Method for preparing 5-hydroxymethylfurfural from glucose through one-pot method

Abstract

The invention provides a method for preparing 5-hydroxymethylfurfural from glucose by a one-pot method, which comprises the following steps: dissolving glucose in a mixed solvent of an organic solvent and water, contacting with a catalyst, placing in a closed high-pressure kettle, heating under inert atmosphere, stirring, reacting, cooling, filtering reaction liquid to remove solid particles, and storing 5-hydroxymethylfurfural in filtrate; wherein the catalyst is a metal modified SAPO-34 molecular sieve catalyst. The catalyst used in the invention has a similar core-shell structure, and the metal component on the outer layer is beneficial to enhancing the adsorption of glucose molecules, and is used as an L acid center to promote the isomerization of glucose into fructose molecules; the fructose continues to diffuse into the SAPO-34 molecular sieve and is subjected to isomerization reaction on B acid active sites of the molecular sieve, self-condensation of glucose molecules is avoided by the aid of shape-selective catalysis of the SAPO-34 molecular sieve, diffusion of the product 5-HMF is facilitated, and selectivity of the product 5-HMF is improved.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis, specifically relating to a method for preparing a bio-based platform compound, 5-hydroxymethylfurfural. Background Technology

[0002] 5-Hydroxymethylfurfural (5-HMF) is a heterocyclic furan molecule containing hydroxides and aldehydes, substituted at the 2,5-position. It is chemically reactive, capable of forming diacids through oxidation and diols through reduction; both methods can be used to synthesize various polymers. Furthermore, 5-HMF is a relatively unsaturated aromatic compound that can be upgraded into fuel molecules through hydrogenation. In addition, the furan heterocyclic structure of 5-HMF is present in a range of biologically active molecules, which have wide applications in the pharmaceutical field. The unique chemical structure of 5-HMF makes it a synthetic or direct substitute for many commercial chemicals.

[0003] Generally, fructose can be efficiently converted into 5-HMF with high yield under the action of dehydration catalysts (such as strong acid cation exchange resins, zeolites or inorganic acids), but the high price of fructose limits the cost of large-scale production of 5-HMF.

[0004] Compared to fructose, glucose has higher utilization rate and lower cost, making it the preferred raw material for the production of 5-HMF. The general pathway for the conversion of glucose to 5-HMF involves the isomerization of glucose with an oxygen ring structure to fructose, followed by three dehydration processes to generate 5-HMF, which is a two-step production process.

[0005] The one-step conversion of glucose to HMF avoids the high operating costs associated with feedstock separation, heat exchange, and recycling, thus offering environmental and economic advantages. Typically, catalysts with acid / base sites are combined in a one-pot process to improve the efficiency of glucose-to-HMF conversion. While L-acids have the ability to catalyze glucose isomerization, compatibility with Bronsted acid catalysts required for fructose dehydration should be considered when selecting a glucose isomerization catalyst.

[0006] Wang Kang et al. (Ca-γ-Al2O3 coupled with acid solution catalysis to prepare 5-HMF from glucose [J]. Chemical Industry and Engineering, 2021, 38(5):20-26.) used glucose as raw material to prepare 5-HMF in a DMSO / water system by coupled catalysis of Ca-γ-Al2O3 and low concentration hydrochloric acid, 0.05 mol·L -1The acid concentration was V(DMSO):V(H2O) = 3:1, the ratio of glucose to catalyst was 2:1 (125mg:63mg), the reaction temperature was 140℃, the reaction time was 3h, and 5-HMF was prepared by catalyzing the dehydration of glucose with Ca(5%)-γ-Al2O3 as the catalyst. The glucose conversion rate was 100%, and the 5-HMF yield was the highest at 58.6%.

[0007] CN110368985A discloses a catalyst for the synthesis of 5-HMF and a method for preparing 5-HMF. The catalyst is a g-C3N4 / kaolin-ionic liquid composite catalyst. Glucose, catalyst and water are mixed and heated to react. The reaction temperature is 180℃ and the reaction time is 2h. The glucose conversion rate is 96% and the 5-HMF yield is 46.7%.

[0008] CN114805254A discloses a method for preparing 5-HMF, in which sugars are converted into 5-HMF by grinding in an inorganic salt bath at 20-100°C under the action of an acid catalyst, with a maximum yield of 87.5% for 5-HMF.

[0009] CN114736175A discloses a method for preparing 5-HMF from glucose in an aqueous phase by catalysis. The bifunctional solid acid catalyst is reacted with glucose at a mass ratio of 1:10 to 1:50 at 130-170℃ for 30-600 min, and the 5-HMF formation rate is up to 27%.

[0010] In existing synthetic methods for preparing 5-HMF from glucose, a multi-step reaction system is often employed. This involves glucose isomerization to fructose, followed by dehydration of the fructose to prepare 5-HMF. This process involves numerous separation and purification steps, is complex, and increases equipment investment and energy consumption. In contrast, one-step methods for 5-HMF preparation show lower glucose conversion rates and lower selectivity compared to fructose. This is because fructose exists primarily as cyclic furanose tautomers and pyranoses in the system, giving it better reactivity than glucose, which mainly exists as a pyranose isomer. Furthermore, during the reaction, glucose is prone to self-condensation reactions, and 5-HMF undergoes rehydration, resulting in lower selectivity. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a one-pot method for preparing 5-HMF from glucose. This method employs a dual-solvent system and a metal-modified molecular sieve catalyst to prepare 5-HMF in a single pot, offering advantages such as simple process, environmental friendliness, and minimal byproducts.

[0012] The technical solution of the present invention is as follows:

[0013] A method for preparing 5-hydroxymethylfurfural from glucose in a one-pot process includes: dissolving glucose in a mixed solvent of organic solvent and water, contacting it with a catalyst, placing it in a closed autoclave, heating it under an inert atmosphere, stirring it, cooling it after the reaction, filtering the reaction solution to remove solid particles, and 5-hydroxymethylfurfural being present in the filtrate.

[0014] The catalyst is a metal-modified SAPO-34 molecular sieve catalyst, which is prepared by the following method:

[0015] Will include Ca 2+ and / or Al 3+ The salt solution was slowly dripped onto the SAPO-34 molecular sieve, the mixture was rotary evaporated, and then dried and calcined to obtain the catalyst.

[0016] Furthermore, the catalyst comprises 5%-15% by weight of CaO and / or Al2O3, preferably 8%-13%.

[0017] Furthermore, the Ca 2+ and / or Al 3+ The salt solution is an aqueous solution comprising at least one of Ca(NO3)2, CaCl2, Al(NO3)3 and AlCl3, preferably Ca(NO3)2.

[0018] Furthermore, the rotary evaporation temperature is 70-95°C, and the rotary evaporation continues until the liquid is completely evaporated.

[0019] Furthermore, during catalyst preparation, the drying temperature is 65-100℃ and the drying time is 10-36h; the calcination temperature is 500-600℃ and the time is 2-8h.

[0020] Furthermore, the SAPO-34 molecular sieve is either a commercially available molecular sieve or a self-made molecular sieve.

[0021] Furthermore, the organic solvent in the mixed solvent is selected from at least one of valerolactone, dimethyl sulfoxide, and tetrahydrofuran, preferably valerolactone. The mixing ratio of the organic solvent to water is 8-12:1 by weight, preferably 9-11:1.

[0022] Furthermore, the total amount of the mixed solvent used is in a weight ratio of 50-65:1 to glucose, preferably 56-60:1.

[0023] Furthermore, the catalyst is added in a weight ratio of 1:1-5 with glucose, preferably 1:2-4.

[0024] Furthermore, the reaction temperature in the sealed high-pressure reactor is 160-200℃, preferably 170-180℃; the reaction time is 0.5-6h, preferably 3-4h.

[0025] Furthermore, after the reaction is complete, cool to 10-30℃.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention uses a rotary impregnation method to prepare a metal-modified SAPO-34 molecular sieve catalyst. The modified metal is dispersed on the outer layer of the molecular sieve catalyst to form a core-shell structure-like catalyst. The metal component on the outer layer is conducive to enhancing the adsorption of glucose molecules and, as an L acid center, promotes the isomerization of glucose into fructose molecules. The fructose continues to diffuse into the interior of the SAPO-34 molecular sieve and undergoes an isomerization reaction at the B acid active site of the molecular sieve. The SAPO-34 molecular sieve has shape-selective catalysis. Its pore diameter is suitable, which is conducive to avoiding the self-condensation of glucose molecules and also helps the diffusion of the product 5-HMF, thereby improving the selectivity of the 5-HMF product.

[0028] (2) The present invention uses a solid catalyst, which avoids the use of liquid acid and has the advantages of simple process, environmental friendliness and high product selectivity. Detailed Implementation

[0029] The following examples further illustrate the preparation method and effects of the 5-HMF of the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0031] In this embodiment of the invention, the contents of reactants and products in the sample solution were determined by high-performance liquid chromatography (HPLC). The 5-HMF determination method used an XDB-C18 column with a 280 nm UV detector, and the column oven temperature was maintained at 303 K. The mobile phase was water / acetonitrile at a volume ratio of 85:15, and the flow rate was 1.0 mL / min. -1 The chromatographic conditions for glucose testing were as follows: column: Aminex HPX-87H; mobile phase: 0.004 mol·L⁻¹ -1 H2SO4; flow rate: 0.6 mL·min -1 The injection volume was 20 μL. All samples were filtered using an aqueous microporous membrane (0.22 μm) before injection.

[0032] Glucose conversion rate = (Amount of glucose at the start of the reaction - Amount of glucose at the end of the reaction) / Amount of glucose at the start of the reaction × 100%.

[0033] 5-HMF selectivity = (amount of 5-HMF generated / amount of glucose consumed in total product) × 100%.

[0034] Example 1

[0035] Preparation of catalysts:

[0036] Homemade SAPO-34 molecular sieve: 85% phosphoric acid was used as the phosphorus source, boehmite as the aluminum source, colloidal silica as the silicon source, and triethylamine as the template agent. A raw material with a molar composition of 1.0Al₂O₃:1.0P₂O₅:0.2SiO₂:3.0Et₃N:50H₂O was added to a beaker and vigorously stirred to form a gel. The resulting gel was transferred to a hydrothermal synthesis reactor and aged (crystallized) at 200℃ for 24 hours in an oven. The crystallized product was filtered, washed with water, dried at 100℃ overnight, and finally calcined in air at 600℃ for 6 hours.

[0037] Preparation of CaO (12.3 wt%)-SAPO-34 catalyst:

[0038] 20.537g Ca(NO3)2 was dissolved in 41.07g water. The solution was slowly dropped onto 50g SAPO-34 molecular sieve. The mixture was rotary evaporated at 90℃ until the liquid was evaporated to dryness. The mixture was dried at 90℃ for 24h and calcined at 600℃ for 6h to obtain the catalyst.

[0039] Preparation of 5-HMF:

[0040] Weigh 1.05g of glucose and place it in a high-pressure reactor. Add 56g of valproic acid and 5.6g of water to dissolve the glucose. Then add 0.5g of Ca(10wt%)-SAPO-34 catalyst. Stir at 300rpm while purging with nitrogen for 30min. After sealing, slowly heat the high-pressure reactor to 180℃ for 4h. After the reaction is complete, place the reactor in a cold water bath. After the high-pressure reactor cools down to room temperature, take out the solution after the reaction and filter to remove solid particles to obtain a filtrate containing 5-HMF.

[0041] Based on the analysis of the components in the filtrate, the conversion rate of glucose was calculated to be 99.5%, and the selectivity of 5-HMF was 60.1%.

[0042] Example 2

[0043] The catalyst was prepared using the same method as in Example 1.

[0044] Preparation of 5-HMF:

[0045] Weigh 1.05g of glucose and place it in a high-pressure reactor. Add 57g of dimethyl sulfoxide and 5.7g of water to dissolve the glucose. Then add 1g of Ca(10wt%)-SAPO-34 catalyst. Stir at 300rpm while purging with nitrogen for 30min. After sealing, slowly heat the high-pressure reactor to 190℃ for 3h. After the reaction is complete, place the reactor in a cold water bath. After the high-pressure reactor cools down to room temperature, take out the solution after the reaction and filter to remove solid particles to obtain a filtrate containing 5-HMF.

[0046] Based on the analysis of the components in the filtrate, the conversion rate of glucose was calculated to be 99.6%, and the selectivity of 5-HMF was 61.2%.

[0047] Example 3

[0048] The catalyst was prepared in the same way as above, except that the catalyst used was Al2O3 (10wt%)-SAPO-34. The preparation method is as follows: 23.23g of Al(NO3)3 was dissolved in 46.46g of water, and the solution was slowly dropped onto 50g of SAPO-34 molecular sieve. The mixture was rotary evaporated at 90℃ until the liquid was evaporated to dryness, dried at 90℃ for 24h, and calcined at 600℃ for 6h to obtain the catalyst.

[0049] The preparation method of 5-HMF is the same as in Example 1. After the reaction is completed, the conversion rate of glucose is calculated to be 98.9% and the selectivity of 5-HMF is 60.3% by measuring the components in the filtrate.

[0050] Example 4

[0051] The catalyst modification method and the preparation process of 5-HMF are the same as in Example 1, except that commercially available SAPO-34 molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd., model NKF-9) is used as the support.

[0052] Based on the analysis of the components in the filtrate, the conversion rate of glucose was calculated to be 99.1%, and the selectivity of 5-HMF was 60.6%.

[0053] Comparative Example 1

[0054] The catalyst used was unmodified SAPO-34 molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd., model NKF-9). The reaction conditions were the same as in Example 1. After the reaction, the filtrate was measured, and the glucose conversion rate was calculated to be 70.6% and the 5-HMF selectivity was 30.4%.

[0055] Comparative Example 2

[0056] The catalyst and reaction conditions were the same as in Example 1, except that only water was used as the solvent, and the amount added was 61.6 g. After the reaction, the filtrate was measured, and the glucose conversion rate was calculated to be 20.1%, and the 5-HMF selectivity was 34.2%.

[0057] Comparative Example 3

[0058] The catalyst and reaction conditions were the same as in Example 1, except that only valproic acid was used as the solvent, and the amount added was 61.6 g. After the reaction, the filtrate was measured, and the glucose conversion rate was calculated to be 78.3%, and the 5-HMF selectivity was 50.2%.

[0059] Comparative Example 4

[0060] The catalyst uses SAPO-34 supported Ca 2+ Uniformly dispersed Ca(10wt%)-SAPO-34 was prepared by conventional equal-volume impregnation method under the same reaction conditions as in Example 1. After the reaction, the filtrate was measured, and the glucose conversion rate was calculated to be 86.1% and the 5-HMF selectivity was 49.2%.

[0061] It is evident that the catalyst obtained by conventional equal-volume impregnation has poor performance. This is because the L-acid (Ca) obtained by the equal-volume impregnation method... 2 + The metal is uniformly distributed on the catalyst, while the catalyst prepared by rotary evaporation has the metal dispersed on the outer layer of the molecular sieve catalyst, forming a core-shell structure-like catalyst. The outer layer has a high metal density, which on the one hand is conducive to enhancing the adsorption of glucose molecules, and on the other hand, it serves as an L acid center to promote the isomerization of glucose into fructose molecules; at the same time, it does not cover the internal Brønsted acid active sites, which helps the dehydration of fructose.

Claims

1. A method for preparing 5-hydroxymethylfurfural from glucose in a one-pot process, comprising: Glucose was dissolved in a mixture of organic solvent and water, brought into contact with a catalyst, placed in a sealed autoclave, heated under an inert atmosphere, stirred, and cooled after reaction. The reaction solution was then filtered to remove solid particles, and 5-hydroxymethylfurfural was present in the filtrate. The catalyst is a metal-modified SAPO-34 molecular sieve catalyst, which is prepared by the following method: Will include Ca 2+ and / or Al 3+ The salt solution was slowly dripped onto the SAPO-34 molecular sieve, the mixture was rotary evaporated, and then dried and calcined to obtain the catalyst.

2. The method according to claim 1, characterized in that: The catalyst has a Ca and / or Al loading of 8%-10%.

3. The method according to claim 1, characterized in that: The Ca 2+ and / or Al 3+ The salt solution is an aqueous solution containing at least one of Ca(NO3)2, CaCl2, Al(NO3)3 and AlCl3.

4. The method according to claim 3, characterized in that: The salt solution is an aqueous solution of Ca(NO3)2.

5. The method according to claim 1, characterized in that: The rotary evaporation temperature is 70-95℃, and the rotary evaporation continues until the liquid is completely evaporated.

6. The method according to claim 1, characterized in that: When preparing the catalyst, the drying temperature is 65-100℃ and the drying time is 10-36h; the calcination temperature is 500-600℃ and the time is 2-8h.

7. The method according to claim 1, characterized in that: The organic solvent in the mixed solvent is selected from at least one of valerol, dimethyl sulfoxide, and tetrahydrofuran.

8. The method according to claim 1, characterized in that: The mixing ratio of organic solvent to water is 8-12:1 by weight.

9. The method according to claim 1, characterized in that: The total amount of the mixed solvent used is in a weight ratio of 50-65:1 to glucose.

10. The method according to claim 1, characterized in that: The catalyst is added in a weight ratio of 1:1-5 with glucose.

11. The method according to claim 1, characterized in that: The reaction is carried out in a sealed high-pressure reactor at a temperature of 160-200℃ for a time of 0.5-6 hours.

12. The method according to claim 1, characterized in that: The reaction is carried out in a sealed high-pressure reactor at a temperature of 170-180℃ for 3-4 hours.