A method for the production of 5-hydroxymethylfurfural from molasses

Abstract

The application discloses a method for preparing 5-hydroxymethylfurfural by molasses conversion, comprising the following steps: preparing a molasses aqueous solution, passing the molasses aqueous solution into an adsorption column filled with a basic adsorbent, adsorbing by the basic adsorbent, separating acid impurities in the molasses aqueous solution, then adding inorganic acid into the molasses aqueous solution, and adjusting the pH of the molasses aqueous solution to 5-7; taking the molasses aqueous solution after pH adjustment and purification as a raw material, introducing an organic solvent, constructing a water / organic phase two-element system, introducing a catalyst, and carrying out conversion reaction at 120-160 DEG C for 0.5-3 h, so as to generate 5-hydroxymethylfurfural. The application creates a method for removing impurities from molasses pretreatment, and constructs a corresponding catalytic system, so that the by-product molasses of sugar industry is recycled, the preparation cost of 5-hydroxymethylfurfural is reduced, and the molasses is also used in a high added value way.

Description

Technical Field

[0001] This invention relates to a method for preparing 5-hydroxymethylfurfural by molasses conversion. Background Technology

[0002] 5-Hydroxymethylfurfural (5-HMF) is a promising platform compound that can be oxidized to 2,5-furandicarboxylic acid, which can then be used as a monomer to produce numerous bio-based materials. Research on 5-HMF preparation has primarily focused on starch-based raw materials such as fructose and glucose. However, due to the principle that chemical production must not compete with food production or land use, and the high price of crystalline fructose, large-scale production of 5-HMF is difficult and costly. Using agricultural and forestry waste such as straw and sawdust as raw materials for 5-HMF production avoids this problem. Furthermore, the production of 5-HMF using these wastes allows for clean resource utilization, reducing raw material costs. Based on these advantages, research on the preparation of 5-HMF using agricultural and forestry waste as raw materials has also been reported. While agricultural and forestry wastes such as straw and sawdust are inexpensive, their pretreatment is challenging. Chemical pretreatment methods are highly polluting and relatively inefficient, while biological pretreatment is limited by the cost of cellulase. Utilizing sugar industry waste or byproducts is easier than directly applying agricultural and forestry waste.

[0003] Molasses is a major byproduct of the sugar industry, generating 3.5 million tons annually from sugarcane processing alone. Molasses contains nearly 50% sucrose, fructose, and glucose, but also contains impurities such as inorganic salts, fats, proteins, and some organic acids. There are still few reports on the preparation of 5-hydroxymethylfurfural from molasses.

[0004] Currently, molasses is mainly used for feed production or industrial ethanol production. Reports on using molasses as a raw material to prepare 5-hydroxymethylfurfural (5-HMF) are scarce. Chinese patent CN114904510 A reports a method for preparing 5-HMF using molasses as a raw material, specifying a catalytic system using zinc tungstic acid solid acid catalyst. However, its primary purpose is to prepare adhesives containing 5-HMF, and the patent does not provide the yield of 5-HMF. Furthermore, the preparation process inevitably generates byproducts, which precipitate in pure water. The heterogeneous system used in 5-HMF preparation faces challenges such as catalyst recovery difficulties and rapid deactivation of active sites. Additionally, 5-HMF exhibits poor stability in pure water. Moreover, the molasses activation process in patent CN114904510A is complex, making the method unsuitable for large-scale production of 5-HMF. Summary of the Invention

[0005] In view of the above-mentioned technical problems in the prior art, the purpose of this application is to provide a method for preparing 5-hydroxymethylfurfural by molasses conversion.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for preparing 5-hydroxymethylfurfural by molasses conversion includes the following steps:

[0008] 1) Mix molasses with deionized water at a mass ratio of 3:1 to 1:3, stir well, and obtain a molasses aqueous solution;

[0009] 2) Pass the molasses aqueous solution obtained in step 1) into an adsorption column filled with alkaline adsorbent. The acidic impurities in the molasses aqueous solution are separated by adsorption by the alkaline adsorbent. Then, an inorganic acid is added to adjust its pH to between 5 and 7.

[0010] 3) Using the pH-adjusted and purified molasses aqueous solution obtained in step 2) as raw material, introduce an organic solvent to construct a water / organic phase binary system. The volume ratio of the molasses aqueous solution to the organic solvent is 1:1-1:4.

[0011] 4) Introduce a catalyst into the water / organic phase binary system constructed in step 3). The catalyst is a Lewis acid or a mixture of Lewis acid and Brønsted acid. The conversion reaction is carried out at 120-160℃ for 0.5-3h to generate 5-hydroxymethylfurfural.

[0012] Further, in step 1), molasses and water are mixed in a mass ratio of 1:1-3.

[0013] Further, in step 2), the alkaline adsorbent is one of alkaline alumina, hydrotalcite, or neutral alumina containing sodium hydroxide, sodium carbonate, or sodium bicarbonate, preferably alkaline alumina, hydrotalcite, or neutral alumina containing sodium carbonate; the mass ratio of the molasses aqueous solution to the alkaline adsorbent is 1-100:1, preferably 10-100:1. In the component of neutral alumina containing sodium hydroxide, sodium carbonate, or sodium bicarbonate, the mass fraction of sodium hydroxide, sodium carbonate, or sodium bicarbonate is 8-15%, preferably 10-12%.

[0014] Further, in step 2), the inorganic acid is sulfuric acid, hydrochloric acid, phosphoric acid, or nitric acid.

[0015] Further, in step 3), the organic solvent is at least one of tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol monomethyl ether, ethyl acetate, acetone, methyl isobutyl ketone, methyl tert-butyl ether, isopropanol, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide; the volume ratio of the molasses aqueous solution to the organic solvent is 1:2-4, preferably 1:3-4.

[0016] Further, in step 4), the catalyst is a Lewis acid, which is a hydrate of at least one of chromium chloride, aluminum chloride, lithium chloride, zinc chloride, ferric chloride, and vanadium chloride. The amount of catalyst used is 0.2-1% of the mass of the molasses aqueous solution, preferably 0.5-0.6%.

[0017] Further, in step 4), the catalyst is a mixture of Lewis acid and Brønsted acid. The Lewis acid is a hydrate of at least one of chromium chloride, aluminum chloride, lithium chloride, zinc chloride, ferric chloride, and vanadium chloride, and its amount is 0.2-1% of the mass of the molasses aqueous solution, preferably 0.5-0.6%. The Brønsted acid is at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and its amount is 0.001-0.01% of the mass of the molasses aqueous solution.

[0018] Furthermore, in step 2), the pH is adjusted to 6-7.

[0019] Furthermore, in step 4), the temperature of the conversion reaction is 130-150℃, and the reaction time is 1-2 hours.

[0020] The key technical point of this invention is:

[0021] 1. Molasses, a waste product from the sugar industry, is recycled after simple pretreatment;

[0022] 2. A suitable conversion system for the preparation of 5-hydroxymethylfurfural from molasses was constructed.

[0023] This invention provides a method for preparing 5-hydroxymethylfurfural (5-HMF) from molasses. The method involves pretreating molasses to obtain a polysaccharide solution, developing a suitable catalytic system, and using the molasses-derived polysaccharide solution as a raw material to prepare 5-HMF. This approach achieves two goals: firstly, it enables resource utilization and high-value-added use of molasses; secondly, it reduces the raw material cost of 5-HMF. Through the resource utilization of sugar industry waste and the use of a suitable catalytic system, the cost of 5-HMF is significantly reduced, providing technical support for the large-scale production of 5-HMF.

[0024] The beneficial effects achieved by this invention are:

[0025] This invention establishes a method for pretreatment of molasses to remove impurities and constructs a corresponding catalytic system, thereby utilizing molasses, a byproduct of the sugar industry, as a resource and reducing the preparation cost of 5-hydroxymethylfurfural (5-HMF). Based on this invention, molasses, a byproduct of the sugar industry, is processed into a high-value-added platform compound, realizing the high-value utilization of molasses. It also pioneers a technical route for preparing 5-HMF from non-grain raw materials, avoiding the problem of chemical production competing with food and land, and reducing the raw material cost for 5-HMF preparation. This invention will contribute to the large-scale application of 5-HMF. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] Example 1:

[0028] A method for preparing 5-hydroxymethylfurfural by molasses conversion includes the following steps:

[0029] 1) Molasses purification

[0030] Molasses was mixed with water at a mass ratio of 1:2 and stirred until homogeneous to obtain a molasses aqueous solution. This solution was then added to an alkaline adsorption column filled with alkaline alumina, with a mass ratio of molasses aqueous solution to alkaline alumina of 10:1. An appropriate amount of hydrochloric acid was added to the molasses aqueous solution passing through the alkaline adsorption column to adjust the pH to 6, resulting in a purified molasses aqueous solution.

[0031] The purified molasses solution was tested, and the equivalent fructose and equivalent glucose contents were calculated. The test method was as follows: The pH of the purified molasses solution was adjusted to 1 with sulfuric acid, and then kept at 90°C for 2 hours. The equivalent fructose and equivalent glucose contents in the molasses solution were then calculated according to the following formulas:

[0032]

[0033]

[0034] The test results showed that the equivalent fructose content in the purified molasses aqueous solution described in Example 1 was 10.5%, and the equivalent glucose content was 12.5%.

[0035] 2) Transformation reaction

[0036] The purified molasses aqueous solution obtained in step 1) was then mixed with tetrahydrofuran at a volume ratio of 1:3. Chromium chloride hexahydrate (0.5% of the mass of the purified molasses aqueous solution) was introduced. The mixture was transferred to a sealed reactor and reacted at 140°C for 1 hour at a pressure of 0.75 MPa. The reaction was then quenched by rapid cooling. Analysis of the reaction solution showed a molar yield of 40% for HMF. The yield of HMF was calculated using the following formula:

[0037]

[0038] Examples 2-7:

[0039] A method for preparing 5-hydroxymethylfurfural by molasses conversion is provided. The experimental steps are repeated in Example 1, except that the conditions for molasses purification in step 1) and the conditions for the conversion reaction in step 2) are changed. The corresponding changes in conditions and the final HMF yield results are summarized in Table 1.

[0040] Table 1

[0041]

[0042] In Table 1, the ratios in the molasses purification conditions column refer to mass ratios. The equivalent fructose and glucose contents are the results of testing and calculating the equivalent fructose and equivalent glucose contents of the purified molasses aqueous solution in each example. The reaction conditions column in Table 1 lists three conditions: 1) the specific selection of the organic solvent and the volume ratio of the molasses aqueous solution to the organic solvent; 2) the specific selection of the catalyst, the percentage ratio of the Lewis acid mass to the molasses aqueous solution mass, and the percentage ratio of the Brønsted acid mass to the molasses aqueous solution mass when Brønsted acid is present; and 3) the temperature and time of the conversion reaction.

[0043] Comparing the experimental results of Examples 2 and 5, it can be found that the yield of unpurified molasses as raw material in the water / DMSO system is low, only about half that of purified molasses under the same conditions. This shows that the molasses purification method created in this invention is quite effective, removing some impurities from the molasses that affect the subsequent preparation of 5-hydroxymethylfurfural. Comparing Examples 1 and 2, and 3 and 4, as the ratio of molasses aqueous solution to adsorbent increases, the equivalent fructose and glucose concentrations decrease. Comparing Examples 2 and 3, the choice of alkaline alumina or hydrotalcite as adsorbent has little effect on the equivalent fructose and glucose concentrations in the purified molasses.

[0044] Example 8:

[0045] A sucrose aqueous solution with a sucrose concentration of 45% was prepared. This solution was mixed with three times its volume of N,N-dimethylacetamide, and aluminum chloride hexahydrate (3% of the sucrose solution by mass) was added. The mixture was then converted at 130°C for 1 hour, yielding an HMF yield of 69%. Hydrolysis of the 45% sucrose aqueous solution as described in Example 1 yielded 22.5% fructose and 22.5% glucose.

[0046] Comparing Examples 8 and 5, it can be found that impurities in molasses have a significant inhibitory effect on the conversion of sugar to 5-hydroxymethylfurfural. Combined with Examples 2, 5, and 8, it can be demonstrated that the molasses purification method provided by this invention can reduce the content of impurities that inhibit the formation of 5-hydroxymethylfurfural, thereby improving the selectivity of sugar conversion to 5-hydroxymethylfurfural in molasses.

[0047] Example 9:

[0048] Repeat Example 1, replacing tetrahydrofuran with DMSO, acetone, ethylene glycol dimethyl ether, DMF, and DMAC respectively, while keeping other conditions unchanged, and obtaining HMF yields of 45%, 32%, 30%, 32%, and 33% respectively.

[0049] Example 10:

[0050] Example 1 was repeated, with the adsorbents replaced by hydrotalcite, neutral alumina mixed with sodium hydroxide (sodium hydroxide:neutral alumina mass ratio = 1:9), neutral alumina mixed with sodium carbonate (sodium carbonate:neutral alumina mass ratio = 1:9), activated carbon, and silicon dioxide, respectively. Other conditions remained unchanged. The experimental results were as follows: equivalent glucose content and equivalent fructose content were 10% and 12%; 6.5% and 7.5%; 7% and 8%; 5% and 5.5%; 11% and 12.5%, respectively; and HMF yields were 38%, 35%, 42%, 44%, and 19%, respectively.

[0051] Example 11:

[0052] Repeat Example 1, changing the volume of tetrahydrofuran so that the volume ratio of honey aqueous solution to tetrahydrofuran is 1:1, 1:2, and 1:4 respectively, while keeping other conditions unchanged. The experimental results are as follows: the yields of HMF obtained are 25%, 33%, and 41% respectively.

[0053] This invention achieves the efficient production of 5-hydroxymethylfurfural from molasses, a byproduct of the sugarcane industry, by developing a molasses purification method and establishing a corresponding catalytic system. This provides a direction for the high-value utilization of molasses and also opens up a path for non-grain sources of 5-hydroxymethylfurfural.

[0054] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for preparing 5-hydroxymethylfurfural by molasses conversion, characterized in that... Includes the following steps: 1) Mix molasses with deionized water at a mass ratio of 3:1 to 1:3, stir well, and obtain a molasses aqueous solution; 2) Pass the molasses aqueous solution obtained in step 1) into an adsorption column filled with alkaline adsorbent. The acidic impurities in the molasses aqueous solution are separated by adsorption by the alkaline adsorbent. Then, an inorganic acid is added to adjust its pH to between 5 and 7. 3) Using the pH-adjusted and purified molasses aqueous solution obtained in step 2) as raw material, introduce an organic solvent to construct a water / organic phase binary system. The volume ratio of the molasses aqueous solution to the organic solvent is 1:1-1:

4. 4) Introduce a catalyst into the water / organic phase binary system constructed in step 3). The catalyst is a Lewis acid or a mixture of Lewis acid and Brønsted acid. The conversion reaction is carried out at 120-160℃ for 0.5-3h to generate 5-hydroxymethylfurfural. The alkaline adsorbent is alkaline alumina, hydrotalcite, or neutral alumina containing sodium carbonate; the mass ratio of molasses aqueous solution to alkaline adsorbent is 10-100:1; in the component containing sodium carbonate, the mass fraction of sodium carbonate is 8-15%.

2. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 1), molasses and water are mixed in a mass ratio of 1:1-3.

3. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 2), the mass fraction of sodium carbonate in the neutral alumina component containing sodium carbonate is 10-12%.

4. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 2), the inorganic acid is sulfuric acid, hydrochloric acid, phosphoric acid, or nitric acid.

5. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 3), the organic solvent is at least one of tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol monomethyl ether, ethyl acetate, acetone, methyl isobutyl ketone, methyl tert-butyl ether, isopropanol, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide; the volume ratio of the molasses aqueous solution to the organic solvent is 1:2-4.

6. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 5, characterized in that... In step 3), the volume ratio of the molasses aqueous solution to the organic solvent is 1:3-4.

7. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 4), the catalyst is a Lewis acid, which is a hydrate of at least one of chromium chloride, aluminum chloride, lithium chloride, zinc chloride, ferric chloride, and vanadium chloride. The amount of catalyst used is 0.2-1% of the mass of the molasses aqueous solution.

8. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 7, characterized in that... In step 4), the amount of catalyst used is 0.5-0.6% of the mass of the molasses aqueous solution.

9. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 4), the catalyst is a mixture of Lewis acid and Brønsted acid. The Lewis acid is a hydrate of at least one of chromium chloride, aluminum chloride, lithium chloride, zinc chloride, ferric chloride, and vanadium chloride, and its amount is 0.2-1% of the mass of the molasses aqueous solution. The Brønsted acid is at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid, and its amount is 0.001-0.01% of the mass of the molasses aqueous solution.

10. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 9, characterized in that... In step 4), the amount of Lewis acid used is 0.5-0.6% of the mass of the molasses aqueous solution.

11. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 2), adjust the pH to 6-7.

12. The method for preparing 5-hydroxymethylfurfural by molasses conversion as described in claim 1, characterized in that... In step 4), the temperature of the conversion reaction is 130-150℃, and the reaction time is 1-2 hours.

Images