Method for preparing fructose by catalyzing glucose isomerization by using tin phosphate / molecular sieve composite material
By preparing tin phosphate/molecular sieve composite materials, the problem of low fructose yield in the fructose preparation from glucose isomerization was solved, achieving a highly efficient catalytic effect and promoting the industrialization process in the field of biomass refining.
Patent Information
- Application Number
- CN202510982821.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-16
- Publication Date
- 2025-11-07
AI Technical Summary
In existing technologies, the reaction equilibrium for the isomerization of glucose to fructose is poor, resulting in low fructose yield. Furthermore, solid Lewis acid catalysts are difficult to synthesize in large quantities, which limits their industrial application in the field of biomass refining.
Using molecular sieves and tin tetrachloride as raw materials, tin phosphate/molecular sieve composite materials were prepared by impregnation. By using phosphoric acid solution pretreatment and calcination steps, combined with the introduction of Sn, tin phosphate/molecular sieve composite materials were formed and used to catalyze the isomerization of glucose to fructose.
It significantly improves the yield and selectivity of fructose, promotes the industrial application of glucose isomerization technology for fructose preparation, and the composite material is suitable for various molecular sieves such as MCM-41, SBA-15 and KIT-6.
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Figure CN120904259A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of catalytic conversion of biomass to high value-added chemicals, and particularly relates to a synthesis method of tin phosphate / molecular sieve composite material and a method for preparing fructose by catalytic isomerization of glucose. BACKGROUND
[0002] Biomass refining technology, as a new technology, can convert biomass into high-value chemicals or liquid fuels, and is expected to replace fossil energy. Compared with using glucose as raw material, using fructose as starting material to produce platform compounds such as 5-hydroxymethylfurfural (HMF), lactic acid, 5-ethoxymethylfurfural (EMF) and biofuels can effectively improve the yield. In addition, fructose is also a widely used sweetener in the food industry, and has high economic value. Therefore, glucose isomerization to produce fructose is one of the key reactions in biomass refining technology, and has been a research hotspot in the past few decades.
[0003] The system of glucose isomerization to prepare fructose reaction mainly includes enzyme catalytic system, homogeneous or heterogeneous acid / base catalytic system. Among them, the enzyme catalytic system has been widely used in food industry due to its high safety, which is one of the largest industrial scale biological catalytic processes at present. The high efficiency of food industry can make up for the high cost of enzyme catalytic system to a certain extent, but it is not practical to apply the fructose produced by this process on a large scale in the field of biomass refining.
[0004] As one of the oldest catalysts, acid is widely used in various reactions, and is still one of the most effective catalysts to date. The characteristic of Bronsted acid is its special H + ion releasing ability, while Lewis acid can form covalent bond with electron pair. Compared with Bronsted acid, the composition, structure and catalytic mechanism of Lewis acid are more complex and difficult to measure. So far, only a few types of solid materials have been fully confirmed to have Lewis acid catalytic activity, which greatly limits the practical application.
[0005] The tin-containing Beta zeolite (Sn-Beta) was first discovered as a highly efficient Lewis acid catalyst in 2010, which can catalyze the isomerization of glucose to fructose through intramolecular hydrogen ion transfer mechanism in pure water as the reaction medium. Since then, the material has become a research hotspot. This Lewis acid catalyzed isomerization process provides a new way for the synthesis of high value-added sugars and also builds a convenient platform for the conversion of biomass resources to chemicals / biofuels. Based on the universality of Sn-Beta as a water-tolerant Lewis acid, a variety of biomass conversion catalytic systems have been successfully developed. In addition, a large number of studies are devoted to optimizing the synthesis process of Sn-Beta, developing post-functionalization methods and in-depth analysis of the structure-effect relationship. However, the fructose yield and selectivity of Sn-Beta catalyzed glucose isomerization are significantly lower than that of the industrial glucose isomerase, and its synthesis process is complex and its stability is poor.
[0006] Recent studies have found that phosphatization modification of siliceous zeolites can significantly improve the Brønsted acid activity, which has certain reference significance for the development of efficient Lewis acid catalysts. In addition, metal nanoparticles, oxides, isolated metal and non-metallic species encapsulated in the pores of zeolites exhibit better catalytic performance than bulk materials in certain reactions, indicating that confinement effect can significantly regulate catalytic performance. SUMMARY
[0007] In view of the above background, the purpose of the present application is to provide a synthesis method of tin phosphate / molecular sieve composite material and a method for catalyzing glucose isomerization to prepare fructose by using the same. The method uses molecular sieve, tin tetrachloride and phosphoric acid as raw materials to prepare tin phosphate / molecular sieve composite material by a simple impregnation method, thereby solving the bottleneck problems of glucose isomerization to prepare fructose, such as limited reaction equilibrium, low fructose yield and difficulty in batch synthesis of solid Lewis acid catalysts, and promoting the industrial application of glucose isomerization to prepare fructose technology.
[0008] The purpose of the present application is achieved by the following technical solutions.
[0009] A method for catalyzing glucose isomerization to prepare fructose by using tin phosphate / molecular sieve composite material, comprising: Using molecular sieve and tin tetrachloride as raw materials, tin phosphate / molecular sieve composite material is prepared by an impregnation method, and fructose is obtained by catalyzing glucose isomerization by a two-step method.
[0010] In the above technical solution, the method comprises the following steps: Step 1: pretreating the molecular sieve with phosphoric acid solution.
[0011] In the step 1, the method for pretreating the molecular sieve is as follows: a certain amount of concentrated phosphoric acid is diluted with water, then the molecular sieve is added to the phosphoric acid solution, stirred for a period of time, the obtained product is dried and ground to obtain a white powder.
[0012] In the above technical solution, the molar ratio of phosphorus to silicon in the phosphoric acid solution and the molecular sieve should be 1:(10-320).
[0013] In the above technical solution, the stirring speed of the mixing and stirring is 100-3000 r / min, and the stirring time is 0.5-1.5 h.
[0014] In the above technical solution, the drying temperature is 40-100℃.
[0015] Step 2, calcine the white powder obtained in step 1 to obtain a P / molecular sieve.
[0016] In the above technical solution, the calcination method is calcination at 400-600℃ in air for 1-3 h, and the temperature rising program is 5-15℃ / min.
[0017] Step 3, introduce Sn into the P / molecular sieve material using an impregnation method.
[0018] In the above technical solution, the molar ratio of SnCl4.5H2O to molecular sieve should be 1:(10-320).
[0019] In the above technical solution, the stirring speed of the mixing process is 100-3000 r / min, and the stirring time is 12-36 h.
[0020] In the above technical solution, the centrifugal separation speed is 5000-10000 r / min, and the centrifugal separation time is 3-10 min.
[0021] In the above technical solution, the drying temperature is 40-100℃.
[0022] Step 4, calcine the white powder obtained in step 3 to obtain a tin phosphate / molecular sieve composite material.
[0023] In the above technical solution, the calcination method is calcination at 400-600℃ in air for 3-6 h. The temperature rising program is 5-15℃ / min. BRIEF DESCRIPTION OF DRAWINGS
[0024] The above technical solution is a schematic diagram of different Sn loadings and a TEM image of Example 2.
[0025] Figure 1
[0026] Figure 2 XPS patterns of MCM-41 molecular sieve and examples 1, 2, 3.
[0027] Figure 3 XRD patterns of MCM-41 molecular sieve and examples 1, 2, 3.
[0028] Figure 4 Pyridine infrared spectrum of example 2.
[0029] Figure 5 Effect diagram of SnPO and examples 1, 2, 3 in the same reaction conditions (1wt% glucose, 1wt% catalyst, 120℃ reaction for 2h in ethanol in the first step, and 120℃ reaction for 2h after adding equal amount of water in the second step) for catalyzing glucose isomerization to prepare fructose.
[0030] Figure 6 Effect diagram of example 2 in different substrate concentration conditions for catalyzing glucose isomerization to prepare fructose.
[0031] Figure 7 Effect diagram of example 2 in different reaction solvents for catalyzing glucose isomerization to prepare fructose.
[0032] Figure 8 Catalytic effect comparison of examples 2, 4, 5 and comparative examples 1, 2 under optimized conditions. DETAILED DESCRIPTION
[0033] The present application is further described in detail by the following examples, but the technical content described in the examples is illustrative rather than limiting, and the protection scope of the present application should not be limited by the examples.
[0034] The related instruments and equipment used in the specific embodiments of the present application are as follows: High performance liquid chromatograph: Waters Arc HPLC The calculation method of the yield of fructose in the examples of the present application is as follows: high-purity fructose is used to configure different concentrations of fructose aqueous solution as a standard solution, the peak area of fructose in the standard solution is detected by high performance liquid chromatography, a relationship curve between the peak area of fructose and the concentration of fructose is established as a standard curve, the peak area of the target product fructose is obtained by detecting the reaction sample solution by high performance liquid chromatography, and the yield of fructose in the sample is calculated by substituting the equation of the standard curve. EXAMPLE
[0035] Step 1, 0.072 g of concentrated phosphoric acid is added to 50 mL of water to configure a phosphoric acid solution, 6 g of MCM-41 molecular sieve is added to the above solution, and mixed and stirred at a speed of 1000 r / min for 1 h. Then it is put into an oven at 60℃ and dried at 60℃ overnight. After complete drying, the obtained solid is ground to obtain a white powder.
[0036] Step 2, the white powder obtained in Step 1 was put into a muffle furnace, and was heated to 550℃ at a temperature increasing rate of 10℃ / min, and was calcined at 550℃ for 1h, and then was naturally cooled to room temperature. The obtained white powder was marked as P-MCM-41(160).
[0037] Step 3, 0.219 g of tin tetrachloride pentahydrate was dissolved in 50 mL of water to prepare a tin tetrachloride solution, and all the P-MCM-41(160) obtained in Step 2 was added into the above solution, and was mixed and stirred at a speed of 1000 r / min for 24 h, and then was centrifuged at a speed of 8000 r / min for 5 min to obtain a solid. The solid was dried in an oven at 60℃ overnight, and the completely dried solid was ground to obtain a white powder.
[0038] Step 4, the white powder obtained in Step 3 was put into a muffle furnace, and was heated to 550℃ at a temperature increasing rate of 10℃ / min, and was calcined at 550℃ for 5h, and then was naturally cooled to room temperature. The obtained white powder was a tin phosphate / molecular sieve composite material, which was named as SnPO-MCM-41(160).
[0039] Step 5, SnPO-MCM-41(160) (50 mg) obtained in Step 4, glucose (50 mg) and ethanol (5 mL) were added into an autoclave, and the autoclave was placed in an oil bath at 120℃ and was heated with stirring for 2 h at a stirring speed of 2500 r / min. Then water (5 mL) was added into the autoclave, and the autoclave was placed in an oil bath at 120℃ and was heated with stirring for 2 h at a stirring speed of 2500 r / min. The obtained product was filtered and diluted through a 0.45 μm filter membrane, and the fructose content was detected by high performance liquid chromatography, and the yield was calculated to be 54.82%. Example
[0040] Step 1, 0.288 g of concentrated phosphoric acid was added into 50 mL of water to prepare a phosphoric acid solution, and 6 g of MCM-41 molecular sieve was added into the above solution, and was mixed and stirred at a speed of 1000 r / min for 1 h. Then the mixture was placed in an oven at 60℃ and was dried at 60℃ overnight, and the obtained solid was ground to obtain a white powder.
[0041] Step 2, the white powder obtained in Step 1 was put into a muffle furnace, and was heated to 550℃ at a temperature increasing rate of 10℃ / min, and was calcined at 550℃ for 1h, and then was naturally cooled to room temperature. The obtained white powder was marked as P-MCM-41(40).
[0042] Step 3: Tin tetrachloride solution was prepared by dissolving 0.876 g of tin tetrachloride pentahydrate in 50 mL of water. The entire P-MCM-41 (40) obtained in step 2 was added to the above solution and mixed at 1000 r / min for 24 h. The solid was then obtained by centrifugation at 8000 r / min for 5 min. The solid was dried in an oven at 60 °C overnight. The white solid obtained after complete drying was ground to obtain a white powder.
[0043] Step 4: The white powder obtained in step 3 was placed in a muffle furnace and heated to 550 °C at a rate of 10 °C / min. The temperature was maintained at 550 °C for 5 h. The furnace was then allowed to cool to room temperature naturally. The powder obtained was a tin phosphate / molecular sieve composite material and was designated as SnPO-MCM-41 (40).
[0044] Step 5: SnPO-MCM-41 (40) obtained in step 4 (50 mg), glucose (50 mg) and ethanol (5 mL) were added to an autoclave. The autoclave was placed in an oil bath and heated at 120 °C for 2 h with stirring at a speed of 2500 r / min. Water (5 mL) was then added to the autoclave and the autoclave was placed in an oil bath and heated at 120 °C for 2 h with stirring at a speed of 2500 r / min. The product obtained was filtered through a 0.45 μm filter membrane and diluted. The fructose content was determined by high performance liquid chromatography and the yield was calculated to be 62.62%. Example
[0045] Step 1: A phosphoric acid solution was prepared by dissolving 1.152 g of concentrated phosphoric acid in 50 mL of water. 6 g of MCM-41 molecular sieve was added to the above solution and mixed at 1000 r / min for 1 h. The solid obtained after complete drying was ground to obtain a white powder.
[0046] Step 2: The white powder obtained in step 1 was placed in a muffle furnace and heated to 550 °C at a rate of 10 °C / min. The temperature was maintained at 550 °C for 1 h. The furnace was then allowed to cool to room temperature naturally. The white powder obtained was designated as P-MCM-41 (10).
[0047] Step 3: Tin tetrachloride solution was prepared by dissolving 3.5 g of tin tetrachloride pentahydrate in 50 mL of water. The entire P-MCM-41 (10) obtained in step 2 was added to the above solution and mixed at 1000 r / min for 24 h. The solid was then obtained by centrifugation at 8000 r / min for 5 min. The solid was dried in an oven at 60 °C overnight. The white solid obtained after complete drying was ground to obtain a white powder.
[0048] Step 4: The white powder obtained in Step 3 was placed in a muffle furnace and heated to 550 °C at a rate of 10 °C / min, and calcined at 550 °C for 5 h, and then naturally cooled to room temperature. The white powder obtained was a tin phosphate / molecular sieve composite material, designated as SnPO-MCM-41(10).
[0049] Step 5: SnPO-MCM-41(10) (50 mg) obtained in Step 4, glucose (50 mg) and ethanol (5 mL) were added to an autoclave, which was placed in an oil bath and heated at 120 °C for 2 h with stirring at a speed of 2500 r / min. Then water (5 mL) was added to the autoclave, which was placed in an oil bath and heated at 120 °C for 2 h with stirring at a speed of 2500 r / min. The product obtained was filtered through a 0.45 μm filter membrane, diluted, and the fructose content was detected by high performance liquid chromatography, and the yield was calculated to be 53.58%. Example
[0050] Step 1: 0.576 g of concentrated phosphoric acid was added to 50 mL of water to prepare a phosphoric acid solution, and 6 g of SBA-15 molecular sieve was added to the solution and stirred at a speed of 1000 r / min for 1 h. Then it was placed in an oven at 60 °C and dried at 60 °C overnight. The solid obtained after complete drying was ground to obtain a white powder.
[0051] Step 2: The white powder obtained in Step 1 was placed in a muffle furnace and heated to 550 °C at a rate of 10 °C / min, and calcined at 550 °C for 1 h, and then naturally cooled to room temperature. The white powder obtained was marked as P-SBA-15(20).
[0052] Step 3: 1.75 g of tin tetrachloride pentahydrate was dissolved in 50 mL of water to prepare a tin tetrachloride solution, and all the P-SBA-15(20) obtained in Step 2 was added to the solution and stirred at a speed of 1000 r / min for 24 h, and then centrifuged at a speed of 8000 r / min for 5 min to obtain a solid. The solid was placed in an oven and dried at 60 °C overnight. The solid obtained after complete drying was ground to obtain a white powder.
[0053] Step 4: The white powder obtained in Step 3 was placed in a muffle furnace and heated to 550 °C at a rate of 10 °C / min, and calcined at 550 °C for 5 h, and then naturally cooled to room temperature. The white powder obtained was a tin phosphate / molecular sieve composite material, designated as SnPO-SBA-15(20).
[0054] Step 5, SnPO-SBA-15(20) obtained from step 4 (50 mg), glucose (50 mg) and ethanol (5 mL) were added into an autoclave, which was placed in an oil bath at 120 ℃ and stirred at 2500 r / min for 3 h. Then water (5 mL) was added into the autoclave, which was placed in an oil bath at 120 ℃ and stirred at 2500 r / min for 2 h. The obtained product was filtered and diluted by 0.45 μm filter membrane. The fructose content was detected by high performance liquid chromatography, and the yield was calculated to be 41.04%. Example
[0055] Step 1, 0.144 g of concentrated phosphoric acid was added into 50 mL of water to prepare a phosphoric acid solution. 6 g of KIT-6 molecular sieve was added into the solution and stirred at 1000 r / min for 1 h. Then it was placed in an oven at 60 ℃ and dried at 60 ℃ overnight. The obtained solid was ground to obtain a white powder.
[0056] Step 2, the white powder obtained in step 1 was placed in a muffle furnace and heated to 550 ℃ at a rate of 10 ℃ / min, and calcined at 550 ℃ for 1 h. Then it was naturally cooled to room temperature. The obtained white powder was marked as P-KIT-6(80).
[0057] Step 3, 0.438 g of tin tetrachloride pentahydrate was dissolved in 50 mL of water to prepare a tin tetrachloride solution. All P-KIT-6(80) obtained in step 2 was added into the solution and stirred at 1000 r / min for 24 h. Then it was centrifuged at 8000 r / min for 5 min to obtain a solid. The solid was placed in an oven and dried at 60 ℃ overnight. The obtained solid was ground to obtain a white powder.
[0058] Step 4, the white powder obtained in step 3 was placed in a muffle furnace and heated to 550 ℃ at a rate of 10 ℃ / min, and calcined at 550 ℃ for 5 h. Then it was naturally cooled to room temperature. The obtained white powder was a tin phosphate / molecular sieve composite material, which was named as SnPO-KIT-6(80).
[0059] Step 5, SnPO-KIT-6(20) (50 mg) obtained from step 4, glucose (50 mg) and ethanol (5 mL) were added into an autoclave, which was placed in an oil bath at 120 °C and stirred for 3 h at a stirring speed of 2500 r / min. Then, water (5 mL) was added into the autoclave, which was placed in an oil bath at 120 °C and stirred for 2 h at a stirring speed of 2500 r / min. The product was diluted by 0.45 μm filter membrane, and the content of fructose was detected by high performance liquid chromatography, and the yield was calculated to be 64.46%.
[0060] Comparative Example 1 MCM-41 without subsequent treatment was used to catalyze the isomerization of glucose to fructose, including the following steps: Commercially purchased MCM-41 molecular sieve without tin phosphate composite (50 mg), glucose (50 mg) and ethanol (5 mL) were added into an autoclave, which was placed in an oil bath at 120 °C and stirred for 2 h at a stirring speed of 2500 r / min. Then, water (5 mL) was added into the autoclave, which was placed in an oil bath at 120 °C and stirred for 2 h at a stirring speed of 2500 r / min. The product was diluted by 0.45 μm filter membrane, and the content of fructose was detected by high performance liquid chromatography, and the yield was calculated to be 0.18%.
[0061] Comparative Example 2 Step 1, synthesis of small pore tin phosphate material without composite with molecular sieve. 1 g of template P123 and 1.15 g of concentrated phosphoric acid were dissolved in 15 mL of water, and the mixture was mixed and stirred at a speed of 1500 r / min at room temperature for 2 h. Then, 5 mL of an aqueous solution of 3.5 g of tin tetrachloride pentahydrate was added to the solution. Continuous stirring was performed until a white colloidal precipitate was formed. The mixture was continuously stirred for 3 h, and then the mixture was transferred to a polyethylene-lined hydrothermal reactor, which was hydrothermally reacted at 100 °C for 72 h. After the reaction was completed, the white material was collected and washed with water and ethanol 5 times, respectively. The white material was completely dried at room temperature and then calcined in a muffle furnace at 700 °C for 5 h. After calcination, SnPO small pore tin phosphate material was obtained.
[0062] Step 2, SnPO material (50 mg) obtained from step 1, glucose (50 mg) and ethanol (5 mL) were added into an autoclave, which was placed in an oil bath at 120 °C and stirred for 2 h at a stirring speed of 2500 r / min. Then, water (5 mL) was added into the autoclave, which was placed in an oil bath at 120 °C and stirred for 2 h at a stirring speed of 2500 r / min. The product was diluted by 0.45 μm filter membrane, and the content of fructose was detected by high performance liquid chromatography, and the yield was calculated to be 33.37%.
[0067] Figure 1 are the schematic diagram and high-resolution transmission electron microscopy (HRTEM) images of three different phosphate intercalation cases. It can be seen from the figure that the phosphate in the sample is mainly distributed in the channels of the molecular sieve, and the porous morphology of MCM-41 is maintained.
[0068] Figure 2 It can be seen that the XPS and ICP test analysis results are consistent, and the XPS peak intensity of Sn and P is positively correlated with the load of Sn and P in the material. The Sn 3d XPS spectrum shows that the binding energy of Sn 3d3 / 2and 3d5 / 2is 495.9 and 487.5 eV, respectively, which is consistent with the binding energy of SnPO, and is obviously higher than that of SnO2(494.8 and 486.4 eV), indicating that tin and phosphorus mainly exist in the form of tin phosphate. The high binding energy of Sn 3d3 / 2and 3d5 / 2reveals the tetrahedral coordination structure of Sn 4+ , thereby forming a strong Lewis acid site.
[0069] Figure 3 The X-ray diffraction pattern (XRD) shows that after the addition of Sn and P, the basic structure of MCM-41 is retained, and the degree of amorphization is slightly improved at high Sn load.
[0070] Figure 4 The pyridine infrared test results confirm the existence of Lewis acid and Bronsted acid sites Figure 4 a). Example 2 shows a high density of Lewis acid sites and a small amount of Bronsted acid sites, which is similar to the acid characteristics of SnPO.
[0071] Figure 5 is a comparison chart of the catalytic effect of glucose isomerization to prepare fructose by examples 1, 2, 3 and SnPO (1 wt% glucose, 1 wt% tin phosphate / molecular sieve composite, 120°C reaction for 2 h in ethanol, 120°C reaction for 2 h after adding an equal amount of water). The highest fructose yield of examples 1, 2, 3 is 54.82%, 62.62% and 56.33%, respectively.
[0072] Figure 6 is the catalytic effect of the tin phosphate / molecular sieve composite prepared by example 2 at different substrate concentrations. With the addition of glucose from 0.5 wt% to 10 wt%, the fructose yield decreases but still maintains high selectivity.
[0073] Figure 7The catalytic effect of tin phosphate / molecular sieve composite prepared in Example 2 was obtained in different solvents. When water was used as solvent, only a little glucose was converted under the same test conditions, which indicated that the catalyst was inert in pure water. When methanol (MeOH), ethanol (EtOH) and isopropanol (PrOH) were used as solvent, the yield of fructose in the first step was limited in organic medium, only 12.5-19.5%, and the selectivity was less than 46%. The hydrolysis reaction in the second step improved the yield and selectivity of fructose significantly.
[0074] The above has made an exemplary description of the present application, it should be explained that, without departing from the core of the present application, any simple modification, change or other equivalent replacement which can not cost the creative labor of the person skilled in the art falls into the protection scope of the present application.
[0075] Figure 8 The catalytic effect of Examples 2, 4, 5 and Comparative Examples 1, 2 was compared under the optimized conditions. As can be seen from the figure, compared with the original MCM-41 molecular sieve or tin phosphate material not compounded with molecular sieve, the conversion rate, yield and selectivity of tin phosphate / molecular sieve composite were greatly improved. And the compounding method is widely applicable to various molecular sieve materials such as MCM-41, SBA-15 or KIT-6.
Claims
1. A method for preparing fructose by isomerization of glucose using a tin phosphate / molecular sieve composite material, characterized in that, The molecular sieve is impregnated with phosphoric acid and calcined to obtain a P / molecular sieve, Sn is introduced into the P / molecular sieve material by impregnation and calcination to obtain a tin phosphate / molecular sieve composite material, and the tin phosphate / molecular sieve composite material is used as a catalyst to prepare fructose by isomerization of glucose through a two-step method.
2. The method of claim 1, wherein, The method for pretreating the molecular sieve comprises diluting a certain amount of concentrated phosphoric acid with water, then adding the molecular sieve into the phosphoric acid solution, stirring for a period of time, and drying and grinding to obtain a white powder. In the above steps, the molar ratio of the concentrated phosphoric acid to the molecular sieve is 1:(10-320), the stirring speed in the mixing process is 100-3000 r / min, the stirring time is 0.5-1.5 h, the drying temperature is 40-100 DEG C, and the calcination method is calcination in air at 400-600 DEG C for 1-3 h, and the temperature rising program is 5-15 DEG C / min.
3. The method of claim 1, wherein, The method for introducing Sn into the P / molecular sieve material by impregnation comprises dissolving a certain amount of tin tetrachloride pentahydrate in water to obtain a tin tetrachloride solution, adding the P / molecular sieve into the solution, stirring for a period of time, centrifuging to obtain a solid, drying and grinding to obtain a white powder, and calcining in an air atmosphere to obtain a tin phosphate / molecular sieve composite material. In the above steps, the molar ratio of the tin tetrachloride pentahydrate to the molecular sieve is 1:(10-320), the stirring speed in the mixing process is 100-3000 r / min, the stirring time is 12-36 h, the centrifuging speed is 5000-10000 r / min, the centrifuging time is 3-10 min, the oven drying temperature is 40-100 DEG C, and the calcination method is calcination in air at 400-600 DEG C for 3-6 h. The temperature rising program is 5-15 DEG C / min.
4. The method according to claim 1, wherein the method for preparing fructose by isomerization of glucose through a two-step method using the tin phosphate / molecular sieve composite material comprises mixing the tin phosphate / molecular sieve composite material, glucose and ethanol, then performing a reaction under heating and stirring, adding a certain amount of water, then performing a hydrolysis reaction under heating and stirring to obtain fructose.