of 2,5-furandimethylamine under mild conditions without directly using ammonia gas or ammonia water. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing 2,5-furandimethylamine, which is simple in reaction, uses an inorganic ammonium salt as the nitrogen source, and effectively avoids the occurrence of side reactions.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing 2,5-furandimethylamine includes the following steps:

[0009] 1) Dissolve 2,5-dicarboxyfuran in a beaker containing solvent to prepare a 2,5-dicarboxyfuran solution for later use;

[0010] 2) Take the 2,5-dicarboxyfuran solution prepared in step 1) into a reaction vessel, add an inorganic amine source, an organic amine stabilizer and a catalyst, and react under a hydrogen atmosphere. After the reaction is completed, cool the reaction solution to room temperature and slowly discharge the remaining hydrogen gas to obtain 2,5-furan dimethylamine.

[0011] Further, in step 1), the solvent used to prepare the 2,5-dicarboxyfuran solution is methanol, ethanol, tetrahydrofuran, or 1,4-dioxane.

[0012] Furthermore, the concentration of the 2,5-dicarboxyfuran solution is 1-10 wt%.

[0013] Further, in step 2), the molar ratio of 2,5-dicarboxyfuran to the inorganic amine source is 1:2-40 mmol; the mass ratio of 2,5-dicarboxyfuran to the catalyst is 1:10-200 mg.

[0014] Furthermore, in step 2), the inorganic amine source is ammonium bicarbonate, ammonium carbonate, ammonium metaphosphate, ammonium phosphate, ammonium nitrate, or ammonium chloride.

[0015] Further, in step 2), the molar ratio of 2,5-dicarboxyfuran to the organic amine stabilizer is 1:0.01-0.5 mmol.

[0016] Further, in step 2), the organic amine stabilizer is triethylamine, n-butylamine, n-pentylamine, benzylamine, pentanediamine, hexamethylenediamine, or p-phenylenediamine.

[0017] Furthermore, in step 2), the catalyst is a commercially available 5% platinum on carbon, 5% palladium on carbon, 5% ruthenium on carbon, Raney nickel, Raney cobalt, or Raney copper.

[0018] Furthermore, in step 2), the hydrogen pressure is 0.5-5 MPa, the reaction temperature is 50-160℃, and the reaction time is 1-10 h.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1) The 2,5-furandimethylamine prepared by the method of the present invention first uses an inorganic ammonium salt as the amine source, which gradually decomposes to produce ammonia gas as the reaction temperature increases. At this temperature, the imine generated can be reduced in situ to a primary amine, avoiding the accumulation and aggregation of the imine intermediate, thereby avoiding the occurrence of side reactions. On the other hand, the use of a small amount of organic amine as a stabilizer further inhibits the occurrence of side reactions and improves the yield of 2,5-furandimethylamine to 95%.

[0021] 2) The nitrogen source of this invention uses inorganic ammonium salt, ammonia is generated in situ, and imine is reduced in situ, thus avoiding the occurrence of side reactions;

[0022] 3) This invention incorporates an organic amine stabilizer, which further enhances the selectivity of BAMF;

[0023] 4) The reaction of this invention is simple, safe and efficient, and suitable for industrial production. Attached Figure Description

[0024] Figure 1 This is the gas chromatography-mass spectrum of the product from Example 1 of the present invention;

[0025] Figure 2 This is a product quality diagram of Embodiment 1 of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the scope described. Example 1

[0027] 1 mmol of 2,5-dicarboxyfuran was dissolved in 12 mL of methanol, 20 mmol of ammonium bicarbonate and 0.1 mmol of benzylamine and 50 mg of 5% platinum carbon catalyst were added, and hydrogen gas was introduced at 2.5 MPa. The mixture was heated to 80 °C and reacted for 6 h. After the reaction was completed, the mixture was cooled to room temperature, and the remaining hydrogen gas was slowly discharged. The reaction solution was diluted with methanol to a final volume of 50 mL. Quantitative analysis was performed by gas chromatography and qualitative analysis by gas chromatography-mass spectrometry.

[0028] Depend on Figure 1 and 2 As shown, the product 2,5-furandimethylamine was confirmed by gas chromatography-mass spectrometry (GC-MS) and comparison with the standard. The conversion rate of the raw material and the yield of the product were determined by external standard gas chromatography, and the average of three tests was taken.

[0029] The conversion rate of 2,5-dicarboxyfuran and the yield of the product 2,5-furandimethylamine were calculated according to the following formula:

[0030] Conversion rate [mol%] = (n0-n) / n0 × 100% (1)

[0031] Yield [mol%] = n i / n0×100%(2)

[0032] In the formula, n0 is the initial molar amount of 2,5-dicarboxyfuran [mol];

[0033] n is the remaining molar amount of 2,5-dicarboxyfuran after the reaction [mol];

[0034] n i The molar amount of the product 2,5-furandimethylamine produced in the reaction is [mol].

[0035] The calculation results show that after the reaction, the conversion rate of 2,5-dicarboxyfuran is >99%, and the yield of the product 2,5-furandimethylamine is 92%.

[0036] Examples 2-9

[0037] To verify the effect of amine source type and organic amine stabilizer on the reductive amination of 2,5-dicarboxyfuran, the reaction conditions of Example 1 were adjusted: except for the amine source type and organic amine stabilizer, the other reaction conditions were the same as in Example 1, and the reaction results are shown in Table 1 below.

[0038] Table 1 shows the experimental results of Examples 2-9.

[0039]

[0040] As shown in Table 1 above, the BAMF yield is only 53% without organic amine stabilizers, indicating that the addition of organic amine stabilizers significantly benefits BAMF formation. With ammonium carbonate as the amine source and benzylamine as the stabilizer, the BAMF yield can reach a maximum of 95%. The reaction is less effective with ammonium metaphosphate and ammonium chloride as amine sources, possibly due to their difficulty in thermal decomposition and the release of ammonia, but the DFF conversion rate is still >99%, with the main product being the DFF hydrogenation product 2,5-furandimethyl. Triethylamine is less effective as a stabilizer compared to primary amines, but the effect of primary amine stabilizers improves significantly with increasing carbon chain length, possibly due to their easier removal after stabilizing the aldehyde group. Pentylene diamine is more effective than n-pentylamine in improving BAMF yield, which is related to its double primary amine functional groups.

[0041] Examples 10-14

[0042] To verify the effect of the catalyst on the reductive amination of 2,5-dicarboxyfuran, the reaction conditions of Example 1 were adjusted: except for the catalyst, all other reaction conditions were the same as in Example 1. The reaction results are shown in Table 2 below.

[0043] Table 2 shows the experimental results of Examples 10-14.

[0044]

[0045] Table 2 shows that the palladium-on-carbon catalyst exhibits poor selectivity for BAMF, mainly due to its strong ability to hydrogenate the furan ring, with the main product being 2,5-tetrahydrofuran dimethylamine. The ruthenium-on-carbon catalyst shows better selectivity for BAMF than the palladium-on-carbon catalyst, but the BAMF yield is still relatively low (31%). Raney nickel and Raney cobalt have good catalytic activity, especially Raney cobalt, whose reducing amination ability is close to that of the platinum-on-carbon catalyst. However, no product formation was detected when using Raney copper, and the reaction solution was very dark in color, possibly due to its poor reducing ability and the polymerization of imines as a side reaction.

Claims

1. A method for preparing 2,5-furandimethylamine, characterized in that... Includes the following steps: 1) Dissolve 2,5-dicarboxyfuran in a beaker containing solvent to prepare a 2,5-dicarboxyfuran solution for later use; 2) Take the 2,5-dicarboxyfuran solution prepared in step 1) into a reaction vessel, add an inorganic amine source, an organic amine stabilizer and a catalyst, and react under a hydrogen atmosphere. After the reaction is completed, cool the reaction solution to room temperature and slowly discharge the remaining hydrogen gas to obtain 2,5-furan dimethylamine. 2) The molar ratio of 2,5-dicarboxyfuran to the inorganic amine source in step 1:2-40; 2) The molar ratio of 2,5-dicarboxyfuran to the organic amine stabilizer in step 1:0.01-0.5; 2) The inorganic amine source in step 1 is ammonium carbonate; 2) The organic amine stabilizer in step 2 is benzylamine; 2) The catalyst in step 2 is commercially available -5% platinum carbon.

2. The method for preparing 2,5-furandimethylamine according to claim 1, characterized in that... 1) The solvent used in the preparation of the 2,5-dicarboxyfuran solution in step 1) is methanol, ethanol, tetrahydrofuran or 1,4-dioxane.

3. The method for preparing 2,5-furandimethylamine according to claim 2, characterized in that... The concentration of the 2,5-dicarboxyfuran solution is 1-10 wt%.

4. The method for preparing 2,5-furandimethylamine according to claim 1, characterized in that... 2) The hydrogen pressure in this step is 0.5-5 MPa, the reaction temperature is 50-160℃, and the reaction time is 1-10 h.

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