Preparation method of 3-acetamido-5-acetylfuran

Abstract

The invention provides a preparation method of 3-acetamido-5-acetylfuran. The preparation method comprises the following steps: preparing 3-acetamido-5-acetylfuran; the chitin and / or crustacean waste are / is subjected to ball milling treatment under the assistance of sulfuric acid, so that the crystal structure of the chitin is broken, the molecular weight is reduced, the accessibility of a substrate is remarkably improved, and the conversion bottleneck caused by a compact three-dimensional structure of a high-molecular polymer is solved; then, in a DMAc / LiCl solvent, hydrolysis and dehydration reactions of chitin are connected in series, and the yield of 3A5AF of 68.3 mol% is obtained from chitin, or the yield of 3A5AF of 52.45 mol% is directly obtained from shrimp shells; according to the method, an extensible efficient path is opened up, the 3-acetamido-5-acetylfuran can be directly prepared from the crustacean waste biomass, tedious separation and purification steps are avoided, and a new path is opened up for economical and efficient biomass refining.

Description

Technical Field

[0001] This invention belongs to the field of biomass conversion technology, and particularly relates to a method for preparing 3-acetamido-5-acetylfuran. Background Technology

[0002] Over-reliance on petroleum resources will lead to serious environmental problems such as global warming and climate change. The effective utilization of biomass to produce fuels, chemicals, materials, and other products is more environmentally friendly and ultimately contributes to sustainable social development. Furan compounds have potential applications in multiple fields, including materials science, fuel production, and medicine. Compared to other aromatic compounds, furans are readily available from biomass. Particularly from a medicinal chemistry perspective, the 3-aminofuran skeleton is frequently found in many bioactive compounds.

[0003] 3-Acetamido-5-acetylfuran (3A5AF) consists of a furan ring, an acetamido group, and a ketone carbonyl group. It can react with a variety of substances to generate a variety of compounds and can generate a series of derivatives through various reactions, showing broad application prospects.

[0004] Currently, the production of 3A5AF mainly relies on petrochemical feedstocks or the chitin monomer N-acetylglucosamine (GlcNAc). However, petrochemical feedstocks are non-renewable, and the complex substitution patterns on the furan ring present inherent challenges. While 3A5AF conversion can be achieved using GlcNAc as a substrate, GlcNAc needs to be extracted from chitin, resulting in high raw material costs. Crustacean waste (such as shrimp and crab shells) is rich in chitin (chitin contains approximately 7 wt% nitrogen), making it an ideal raw material for the production of nitrogen-containing biochemicals. However, existing methods for producing 3A5AF from crustacean biomass require three steps: chitin extraction, degradation, and GlcNAc dehydration. These steps are cumbersome and require multiple separation and purification processes, leading to high total energy consumption, low atom utilization, and high production costs. Furthermore, due to its recalcitrant crystal structure and dense hydrogen bond network, chitin has extremely low direct conversion efficiency (yield ≤37%), and there are currently no reports of technologies for directly producing 3A5AF from raw crustacean waste. Therefore, developing a method for the direct conversion of crustacean waste into 3A5AF that is efficient and low-cost, without the need for cumbersome separation and purification, has become a pressing technical problem to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing 3-acetamido-5-acetylfuran. This invention offers a highly efficient mechanocatalytic strategy, achieving a one-step conversion of chitin and raw chitin-like waste into the high-value-added nitrogen-containing compound 3A5AF. By using sulfuric acid-assisted ball milling pretreatment, the crystal structure of chitin is broken down, the molecular weight is reduced, and substrate accessibility is significantly improved, overcoming the conversion bottleneck caused by the dense three-dimensional structure of polymers. Then, in a DMAc (N,N-dimethylacetamide) / LiCl solvent, the hydrolysis and dehydration reactions of chitin are cascaded, yielding 68.3 mol% 3A5AF from chitin, or 52.45 mol% 3A5AF directly from shrimp shells. This invention opens up a scalable and efficient route for the direct preparation of 3-acetamido-5-acetylfuran from chitin-like waste biomass, avoiding cumbersome separation and purification steps, and opening up a new avenue for economical and efficient biomass refining.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing 3-acetamido-5-acetylfuran, comprising the following steps:

[0008] Chitin and / or crustacean waste, H2SO4 solution are mixed and then ball-milled to obtain the ball-milled product.

[0009] The ball-milled product was mixed with an N,N-dimethylacetamide solution containing LiCl to obtain a mixture.

[0010] Boric acid was added to the mixture, and the mixture was heated to react and give 3-acetamido-5-acetylfuran.

[0011] Preferably, chitin and / or crustacean waste and H2SO4 solution are mixed and placed in a ball mill and ball-milled using zirconium dioxide balls, wherein the ball milling rate is 400~500 rpm and the time is 6~12 h.

[0012] Preferably, boric acid is added to the mixture, and the mixture is reacted at 140-160°C for 10-120 min to obtain 3-acetamido-5-acetylfuran.

[0013] Preferably, the mass-to-volume ratio of the chitin and / or crustacean waste, zirconium dioxide spheres, and H2SO4 solution is (1.5~2)g:(130~140)g:(0.124~1.113)mL;

[0014] The mass fraction of the H2SO4 solution is 95-98%.

[0015] Preferably, the mass fraction of LiCl in the N,N-dimethylacetamide solution is 5-10%.

[0016] Preferably, the mass-to-volume ratio of the chitin and / or crustacean waste to the N,N-dimethylacetamide solution containing LiCl is (1.5~2)g:(25~75)mL.

[0017] Preferably, the volume-to-mass ratio of the mixture to boric acid is (5~10) mL:(0.055~0.165) g.

[0018] Preferably, the diameter of the zirconium dioxide sphere is 1 to 10 mm.

[0019] The method for preparing 3-acetamido-5-acetylfuran of the present invention has the following advantages compared with the prior art:

[0020] The method for preparing 3-acetamido-5-acetylfuran of the present invention involves ball milling chitin and / or crustacean waste with sulfuric acid assistance, which breaks down the crystal structure of chitin, reduces its molecular weight, significantly improves substrate accessibility, and solves the conversion bottleneck caused by the dense three-dimensional structure of polymers. Then, in a DMAc (N,N-dimethylacetamide) / LiCl solvent, the hydrolysis and dehydration reactions of chitin are carried out in series to obtain a 3A5AF yield of 68.3 mol% from chitin, or a 3A5AF yield of 52.45 mol% directly from shrimp shells. The present invention opens up a scalable and efficient route to directly prepare 3-acetamido-5-acetylfuran from crustacean waste biomass, avoiding cumbersome separation and purification steps, and opening up a new way for economical and efficient biomass refining. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram illustrating the principle of the preparation method of 3-acetamido-5-acetylfuran of the present invention;

[0023] Figure 2 The conversion reaction process of BM-chitosan in Comparative Example 1;

[0024] Figure 3 To compare the catalytic effects of different acid catalysts in Example 1 on the production of 3A5AF from BM-chitosan;

[0025] Figure 4 To compare the effects of different reaction temperatures and times on the yield of BM-chitosan to 3A5AF in Example 2;

[0026] Figure 5 The effects of sulfuric acid dosage during the grinding process and boric acid addition during high-temperature reaction on the yield of 3A5AF in Example 3 and Comparative Example 3;

[0027] Figure 6 The effect of different chitin to boric acid molar ratios on the yield of 3A5AF in Example 4;

[0028] Figure 7 The high-performance liquid chromatography (HPLC) chromatogram of 3A5AF in Example 1 is shown.

[0029] Figure 8 This is the standard curve for high-performance liquid chromatography analysis of A5AF in Example 1;

[0030] Figure 9 For raw chitin, ball-milled chitin (BM-chitin), and acid-milled chitin (H + Scanning electron microscope image, XRD pattern, and FT-IR pattern of -BM-chitin. 1 1H NMR spectrum, acetylation degree, viscosity, and average molecular weight characterization data. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0032] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0033] This invention provides a method for preparing 3-acetamido-5-acetylfuran, comprising the following steps:

[0034] S1. Chitin and / or crustacean waste and H2SO4 solution are mixed and then ball-milled to obtain the ball-milled product.

[0035] S2. Mix the ball-milled product with an N,N-dimethylacetamide solution containing LiCl to obtain a mixture;

[0036] S3. Add boric acid to the mixture and heat to react, to obtain 3-acetamido-5-acetylfuran.

[0037] This invention provides a highly efficient mechanocatalytic strategy for the one-step conversion of chitin and raw chitin-like waste into the high-value-added nitrogen-containing compound 3A5AF. By ball milling chitin and / or chitin-like waste with sulfuric acid assistance, the crystal structure of chitin is broken down, the molecular weight is reduced, and substrate accessibility is significantly improved, overcoming the conversion bottleneck caused by the dense three-dimensional structure of polymers. Then, in a DMAc (N,N-dimethylacetamide) / LiCl solvent, the hydrolysis and dehydration reactions of chitin are cascaded to obtain a 68.3 mol% yield of 3A5AF from chitin, or a 52.45 mol% yield directly from shrimp shells. This invention opens up a scalable and efficient pathway, enabling a one-pot process from chitin or shrimp / crab shells to 3A5AF without the need to separate various intermediate products. It can directly prepare 3-acetamido-5-acetylfuran from chitin-like waste biomass, avoiding cumbersome separation and purification steps, and opening up a new avenue for economical and efficient biomass refining.

[0038] Specifically, ball milling a mixture of sulfuric acid and chitin and / or chitosan waste can effectively break the tight cross-linking between the components, powerfully disrupt the dense hydrogen bond structure between chitin / chitosan waste molecules, promote glycosidic bond cleavage, and generate low-polymerization-degree chitosan oligosaccharides. Simultaneously, the ball-milled product is mixed with an N,N-dimethylacetamide solution containing LiCl, and then boric acid is added and heated to react, yielding 3-acetamido-5-acetylfuran. Among these, there is a synergistic effect between boric acid and chloride ions, which significantly promotes the production of 3-acetamido-5-acetylfuran (3A5AF).

[0039] Furthermore, Figure 1 This is a schematic diagram illustrating the principle of the preparation method of 3-acetamido-5-acetylfuran of the present invention, as shown below. Figure 1 As shown, sulfuric acid and chitin were mixed and ball-milled together. The resulting chitin was named H. + -BM-chitin(H +-BM-chitosan, also known as the ball-milled product mentioned above), was added to an N,N-dimethylacetamide solution (DMAc / LiCl) containing LiCl, and boric acid H3BO3 was added. The mixture was heated to obtain 3-acetamido-5-acetylfuran (3A5AF).

[0040] In some embodiments, chitin and / or crustacean waste and H2SO4 solution are mixed and placed in a ball mill using a zirconium dioxide ball mill jar and zirconium dioxide balls, and ball milled at 400-500 rpm for 6-12 h to obtain the ball milled product.

[0041] In some embodiments, crustacean waste includes shrimp shells, crab shells, etc.

[0042] In some embodiments, boric acid is added to the mixture and reacted at 140-160°C for 10-120 min to obtain 3-acetamido-5-acetylfuran.

[0043] In some embodiments, the mass concentration of the H2SO4 solution is 95-98%.

[0044] In some embodiments, the mass fraction of LiCl in the N,N-dimethylacetamide solution is 5-10%.

[0045] In some embodiments, the mass-to-volume ratio of chitin and / or crustacean waste, zirconium dioxide spheres, and H2SO4 solution is (1.5~2)g:(130~140)g:(0.124~1.113)mL.

[0046] In some embodiments, the mass-to-volume ratio of chitin and / or crustacean waste to N,N-dimethylacetamide solution containing LiCl is (1.5~2) g:(25~75) mL.

[0047] In some embodiments, the volume-to-mass ratio of the mixture to boric acid is (5~10) mL:(0.055~0.165) g;

[0048] The molar ratio of H2SO4 to boric acid in the H2SO4 solution used is (1~3):(1~3).

[0049] In some embodiments, the diameter of the zirconia spheres is 1 to 10 mm, specifically, the diameter of the zirconia spheres can be 1 mm, 5 mm, or 10 mm.

[0050] The preparation method of 3-acetamido-5-acetylfuran of the present invention is further illustrated below with specific embodiments. This section further illustrates the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0051] Example 1

[0052] This embodiment provides a method for preparing 3-acetamido-5-acetylfuran, including the following steps:

[0053] S1. 1.5g of chitin (calculated as monomeric N-acetylglucosamine (GlcNAc), the molar amount of chitin is 6.78 × 10⁻⁶) -3 After mixing 0.74 mL of 98% H2SO4 (mol) and placing it in a ball mill (specifically a Miqi YXQM-4L planetary ball mill), 130 g of zirconium dioxide balls (1 / 3 of the mass of zirconium dioxide balls with diameters of 1, 5, and 10 mm) were added at the same time, the mixture was ball-milled at 400 rpm for 10 h to obtain the ball-milled product.

[0054] S2. Mix the ball-milled product with 75 mL of N,N-dimethylacetamide solution containing 5 wt% LiCl to obtain a mixture;

[0055] S3. Take 5 mL of the mixture (containing 0.1 g chitosan, calculated as GlcNAc, with a molar volume of 4.52 × 10⁻⁶). -4 0.11 g boric acid (1.78 × 10⁻⁶ mol) was added to 5 mL of the mixture. -3 The mixture (containing mol of chitin and boric acid in a molar ratio of approximately 1:4) was reacted at 160 °C for 30 min to obtain the reaction product.

[0056] S4. The product was analyzed using an Agilent 1260 high-performance liquid chromatography system (Agilent, USA). Measurements were taken at 230 nm using a UV detector, employing an Agilent HC-C18 column (4.6 mm × 250 mm, 5 μm; HC-C18: indicates the stationary phase is octadecylsilane (C18); 4.6 mm (inner diameter): the inner diameter of the column, 4.6 mm is the typical inner diameter of an analytical column; 250 mm (length): the length of the column; 5 μm (particle size): the average diameter of the stationary phase particles). The mobile phase was methanol / water (40:60, v / v), the flow rate was 0.6 mL / min, and the temperature was 40 ℃ (column temperature). In this embodiment of the invention, a 3A5AF yield of 68.3 mol% can be obtained from chitosan. The 3A5AF yield is calculated as: (3A5AF molar amount / chitosan molar amount (based on 0.1 g chitosan in 5 mL of the mixture, calculated as monomeric N-acetylglucosamine (GlcNAc))) × 100%.

[0057] Example 2

[0058] This embodiment provides a method for preparing 3-acetamido-5-acetylfuran, which is the same as in Example 1, except that 1.5g of chitin in Example 1 is replaced with 1.5g of shrimp shell powder; the yield of 3A5AF is 52.45 mol.

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing 3-acetamido-5-acetylfuran, comprising the following steps:

[0061] S1. Place 1.5g of chitin in a ball mill (specifically, a Miqi YXQM-4L planetary ball mill), and add 130g of zirconium dioxide balls (1 / 3 of the mass of zirconium dioxide balls with diameters of 1, 5, and 10 mm). Ball mill at 400 rpm for 10 h to obtain the ball-milled product BM-chitin.

[0062] S2. Mix 0.1 g of the ball-milled product BM-chitosan with 5 mL of N,N-dimethylacetamide solution containing 5 wt% LiCl to obtain a mixture.

[0063] S3. Add 0.2 g Amberlyst-15 (ion exchange resin, polymer of vinylbenzene sulfonic acid and divinylbenzene) (or 0.2 g SAPO-34 (zeolite molecular sieve catalyst) or 0.2 g AlCl3 or 0.05 mL sulfuric acid (H2SO4, mass fraction 98%) or 0.1 mL hydrochloric acid (HCl, mass fraction 36%) to the mixture to test the catalytic effect of different catalysts), and react at 140 ℃ for 60 min to obtain the reaction product;

[0064] S4. The product was analyzed using an Agilent 1260 high-performance liquid chromatography system (Agilent, USA). Measurements were taken at 230 nm using a UV detector, employing an Agilent HC-C18 column (4.6 mm × 250 mm, 5 μm; HC-C18: indicates the stationary phase is octadecylsilane (C18); 4.6 mm (inner diameter): the inner diameter of the column, 4.6 mm is the typical inner diameter of an analytical column; 250 mm (length): the length of the column; 5 μm (particle size): the average diameter of the stationary phase particles). The mobile phase was methanol / water (40:60, v / v), the flow rate was 0.6 mL / min, and the temperature was 40 ℃ (column temperature).

[0065] Figure 2 The conversion reaction process of BM-chitosan in Comparative Example 1 is shown.

[0066] Comparative Example 1 tested the catalytic effects of several commonly used acid catalysts on the one-step production of 3A5AF from BM-chitosan, and obtained the yield of 3-acetamido-5-acetylfuran (3A5AF). The results are as follows: Figure 3 As shown. Figure 3 "None" indicates the control group, in which no catalyst was added.

[0067] from Figure 3 As can be seen from the data, the yield of 3A5AF is the highest when sulfuric acid is used as the catalyst. Therefore, sulfuric acid is selected as the catalyst in this invention.

[0068] Comparative Example 2

[0069] This comparative example provides a method for preparing 3-acetamido-5-acetylfuran, comprising the following steps:

[0070] S1. Place 1.5g of chitin in a ball mill (specifically, a Miqi YXQM-4L planetary ball mill), and add 130g of zirconium dioxide balls (1 / 3 of the mass of zirconium dioxide balls with diameters of 1, 5, and 10 mm). Ball mill at 400 rpm for 10 h to obtain the ball-milled product BM-chitin.

[0071] S2. Mix 0.1 g of the ball-milled product BM-chitosan with 5 mL of N,N-dimethylacetamide solution containing 5 wt% LiCl to obtain a mixture.

[0072] S3. Add 0.05 mL of sulfuric acid (H2SO4, mass fraction 98%) to the mixture and react at 140~160℃ (specifically 140℃, 150℃, 160℃) for 30~180 min (30 min, 60 min, 90 min, 120 min, 150 min, 160 min) to obtain the reaction product;

[0073] S4. The product was analyzed using an Agilent 1260 high-performance liquid chromatography system (Agilent, USA). Measurements were taken at 230 nm using a UV detector, employing an Agilent HC-C18 column (4.6 mm × 250 mm, 5 μm; HC-C18: indicates the stationary phase is octadecylsilane (C18); 4.6 mm (inner diameter): the inner diameter of the column, 4.6 mm is the typical inner diameter of an analytical column; 250 mm (length): the length of the column; 5 μm (particle size): the average diameter of the stationary phase particles). The mobile phase was methanol / water (40:60, v / v), the flow rate was 0.6 mL / min, and the temperature was 40 ℃ (column temperature).

[0074] Comparative Example 2 investigated the yields of 3-acetamido-5-acetylfuran (3A5AF) at different reaction temperatures and times, as shown in Figure 2. Figure 4 As shown.

[0075] from Figure 4 As can be seen, the yield of 3-acetamido-5-acetylfuran (3A5AF) is the highest when the reaction temperature is 160℃ and the reaction time is 30min. Therefore, the reaction temperature selected in this invention is 160℃ and the reaction time is 30min.

[0076] Example 3

[0077] This embodiment provides a method for preparing 3-acetamido-5-acetylfuran, including the following steps:

[0078] S1. 1.5g of chitosan (calculated as N-acetylglucosamine monomer (GlcNAc), the molar amount of chitosan is 6.78 × 10⁻⁶) -30.124~1.113 mL (specifically 0.124 mL, 0.185 mL, 0.369 mL, 0.738 mL, and 1.113 mL, with corresponding molar ratios of chitin to H2SO4 of 3:1, 2:1, 1:1, 1:2, and 1:3) were mixed with 98% H2SO4 and placed in a ball mill (specifically a Miqi YXQM-4L planetary ball mill). 130 g of zirconium dioxide balls (each with a diameter of 1, 5, or 10 mm, representing 1 / 3 of the total mass) were added simultaneously. The mixture was ball-milled at 400 rpm for 10 h to obtain the ball-milled product.

[0079] S2. The ball-milled products with different sulfuric acid dosages were mixed with 75 mL of N,N-dimethylacetamide solution containing 5 wt% LiCl to obtain a mixture.

[0080] S3. Take 5 mL of the mixture (containing 0.1 g chitosan, calculated as GlcNAc, with a molar volume of 4.52 × 10⁻⁶). -4 Add 0.055 g of boric acid (molar amount 8.895 × 10⁻⁶) to 5 mL of the mixture. -4 (The molar ratio of chitin to boric acid was approximately 1:2), and the reaction was carried out at 160 °C for 30 min to obtain the reaction product;

[0081] S4. The product was analyzed using an Agilent 1260 high-performance liquid chromatography system (Agilent, USA). Measurements were taken at 230 nm using a UV detector, employing an Agilent HC-C18 column (4.6 mm × 250 mm, 5 μm; HC-C18: indicates the stationary phase is octadecylsilane (C18); 4.6 mm (inner diameter): the inner diameter of the column, 4.6 mm is the typical inner diameter of an analytical column; 250 mm (length): the length of the column; 5 μm (particle size): the average diameter of the stationary phase particles). The mobile phase was methanol / water (40:60, v / v), the flow rate was 0.6 mL / min, and the temperature was 40 ℃ (column temperature).

[0082] Comparative Example 3

[0083] This comparative example provides a method for preparing 3-acetamido-5-acetylfuran, comprising the following steps:

[0084] S1. 1.5g of chitosan (calculated as N-acetylglucosamine monomer (GlcNAc), the molar amount of chitosan is 6.78 × 10⁻⁶) -30.124~1.113 mL (specifically 0.124 mL, 0.185 mL, 0.369 mL, 0.738 mL, and 1.113 mL, with corresponding molar ratios of chitin to H2SO4 of 3:1, 2:1, 1:1, 1:2, and 1:3) were mixed with 98% H2SO4 and placed in a ball mill (specifically a Miqi YXQM-4L planetary ball mill). 130 g of zirconium dioxide balls (each with a diameter of 1, 5, or 10 mm, representing 1 / 3 of the total mass) were added simultaneously. The mixture was ball-milled at 400 rpm for 10 h to obtain the ball-milled product.

[0085] S2. The ball-milled products with different sulfuric acid dosages were mixed with 75 mL of N,N-dimethylacetamide solution containing 5 wt% LiCl to obtain a mixture.

[0086] S3. Take 5 mL of the mixture and react it at 160 °C for 30 min to obtain the reaction product;

[0087] S4. The product was analyzed using an Agilent 1260 high-performance liquid chromatography system (Agilent, USA). Measurements were taken at 230 nm using a UV detector, employing an Agilent HC-C18 column (4.6 mm × 250 mm, 5 μm; HC-C18: indicates the stationary phase is octadecylsilane (C18); 4.6 mm (inner diameter): the inner diameter of the column, 4.6 mm is the typical inner diameter of an analytical column; 250 mm (length): the length of the column; 5 μm (particle size): the average diameter of the stationary phase particles). The mobile phase was methanol / water (40:60, v / v), the flow rate was 0.6 mL / min, and the temperature was 40 ℃ (column temperature).

[0088] Example 3 investigated the yield of 3-acetamido-5-acetylfuran (3A5AF) with varying molar ratios of chitin to sulfuric acid, including the addition of boric acid. The results are as follows: Figure 5 As shown.

[0089] Comparative Example 3 investigated the yield of 3-acetamido-5-acetylfuran (3A5AF) with varying molar ratios of chitin to sulfuric acid, without the addition of boric acid. The results are as follows: Figure 5 As shown.

[0090] Figure 5 In Example 3, "With B(OH)3" indicates the yield change of 3A5AF when boric acid was added; "Without B(OH)3" indicates the yield change of 3A5AF when boric acid was added in Comparative Example 3. Figure 5The horizontal axis represents the molar ratio of chitin to H2SO4 (specifically 3:1, 2:1, 1:1, 1:2, and 1:3).

[0091] from Figure 5 As can be seen, the content of 3A5AF gradually increases with the increase of sulfuric acid and the addition of boric acid. The addition of boric acid approximately doubles the yield of 3A5AF. Finally, during ball milling, the molar ratio of sulfuric acid to the substrate chitin was 2:1, and with the addition of boric acid at a molar ratio of 2:1 to the substrate, the reaction was carried out at 160 °C for 30 min, yielding 55 mol% of 3A5AF.

[0092] Example 4

[0093] This embodiment provides a method for preparing 3-acetamido-5-acetylfuran, including the following steps:

[0094] S1. 1.5g of chitosan (calculated as N-acetylglucosamine monomer (GlcNAc), the molar amount of chitosan is 6.78 × 10⁻⁶) -3 After mixing 0.74 mL of 98% H2SO4 (0.0136 mol), the mixture was placed in a ball mill (specifically a Miqi YXQM-4L planetary ball mill), and 130 g of zirconium dioxide balls (1 / 3 of the mass of zirconium dioxide balls with diameters of 1, 5, and 10 mm) were added. The mixture was then ball-milled at 400 rpm for 10 h to obtain the ball-milled product.

[0095] S2. The ball-milled products with different sulfuric acid dosages were mixed with 75 mL of N,N-dimethylacetamide solution containing 5 wt% LiCl to obtain a mixture.

[0096] S3. Take 5 mL of the mixture (containing 0.1 g chitosan, calculated as GlcNAc, with a molar volume of 4.52 × 10⁻⁶). -4 Add 0.055~0.165 g (specifically 0.055 g, 0.0839 g, 0.11 g, 0.140 g, and 0.165 g, with corresponding molar ratios of chitin to boric acid of 1:2, 1:3, 1:4, 1:5, and 1:6, respectively) of boric acid to a 5 mL mixture, and react at 160 °C for 30 min to obtain the reaction product;

[0097] S4. The product was analyzed using an Agilent 1260 high-performance liquid chromatography system (Agilent, USA). Measurements were taken at 230 nm using a UV detector, employing an Agilent HC-C18 column (4.6 mm × 250 mm, 5 μm; HC-C18: indicates the stationary phase is octadecylsilane (C18); 4.6 mm (inner diameter): the inner diameter of the column, 4.6 mm is the typical inner diameter of an analytical column; 250 mm (length): the length of the column; 5 μm (particle size): the average diameter of the stationary phase particles). The mobile phase was methanol / water (40:60, v / v), the flow rate was 0.6 mL / min, and the temperature was 40 ℃ (column temperature).

[0098] Example 4 investigated the effect of different chitosan to boric acid molar ratios on the yield of 3-acetamido-5-acetylfuran (3A5AF), and the results are as follows: Figure 6 As shown.

[0099] Figure 6 The horizontal axis represents the molar ratio of chitin to B(OH)3 (specifically 1:2, 1:3, 1:4, 1:5, and 1:6).

[0100] from Figure 6 As can be seen, when the molar ratio of chitin to sulfuric acid is 1:2 and the molar ratio of chitin to boric acid is 1:4, the yield of 3A5AF reached 68.3 mol% after reacting at 160℃ for 30 min (i.e., the process parameters corresponding to Example 1).

[0101] Specifically, following the method in Example 1, 3-acetamido-5-acetylfuran was analyzed using a high-performance liquid chromatography (HPLC) system. The HPLC chromatogram of 3A5AF is shown below. Figure 7 As shown, the standard curve for 3A5AF high-performance liquid chromatography analysis is as follows: Figure 8 As shown.

[0102] Figure 9 The chitin consisted of raw chitin, ball-milled chitin (BM-chitin, i.e., the ball-milled product BM-chitin in step S1 of Comparative Example 1), and acid-milled chitin (H). + -BM-chitin(H + Characterization data of -BM-chitoxin (i.e., the ball-milled product in step S1 of Example 1);

[0103] in, Figure 9 In this context, 'a' represents chitin, BM-chitin, and H. +-Scanning electron microscope image of BM-chitin; b represents chitin, BM-chitin, and H. + XRD pattern of BM-chitin; c represents chitin, BM-chitin, and H. + - FT-IR spectrum of BM-chitin; d represents chitin, BM-chitin, and H. + -BM-chitin and the monomer GlcNAc 1 H NMR spectrum; e represents chitin, BM-chitin, and H. + -BM-chitin's acetylation and viscosity average molecular weight

[0104] Figure 9 Scanning electron microscopy (SEM) images showed that untreated chitin exhibited a distinct fibrous structure. After ball milling, the fibrous structure was no longer observable in BM-chitin; the particle size decreased significantly, to approximately 300 nm or less, and the pore structure on the surface of large particles was visible. (Compared to H...) + Compared to the smoother appearance of BM-chitin, BM-chitin exhibits a cone-like shape. This may be because, without sulfuric acid coating, the long axis of chitin fibers is more susceptible to impact. When the impact force is at a certain angle to the fiber axis, it preferentially breaks from the fiber end or amorphous region, forming a cone-shaped cross-section. Figure 9 (as shown in a).

[0105] Figure 9 Figure b shows the XRD patterns of the samples before and after pretreatment. Untreated chitin exhibits three sharp peaks at 9.3°, 19.2°, and 26.4°, corresponding to the 020, 110, and 130 planes of the chitin crystal structure, respectively, along with some weak peaks. In both pretreated chitin samples, the weak peaks are completely obscured, and the intensity of the three sharp peaks is significantly reduced, indicating obvious crystal structure damage. Pretreated chitin shows XRD patterns at 3200 cm⁻¹. -1 - 3500 cm -1 In the infrared spectrum within the range of (stretching vibration absorption peaks of OH and NH groups), the two peaks gradually tend to overlap into one peak, and this overlap is particularly pronounced at 1628 cm⁻¹. -1 The absorption peak at 1029 cm⁻¹ (the absorption peak of hydrogen bonds formed by the carbonyl group with the amino group on the same chain and the -CH₂OH group on adjacent molecular chains) was almost undetectable, indicating a significant weakening of hydrogen bonding in chitin, consistent with the XRD analysis results. -1 and 1069 cm -1The peak values ​​represent the stretching vibrations of the glycosidic CO bonds between GlcNAc units. The absorption peak of H⁺-BM-chitin at this point is significantly different from that of chitin and BM-chitin, indicating the breaking of glycosidic bonds during ball milling.

[0106] From d in Figure 9 1 The same conclusion can be drawn from H₂ spectroscopy: the peaks at d = 3.64 and 3.18 ppm in pure GlcNAc belong to protons at α-OH⁻¹ and α-OH⁻⁴. These are the positions where glycosidic bonds are formed, as shown in H₂. + -BM-chitin 1 The presence of these two proton peaks on the H spectrum indicates the hydrolysis of glycosidic bonds and a decrease in the degree of polymerization of chitin. Although the proton peaks of α-NH and α-OH-6, which are mainly involved in forming hydrogen bonds, have shifted, they can still be seen on the H spectrum. + -Observed in BM-chitin. Finally, we quantitatively analyzed the changes in the degree of acetylation and molecular weight of chitin before and after pretreatment. The degree of acetylation of pretreated chitin decreased slightly, and the average molar mass decreased significantly. The average molar mass of BM-chitin decreased to 9.17% of that of the original chitin. H + -BM-chitin has an average molar mass as low as 1057 g / mol (degree of polymerization approximately 5).

[0107] As can be seen from Figure 9e, the chitin after acid milling has lower crystallinity and molecular weight than the original chitin and ball-milled chitin, with the viscosity-average molecular weight decreasing to 1057 g / mol (degree of polymerization approximately 5).

[0108] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A method for preparing 3-acetamido-5-acetylfuran, characterized in that, Includes the following steps: Chitin and / or crustacean waste, H2SO4 solution are mixed and then ball-milled to obtain the ball-milled product. The ball-milled product was mixed with an N,N-dimethylacetamide solution containing LiCl to obtain a mixture. Boric acid was added to the mixture, and the mixture was heated to react and give 3-acetamido-5-acetylfuran.

2. The method for preparing 3-acetamido-5-acetylfuran as described in claim 1, characterized in that, Chitin and / or crustacean waste and H2SO4 solution are mixed and placed in a ball mill and ball-milled using zirconium dioxide balls. The ball milling rate is 400-500 rpm and the time is 6-12 h.

3. The method for preparing 3-acetamido-5-acetylfuran as described in claim 1, characterized in that, Boric acid was added to the mixture, and the reaction was carried out at 140-160℃ for 10-120 min to obtain 3-acetamido-5-acetylfuran.

4. The method for preparing 3-acetamido-5-acetylfuran as described in claim 1, characterized in that, The mass-to-volume ratio of the chitin and / or crustacean waste, zirconium dioxide spheres, and H2SO4 solution is (1.5~2)g:(130~140)g:(0.124~1.113)mL; The mass fraction of the H2SO4 solution is 95-98%.

5. The method for preparing 3-acetamido-5-acetylfuran as described in claim 1, characterized in that, The mass fraction of LiCl in the N,N-dimethylacetamide solution is 5-10%.

6. The method for preparing 3-acetamido-5-acetylfuran as described in claim 2, characterized in that, The mass-to-volume ratio of the chitin and / or crustacean waste to the N,N-dimethylacetamide solution containing LiCl is (1.5~2)g:(25~75)mL.

7. The method for preparing 3-acetamido-5-acetylfuran as described in claim 4, characterized in that, The volume-to-mass ratio of the mixture to boric acid is (5~10) mL:(0.055~0.165) g.

8. The method for preparing 3-acetamido-5-acetylfuran as described in claim 2, characterized in that, The diameter of the zirconium dioxide spheres is 1~10 mm.

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