Method for preparing modified molecular sieve and application of the modified molecular sieve in synthesizing deoxyfructosazine

Abstract

The application provides a modified molecular sieve preparation method and application of the modified molecular sieve in synthesis of deoxyfructosazine, wherein 1-butyl-3-methylimidazole hydroxide ionic liquid is mixed with a modified molecular sieve matrix to perform reflux reaction, and the modified molecular sieve is prepared through filtration, washing and drying treatment; wherein the modified molecular sieve matrix is obtained by treating ZSM-5 molecular sieve with alkali liquor and then introducing metal Cr through ion exchange. The method can promote dehydration reaction, inhibit dehydrogenation reaction, reduce the content of fructosazine FZ in the product, improve the conversion rate of glucosamine and the selectivity of deoxyfructosazine DOF in the preparation process, and is also convenient for directly filtering and separating the product from the solution.

Description

Technical Field

[0001] This invention relates to the field of molecular sieves, and more specifically, to a method for preparing modified molecular sieves and their application in synthesizing deoxyfructosine. Background Technology

[0002] Chitosan-based nitrogenous biomass is the second most abundant class of biomass polymers after cellulose, and it is also the most abundant natural nitrogenous organic compound besides protein. Furthermore, it is a natural basic amino polysaccharide. The condensation and dehydration of chitosan-derived monomer glucosamine (GlcNH2) to prepare nitrogenous compounds is an important reaction in the field of biomass conversion. Deoxyfructosazine (DOF) is an important pyrazine-based nitrogenous aromatic heterocyclic compound containing multiple functional groups, including hydroxyl groups, carbon-nitrogen double bonds, and pyrazine rings. Due to its unique structural characteristics, DOF is not only an important fragrance ingredient but also possesses strong physiological activity and medicinal value. Deoxyfructosazine is mainly prepared through the Maillard reaction, a series of complex reactions involving reducing sugars, carbohydrates, fructose, glucose, etc., with amino acids / proteins under ambient or heated conditions. The main component of the product is a pyrazine-based heterocyclic compound. Depending on the catalyst and reaction process, glucosamine (GlcNH2) can be converted into deoxyfructose DOF via dehydration reaction and into fructose FLZ via dehydrogenation reaction. However, dehydration and dehydrogenation reactions usually occur simultaneously, resulting in the presence of deoxyfructose, fructose, and other byproducts in the product, which affects the product quality.

[0003] To reduce the content of byproducts, patent application CN 110117259 B discloses a method for preparing 2,5-deoxyfructose using ionic liquid catalysis. The method includes the following steps: uniformly mixing chitin-based biomass and an ionic liquid in a dimethyl sulfoxide reaction medium; placing the mixed solution in a reaction vessel and heating it to the reaction temperature to generate a mixture containing crude 2,5-deoxyfructose; mixing the mixture containing the crude 2,5-deoxyfructose with a crystallization solvent, filtering, removing insoluble impurities, allowing the filtrate to stand, and crystallizing to obtain the 2,5-deoxyfructose product. While this patent overcomes the problems of requiring an external nitrogen source and using inorganic bases as catalysts leading to increased byproducts and environmental pollution in existing 2,5-deoxyfructose preparation reactions, the conversion rate of chitin-based biomass still needs improvement, the product still contains a relatively high amount of fructose fluoride (FZ), the selectivity of deoxyfructose fluoride (DOF) needs improvement, and the reaction system is entirely liquid, making direct filtration and separation of the product from the liquid difficult. Summary of the Invention

[0004] To reduce the content of fructosine FZ in the product during the preparation of deoxyfructosine, improve the conversion rate of glucosamine and the selectivity of deoxyfructosine DOF during the preparation process, and facilitate direct filtration and separation of the product from the solution, the technical solution adopted in this invention is: a method for preparing modified molecular sieves, comprising the following steps:

[0005] The modified molecular sieve was prepared by mixing 1-butyl-3-methylimidazolium hydroxide ionic liquid with a modified molecular sieve matrix under reflux, followed by filtration, washing, and drying. The modified molecular sieve matrix was obtained by treating ZSM-5 molecular sieve with alkali solution and then introducing metallic Cr through ion exchange.

[0006] Based on the above, the modified molecular sieve matrix is ​​prepared through the following steps:

[0007] Tetrapropylammonium hydroxide and aluminum isopropoxide were added to deionized water to form a clear solution. Then, tetraethyl orthosilicate was added dropwise to the clear solution. After stirring in a water bath, drying, washing, filtering, and calcining, the solution was added to an alkaline solution for ion exchange. Finally, after washing, filtration, and drying, the solution was impregnated with chromium nitrate solution and dried to obtain the modified molecular sieve matrix. The alkaline solution included NaOH, CH3ONa, and CH3COONa.

[0008] Based on the above, the 1-butyl-3-methylimidazolium hydroxide ionic liquid is obtained through the following steps:

[0009] 1-Bromobutane was added dropwise to N-methylimidazolium under water bath heating and stirring. After reflux reaction, the mixture was washed with ethyl acetate, shaken, allowed to stand and separate into layers, and the lower layer solution was taken and dried by vacuum distillation to obtain 1-butyl-3-methylimidazolium bromide.

[0010] A 1-butyl-3-methylimidazolium bromide was reacted with KOH methanol solution, and the resulting 1-butyl-3-methylimidazolium hydroxide ionic liquid was obtained by filtration, washing, and distillation.

[0011] The present invention also provides a modified molecular sieve, which is prepared by the above-described preparation method. The modified molecular sieve comprises a modified molecular sieve matrix and a 1-butyl-3-methylimidazolium hydroxide ionic liquid supported on the modified molecular sieve matrix, wherein the amount of the 1-butyl-3-methylimidazolium hydroxide ionic liquid supported on each gram of the modified molecular sieve matrix is ​​1 mmol to 10 mmol.

[0012] The present invention also provides an application of the modified molecular sieve described above, which is used to synthesize deoxyfructosine.

[0013] This invention also provides a method for synthesizing deoxyfructose, comprising the following steps:

[0014] Step 1: ZSM-5 molecular sieve is treated with alkaline solution and then Cr is introduced by ion exchange to obtain a modified molecular sieve matrix. A reaction is carried out using N-methylimidazolium, 1-bromobutane, and KOH methanol solution. After washing and distillation, 1-butyl-3-methylimidazolium hydroxide ionic liquid is obtained. The 1-butyl-3-methylimidazolium hydroxide ionic liquid is mixed with the modified molecular sieve matrix and refluxed. After filtration, washing, and drying, the modified molecular sieve is obtained.

[0015] Step 2 involves mixing and reacting glucosamine with the modified molecular sieve, followed by solid-liquid separation to obtain deoxyfructosine.

[0016] Based on the above, step two includes: weighing glucosamine and modified molecular sieve, adding dimethyl sulfoxide as a co-solvent and mixing evenly, placing it in a reaction vessel for stirring and constant temperature reaction, cooling with ice water after the reaction is completed, and obtaining deoxyfructosamine after centrifugation and filtration.

[0017] Based on the above, in step two, the mass ratio of glucosamine to the modified molecular sieve is 1:(8-13), the reaction temperature is 80℃-140℃, and the reaction time is 0.5h-3h.

[0018] Specifically, compared with inorganic strong base catalysts, basic ionic liquids (ILs) are mildly alkaline, highly stable, and structurally tunable, effectively avoiding side reactions caused by inorganic strong bases. This invention, based on basic ionic liquids, introduces new reactive sites to construct a bifunctional ionic liquid catalytic system, selectively controlling the transformation pathway of intermediate species. This enables highly efficient catalysis of the directed synthesis of DOF from GlcNH2, avoiding complex product distributions that cannot be separated.

[0019] Molecular sieves are porous compounds or materials with regular and uniform pore structures. The basic structure of molecular sieves mainly consists of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra, which form a three-dimensional framework by sharing vertex oxygen atoms. The silicon or aluminum in the molecular sieve framework can be replaced by atoms such as Cr, Ti, Mn, Co, and Cu. Based on their pore size, they can be classified into type A, type Z, and type Y molecular sieves. Specifically, the ZSM-5 molecular sieve catalyst in this case has wide applications in catalysis, adsorption, and separation due to its excellent shape-selective catalytic performance, stable framework structure, high specific surface area, good thermal and hydrothermal stability, and high acid catalytic activity. The high specific surface area of ​​ZSM-5 molecular sieve facilitates the uniform distribution of ionic liquids within its framework, fully exposing active sites and increasing the contact between active sites and the reactant GlcNH2. Its uniform pore structure also facilitates the introduction and grafting of ionic liquids and the transport of reactant molecules.

[0020] More specifically, during the conversion of monomeric glucosamine (GlcNH2) into DOF, a dihydrofructosazine (DiFZ) intermediate is formed. DiFZ then undergoes a dehydration reaction to form DOF. Therefore, introducing dehydration active sites can improve the conversion of DiFZ to DOF via the dehydration pathway. Chromium salts can form five-membered rings by complexing with adjacent hydroxyl groups on sugar molecules. Therefore, introducing chromium into NaZSM-5 molecular sieves can act as a mild Lewis acid, allowing for the regulation of the L / B acid ratio in the modified ZSM-5 molecular sieve and promoting the dehydration reaction. The Lewis acid can non-selectively catalyze the reverse aldol reaction between the C atoms at the 2 and 3 positions of glucose, leading to C2 and C4 compounds such as glycolaldehyde and erythrose. Since aldoses and ketoses, except for the carbonyl group, contain a large number of hydroxyl groups with similar physicochemical properties, the same Lewis acid can catalyze different carbonyl and hydroxyl groups, ultimately reducing the selectivity of specific catalytic reactions (such as the reverse aldol reaction). When a large amount of Brønsted acid is present in the reaction system, glucose can be dehydrated to produce 5-hydroxymethylfurfural (HMF). Through multiple stages of reactions such as ring opening, hydrogen transfer, hydrolysis / alcoholization, HMF can be further converted into levulinic acid (LA) or levulinic ester.

[0021] However, if ionic liquids are mechanically loaded into molecular sieves with acidic centers, the strong interaction between the two will cause the active sites in the ionic liquid or molecular sieve structure to be occupied, affecting the synergistic effect of acid-base active centers.

[0022] This study employs a post-synthetic modification strategy, precisely binding the ionic liquid side chains to the molecular sieve framework through chemical bonding. This confines the basic centers of the ionic liquid within the pores of the molecular sieve framework, allowing them to coexist synergistically with the unsaturated acidic centers of the molecular sieve. This enables the formation of the DiFZ intermediate species from the basic centers of GlcNH2 in the catalyst. The DiFZ intermediate species then undergoes directional dehydration and transformation into DOF under the influence of the unsaturated acidic centers within the molecular sieve framework. This demonstrates how the reaction pathway of the intermediate species can be controlled to promote DOF formation.

[0023] Therefore, this invention has substantial features and advancements compared to existing technologies. Specifically, the modified molecular sieve preparation method and its application in synthesizing deoxyfructosamine provided by this invention achieves appropriate adjustment of the pore size and acidity of the ZSM-5 catalyst through alkaline solutions of different concentrations, thereby facilitating the transfer of reactant and product molecules. Introducing metallic Cr via ion exchange allows for control of the L / B acid ratio of the modified ZSM-5 molecular sieve. Finally, basic ionic liquids are loaded into the Cr-NaZSM-5 molecular sieve framework containing Lewis acidic sites using hydrothermal and chemical bonding methods to construct an acid-base bifunctional catalyst. This achieves synergistic catalysis of acidic and basic centers, effectively controls the reaction pathway, and promotes the directed synthesis of DOF.

[0024] Compared with traditional catalysts such as ionic liquids, the present invention has the following advantages:

[0025] Firstly, the pore structure and acid properties of ZSM-5 molecular sieves can be modified by using alkaline solutions, thereby appropriately altering the microenvironment of the molecular sieve, further optimizing the structure and properties of the catalyst, and facilitating the mass transfer process.

[0026] Then, unsaturated metal ligands are introduced through ion exchange, which increases the dehydration active sites. At the same time, they can act as mild Lewis acids to inhibit dehydrogenation reactions and promote dehydration reactions, thereby promoting the efficient conversion of reactants to DOF.

[0027] Furthermore, the metal-organic framework structure contains a sufficient number of unsaturated metal ligands, providing reaction sites for the directed synthesis of DOF from the dehydration conversion of the reactant GlcNH2. This allows the basic ionic liquid, after being loaded onto the Cr-NaZSM-5 support, to be dispersed throughout the pores, increasing the contact between the basic centers of the ionic liquid and GlcNH2, which is beneficial for improving the catalytic efficiency of the ionic liquid.

[0028] Therefore, this modified molecular sieve preparation method and its application in the synthesis of deoxyfructose DOF can simplify the synthetic pathway for the conversion of chitin-based biomass glucosamine into DOF and FZ, promote dehydration reactions, inhibit dehydrogenation reactions, reduce the content of fructose DOF in the product, and improve the conversion rate of glucosamine and the selectivity of deoxyfructose DOF during the preparation process. Simultaneously, since the ionic liquid in the reaction system is attached to the solid particulate modified molecular sieve, and the catalytic process mostly takes place on the modified molecular sieve, most of the reaction products are generated attached to the modified molecular sieve. After the reaction, the modified molecular sieve can be directly filtered and separated from the solution, thus achieving direct filtration and separation of the reaction products from the reaction system. Finally, extraction and other processes can be used to further improve the purity of deoxyfructose DOF. Attached Figure Description

[0029] Figure 1 This is the 1H NMR spectrum of the deoxyfructose prepared by this invention.

[0030] Figure 2 This is the carbon NMR spectrum of the deoxyfructose prepared by this invention. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0032] Example 1

[0033] This embodiment provides a method for preparing modified molecular sieves, including the following steps:

[0034] Preparation of modified molecular sieve matrix Cr-NaZSM-5:

[0035] (1) Add 9.151g of 25% tetrapropylammonium hydroxide (TPAOH) and 0.273g of aluminum isopropoxide to 85mL of deionized water and mix to form a clear solution. Then add 20.833g of tetraethyl orthosilicate dropwise to the above solution and stir for 0.5h.

[0036] (2) Transfer the solution mixture from step (1) to a hydrothermal reactor and place it in a drying oven to dry at 180°C for 72 hours. After drying, wash and filter the sample and dry it overnight at 100°C.

[0037] (3) Place the dried sample in a tube furnace and calcine it in flowing air at 550℃ for 5h. Then add the calcined sample to 1mol / L CH3COONa solution at a solid-liquid ratio of 1:10 for ion exchange. Perform three ion exchanges at 90℃ for 2h each time. After washing thoroughly with deionized water and filtration, dry at 120℃ for 12h to obtain NaZSM-5 catalyst.

[0038] (4) The product obtained in step (3) is soaked in chromium nitrate solution for 12 hours. The amount of chromium nitrate solution used is 15% of the amount of chromium oxide loaded (calculated with the total weight of product and chromium oxide as 100%), and a general chromium nitrate solution is selected.

[0039] (5) The product obtained in step (4) is dried overnight at 120°C, and the prepared sample is named Cr-NaZSM-5.

[0040] Preparation of the ionic liquid 1-butyl-3-methylimidazolium hydroxide ([Bmim]OH):

[0041] (1) Weigh 8 mL of 0.1 mol N-methylimidazole and put it into a three-necked flask. Heat it to 70°C in a water bath. While stirring at 300 r / min, slowly add 13 mL of 0.12 mol 1-bromobutane. Reflux the mixture at 70°C for 20 h to obtain a pale yellow liquid.

[0042] (2) Wash the pale yellow liquid twice with ethyl acetate, shake, let it stand to separate the layers, put the lower layer into a single-necked flask, remove ethyl acetate by vacuum distillation, and dry at 80℃ for 20h to obtain purified 1-butyl-3-methylimidazolium bromide [Bmim]Br.

[0043] (3) Weigh 13g of 1-butyl-3-methylimidazolium bromide into a wide-mouth bottle, slowly add 20mL of KOH methanol solution, react for 10h under constant temperature stirring, filter, wash with methanol several times during the process, distill the filtrate under reduced pressure to remove methanol, and obtain the target product 1-butyl-3-methylimidazolium hydroxide ([Bmim]OH).

[0044] Preparation of supported and modified molecular sieve IL / Cr-NaZSM-5 catalyst:

[0045] 3 mmol of 1-butyl-3-methylimidazolium hydroxide ([Bmim]OH) was dissolved in 30 mL of toluene. Then, 1 g of Cr-NaZSM-5 was added to the solution, and the dispersed mixture was refluxed for 24 hours. The reaction mixture was filtered, washed with acetone, and then washed with a hot mixture of diethyl ether and dichloromethane (6:6, v / v) to remove excess basic ionic liquid (IL). Finally, it was dried in a vacuum oven at 353 K for 8 h to obtain the modified molecular sieve IL / Cr-NaZSM-5 catalyst.

[0046] Example 2

[0047] This embodiment provides a modified molecular sieve prepared by the preparation method provided in Example 1. The modified molecular sieve includes a modified molecular sieve matrix and an alkaline ionic liquid supported on the modified molecular sieve matrix.

[0048] The modified molecular sieve matrix is ​​obtained by treating ZSM-5 molecular sieve with alkaline solution and then introducing metal ions through ion exchange.

[0049] The alkaline ionic liquid includes an imidazole group, the alkaline solution includes NaOH, CH3ONa, and CH3COONa, and the metal ion includes chromium ions.

[0050] Example 3

[0051] This embodiment provides an application of the modified molecular sieve described in Embodiment 2, which is used to synthesize deoxyfructosine.

[0052] Example 4

[0053] This embodiment provides a method for synthesizing deoxyfructosamine, including the following steps:

[0054] (1) Weigh 0.2g of glucosamine and 2g of [Bmim]OH / Cr-NaZSM-5 catalyst, add 2ml of dimethyl sulfoxide (DMSO) as a co-solvent, and mix them evenly;

[0055] (2) Place the prepared solution in a 10ml reaction vessel, turn on the constant temperature oil bath, set the reaction temperature to 80℃ and the reaction time to 3h, adjust the magnetic stirring speed to 300r / min, and start timing the reaction.

[0056] (3) After the reaction is completed, the solution after the reaction is placed in ice water for rapid cooling, and then the solution after the reaction is centrifuged and filtered to obtain deoxyfructose.

[0057] During the process, 0.1 mL of the reaction liquid was mixed with 0.4 mL of pyrazine internal standard solution and added to an NMR tube for NMR testing, thereby performing quantitative analysis.

[0058] Example 5:

[0059] This embodiment provides a method for synthesizing deoxyfructosamine. The difference between this method and that in Example 4 is that in this embodiment, the volume of dimethyl sulfoxide is 3 ml and the reaction temperature is 100°C.

[0060] Example 6:

[0061] This embodiment provides a method for synthesizing deoxyfructosamine. The difference between this method and that in Example 4 is that in this embodiment, the volume of dimethyl sulfoxide is 4 ml and the reaction temperature is 120°C.

[0062] Example 7:

[0063] This embodiment provides a method for synthesizing deoxyfructosamine. The difference between this method and that in Example 4 is that in this embodiment, the volume of dimethyl sulfoxide is 4 ml and the reaction temperature is 140°C.

[0064] Comparative Example 1

[0065] The method for synthesizing deoxyfructazine provided in this comparative example differs from that in Example 4 in that:

[0066] ZSM-5 was used instead of [Bmim]OH / Cr-NaZSM-5 catalyst to catalyze the preparation of deoxyfructazine from glucosamine (GlcNH2).

[0067] Comparative Example 2:

[0068] The method for synthesizing deoxyfructazine provided in this comparative example differs from that in Example 4 in that:

[0069] NaZSM-5 was used instead of [Bmim]OH / Cr-NaZSM-5 catalyst to catalyze the preparation of deoxyfructazine from glucosamine (GlcNH2).

[0070] Comparative Example 3:

[0071] The method for synthesizing deoxyfructazine provided in this comparative example differs from that in Example 4 in that:

[0072] The preparation of deoxyfructidine from glucosamine (GlcNH2) was carried out using Cr-ZSM-5 instead of [Bmim]OH / Cr-NaZSM-5 catalyst.

[0073] Comparative Example 4:

[0074] The method for synthesizing deoxyfructazine provided in this comparative example differs from that in Example 4 in that:

[0075] The preparation of deoxyfructidine from glucosamine (GlcNH2) was carried out using Cr-NaZSM-5 instead of [Bmim]OH / Cr-NaZSM-5 catalyst.

[0076] Comparative Example 5:

[0077] The method for synthesizing deoxyfructazine provided in this comparative example differs from that in Example 4 in that:

[0078] The [Bmim]OH / ZSM-5 catalyst was used instead of the [Bmim]OH / Cr-NaZSM-5 catalyst to catalyze the preparation of deoxyfructazine from glucosamine (GlcNH2).

[0079] Comparative Example 6:

[0080] The method for synthesizing deoxyfructazine provided in this comparative example differs from that in Example 4 in that:

[0081] The [Bmim]OH / NaZSM-5 catalyst was used instead of the [Bmim]OH / Cr-NaZSM-5 catalyst to catalyze the preparation of deoxyfructose from glucosamine (GlcNH2).

[0082] Comparative Example 7:

[0083] The method for synthesizing deoxyfructazine provided in this comparative example differs from that in Example 4 in that:

[0084] The [Bmim]OH / Cr-ZSM-5 catalyst was used instead of the [Bmim]OH / Cr-NaZSM-5 catalyst to catalyze the preparation of deoxyfructose from glucosamine (GlcNH2).

[0085] Product testing:

[0086] Specifically, the methods for evaluating catalytic activity and calculating products during the detection process are as follows:

[0087] The activity of the catalyst prepared by this method was evaluated as follows:

[0088] (1) Prepare the reaction solution and reaction solvent according to the experimental plan, and put them into the polytetrafluoroethylene liner of the pressure vessel.

[0089] (2) Add the catalyst to the polytetrafluoroethylene liner, add the stirring magnet, and tighten the pressure vessel.

[0090] (3) First, check whether the thermocouple device of the thermostatic stirrer is connected correctly.

[0091] (4) Turn on the thermostatic oil bath switch and set the required reaction temperature;

[0092] (5) When the temperature reaches the predetermined temperature, the pressure vessel containing the reaction mixture is placed into the oil bath in sequence;

[0093] (6) Adjust the speed control knob to the preset speed and start timing;

[0094] (7) When the reaction reaches the preset time, first turn off the power switch of the constant temperature oil bath, remove the pressure vessel, drain the silicone oil, and quickly place it in an ice water bath to cool it down and end the reaction.

[0095] (8) Take out the reaction product mixture and analyze the raw material conversion rate and product yield;

[0096] (9) Clean the polytetrafluoroethylene container and the stirring magnet for experimental use.

[0097] The analysis and calculation of the catalytic products are as follows:

[0098] The analysis of the product can be performed through... 1 Characterized by H NMR nuclear magnetic spectroscopy:

[0099] During sample preparation, the sample is first placed in a centrifuge tube (1.5 mL), dissolved with 0.5 mL of deuterated reagent, and then transferred into a clean and dry NMR sample tube (5 mm in diameter) that is compatible with the spectrometer frequency.

[0100] Then, wipe the outer wall of the NMR sample tube clean, plug it with a NMR-specific test tube cap, and mark it so as not to affect the sample testing. Finally, adjust the depth of the NMR sample tube using a depth gauge.

[0101] Finally, the NMR sample tube is placed in the autosampler, and the sample tube is propelled into the NMR magnet by airflow. In the spectrometer's icon interface, the sampling pulse program is set, and the tuning, field locking, and shimming steps are performed. The experimental parameters mentioned above are set, and data acquisition is initiated. After data acquisition, baseline and phase corrections are performed on the FID, post-processing experimental parameters are set, and the spectrum is plotted.

[0102] Specifically, pyrazine or maleic anhydride can be selected as internal standards during sample preparation. The specific steps are as follows: In heavy water, the concentration of pyrazine or maleic anhydride is 0.3 mg / mL. To prepare the NMR sample, 0.1 mL of the reaction mixture is mixed with 0.4 mL of the internal standard solution, and the mixture is sonicated until the sample is completely dissolved. Then, it is transferred to an NMR tube for quantitative analysis. The detection results are as follows: Figure 1 and Figure 2 As shown. Among them, in Figure 1 The peak at 8.989 ppm represents the characteristic peak of hydrogen atoms in ionic liquids, while the peak at 8.851 ppm represents the characteristic peak of hydrogen atoms in DOFs. Figure 2 The peaks at 145.69 ppm and 157.27 ppm correspond to the characteristic peaks of different carbon atoms in DOF. The results of both 1H NMR and 1C NMR indicate that DOF was produced in the catalytic product and had a high relative content, while the content of FZ was relatively low.

[0103] The quantitative analysis calculations for the product are as follows:

[0104] Recording standards during data acquisition. 1 The H NMR spectrum should have a sufficiently large spectral width to ensure a good signal-to-noise ratio. Load the ZG pulse program; the pulse repetition time must be long enough to achieve sufficient relaxation. Set the following experimental parameters: D1 is set to 30 s; TD: 16 kJ; spectral width SW: 10 ppm; center frequency (O1) is set... 1 The center of the H NMR spectrum; P1: 45° 1 H transmitter pulse; DS: 2; NS: 16.

[0105] The quantitative calculation formula based on proton spectrum is as follows:

[0106]

[0107] In the formula: m(x) represents the mass of the target substance; p(std) represents the concentration of the internal standard; mw(x) represents the molecular weight of the target substance; nH(std) represents the number of protons selected for integration on the internal standard; m(std) represents the mass of the target substance and the internal standard; A(x) represents the integration area of ​​the target substance; mw(std) represents the molecular weight of the internal standard; nH(x) represents the number of protons selected for integration on the target substance; p(x) represents the purity of the target substance; A(std) represents the integration area of ​​the internal standard.

[0108] The conversion rate of reactants and the yield of products are calculated as follows:

[0109]

[0110]

[0111] In the formula: Y DOF n represents the yield of deoxyfructose; products Represents the number of moles of the product;

[0112] n substrates X represents the number of moles of substrate added; DOF Represents the conversion rate of deoxyfructose;

[0113] n final This represents the number of moles of substrate remaining after the reaction.

[0114] The conversion rate and selectivity of deoxyfructose prepared in Examples 4 to 7, and Comparative Examples 1 to 7 were detected and calculated, and the results are shown in Table 1:

[0115] Table 1. Conversion Rate and Selectivity

[0116] Example 4 99.82 25.11 Example 5 99.80 27.88 Example 6 99.93 35.40 Example 7 99.91 30.31 Comparative Example 1 15.88 5.32 Comparative Example 2 16.72 5.88 Comparative Example 3 20.10 6.22 Comparative Example 4 22.21 6.85 Comparative Example 5 35.47 15.12 Comparative Example 6 36.60 18.21 Comparative Example 7 40.58 18.99

[0117] As can be clearly seen from the table, the synthesis of deoxyfructosamine using the modified molecular sieve provided by this invention simplifies the synthetic route for the conversion of chitin-based biomass glucosamine to prepare DOF and FZ, improves the conversion rate, and enhances the selectivity of deoxyfructosamine. Simultaneously, combined with... Figure 1 Figure 2 As can be seen from the aforementioned principle analysis, the present invention can promote the dehydration reaction and inhibit the dehydrogenation reaction. While improving the selectivity of deoxyfructose, it can also inhibit the selectivity of fructose, thereby reducing the content of fructose FZ in the product.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. An application of a modified molecular sieve, characterized in that: This modified molecular sieve is used to catalyze the dehydration of glucosamine to synthesize deoxyfructozamine; The modified molecular sieve includes a modified molecular sieve matrix and a 1-butyl-3-methylimidazolium hydroxide ionic liquid loaded on the modified molecular sieve matrix, wherein the amount of the 1-butyl-3-methylimidazolium hydroxide ionic liquid loaded on each gram of the modified molecular sieve matrix is ​​1 mmol to 10 mmol. The modified molecular sieve is prepared by mixing and refluxing the 1-butyl-3-methylimidazolium hydroxide ionic liquid with the modified molecular sieve matrix, followed by filtration, washing, and drying. The modified molecular sieve matrix is ​​obtained by treating ZSM-5 molecular sieve with alkali solution and then introducing metallic Cr through ion exchange.

2. The application of the modified molecular sieve according to claim 1, characterized in that: The 1-butyl-3-methylimidazolium hydroxide ionic liquid is obtained through the following steps: 1-Bromobutane was added dropwise to N-methylimidazolium under water bath heating and stirring. After reflux reaction, the mixture was washed with ethyl acetate, shaken, allowed to stand and separate into layers, and the lower layer solution was taken. After drying by vacuum distillation, 1-butyl-3-methylimidazolium bromide was obtained. The 1-butyl-3-methylimidazolium bromide was prepared by adding KOH methanol solution to react with 1-butyl-3-methylimidazolium bromide, followed by filtration, washing, and distillation.

3. A method for synthesizing deoxyfructazine, comprising the following steps: Step 1: ZSM-5 molecular sieve is treated with alkaline solution and then Cr is introduced by ion exchange to obtain a modified molecular sieve matrix. A reaction is carried out using N-methylimidazolium, 1-bromobutane, and KOH methanol solution. After washing and distillation, 1-butyl-3-methylimidazolium hydroxide ionic liquid is obtained. The 1-butyl-3-methylimidazolium hydroxide ionic liquid is mixed with the modified molecular sieve matrix and refluxed. After filtration, washing, and drying, the modified molecular sieve is obtained. Step 2 involves mixing and reacting glucosamine with the modified molecular sieve, followed by solid-liquid separation to obtain deoxyfructosine; the mass ratio of glucosamine to the modified molecular sieve is 1:(8-13), the reaction temperature is 80 ℃ to 140 ℃, and the reaction time is 0.5 h to 3 h.

4. The method for synthesizing deoxyfructazine according to claim 3, characterized in that: Step two includes: Weigh the glucosamine and the modified molecular sieve, add the co-solvent dimethyl sulfoxide and mix well, place in a reaction vessel and stir and react at a constant temperature. After the reaction is completed, cool with ice water, and obtain deoxyfructosine by centrifugation and filtration.

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