Method for preparing 5-hydroxymethylfurfural

Abstract

To provide a method for preparing 5-hydroxymethylfurfural with high yield and purity.SOLUTION: There is provided a method for preparing 5-hydroxymethylfurfural including the following steps: step S1, drying and then grinding humin into powder, suspending it in water to obtain a suspension, adding a stannic chloride aqueous solution to the suspension under rapid stirring, stirring continuously after addition, standing overnight for aging, performing concentrating and drying, grinding the resultant into second powder, and calcining the second powder in the air to obtain a humin-supported Sn catalyst; step S2, injecting a sugar-containing raw material and an organic solvent using a metering pump into a reaction device filled with the humin-supported Sn catalyst respectively, and after the reaction, performing separation and purification to obtain 5-hydroxymethylfurfural, wherein the sugar-containing raw material is at least one of fructose syrup, glucose syrup, dextrose syrup, molasses and straw sugar syrup.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of synthesis of 5-hydroxymethylfurfural, and specifically to a method for producing 5-hydroxymethylfurfural. [Background technology]

[0002] 5-Hydroxymethylfurfural (5-HMF) is a platform compound with the advantages of high added value and wide applicability. It can be used as a monomer to synthesize bio-based materials, biofuels, pharmaceutical intermediates, liquid fuels and various chemical products, and has the potential for extensive applications in green, low-carbon and sustainable development. The added value products derived from 5-HMF mainly include 2,5-furandicarboxylic acid (FDCA), 2,5-furandialdehyde, 2,5-furandiethanol, 5-hydroxymethyl-2-furancarboxylic acid, levulinic acid, 2,5-dimethylfuran, etc. At present, the raw materials used to produce 5-HMF are mainly cellulose, fructose, sucrose, glucose, etc.

[0003] In order to realize the efficient conversion of biomass sugar to 5-HMF, the design and development of catalysts is very important. Many scholars have been working on the development of high-performance catalysts, and in the early stages, they focused on homogeneous catalysts including organic acids (e.g., oxalic acid, formic acid, citric acid), inorganic acids (e.g., hydrochloric acid, sulfuric acid), metal salts (metal chlorides), etc., and the organic and inorganic acids in homogeneous catalysts have high catalytic efficiency, but they have problems such as corroding the equipment and polluting the environment. Later, researchers gradually developed heterogeneous catalysts including strong acid cation exchange resins, molecular sieves, heteropolyacids, etc. Compared with homogeneous catalysts, heterogeneous catalysts have problems such as high cost, low catalytic efficiency, and complicated production process. The choice of solvent also has a great impact on the synthesis of 5-HMF, and the solvents are mainly divided into water, organic solvents, water-organic mixed solvents, and ionic liquids. Water is an ideal green solvent for producing 5-HMF from biomass sugars (glucose, fructose, cellulose, etc.), but it has the problem of low selectivity for 5-HMF and is prone to producing by-products such as humin, levulinic acid, and formic acid under the action of acid catalyst. One of the main reasons for the low utilization rate of sugar resources is the production of humin, which is a low-carbon high polymer that is insoluble in water and has characteristics such as high molecular weight, high stability, and difficult conversion.

[0004] Patent with publication number CN107556271A provides a method for producing 5-HMF from glucose, which uses glucose and choline chloride as raw materials to form a deep eutectic solvent, and catalyzes it under the action of a solid acid catalyst to obtain 5-HMF, with a maximum yield of 36.23%. This patent uses a deep eutectic solvent instead of an aqueous phase to avoid the disadvantage that 5-HMF is not stable in acidic solutions, and the solid acid catalyst is easy to prepare and obtain, but the yield of 5-HMF produced according to this method is still low. Patent with publication number CN106669655A provides a method for producing 5-HMF from sugar compounds catalyzed by a niobium carbon solid acid catalyst. This method synthesizes catalysts with different strengths by adjusting the types and ratios of the carbon source and niobium precursor, and the characteristics of the catalyst show that such a solid acid catalyst exhibits excellent circulation stability, but the yield of 5-HMF produced using this catalyst is only 56% at most. Patent with publication number CN112625012A provides a method for producing 5-HMF by catalyzing glucose with a tin-modified molecular sieve catalyst, which has high stability, low cost, and a simple manufacturing process, and can realize the one-step conversion of catalyzed glucose to 5-HMF, but the yield of 5-HMF is still low, only 58.0% at best.

[0005] With the ever-increasing problem of energy crisis and environmental pollution, the utilization of industrial waste has already become the focus of scholars' research. For example, the furfural residue generated in the hydrolysis process of biomass contains a large amount of cellulose, and fully utilizing the added value of the furfural residue is of great significance to industries that generate furfural. As an industrial waste, humin is generally directly burned for heating, but as a potential carbon material, it can be manufactured into chemical products or materials with high added value. Therefore, the rational utilization of humin with low added value is of great significance to improving the carbon utilization rate in the hydrolysis process of sugars. In the present invention, a tin-supported humin-based catalyst is designed and synthesized, and applied to catalyze biomass sugars (fructose liquid sugar, glucose liquid sugar, fructose glucose liquid sugar, blackstrap molasses, straw sugar, etc.) to produce 5-HMF. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] CN107556271A [Patent Document 2] CN106669655A [Patent Document 3] CN112625012A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide a method for producing 5-hydroxymethylfurfural in order to solve the problems of low utilization rate of raw materials for producing 5-HMF and low purity of the product. [Means for solving the problem]

[0008] The object of the present invention can be achieved by the following technical means.

[0009] The method for producing 5-hydroxymethylfurfural is as follows: Step S1: humin is dried, crushed into powder, suspended in water, and then rapidly stirred while adding tin tetrachloride aqueous solution, followed by stirring continuously, and then left overnight to mature, concentrated, dried, crushed into powder, and then calcined in air to obtain a tin-supported humin-based catalyst; The method includes step S2 of injecting the saccharide-containing raw material and the organic solvent into a reactor filled with a tin-supported humic catalyst using a metering pump to react them, and then separating and purifying them to obtain 5-hydroxymethylfurfural.

[0010] As a further technical means of the present invention, the sugar-containing raw material is at least one of fructose liquid sugar, glucose liquid sugar, fructose-glucose liquid sugar, blackstrap molasses, and straw sugar liquid sugar.

[0011] As a further technical means of the present invention, the concentration of said fructose liquid sugar, glucose liquid sugar and fructose-glucose liquid sugar is 1% to 75%, and the concentration of said blackstrap molasses and straw sugar liquid sugar is 1% to 50%.

[0012] As a further technical means of the present invention, the organic solvent is at least one of ethyl acetate, acetonitrile, tetrahydrofuran, acetone, toluene, methyl isobutyl ketone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 2-methyltetrahydrofuran, dimethyl carbonate, 1,4-dioxane, methanol, isopropyl alcohol, n-butanol, methyl tert-butyl ether, chloroform, butanone, butyl acetate, valerolactone and butyrolactone.

[0013] As a further technical means of the present invention, the volume ratio of the organic solvent to the saccharide-containing raw material is in the range of 0.5:1 to 10:1.

[0014] As a further technical means of the present invention, in step S2, nitrogen gas is filled during the reaction to set the reaction pressure to 0.1 to 6 MPa, the reaction flow rate to 1 to 100 mL / min, the reaction time to 0.1 to 10 min, and the reaction temperature to 50 to 200°C.

[0015] As a further technical means of the present invention, the amount of tin supported on the tin-supported humic catalyst is 0.5% to 9%.

[0016] As a further technical means of the present invention, the tin-supported humic-based catalyst is fixed in a tubular reactor R01, and the packed volume of the catalyst bed occupies 50%-100% of the reactor, and the remaining volume is filler.

[0017] As a further technical means of the present invention, the reaction apparatus includes a balance, a liquid feed metering pump P01, a liquid feed metering pump P02, a tubular reactor R01, a condenser E01, a circulating oil bath F01, a gas-liquid separation tank V01, a sampling valve group, and a collection tank.

[0018] As a further technical means of the present invention, the saccharide-containing raw material and the organic solvent are respectively placed in two supply bottles, preheated, and then sent to the tubular reactor R01 by the metering pumps P01 and P02 to carry out a heating reaction. The resulting product is cooled in the condenser E01, separated in the gas-liquid separation tank V01, and collected in the collection tank V02 to obtain the reaction liquid, which is then discharged through the discharge valve and separated and purified to obtain the product 5-HMF.

[0019] As a further technical means of the present invention, the tubular reactor R01 is heated by a circulating oil bath F01, and a water cooler F02 supplies a constant flow rate of cooling water to the condenser E01.

[0020] As a further technical means of the present invention, after the reaction system reacts in the tubular reactor R01, the water vapor and product vapor are carried out by nitrogen gas, passed through a condenser, and separated into gas phase and liquid phase in the gas-liquid separation tank, and the gas produced by the reaction is safely discharged through a valve.

[0021] As another technical means of the present invention, a group of sampling valves is connected to the gas-liquid separation tank V01, and the group of sampling valves can realize online sampling of the reaction liquid, thereby monitoring the production status of 5-HMF in a timely manner. Effect of the Invention

[0022] The beneficial effects of the present invention are as follows:

[0023] In the present invention, a tin-supported humin-based catalyst is synthesized and applied to catalyze biomass sugar (fructose liquid sugar, glucose liquid sugar, fructose glucose liquid sugar, blackstrap molasses, straw sugar, etc.) to produce 5-HMF. The biomass sugar liquid sugar used in the present invention is easy to obtain. For example, fructose glucose liquid sugar contains a large amount of fructose and is obtained by hydrolysis of corn starch, and is an ideal raw material for producing 5-HMF. In addition, the present invention rationally utilizes humin, which is an industrial waste, to produce a catalyst, which has an important promoting effect on the production of high-value-added chemical products by hydrolysis of sugars. Considering that tin-based catalysts have high activity in the dehydration reaction of sugars, introducing tin into the humin-based catalyst is advantageous for the isomerization and dehydration reaction of sugars. The catalyst has advantages such as easy production, mild reaction conditions, and low cost, and has a high catalytic effect on the synthesis of 5-HMF from sugars.

[0024] In the present invention, biomass sugar is used as the raw material, and homemade tin-loaded humin is used as the catalyst. The reaction is carried out for a certain period of time to obtain a reaction liquid containing 5-HMF, which is then separated and purified to obtain 5-HMF. The present invention rationally utilizes humin, which is an industrial waste, to produce a tin-loaded humin-based catalyst, which has an important promoting effect on the production of high-added-value chemical products through the hydrolysis of sugars, and the catalyst has the advantages of being simple to produce and requiring mild reaction conditions.

[0025] The present invention can monitor the production status of 5-HMF in real time by combining with an online monitoring device, and the tubular reactor used can reduce backmixing, greatly shorten the reaction time, and reduce the production of by-products such as humins, providing ideas for the realization of industrial-scale production. From the above, the present invention has the advantages of a simple process, mild reaction conditions, low energy consumption, high yield, and reduced cost. [Brief description of the drawings]

[0026] The present invention will now be further described with reference to the drawings. [Figure 1]1 is a flow chart of a reaction apparatus according to the present invention. [Diagram 2] 1 is an XRD pattern of a tin-supported humic-based catalyst according to the present invention. [Diagram 3] FIG. 2 is an analysis diagram of the tin-supported humic catalyst of the present invention by Fourier transform infrared spectroscopy (FTIR). [Figure 4] 1 is a Raman spectrum of a tin-supported humic catalyst according to the present invention. [Diagram 5] 1 is an XPS pattern of a tin-supported humic catalyst according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The following embodiments of the present invention will be combined to clearly and completely describe the technical means in the embodiments of the present invention, but obviously, the described embodiments are only some of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art on the basis of the embodiments of the present invention without creative labor are all included in the protection scope of the present invention.

[0028] Example 1 The method for synthesizing 5-HMF includes the following steps S1 and S2.

[0029] S1, Preparation of tin-supported humic catalyst: The separated humic was dried at high temperature, ground into dry powder, suspended in water, and SnCl4·5H2O was dissolved in water to prepare a 10% SnCl4·5H2O solution. The humic suspension was stirred rapidly while adding the 10% SnCl4·5H2O solution and stirred for 2 hours, then left overnight to mature, concentrated and dried, vacuum dried to remove water, ground into powder, and calcined in nitrogen gas. Calcination process: In a nitrogen gas atmosphere, the temperature was raised to 200°C within 1 hour, held for 6 hours, and then raised to 550°C within 2 hours and held for 6 hours. The mixture was cooled to room temperature to obtain a tin-supported humic catalyst.

[0030] S2, Production of 5-hydroxymethylfurfural: The aqueous solution of sugar raw material and the organic solvent were placed in two supply bottles, respectively, and a tin-supported humic catalyst was fixed in a tubular reactor, with the catalyst bed filled to 100 mL. The reaction was carried out in the tubular reactor under a nitrogen gas atmosphere, with the reaction pressure set to 0.1-6 MPa, the reaction flow rate set to 1-100 mL / min, and the reaction carried out at 50-200 °C for 0.1-10 min. The reaction was carried out continuously to obtain a 5-HMF-containing reaction liquid, which was then purified to obtain pure 5-HMF.

[0031] The apparatus for synthesizing 5-HMF in this example is as shown in Figure 1, and the reaction apparatus includes an assembly of a balance, a liquid delivery metering pump P01, a metering pump P02, a tubular reactor R01, a condenser E01, a circulating oil bath F01, a gas-liquid separation tank V01, a sampling valve group, a collection tank, etc. The tubular reactor R01 is heated by the circulating oil bath F01, and the water cooler F02 supplies a constant flow rate of cooling water to the condenser E01.

[0032] When in use, the aqueous solution of the saccharide-containing raw material and the solvent are placed in two supply bottles, respectively, and preheated. Then, they are sent to the tubular reactor R01 by the metering pumps P01 and P02 to carry out a heating reaction. The resulting product is cooled in the condenser E01, separated in the gas-liquid separation tank V01, and collected in the collection tank V02 to obtain the reaction liquid, which is discharged from the discharge valve and then separated and purified to obtain the above-mentioned product 5-HMF.

[0033] In addition, the flow rate of the aqueous solution of the saccharide raw material and the solvent is controlled by adjusting the metering pumps P01 and P02, and after the reaction system reacts in the tubular reactor, the water vapor and product vapor are carried out by nitrogen gas, and separated into gas and liquid phases in the gas-liquid separation tank through the condenser, and the gas generated by the reaction is safely discharged through the valve. In addition, a group of sampling valves is connected to the gas-liquid separation tank V01, and the sampling valve group can realize online sampling of the reaction liquid, so that the production status of 5-HMF can be monitored in a timely manner.

[0034] Example 2 The method for synthesizing 5-HMF includes the following steps S1 and S2.

[0035] S1, preparation of tin-supported humic catalyst: The separated humic was dried at high temperature and ground into 52.5g of dry powder, suspended in 525g of water, and 7.7g of SnCl4·5H2O was dissolved in 69.3g of water to prepare a 10% SnCl4·5H2O solution. The humic suspension was stirred rapidly while adding the 10% SnCl4·5H2O solution and stirred for 2h, then left overnight to mature, concentrated and dried, vacuum dried at 120℃ to remove water, ground into powder, and calcined in nitrogen gas. Calcination process: In a nitrogen gas atmosphere, the temperature was raised to 200℃ within 1h, held for 6h, and then raised to 550℃ within 2h and held for 6h. After cooling to room temperature, 28.9g of tin-supported humic catalyst was obtained, and the tin content was detected to be 9% by ICP.

[0036] S2, Production of 5-hydroxymethylfurfural: 1L of 75% fructose liquid sugar and 9L of acetonitrile were placed in two supply bottles, respectively, and a tin-supported humic catalyst was fixed in a tubular reactor, with a catalyst bed of 100mL. The reaction was carried out in the tubular reactor under a nitrogen gas atmosphere, with a reaction pressure of 1MPa and a reaction flow rate of 20mL / min (flow rates of fructose liquid sugar and acetonitrile were 2mL / min and 18mL / min, respectively), and a reaction time of 5min at 180°C. The sampling valve was opened, and the samples were sampled and detected. The detection conditions were as follows: Hitachi L2000 HPLC System, Alltech C18 column, mobile phase CH3OH:H2O=20:80, flow rate 1.0mL / min, column temperature 30°C, DAD as detector, and detection wavelength 284nm. The product was confirmed to be 5-hydroxymethylfurfural (5-HMF) by HPLC, and finally the reaction was continued to obtain a 5-HMF-containing reaction liquid, which was purified and the yield of 5-HMF was determined to be 93% and the purity was 97%.

[0037] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0038] Example 3 The synthesis method of 5-HMF includes the following steps:

[0039] Compared with Example 2, only the amount of tin supported in the tin-supported humic catalyst in step S1 was changed, and 2.2 g of SnCl4·5H2O was dissolved in 19.8 g of water to prepare a 10% SnCl4·5H2O solution. The remaining components and steps were completely consistent. Finally, 25.3 g of tin-supported humic catalyst was obtained, and the tin content was detected to be 3% by ICP. The components and steps in step S2 were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 86% and the purity was measured to be 98%.

[0040] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0041] Example 4 The synthesis method of 5-HMF includes the following steps:

[0042] Compared with Example 2, only the amount of tin supported in the tin-supported humic catalyst in step S1 was changed, and 4.7 g of SnCl4·5H2O was dissolved in 42.3 g of water to prepare a 10% SnCl4·5H2O solution. The remaining components and steps were completely consistent. Finally, 26.3 g of tin-supported humic catalyst was obtained, and the tin content was detected to be 6% by ICP. The components and steps in step S2 were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 90% and the purity was measured to be 98%.

[0043] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0044] Example 5 The synthesis method of 5-HMF includes the following steps:

[0045] Compared to Example 2, the reaction temperature in step S2 was replaced with 160°C, the remaining components and steps were completely consistent, and after the reaction was completed, the yield of 5-HMF was measured to be 80% and the purity was measured to be 98%.

[0046] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0047] Example 6 The synthesis method of 5-HMF includes the following steps:

[0048] Compared to Example 2, the reaction temperature in step S2 was replaced with 170°C, the remaining components and steps were completely consistent, and after the reaction was completed, the yield of 5-HMF was measured to be 84% and the purity was measured to be 97%.

[0049] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0050] Example 7 The synthesis method of 5-HMF includes the following steps:

[0051] Compared to Example 2, the reaction temperature in step S2 was replaced with 200°C, the remaining components and steps were completely consistent, and after the reaction was completed, the yield of 5-HMF was measured to be 82% and the purity was measured to be 97%.

[0052] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0053] Example 8 The synthesis method of 5-HMF includes the following steps:

[0054] Compared to Example 2, the reaction flow rate in step S2 was changed to 33 mL / min (the flow rates of fructose syrup and acetonitrile were 3.3 mL / min and 29.7 mL / min, respectively), the remaining components and steps were perfectly matched, and after the reaction was completed, the yield of 5-HMF was measured to be 80% and the purity was measured to be 98%.

[0055] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0056] Example 9 The synthesis method of 5-HMF includes the following steps:

[0057] Compared with Example 2, the reaction flow rate in step S2 was changed to 14 mL / min (the flow rates of fructose syrup and acetonitrile were 1.4 mL / min and 12.6 mL / min, respectively), the remaining components and steps were perfectly matched, and after the reaction was completed, the yield of 5-HMF was measured to be 85% and the purity was measured to be 98%.

[0058] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0059] Example 10 The synthesis method of 5-HMF includes the following steps:

[0060] Compared with Example 2, the reaction flow rate in step S2 was replaced with 10 mL / min (the flow rates of fructose syrup and acetonitrile were 1 mL / min and 9 mL / min, respectively), the remaining components and steps were perfectly matched, and after the reaction was completed, the yield of 5-HMF was measured to be 83% and the purity was measured to be 97%.

[0061] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0062] Example 11 The synthesis method of 5-HMF includes the following steps:

[0063] Compared to Example 2, the reaction pressure in step S2 was replaced with 0.5 MPa, the remaining components and steps were perfectly matched, and after the reaction was completed, the yield of 5-HMF was measured to be 91% and the purity was measured to be 98%.

[0064] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0065] Example 12 The synthesis method of 5-HMF includes the following steps:

[0066] Compared to Example 2, the reaction pressure in step S2 was replaced with 2 MPa, the remaining components and steps were perfectly matched, and after the reaction was completed, the yield of 5-HMF was measured to be 94% and the purity was measured to be 98%.

[0067] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0068] (Example 13) The synthesis method of 5-HMF includes the following steps:

[0069] Compared to Example 2, the reaction solvent in step S2 was replaced with acetone, and the remaining components and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 83% and the purity was measured to be 98%.

[0070] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0071] Example 14 The synthesis method of 5-HMF includes the following steps:

[0072] Compared to Example 2, the reaction solvent in step S2 was replaced with tetrahydrofuran, and the remaining components and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 88% and the purity was measured to be 98%.

[0073] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0074] Example 15 The synthesis method of 5-HMF includes the following steps:

[0075] Compared to Example 2, the reaction solvent in step S2 was replaced with ethyl acetate, and the remaining components and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 80% and the purity was measured to be 97%.

[0076] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0077] (Example 16) The synthesis method of 5-HMF includes the following steps:

[0078] Compared with Example 2, 1 L of 75% fructose liquid sugar and 9 L of acetonitrile in step S2 were replaced with 3 L of 75% fructose liquid sugar and 7 L of acetonitrile, the flow rates of fructose liquid sugar and acetonitrile were changed to 6 mL / min and 14 mL / min, respectively, and the remaining components and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 86% and the purity was measured to be 98%.

[0079] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0080] (Example 17) The synthesis method of 5-HMF includes the following steps:

[0081] Compared with Example 2, 1L of 75% fructose liquid sugar and 9L of acetonitrile in step S2 were replaced with 5L of 75% fructose liquid sugar and 5L of acetonitrile, the flow rates of fructose liquid sugar and acetonitrile were changed to 10mL / min and 10mL / min, respectively, and the remaining components and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 81% and the purity was measured to be 98%.

[0082] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0083] (Example 18) The synthesis method of 5-HMF includes the following steps:

[0084] Compared to Example 2, the 75% fructose syrup in step S2 was replaced with 50% fructose syrup, and the remaining ingredients and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 88% and the purity was measured to be 97%.

[0085] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0086] (Example 19) The synthesis method of 5-HMF includes the following steps:

[0087] Compared to Example 2, the 75% fructose syrup in step S2 was replaced with 25% fructose syrup, and the remaining ingredients and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 83% and the purity was measured to be 98%.

[0088] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0089] (Example 20) The synthesis method of 5-HMF includes the following steps:

[0090] Compared to Example 2, the 75% fructose liquid sugar in step S2 was replaced with 75% glucose liquid sugar, and the remaining ingredients and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 80% and the purity was measured to be 97%.

[0091] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0092] Example 21 The synthesis method of 5-HMF includes the following steps:

[0093] Compared to Example 2, the 75% fructose syrup in step S2 was replaced with 75% fructose glucose syrup, and the remaining ingredients and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 90% and the purity was measured to be 96%.

[0094] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0095] Example 22 The synthesis method of 5-HMF includes the following steps:

[0096] Compared to Example 2, the 75% fructose liquid sugar in step S2 was replaced with 50% straw sugar, and the remaining ingredients and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 70% and the purity was 98%.

[0097] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0098] (Example 23) The synthesis method of 5-HMF includes the following steps:

[0099] Compared to Example 2, 75% fructose liquid sugar in step S2 was replaced with 50% blackstrap molasses, and the remaining ingredients and steps were completely consistent. After the reaction was completed, the yield of 5-HMF was measured to be 70% and the purity was measured to be 98%.

[0100] The apparatus for synthesizing 5-HMF in this example is the same as in Example 1.

[0101] In this Example 2, the prepared tin-loaded humic catalyst was characterized. The tin content was detected to be 9% by ICP, and the specific surface area of ​​the catalyst was 158.3027 m according to the BET results. 2 / g, and the large specific surface area is favorable for the contact between the Sn species in the active center and the substrate, which is favorable for the activation and reaction of the substrate. The XRD pattern of the tin-supported humic catalyst is shown in Figure 2. As can be seen from Figure 2, the catalyst contains obvious diffraction peaks of the SnO2 phase. The Fourier transform infrared spectroscopy (FTIR) analysis of the tin-supported humic catalyst is shown in Figure 3. From the figure, the type of surface functional group can be seen. The carbon support has a carboxyl group (the stretching vibration of CO is 1081 cm -1 The C=O stretching vibration is at 1632 cm -1 ), and the alcohol functional group (-OH plane bending at 1384 cm -1 The -OH stretching vibration is at 3425 cm -1 ) and furan ring (CO stretching vibration at 871 cm-1 The Raman spectrum of the tin-supported humic catalyst is shown in Figure 4, which provides structural information about the related carbon material. The figure shows two characteristic peaks, the D band (1346 cm -1 ) and G band (1588cm -1 ) is shown to be located in the D band (sp 3 Carbon) is related to defects in graphene due to pentagons or heptagons, indicating the degree of surface defects and disorder of the carbon support, and the G band is sp 2 This corresponds to the stretching vibration in the plane of the carbon atom, indicating that the carbon support has a graphene structure in the order of C atoms. The XPS pattern of the tin-supported humin-based catalyst is shown in Figure 5, and as can be seen from the figure, the catalyst contains Sn, O, and C elements. As can be seen from the above analysis, the catalyst prepared using humin as a support has obvious active Sn material, and the support has a large specific surface area, which is favorable for the binding of the active center with the substrate, and the existing graphene structure is favorable for the transfer of electrons and the regeneration of the center, both of which give the catalyst high catalytic activity.

[0102] As can be seen from Examples 2-4 and 8-10, under the same conditions, the reaction flow rate (residence time) and the amount of tin loaded on the catalyst have a comprehensive effect on the product yield. The higher the reaction flow rate, i.e., the shorter the residence time, the higher the catalyst loading and the higher the reaction yield. When the reaction time is 5 min, the amount of tin loaded is 9% and the yield of 5-HMF is 93%, which is optimal. When the reaction residence time under the same conditions exceeds 5 min, the product yield begins to decrease, which is mainly due to the decomposition and polymerization of the product, so the optimal reaction time is 5 min. As can be seen from Examples 2 and 5-7, under the same conditions, the yield of 5-HMF increases with increasing reaction temperature below 180°C, but when the temperature exceeds 180°C, the yield decreases slightly with increasing temperature, which is mainly because the production rate of by-products also increases and the product further undergoes other reactions. As can be seen from Examples 2 and 11-12, the pressure of nitrogen gas does not have a large effect on the reaction yield, and as can be seen from Examples 2 and 13-15, As seen above, when reacting in different solvents (acetone, acetonitrile, tetrahydrofuran, ethyl acetate), the reaction yield was highest when acetonitrile was used as the solvent under the same conditions, followed by tetrahydrofuran. As seen from Examples 2 and 16 to 19, the product yield can be improved by changing the blending ratio of the solvent and fructose syrup and the mass fraction of fructose syrup. As seen from Examples 2 and 20 to 23, when different types of sugars (fructose syrup, glucose syrup, fructose glucose syrup, straw sugar, blackstrap molasses) are used as reaction raw materials, the reaction yield was highest when fructose syrup was used, followed by fructose glucose syrup.

[0103] As can be seen from the above examples, the reaction flow rate, temperature, pressure, type and concentration of sugar, organic solvent, amount of tin loaded catalyst, etc. are all factors that affect the yield of 5-HMF. By screening and optimizing the experimental conditions and controlling the experimental variables, the reaction conversion rate can be improved, which also provides new ideas and directions for obtaining 5-HMF with a higher yield in the future.

[0104] From the above, the present invention provides a method for producing 5-HMF, which uses biomass sugar as a raw material and homemade tin-loaded humin as a catalyst, reacts for a certain period of time to obtain a 5-HMF-containing reaction solution, and separates and purifies it to obtain 5-HMF. The present invention produces a tin-loaded humin-based catalyst with high catalytic activity by rationally utilizing humin, which is an industrial waste, and has the advantages of a simple production method and mild reaction conditions, and has an important promoting effect on the production of high-value-added chemicals by hydrolysis of sugars. In addition, the present invention can monitor the production status of 5-HMF in real time by combining with an online monitoring device, and the tubular reactor used can reduce backmixing, significantly shorten the reaction time, and reduce the generation of humin, providing an idea for realizing industrial-scale production. Therefore, the present invention has the advantages of a simple process, mild reaction conditions, low energy consumption, high yield, and reduced cost.

[0105] It should be noted that, in this specification, relational terms such as first and second, etc., are merely intended to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that such an actual relationship or order exists between those entities or operations. Also, the terms "comprise", "comprise", or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a set of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article, or apparatus.

[0106] Although embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is limited by the appended claims and their equivalents.

Claims

1. Step S1: drying humin, grinding it into powder, suspending it in water, adding tin tetrachloride aqueous solution while stirring rapidly, continuing to stir, leaving it overnight to mature, concentrating, drying, grinding it into powder, and calcining it in air to obtain a tin-supported humin-based catalyst; A method for producing 5-hydroxymethylfurfural, comprising: a step S2 of injecting a saccharide-containing raw material and an organic solvent into a reactor filled with a tin-supported humic catalyst using a metering pump to react them, and then separating and purifying the resulting 5-hydroxymethylfurfural.

2. The method for producing 5-hydroxymethylfurfural according to claim 1, characterized in that the sugar-containing raw material is at least one of fructose liquid sugar, glucose liquid sugar, fructose-glucose liquid sugar, blackstrap molasses, and straw sugar liquid sugar.

3. The method for producing 5-hydroxymethylfurfural according to claim 2, characterized in that the concentrations of the fructose liquid sugar, glucose liquid sugar, and fructose-glucose liquid sugar are 1% to 75%, and the concentrations of the blackstrap molasses and straw sugar liquid sugar are 1% to 50%.

4. The method for producing 5-hydroxymethylfurfural according to claim 1, characterized in that the organic solvent is at least one of ethyl acetate, acetonitrile, tetrahydrofuran, acetone, toluene, methyl isobutyl ketone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 2-methyltetrahydrofuran, dimethyl carbonate, 1,4-dioxane, methanol, isopropyl alcohol, n-butanol, methyl tert-butyl ether, chloroform, butanone, butyl acetate, valerolactone, and butyrolactone.

5. 2. The method for producing 5-hydroxymethylfurfural according to claim 1, wherein the volume ratio of the organic solvent to the saccharide-containing raw material is in the range of 0.5:1 to 10:

1.

6. The method for producing 5-hydroxymethylfurfural according to claim 1, characterized in that in step S2, nitrogen gas is filled during the reaction to set the reaction pressure at 0.1 to 6 MPa, the reaction flow rate at 1 to 100 mL / min, the reaction time at 0.1 to 10 min, and the reaction temperature at 50 to 200° C.

7. 2. The method for producing 5-hydroxymethylfurfural according to claim 1, wherein the amount of tin supported on the tin-supported humic catalyst is 0.5% to 9%.

8. The method for producing 5-hydroxymethylfurfural according to claim 1, characterized in that the tin-supported humic catalyst is fixed in a tubular reactor, the packed volume of the catalyst bed occupies 50% to 100% of the reactor, and the remaining volume is a filler.

9. The method for producing 5-hydroxymethylfurfural according to claim 1, characterized in that the reaction apparatus includes a balance, a liquid delivery metering pump, a tubular reactor, a condenser, a circulating oil bath, a gas-liquid separation tank, a sampling valve group, and a collection tank, and an aqueous solution of the saccharide-containing raw material and a solvent are injected into the tubular reactor using two liquid delivery metering pumps to mix and react with each other.

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