Method for preparing HMF by taking burdock as raw material

Abstract

The invention discloses a method for preparing HMF by taking burdock as a raw material, which specifically comprises the following steps: mixing fresh treated shredded burdock and water according to a ratio, extracting by a water bath or an enzyme method until synanthrin is dissolved, filtering to obtain filtrate, and removing impurities and purifying by a calcium hydroxide method or an ethanol method to obtain burdock extract with the synanthrin content of 30-60%; adding an organic phase into the burdock extracting solution to form a two-phase system, and reacting in a pressure-resistant kettle under the synergistic catalysis of Lewis acid and Bronsted acid to prepare HMF. According to the method, the HMF is prepared by taking the burdock as the raw material, and a small amount of lewis acid is added in the preparation process, so that glucose can be converted into fructose through an isomerization reaction, and the content of the fructose is increased; the reaction efficiency of the HMF is favorably improved, and a raw material source is expanded for the production of the HMF.

Description

Technical Field

[0001] The invention relates to a method for preparing HMF (5-hydroxymethylfurfural) by continuous reaction of inulin byproduct syrup. Background Art

[0002] HMF (5-hydroxymethylfurfural) as a bio-based platform compound has great potential in future material production. At present, the raw materials for the production of 5-hydroxymethylfurfural are mainly fructose and glucose, and fructose and glucose are mainly derived from food corn starch. Therefore, the development of non-food biomass as raw materials to prepare HMF has far-reaching significance. The rhizome of burdock is rich in inulin. At present, only a few crops such as Jerusalem artichoke have been reported to be used as plant sources for the preparation of HMF. Whether burdock can be used as a biomass raw material to produce 5-hydroxymethylfurfural will expand the source of raw materials for the production of HMF, which is worthy of in-depth study. Summary of the invention

[0003] In view of the above problems existing in the prior art, the object of the present invention is to provide a method for preparing HMF using burdock as raw material, which expands the raw material source for the production of HMF by using burdock as raw material, and provides another method for directly producing HMF using biomass as raw material.

[0004] The present invention provides a method for preparing HMF using burdock as a raw material, which specifically comprises the following steps:

[0005] 1) Raw material processing: fresh burdock rhizomes are washed, drained, peeled, and shredded, and the burdock shreds are mixed with water in a certain proportion, and extracted by water bath or enzymatic method until inulin is dissolved, and the residue is filtered to produce feed, fertilizer, etc. The filtrate is the burdock inulin extract, which is processed in the next step;

[0006] 2) Purification of sugar solution: The filtrate is concentrated to a burdock extract containing 30-60% inulin, and the extract is set aside. The concentration method is selected from any one of the following:

[0007] Calcium hydroxide is added to the filtrate to adjust the pH to 10-11, the temperature is raised to 50-75°C and the mixture is stirred for 30 minutes, and then carbon dioxide is introduced to adjust the pH to neutral, thereby generating calcium carbonate precipitation, and adsorbing protein to precipitate, filtering and dissolving to obtain a burdock extract with a high sugar content; in this method, some metal ions can be precipitated under alkaline conditions, and the alkaline conditions can inactivate some proteins, and the introduction of carbon dioxide can remove excess calcium hydroxide and generate calcium carbonate precipitation, which can adsorb protein precipitation while the precipitation is aggregated, thereby reducing the impurities in the solution;

[0008] Alternatively, the filtrate is directly concentrated, and then ethanol is added after concentration. Ethanol destroys the hydrogen bonds in the polysaccharide aqueous solution, and the polysaccharide is precipitated. The solution is placed at 4°C overnight, centrifuged, and dried to obtain a solid polysaccharide, which is dissolved in water to obtain a high-sugar burdock extract. Since polysaccharides are polyhydroxy aldehydes or ketones and are soluble in water, in this method, the addition of ethanol destroys the hydrogen bonds in the polysaccharide aqueous solution, thereby reducing the solubility of the polysaccharide in water and causing the polysaccharide to precipitate.

[0009] 3) Preparation of HMF: Using burdock inulin liquid as raw material, adding organic phase to form a two-phase system, reacting in a pressure autoclave under the synergistic catalysis of Lewis acid and Bronsted acid to obtain HMF. Since the temperature during the reaction exceeds the boiling point of water and the solvent, pressure is generated by itself. The pressure autoclave used in the present invention is a pressure autoclave that can withstand at least 5MPa.

[0010] Furthermore, the present invention also defines the water bath extraction method in step 1) as: stirring a mixture of water and burdock silk in a mass ratio of 2-8:1 at a water bath temperature of 60-90°C for extraction for 0.5-2h.

[0011] Furthermore, the present invention also stipulates that the water bath extraction is carried out under ultrasonic conditions, specifically: on the basis of water bath extraction, an ultrasonic device is added to the burdock silk solution for ultrasonic treatment, which can accelerate the inulin extraction and make the inulin extraction more complete.

[0012] Furthermore, the present invention also limits the water bath extraction to be carried out under microwave conditions, and adds a microwave process during the water bath extraction process, with the microwave duration being no more than 4 minutes. The high energy of microwaves is used to destroy plant cell tissues, thereby improving the extraction rate to a certain extent. This auxiliary method is suitable for small-scale extraction in the laboratory.

[0013] Furthermore, the present invention also defines that the burdock inulin solution in step 3) is a burdock extract solution containing 30-60% inulin.

[0014] Furthermore, the present invention also defines that the organic phase system includes but is not limited to one or more of cyclohexane, 1,4-dioxane, acetone, n-hexane, toluene, tetrahydrofuran, isopropanol, 1-butyl-3-methylimidazole chloride, 1-butyl-3-methylimidazole bromide, and dimethyl sulfoxide.

[0015] Furthermore, the present invention also defines Lewis acids as including one or more combinations of copper chloride, magnesium chloride, chromium chloride, vanadium chloride, iron chloride, aluminum chloride, calcium chloride, lithium chloride or nickel chloride; Bronsted acids include but are not limited to one or more combinations of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, citric acid, maleic acid, oxalic acid, p-toluenesulfonic acid, etc.

[0016] Furthermore, the present invention also defines the reaction temperature in step 3) as 100° C.-160° C., and the reaction time as 0.5-10 hours.

[0017] Furthermore, the present invention also limits the mass ratio of the aqueous phase to the organic phase to be 1:1 to 1:10.

[0018] Furthermore, the present invention also limits the conversion process of the burdock extract to be carried out in a closed pressure-resistant reactor: the reaction raw materials, the organic phase, and the catalyst are added to the reactor, and after the reaction is completed, the organic phase is removed by rotary evaporation, and HMF is extracted from the aqueous phase by an organic solvent, and the HMF product is obtained by rotary evaporation after phase separation.

[0019] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1) The present invention prepares HMF by using burdock as a raw material. During the preparation process, a small amount of Lewis acid is added to convert glucose into fructose through an isomerization reaction, thereby increasing the fructose content, which is beneficial to improving the reaction efficiency of HMF;

[0021] 2) The present invention prepares HMF by using burdock as a raw material, replacing inulin and the like, thereby expanding the raw material source for the production of HMF and providing another way to directly produce 5-hydroxymethylfurfural using biomass as a raw material. 5-Hydroxymethylfurfural, as a platform compound of bio-based materials, has broad application prospects. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with the embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0023] Method 1: Preparation of burdock extract (calcium hydroxide treatment method):

[0024] Wash, drain, peel and shred fresh burdock rhizomes, mix burdock shreds and water in a mass ratio of 1:6, extract in a water bath at 60-90°C with stirring for 1 hour until inulin dissolves, filter the residue to produce feed, fertilizer, etc., add calcium hydroxide to the filtrate to adjust the pH to 10-11, heat to 50-75°C and keep stirring for 30 minutes, then introduce carbon dioxide to adjust the pH to neutral, produce calcium carbonate precipitation, and adsorb protein precipitation at the same time, filter and dissolve to obtain a burdock extract with high sugar content;

[0025] Method 2: Preparation method 2 of burdock extract (ethanol treatment method):

[0026] Wash, drain, peel and shred fresh burdock rhizomes, mix burdock shreds and water in a mass ratio of 1:6, extract in a water bath with stirring at 60-90°C for 1 hour until inulin dissolves, filter and use the residue to produce feed, fertilizer, etc. The filtrate is directly concentrated and ethanol is added after concentration. Ethanol destroys the hydrogen bonds in the polysaccharide aqueous solution, and the polysaccharide precipitates. The mixture is placed at 4°C overnight, centrifuged, and dried to obtain solid polysaccharides, which are dissolved in water to obtain a burdock extract with a high sugar content.

[0027] The sugar solutions obtained by the calcium hydroxide treatment method (method 1) and the ethanol treatment method (method 2) were respectively concentrated or diluted to prepare the inulin content of 30%, 40%, 50%, and 60%. 10g of the prepared burdock extract was added to a 50ml reactor, and 20g of isopropanol was added at the same time. 0.3g of sulfuric acid and 0.05g of aluminum chloride were added as catalysts for the two groups with 30% sugar content, and sulfuric acid and aluminum chloride (the mass ratio of inulin, sulfuric acid, and aluminum chloride was 3:0.3:0.05) were added to the other 6 groups according to the proportion of sugar content. The reaction temperature was 150°C and the reaction time was 1.5h. Finally, the 5-hydroxymethylfurfural yield was calculated based on the sum of fructose and glucose obtained by hydrolysis of the syrup. The results are shown in Table 1.

[0028] Table 1 Preparation of HMF using burdock extracts obtained by different methods as raw materials

[0029] Example Organic solvent 20g Sugar content of raw materials Reaction temperature℃ HMF yield 1 Isopropyl alcohol 30% (Method 1) 150 70.9％ 2 Isopropyl alcohol 30% (Method 2) 150 69.7％ 3 Isopropyl alcohol 40% (Method 1) 150 68.3％ 4 Isopropyl alcohol 40% (Method 2) 150 68.6％ 5 Isopropyl alcohol 50% (Method 1) 150 66.8％ 6 Isopropyl alcohol 50% (Method 2) 150 67.1％ 7 Isopropyl alcohol 60% (Method 1) 150 62.0％ 8 Isopropyl alcohol 60% (Method 2) 150 62.1％

[0030] As can be seen from Table 1, there is no significant difference in the preparation of HMF from the raw materials with the same sugar content obtained by the two treatment methods, and the HMF yield decreases to a certain extent when the concentration is increased. Subsequent experiments used the raw materials obtained by method 1 with a sugar content of 30%.

[0031] Effect of reaction temperature on the reaction of Example 1-6

[0032] 10g of burdock extract obtained by method 1 with a sugar content of 30% was added to a 50ml reactor, and 0.3g of sulfuric acid, 0.05g of aluminum chloride, (the constituent monosaccharide of inulin is mainly fructose, and aluminum chloride is added only to isomerize a small amount of glucose into fructose, and other Lewis acids also have the same effect, with a small amount, and aluminum chloride is cheap, so aluminum chloride is used, and other Lewis acids can be substituted) 20g of isopropanol, the reaction temperatures are 110°C, 120°C, 130°C, 140°C, 150°C, and 160°C, respectively, and the reaction time is 1.5h. Finally, the yield of 5-hydroxymethylfurfural is calculated by the sum of fructose and glucose obtained by hydrolysis of syrup. (Use liquid chromatograph to analyze by ultraviolet detector, use C18 chromatographic column for detection, column temperature 40°C, detector temperature 40°C, mobile phase 5% methanol solution, flow rate 1ml / min, and the following detection conditions are used), and the results are shown in Table 2.

[0033] Table 2 Effect of reaction temperature on HMF yield

[0034]

[0035] It can be seen from Table 2 that with the increase of reaction temperature, the yield of HMF first increases and then decreases. If the temperature is too high or the time is too long, there will be side reactions, and the formic acid and levulinic acid produced by the reaction will increase, affecting the collection of HMF. Therefore, the preferred temperature is 140-150°C, and the optimal temperature is 150°C.

[0036] Effect of reaction time in Examples 7-12

[0037] 10g of burdock extract with a sugar content of 30% was added to a 50ml reactor, and 0.3g of sulfuric acid, 0.05g of aluminum chloride, and 20g of isopropanol were added. The reaction temperature was 150°C, and the reaction times were 0.5h, 1h, 1.5h, 2h, 5h, and 10h, respectively. Finally, the yield of 5-hydroxymethylfurfural was calculated based on the sum of fructose and glucose obtained by hydrolysis of the syrup. The results are shown in Table 3.

[0038] Table 3 Effect of reaction time on HMF yield

[0039]

[0040]

[0041] It can be seen from Table 3 that with the extension of reaction time, the yield of HMF first increases and then decreases. If the reaction time is too long, there will be by-products, which will convert HMF into other substances and reduce the yield. Therefore, the reaction time is 1-2h, and the optimal time is 1.5h.

[0042] Burdock transformation examples 13-17 Effect of Bronsted acid

[0043] 10g of burdock extract with a sugar content of 30% was added to a 50ml reactor, and 0.3g of sulfuric acid, 0.3g of phosphoric acid, 0.3g of p-toluenesulfonic acid, 0.3g of hydrochloric acid or 0.3g of oxalic acid, 0.05g of aluminum chloride and 20g of isopropanol were added at the same time. The reaction temperature was 150°C and the reaction time was 1.5h. Finally, the yield of 5-hydroxymethylfurfural was calculated based on the sum of fructose and glucose obtained by hydrolysis of the syrup. The results are shown in Table 4.

[0044] Table 4 Effect of reaction time on HMF yield

[0045]

[0046]

[0047] It can be seen from Table 4 that when the Bronsted acid is sulfuric acid, phosphoric acid or hydrochloric acid, the yield of HMF is relatively high relative to p-toluenesulfonic acid and oxalic acid. The Bronsted acid is preferably sulfuric acid, phosphoric acid or hydrochloric acid, and sulfuric acid is the best.

[0048] Effect of organic solvents in Examples 18-22

[0049] 10g of burdock extract with a sugar content of 30% was added to a 50ml reactor, and 0.3g of sulfuric acid, 0.05g of aluminum chloride, and 20g of isopropanol, cyclohexane, 1,4-dioxane, 1-butyl-3-methylimidazole chloride or n-hexane were added at the same time. The reaction temperature was 150°C, the reaction time was 1.5h, and the 5-hydroxymethylfurfural yield was finally calculated based on the sum of fructose and glucose obtained by hydrolysis of the syrup, and the results are shown in Table 5.

[0050] Table 5 Effect of organic solvent on HMF yield

[0051]

[0052]

[0053] As can be seen from Table 5, the present invention uses isopropanol and 1-butyl-3-methylimidazole chloride as organic solvents, and the yield of HMF is more than 70%, preferably isopropanol or 1-butyl-3-methylimidazole chloride.

Claims

1. A method for preparing HMF using burdock as raw material, characterized in that The steps include: 1) Raw material processing: fresh burdock rhizomes are washed, drained, peeled, and shredded, and the shredded burdock and water are mixed in a certain proportion, and extracted by water bath or enzymatic method until inulin is dissolved, and the residue after filtering is used to produce feed, fertilizer, etc., and the filtrate is processed in the next step; 2) Sugar solution purification Add calcium hydroxide to the filtrate to adjust the pH to 10-11, heat to 50-75°C and stir for 30 minutes, then introduce carbon dioxide to adjust the pH to neutral, generate calcium carbonate precipitation, adsorb protein and precipitate, filter and dissolve to obtain a burdock extract with high sugar content; Alternatively, the filtrate is directly concentrated, and ethanol is added after concentration. Ethanol destroys the hydrogen bonds in the polysaccharide aqueous solution, and the polysaccharide precipitates out. The filtrate is placed at 4°C overnight, centrifuged, and the solid polysaccharide is dried and precipitated to obtain a burdock extract with a high sugar content. 3) Preparation of HMF: Burdock extract was used as raw material, and an organic phase was added to form a two-phase system. Under the synergistic catalysis of Lewis acid and Bronsted acid, the reaction was carried out in a pressure vessel to obtain HMF.

2. The method for preparing HMF using burdock as raw material according to claim 1, characterized in that The water bath extraction method in step 1) is as follows: a mixture of water and burdock silk in a mass ratio of 2-8:1 is stirred and extracted at a water bath temperature of 60-90° C. for 0.5-2 h.

3. A method for preparing HMF using burdock as raw material according to claim 2, characterized in that The water bath extraction is carried out under ultrasonic conditions, specifically: on the basis of the water bath extraction, an ultrasonic device is added to the burdock silk solution for ultrasonic treatment.

4. The method for preparing HMF using burdock as raw material according to claim 2, characterized in that The water bath extraction was carried out under microwave conditions. A microwave process was added during the water bath extraction process, and the microwave time was no more than 4 minutes.

5. A method for preparing HMF using burdock as raw material according to any one of claims 1 to 4, characterized in that The burdock inulin solution in step 3) is a burdock extract containing 30-60% inulin.

6. A method for preparing HMF using burdock as raw material according to any one of claims 1 to 4, characterized in that The organic phase system includes, but is not limited to, one or more of cyclohexane, 1,4-dioxane, acetone, n-hexane, toluene, tetrahydrofuran, isopropanol, 1-butyl-3-methylimidazole chloride, 1-butyl-3-methylimidazole bromide, and dimethyl sulfoxide.

7. A method for preparing HMF using burdock as raw material according to any one of claims 1 to 4, characterized in that Lewis acids include one or more combinations of copper chloride, magnesium chloride, chromium chloride, vanadium chloride, iron chloride, aluminum chloride, calcium chloride, lithium chloride or nickel chloride; Bronsted acids include but are not limited to one or more combinations of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, citric acid, maleic acid, oxalic acid, p-toluenesulfonic acid, etc.

8. A method for preparing HMF using burdock as raw material according to any one of claims 1 to 4, characterized in that The reaction temperature in step 3) is 100°C-160°C, and the reaction time is 0.5-10 hours.

9. A method for preparing HMF using burdock as raw material according to any one of claims 1 to 4, characterized in that The mass ratio of the aqueous phase to the organic phase in step 3) is 1:1 to 1:

10.

10. A method for preparing HMF using burdock as raw material according to any one of claims 1 to 4, characterized in that The conversion process of the burdock extract is carried out in a closed pressure-resistant reactor: the reaction raw materials, organic phase and catalyst are added to the reactor. After the reaction is completed, the organic phase is removed by rotary evaporation, and HMF is extracted from the aqueous phase by an organic solvent. After phase separation, the HMF product is obtained by rotary evaporation.

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