Method for preparing reducing sugar through cellulose hydrolysis

Abstract

The invention discloses a method for preparing reducing sugar through cellulose hydrolysis, and belongs to the technical field of fiber raw material biomass conversion and utilization. According to the method, a graphene oxide and molecular sieve composite material is prepared and used as a catalyst to hydrolyze a cellulose raw material to obtain reducing sugar with high application value and additional value. The method has the advantages of high reducing sugar yield, low catalyst consumption, high efficiency and the like. And the synthesis method of the graphene oxide and molecular sieve composite material is simple and convenient, and the catalyst structure is easy to control according to the property of the cellulose raw material, so that a low-cost novel catalyst preparation method and an efficient gain utilization method of a cellulose-containing biomass material are provided for preparing reducing sugar through cellulose hydrolysis.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber raw material biomass conversion and utilization, and relates to a method for preparing reducing sugar by hydrolyzing cellulose, and specifically to a method for improving the yield of preparing reducing sugar by hydrolyzing cellulose. Background Art

[0002] Cellulose is the most abundant biomass resource with a wide range of sources and low prices. Cellulose hydrolysis products have great utilization value and good industrial development prospects. For example, glucose produced by cellulose hydrolysis can be converted into renewable biofuels such as bioethanol, biobutanol and hydrocarbons, as well as valuable downstream chemicals such as furfural, 5-hydroxymethylfurfural, levulinic acid, etc. Converting cellulose into reducing sugars with low polymerization degree such as glucose is the key to utilizing cellulose. Although there are many common cellulose hydrolysis methods (including enzyme hydrolysis, super / subcritical water hydrolysis, liquid acid hydrolysis and solid acid hydrolysis), these methods have the problems of high cost, harsh reaction conditions, strong corrosion to equipment, difficulty in separation and recycling after reaction, and potential environmental pollution. In particular, they consume too much life of reaction equipment, which is not conducive to industrial production. In contrast, the use of solid acid catalysis to hydrolyze cellulose is more efficient. In recent years, researchers have been committed to the research and development of solid acid catalysts with the advantages of low cost, good thermal stability, easy separation, recyclability, and weak corrosion to equipment. Summary of the invention

[0003] In order to improve the above technical problems, the present invention provides a method for preparing reducing sugars by hydrolyzing cellulose. The method is carried out in the presence of graphene oxide and molecular sieve composite catalyst, and is a method for efficiently improving the yield of preparing reducing sugars by hydrolyzing cellulose.

[0004] The technical method of the present invention is as follows:

[0005] A method for preparing reducing sugar by hydrolyzing cellulose, the method comprising: preparing reducing sugar by subjecting cellulose raw material to a hydrothermal reaction in the presence of a catalyst; wherein the catalyst is selected from graphene oxide and molecular sieve composite materials.

[0006] According to an embodiment of the present invention, the mass ratio of the cellulose raw material to the graphene oxide and molecular sieve composite material is 1:0.5 to 1:4, exemplified by 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, and 1:4.

[0007] According to an embodiment of the present invention, the temperature of the hydrothermal reaction is 80-280°C, preferably 90-150°C, more preferably 100-130°C, and exemplarily 80°C, 100°C, 110°C, 120°C, 130°C, 150°C, 200°C, 250°C, and 280°C; the time of the hydrothermal reaction is 0.5-6h, preferably 2-6h, and exemplarily 0.5h, 1h, 1.5h, 2h, 4h, and 6h.

[0008] According to an embodiment of the present invention, the graphene oxide and molecular sieve composite material is prepared by mixing graphene oxide and molecular sieve; or, is prepared by in-situ reaction of molecular sieve synthesis raw materials on graphene oxide.

[0009] According to an embodiment of the present invention, the weight ratio of graphene oxide to molecular sieve is 1:0.25 to 1:5, exemplified by 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:4, and 1:5.

[0010] According to an embodiment of the present invention, the ratio of the weight of graphene oxide to the weight of the molecular sieve synthesis raw material is 1:0.25 to 1:5, exemplified by 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:4, and 1:5.

[0011] According to an embodiment of the present invention, the molecular sieve is selected from zeolite, specifically, it can be at least one of MFI type zeolite (such as ZSM-5, HZSM-5, Silicate-1), Y type zeolite molecular sieve and the like.

[0012] According to an embodiment of the present invention, the molecular sieve synthesis raw material includes a silicon source, an aluminum source, a mineralizer and a structure directing agent.

[0013] According to an exemplary embodiment of the present invention, the molecular sieve (such as zeolite, specifically at least one of MFI zeolite (such as ZSM-5, HZSM-5, Silicate-1), Y-type zeolite molecular sieve, etc.) is a molecular sieve treated with an alkaline solution. For example, a molecular sieve (such as zeolite, specifically at least one of MFI zeolite (such as ZSM-5, HZSM-5, Silicate-1), Y-type zeolite molecular sieve, etc.) is added to a sodium hydroxide solution, heated and stirred for the first time, then filtered and washed, and then placed in an ammonium nitrate solution and heated and stirred for the second time (the first heating and stirring step, the second heating and stirring step, the order can be changed; any heating and stirring step can also be selected), and then low-temperature drying (such as room temperature to 120°C) or high-temperature calcination or first room temperature drying and then high-temperature calcination, that is, an alkali-treated molecular sieve is obtained.

[0014] Preferably, the usage ratio of the molecular sieve to the sodium hydroxide solution is 1 g of the molecular sieve in 10 to 100 mL of a sodium hydroxide solution with a concentration of 0.05 to 3 mol / L.

[0015] Preferably, the temperature of the first heating and stirring is 50-80°C, exemplarily 65°C; the time of the first heating and stirring is 0.5-6h, exemplarily 30min, 60min, 90min, 120min.

[0016] Preferably, the temperature of the second heating and stirring is 50-100° C.; and the time of the second heating and stirring is 2-6 hours.

[0017] Preferably, the temperature of the high-temperature calcination is 350-550° C.; and the time of the high-temperature calcination is 0.5-6 hours.

[0018] For example, the silicon source includes at least one of silicon dioxide, silicon alkoxide, tetraethyl orthosilicate, and the like.

[0019] For example, the aluminum source includes at least one of sodium aluminate, aluminum hydroxide, aluminum nitrate, aluminum oxide, alumina alumina, aluminum isopropoxide, and the like.

[0020] For example, the mineralizer includes at least one of hydroxyl ions, hydroxide ions, fluoride ions, and the like.

[0021] For example, the structure directing agent includes a water-soluble organic substance (such as at least one of quaternary ammonium salt ions, tetrapropylammonium bromide, etc.).

[0022] According to an exemplary embodiment of the present invention, the mixing is performed at room temperature. In another example, the mixing is performed under stirring. In another example, the mixing is performed in the presence of a solvent such as ethanol.

[0023] According to an exemplary embodiment of the present invention, the in-situ reaction is carried out at room temperature or under hydrothermal reaction conditions at 80 to 280° C. For example, the in-situ reaction is carried out under stirring. For example, the in-situ reaction is carried out in the presence of a solvent such as ethanol.

[0024] According to an exemplary embodiment of the present invention, the graphene oxide and molecular sieve composite material is prepared by a method comprising the following steps: adding graphene oxide to a solvent (such as water or ethanol) and stirring or dispersing by ultrasonic wave to form a suspension, then adding molecular sieve, stirring at room temperature until the liquid evaporates (or partially evaporates), or directly filtering after stirring to obtain a solid; then washing, drying, and grinding to obtain the graphene oxide and molecular sieve composite material.

[0025] According to an exemplary embodiment of the present invention, the graphene oxide and molecular sieve composite material is prepared by a method comprising the following steps: mixing a molecular sieve synthesis raw material with graphene oxide, and then preparing the graphene oxide and molecular sieve composite material through a hydrothermal synthesis reaction.

[0026] According to an exemplary embodiment of the present invention, the molecular sieve synthesis raw material has the above definition.

[0027] According to an exemplary embodiment of the present invention, the hydrothermal synthesis reaction is carried out in a reactor.

[0028] According to an exemplary embodiment of the present invention, in the preparation method of the above-mentioned composite material, after the hydrothermal synthesis reaction, it also includes: separating, washing, and drying the hydrothermal reaction product, and then high-temperature oxidation to remove the structure directing agent to obtain a hierarchical porous graphene oxide-loaded molecular sieve, that is, the graphene oxide and molecular sieve composite material.

[0029] According to an embodiment of the present invention, the cellulose raw material comes from biomass such as wood, bamboo, cotton, cotton linter, wheat straw, rice straw, reed, hemp, mulberry bark, tea, paper mulberry bark and bagasse, and cellulose from coniferous and broad-leaved materials, and cellulose from grass stems.

[0030] According to an embodiment of the present invention, the preparation method further comprises pretreating the cellulose raw material. For example, the cellulose raw material is dispersed in water or an ionic liquid (such as 1-butyl-3-methylimidazolium chloride solution) system, and heated and stirred to obtain a pretreated cellulose raw material.

[0031] Preferably, the mass ratio of cellulose to water or ionic liquid is 1:5 to 1:50, preferably 1:5 to 1:30, exemplified by 1:5, 1:10, 1:15, 1:20, 1:30, 1:50.

[0032] Preferably, the heating and stirring temperature is 50-100°C, exemplified by 50°C, 60°C, 80°C, and 100°C; the heating and stirring time is 0.5-24h, preferably 0.5-3.0h, exemplified by 0.5h, 1h, 2h, 3h, 6h, 12h, and 24h.

[0033] According to an embodiment of the present invention, the method for preparing reducing sugars by hydrolyzing cellulose specifically comprises:

[0034] The cellulose raw material is dispersed in water or an ionic liquid (such as 1-butyl-3-methylimidazolium chloride solution) system, and subjected to heating, stirring or ultrasonic treatment to obtain a pretreated cellulose raw material; the cellulose raw material is then mixed with graphene oxide and a molecular sieve composite material, and reducing sugar is obtained through a hydrothermal reaction.

[0035] The present invention also provides reducing sugar prepared by the above preparation method.

[0036] The solution of the present invention achieves the following effects:

[0037] The present invention provides a graphene oxide and molecular sieve composite material and a synthesis method thereof, and the composite material is used as a catalyst to improve the yield of the reaction of preparing reducing sugars by hydrolyzing cellulose. Specifically, the total reducing sugar yield in the preparation method of the present invention reaches 60.0-96.0%. Moreover, the yield of reducing sugar produced by hydrolyzing cellulose using the graphene oxide and molecular sieve composite material as a catalyst is greatly improved compared with the yield of reducing sugar produced by hydrolyzing cellulose using graphene oxide or molecular sieve alone as a catalyst. Under the same reaction conditions, the yield of reducing sugar produced by hydrolyzing cellulose using graphene oxide or molecular sieve alone as a catalyst can only reach 25.0-60.0% at most, which is significantly lower than the 60.0-96.5% of the present invention. Moreover, the synthesis method of the present invention also has many advantages such as simplicity, small amount of catalyst, high efficiency, and convenient structure control. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The effect of the ratio of graphene oxide and zeolite molecular sieve in the composite catalyst on the yield of reducing sugars prepared by cellulose hydrolysis.

[0039] Figure 2 This is the effect of the ratio of composite catalyst to cellulose on the yield of reducing sugars.

[0040] Figure 3 This is a scanning electron microscope image of the composite catalyst, and the inset is the reducing sugar yield obtained under the optimal reaction conditions. DETAILED DESCRIPTION

[0041] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0042] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0043] A method for improving the yield of reducing sugars prepared by cellulose hydrolysis, the steps are as follows: first pre-treat a cellulose raw material (preferably microcrystalline cellulose as the raw material), and the microcrystalline cellulose can be pre-treated with an ionic liquid [BMIm]Cl. Cellulose and [BMIm]Cl with a mass ratio of 1:5 to 1:30 are placed in a reactor, and magnetically stirred in a water bath of 50 to 100°C for 0.5 to 3.0 hours to obtain a yellow liquid. Then, the graphene oxide and molecular sieve composite material prepared by the present invention are added and stirred evenly, and then water is added in a ratio of 0.1:1 to 2:1 in weight ratio of water to ionic liquid [BMIm]Cl, and the reaction is carried out at 90 to 150°C for 0.5 to 6 hours to obtain a high-content and high-yield reducing sugar product.

[0044] A method for improving the yield of reducing sugars prepared by cellulose hydrolysis, comprising the following steps: pre-treating a cellulose raw material (preferably microcrystalline cellulose) and pre-treating the cellulose with water. Putting cellulose and water in a mass ratio of 1:5 to 1:50 in a reaction kettle, magnetically stirring for 0.5 to 24 hours in a water bath at 50 to 100°C, then adding the graphene oxide and zeolite molecular sieve composite material catalyst prepared by the present invention, stirring evenly, and reacting at 90 to 150°C for 0.5 to 6 hours to obtain a reducing sugar product.

[0045] It is worth noting that the pretreatment effect of water on microcrystalline cellulose is not as good as the pretreatment effect of ionic liquid [BMIm]Cl on microcrystalline cellulose.

[0046] The total reducing sugar content of the product can be tested using DNS colorimetric reagent (prepared from potassium sodium tartrate, 3,5-dinitrosalicylic acid, sodium hydroxide, redistilled phenol, anhydrous sodium sulfite and ultrapure water, which is yellow): the colorimetric reagent and reducing sugar undergo an oxidation-reduction reaction under boiling water bath conditions to generate brown-red 3-amino-5-nitrosalicylic acid. The product can absorb visible light at 540nm, and its absorbance and concentration meet the Lambert-Beer quantification within a certain concentration range. This allows quantitative detection of the reducing sugar content.

[0047] In order to improve the efficiency of the graphene oxide and zeolite molecular sieve composite catalyst, the molecular sieve treated with an alkaline solution (specifically, at least one of MFI type zeolite (such as ZSM-5, HZSM-5, Silicate-1), Y type zeolite molecular sieve, etc.) can be used to compound with graphene oxide to obtain a graphene oxide and zeolite molecular sieve composite catalyst with more mesopores. Alternatively, the prepared graphene oxide and molecular sieve composite material can be treated with an alkaline solution to increase its mesoporous porosity and increase its pore size.

[0048] In the present invention, the preparation method of the composite material of graphene oxide and zeolite molecular sieve comprises the following steps:

[0049] (1) Add 1g of zeolite ZSM-5 to 10-100mL of 0.05-3mol / L sodium hydroxide solution and stir at 60-80°C (e.g. 60°C) for 30min. Then filter, wash with water, and place it in 1.0mol / L ammonium nitrate solution at 50-100°C with magnetic stirring for 2-6h, and repeat once. Finally, calcine at 350-550°C for 0.5-6h to obtain alkali-treated zeolite ZSM-5 for standby use.

[0050] (2) Weigh graphene oxide and add it to a reaction kettle, add anhydrous ethanol, and stir it magnetically to form a suspension. Then add alkali-treated zeolite such as ZSM-5, and stir it magnetically at room temperature until the liquid evaporates. Then wash it with water for several times, dry it in an oven or naturally, and grind it to obtain a composite material of graphene oxide and zeolite (alkali-treated zeolite ZSM-5).

[0051] In order to obtain a composite catalyst of graphene oxide and zeolite molecular sieve, zeolite such as ZSM-5 can also be grown in situ on graphene oxide to obtain a hierarchical porous composite catalyst of graphene oxide and zeolite molecular sieve. The steps are as follows: after mixing zeolite synthesis raw materials such as silicon source and aluminum source with graphene oxide, a hydrothermal synthesis reaction is carried out in a reactor; the silicon source includes at least one of silicon dioxide, silicon alkoxide, tetraethyl orthosilicate, etc.; the aluminum source includes at least one of sodium aluminate, aluminum hydroxide, aluminum nitrate, aluminum oxide, alumina alumina, aluminum isopropoxide, etc.; the mineralizer includes hydroxyl ions, hydroxide, fluoride ions; the structure directing agent includes water-soluble organic matter (such as at least one of quaternary ammonium salt ions, tetrapropylammonium bromide, etc.). After separating, washing and drying the hydrothermal reaction product, the structure directing agent is removed by high-temperature oxidation to obtain a hierarchical porous graphene oxide loaded zeolite molecular sieve, that is, a composite catalyst of graphene oxide and zeolite molecular sieve.

[0052] Example 1

[0053] A method for preparing reducing sugar by hydrolyzing cellulose, comprising the following steps:

[0054] Weigh 0.24g, 0.125g, 0.125g, 0.060g, 0.0625g of graphene oxide respectively and add them to a beaker, add 30ml of anhydrous ethanol, disperse by magnetic stirring, and further disperse by ultrasonic for 4h to obtain a graphene oxide suspension. Then add 0.06g, 0.0625g, 0.125g, 0.090g, 0.125g of zeolite molecular sieve ZSM-5 respectively, stir magnetically for 4h at room temperature, and then disperse by ultrasonic for 2h. After centrifugal filtration, the obtained suspension is washed alternately with water and anhydrous ethanol for 3 times, placed in a 60°C oven and dried for 12h, and the obtained solid is ground to obtain a graphene oxide and zeolite molecular sieve composite catalyst, that is, a graphene oxide and zeolite composite catalyst with a ratio of graphene oxide to zeolite molecular sieve of 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2 is obtained.

[0055] Weigh 1g [BMIm]Cl, heat and melt it in a reactor, add 50mg microcrystalline cellulose, and stir it in a 90℃ water bath for 1.5h. Then add 0.3ml water, transfer it to a 100ml hydrothermal reactor, add 75mg of the above-mentioned graphene oxide and zeolite molecular sieve composite catalyst with a ratio of 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, and place the reactor at 130℃ for 4h to obtain reducing sugar. The relationship between the total reducing sugar yield and the graphene oxide and zeolite molecular sieve composite catalyst is as follows: Figure 1 As shown. The reducing sugar yield of the composite catalyst of graphene oxide and zeolite molecular sieve with a ratio of graphene oxide to zeolite molecular sieve of 1:1 and 1:1.5 is greater than 88%. When the ratio of graphene oxide to zeolite molecular sieve (weight percentage) is graphene oxide: zeolite molecular sieve = 1:0.25 to 1:2, under the conditions of optimized reaction temperature of 130°C and reaction time of 4h, the total reducing sugar yield reaches 63.0 to 96.0%.

[0056] Example 2

[0057] A method for preparing reducing sugars by hydrolyzing cellulose, compared with Example 1, the only difference is that the weight ratios of graphene oxide and zeolite molecular sieve composite catalyst (the ratio of graphene oxide to zeolite molecular sieve is 1:1.5) to cellulose are 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, and 1:3, respectively.

[0058] Figure 2The effect of the weight ratio of the composite catalyst to cellulose on the reducing sugar yield was studied. The experimental results showed that when the weight ratio of the composite catalyst to cellulose was between 1:1 and 1:3, under the optimized reaction temperature of 130°C and reaction time of 4h, the total reducing sugar yield reached 68.0-96.0%.

[0059] Example 3

[0060] A method for preparing reducing sugar by hydrolyzing cellulose, the steps are as follows: weigh 0.125g of graphene oxide and add it to a beaker, add 30ml of anhydrous ethanol, disperse it by magnetic stirring, and further disperse it by ultrasonication for 4 hours to obtain a graphene oxide suspension. Then add 0.125g of zeolite molecular sieve ZSM-5, stir it magnetically at room temperature for 4 hours, and then disperse it by ultrasonication for 2 hours. After centrifugal filtration, the obtained suspension is washed alternately with water and anhydrous ethanol for 3 times, placed in a 60°C oven and dried for 12 hours, and the obtained solid is ground to obtain a graphene oxide and zeolite molecular sieve composite catalyst;

[0061] Weigh 1g of [BMIm]Cl, heat and melt it in a reactor, add 50mg of microcrystalline cellulose, and stir it in a 90°C water bath for 1.5h. Then add 0.3ml of water, transfer it to a 100ml hydrothermal reactor, add 75mg of the above-mentioned graphene oxide and zeolite molecular sieve composite catalyst, and place the reactor at 130°C for 4h to obtain reducing sugar.

[0062] Figure 3 This is a scanning electron microscope image of the graphene oxide and zeolite molecular sieve composite catalyst prepared in this example, and the inset is the reducing sugar yield obtained by catalyzing the hydrolysis of cellulose by the graphene oxide and zeolite molecular sieve composite catalyst, and the total reducing sugar yield is more than 90%.

[0063] Example 4

[0064] A method for preparing reducing sugar by hydrolyzing cellulose, compared with Example 3, the only difference is that the graphene oxide and zeolite molecular sieve composite catalyst is prepared by using zeolite treated with an alkaline solution, and the specific method is as follows:

[0065] (1) Add 1 g of zeolite ZSM-5 to 30 mL of 0.2 mol / L sodium hydroxide solution and stir at 60°C for 30 min. Then filter, wash with water, and place it in 1.0 mol / L ammonium nitrate solution at 80°C for 4 h with magnetic stirring, and repeat once. Finally, calcine at 550°C for 5 h to obtain alkali-treated zeolite ZSM-5, which is ready for use.

[0066] (2) Weigh 0.060g of graphene oxide and add it to a beaker, add 30ml of anhydrous ethanol, disperse it by magnetic stirring, and further disperse it by ultrasonic for 4h to obtain a graphene oxide suspension. Then add 0.090g of the zeolite molecular sieve ZSM-5 treated with alkali in step (1), stir it by magnetic stirring at room temperature for 4h, and then disperse it by ultrasonic for 2h. After centrifugal filtration, the obtained suspension is washed alternately with water and anhydrous ethanol for 3 times, placed in a 60℃ oven and dried for 12h, and the obtained solid is ground to obtain a graphene oxide and zeolite molecular sieve composite catalyst, that is, a graphene oxide and zeolite composite catalyst is obtained.

[0067] (3) Weigh 1 g of [BMIm]Cl, heat and melt it in a reactor, add 50 mg of microcrystalline cellulose, and stir it in a 90°C water bath for 1.5 h. Then add 0.3 ml of water, transfer it to a 100 ml hydrothermal reactor, add 75 mg of the above-mentioned graphene oxide and zeolite molecular sieve composite catalyst, and place the reactor at 130°C for 3 to 4 hours to obtain reducing sugars, with a total reducing sugar yield of 91.0 to 96.5%.

[0068] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing reducing sugars by hydrolyzing cellulose, characterized in that: The method comprises: in the presence of a catalyst, subjecting a cellulose raw material to a hydrothermal reaction to prepare reducing sugar; wherein the catalyst is selected from graphene oxide and a molecular sieve composite material.

2. The method according to claim 1, characterized in that The mass ratio of the cellulose raw material to the catalyst is 1:0.5 to 1:4; Preferably, the temperature of the hydrothermal reaction is 80-280° C.; the time of the hydrothermal reaction is 0.5-6 h.

3. The method according to claim 1 or 2, characterized in that The graphene oxide and molecular sieve composite material is prepared by mixing graphene oxide and molecular sieve; or, it is prepared by in-situ reaction of molecular sieve synthesis raw materials on graphene oxide.

4. The method according to claim 3, characterized in that The weight ratio of graphene oxide to molecular sieve is 1:0.25 to 1:5; Alternatively, the ratio of the weight of graphene oxide to the weight of the molecular sieve synthesis raw materials is 1:0.25 to 1:

5.

5. The method according to claim 3, characterized in that The molecular sieve is selected from zeolite; Alternatively, the molecular sieve synthesis raw materials include a silicon source, an aluminum source, a mineralizer and a structure directing agent; Alternatively, the molecular sieve is a molecular sieve treated with an alkaline solution.

6. The method according to any one of claims 3 to 5, characterized in that: The graphene oxide and molecular sieve composite material is prepared by a method comprising the following steps: adding graphene oxide to a solvent and stirring or dispersing by ultrasonic wave to form a suspension, then adding molecular sieve, stirring at room temperature until the liquid evaporates (or partially evaporates and then filters), or stirring and then directly filtering to obtain a solid; then washing, drying and grinding to obtain the graphene oxide and molecular sieve composite material.

7. The method according to any one of claims 3 to 5, characterized in that: The graphene oxide and molecular sieve composite material is prepared by a method comprising the following steps: mixing molecular sieve synthesis raw materials with graphene oxide, and then performing a hydrothermal synthesis reaction to prepare the graphene oxide and molecular sieve composite material.

8. The method according to any one of claims 1 to 7, characterized in that: The cellulose raw material comes from biomass wood, bamboo, cotton, cotton linter, wheat straw, rice straw, reed, hemp, mulberry bark, tea, paper mulberry bark, bagasse and other coniferous and broad-leaved cellulose, and grass stems.

9. The method according to any one of claims 1 to 8, characterized in that: The preparation method further comprises pretreating the cellulose raw material; Preferably, the pretreatment of the cellulose raw material specifically comprises: dispersing the cellulose raw material in water or an ionic liquid system, heating and stirring, to obtain the pretreated cellulose raw material.

10. A reducing sugar prepared by the preparation method according to any one of claims 1 to 9.

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