A molybdenum-based biomass-based heterogeneous catalyst and a preparation method and application thereof

Abstract

The application belongs to the technical field of chemical synthesis and provides a molybdenum-based biomass-based heterogeneous catalyst and a preparation method and application thereof.The preparation method comprises the following steps: dissolving deacetylated chitosan in a dilute glacial acetic acid solution, adding a phosphomolybdic acid solution dropwise to the solution and continuously stirring, obtaining a gel suspension of chitosan cross-linked phosphomolybdic acid; performing solvothermal stirring on the gel suspension, obtaining a precursor; washing the precursor with ultrapure water, and obtaining the molybdenum-based biomass-based heterogeneous catalyst after drying.The application forms an interface polarization microenvironment by electrostatic cross-linking of chitosan and phosphomolybdic acid, constructs an interface polarization microenvironment high-activity catalytic system, and can efficiently and rapidly produce rare sugars, thereby providing a low-cost green synthesis path for food additives, cosmetics and the synthesis of medicines.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, and particularly relates to a molybdenum-based biomass-based heterogeneous catalyst, its preparation method, and its application. Background Technology

[0002] Biomass-based monosaccharides are abundant renewable monosaccharide resources in nature and important platform compounds for constructing high-value-added fine chemicals. The selective isomerization of common biomass monosaccharides to prepare rare monosaccharides with scarce natural reserves aligns with the trend of green and high-value development of biomass. For example, mannose, as a C-2 epimer of glucose, can not only serve as a functional nutritional additive but also possesses pharmacological activity that inhibits tumor proliferation. Therefore, achieving selective isomerization of bulk biomass monosaccharides into rare functional monosaccharides is a high-quality resource utilization pathway that combines atom economy and sustainability.

[0003] The reaction for converting biomass monosaccharides into rare sugars is essentially a stereoconfiguration inversion between the hydrogen atom and hydroxyl group at the C-2 chiral site of the molecule. Current mainstream preparation processes are mainly divided into natural extraction, bio-enzyme catalysis, and chemical catalytic isomerization. Natural extraction is constrained by factors such as raw material origin and harvesting cycle, making it unsuitable for industrial-scale production. Bio-enzyme catalysis systems exhibit excellent stereoisomerization selectivity, but have a narrow tolerance range for process parameters such as reaction temperature and system pH. Furthermore, the enzyme preparation separation and purification process is complex, resulting in high production costs, which severely restricts industrialization. In contrast, chemical catalytic isomerization technology offers strong process adjustability, a wide range of operating conditions, and is easy to implement in continuous production systems, possessing significant potential for industrial application.

[0004] Currently, catalytic systems used for the epimerization reaction of biomass monosaccharides mainly include molybdenum-based catalysts, tin-based molecular sieves, and metal-organic frameworks. However, existing catalytic systems still have significant technical shortcomings. Homogeneous molybdenum-based catalysts have poor recyclability and the active components are prone to dissolution and loss. Heterogeneous catalysts generally require multiple modification steps, use toxic crosslinking agents, and have complicated preparation processes with high energy consumption. Moreover, they often require high-temperature conditions to drive the reaction, which can easily induce various side reactions, significantly reducing the yield and selectivity of the target product and making process scale-up difficult.

[0005] In summary, existing technologies cannot simultaneously meet the requirements of green preparation, extremely simple steps, rapid catalysis, high selectivity, universality to multiple substrates, and ease of industrialization. Developing low-cost, green, and efficient molybdenum-derived catalysts is a core technological challenge for the large-scale production of rare monosaccharides. Summary of the Invention

[0006] The purpose of this invention is to provide a molybdenum-based biomass-based heterogeneous catalyst, its preparation method, and its application, in order to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: On the one hand, the present invention provides a method for preparing a molybdenum-based biomass-based heterogeneous catalyst, comprising the following steps: Step S1: Deacetylated chitosan (viscosity less than 200 mPa·s) is dissolved in a dilute glacial acetic acid solution, while phosphomolybdic acid solution is added dropwise and stirred continuously to obtain a gel suspension of chitosan crosslinked with phosphomolybdic acid; the mass-volume ratio of the deacetylated chitosan, the dilute glacial acetic acid solution, and the phosphomolybdic acid solution is 1:60:20 (g:mL:mL), the volume fraction of the dilute glacial acetic acid solution is 1%-2%, and the molar concentration of the phosphomolybdic acid solution is 0.05 mol / L-0.1 mol / L; Step S2: The gel suspension obtained in step S1 is subjected to solvothermal stirring at 50°C for 12 h to obtain the precursor. Step S3: Wash the precursor obtained in step S2 with ultrapure water and dry it to obtain a molybdenum-based biomass-based heterogeneous catalyst.

[0008] On the other hand, the present invention provides a molybdenum-based biomass-based heterogeneous catalyst, which is prepared by the above-described preparation method.

[0009] On the other hand, the present invention provides an application of a molybdenum-based biomass-based heterogeneous catalyst in the catalytic production of rare sugars from common monosaccharides.

[0010] Compared with the prior art, the specific beneficial effects of the present invention are as follows: This invention uses chitosan as a base and electrostatically crosslinks it with phosphomolybdic acid to form an interfacial polarized microenvironment, thus constructing a highly active catalytic system with an interfacial polarized microenvironment. On the one hand, the synthesis is completed in one step via a solvothermal method in water, which is simple, green, and safe, and the parameters are clear and easy to scale up. On the other hand, the crosslinking of chitosan with phosphomolybdic acid provides effective differential isomerization sites, which can realize the differential isomerization of ordinary monosaccharides into rare sugars in a very short time, with short reaction time and high selectivity. This invention not only synthesizes green, low-cost heterogeneous biomass-derived catalysts to promote the high-value utilization of biomass resources, but also enables the efficient and rapid production of rare sugars with simple catalysts, providing a low-cost green synthesis route for food additives, cosmetics, and synthetic pharmaceuticals. It shows outstanding advantages in terms of energy consumption, safety, process simplicity, and industrialization feasibility. Attached Figure Description

[0011] Figure 1 The image shows the XRD pattern of the CS-PMA prepared in Example 1 of this invention. Figure 2 The FT-IR image of the CS-PMA prepared in Example 1 of this invention; Figure 3 XPS image of CS-PMA prepared in Example 1 of this invention; Figure 4 The results show the conversion rate, yield, and selectivity of the CS-PMA prepared in Example 1 of this invention in the production of rare sugars from common monosaccharides at 110 °C. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0013] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0014] Example 1: A molybdenum-based biomass-based heterogeneous catalyst, the preparation method of which includes the following steps: Step S1: Weigh 1g of chitosan and dissolve it in 60 mL of 1.5% glacial acetic acid solution. Stir until dissolved and homogeneous. Add 20 mL of heteropolyacid solution (0.075 mol / L) containing 2.7g of phosphomolybdic acid hydrate dropwise. Stir the mixture at 700 rpm for 4 h at room temperature to disperse the suspension evenly and obtain a chitosan crosslinked phosphomolybdic acid gel suspension. Step S2: Transfer the gel suspension to an oil bath at 50°C and continue stirring for 12 h. After the reaction is complete, cool to room temperature to obtain the precursor. Step S3: Wash the precursor 1-2 times with ultrapure water (mix the precursor with ultrapure water, stir magnetically at 300 rpm for 5 min, and remove the supernatant by centrifugation (10000 rpm, 3 min), and dry in a 60℃ forced-air drying oven for 12 h to constant weight to obtain a molybdenum-based biomass-based heterogeneous catalyst, denoted as CS-PMA.

[0015] CS-PMA analysis yielded the XRD pattern (X-ray diffraction pattern) as follows: Figure 1 As shown, this demonstrates that CS-PMA contains the inherent structure of chitosan and phosphomolybdic acid; FT-IR (Fourier Transform Infrared Spectroscopy) as shown Figure 2 As shown, this demonstrates that chitosan and phosphomolybdic acid were successfully cross-linked; XPS plot (X-ray photoelectron spectroscopy) as shown Figure 3 As shown, this demonstrates that CS-PMA possesses molybdenum (Mo) active sites.

[0016] Application Example 1: A method for synthesizing mannose, comprising the following steps: 0.06 g of the molybdenum-based biomass-based heterogeneous catalyst CS-PMA prepared in Example 1, 0.18 g of glucose, and 5 mL of water were mixed evenly to obtain a mixture (the mass concentration of glucose in the mixture was 36 g / L, and the mass ratio of CS-PMA to glucose was 1:3). The mixture was magnetically stirred at 110 °C at a stirring rate of 600 rpm. The reaction ended after 10 min. The mixture was then filtered through a 0.22 μm PES (polyethersulfone) membrane. The filtered solution was subjected to liquid chromatography to determine the product, and the conversion rate of glucose and the yield of mannose were calculated. The liquid chromatography conditions were as follows: the chromatographic column was an Aminex HPX-87H, the mobile phase was 0.6 mL / min sulfuric acid solution (5 mM), the column temperature was 50 ℃, and the injection volume was 20 μL; the glucose and mannose detectors were differential detectors, which measured the sample components at 410 nm, and the detector temperature was 35 ℃. like Figure 4 As shown, the yield of mannose was 30.7%, and the conversion rate of glucose was 31.1%.

[0017] Application Example 2: A method for synthesizing lysose, comprising the following steps: 0.06 g of the molybdenum-based biomass-based heterogeneous catalyst CS-PMA prepared in Example 1, 0.15 g of xylose, and 5 mL of water were mixed evenly to obtain a mixture (the mass concentration of xylose in the mixture was 30 g / L, and the mass ratio of CS-PMA to xylose was 1:2.5). The mixture was magnetically stirred at 110 °C at a stirring rate of 600 rpm. The reaction ended after 10 min. The mixture was then filtered through a 0.22 μm PES membrane. The filtered solution was subjected to liquid chromatography to determine the product, and the conversion rate of xylose and the yield of lythreose were calculated. The conditions for liquid chromatography were as follows: the chromatographic column was Aminex HPX-87H, the mobile phase was 0.6 mL / min sulfuric acid solution (5 mM), the column temperature was 50 ℃, the injection volume was 20 μL, the xylose and lythose detectors were differential detectors, the sample components were determined at 410 nm, and the detector temperature was 35 ℃. like Figure 4 As shown, the yield of lysose was 32.5%, and the conversion rate of xylose was 46.5%.

[0018] Application Example 3: A method for synthesizing ribose, comprising the following steps: 0.06 g of the molybdenum-based biomass-based heterogeneous catalyst CS-PMA prepared in Example 1, 0.15 g of arabinose, and 5 mL of water were mixed evenly to obtain a mixture (the mass concentration of arabinose in the mixture was 30 g / L, and the mass ratio of CS-PMA to arabinose was 1:2.5). The mixture was magnetically stirred at 110 °C at a stirring rate of 600 rpm. After 30 min, the reaction was completed. The mixture was then filtered through a 0.22 μm PES membrane. The filtered solution was subjected to liquid chromatography to determine the product, and the conversion rate of arabinose and the yield of ribose were calculated. The conditions for liquid chromatography were as follows: the chromatographic column was Shodex SH1011, the mobile phase was 0.5 mL / min sulfuric acid solution (5 mM), the column temperature was 50 ℃, the injection volume was 10 μL, the arabinose and ribose detectors were differential detectors, the sample components were determined at 410 nm, and the detector temperature was 35 ℃. like Figure 4 As shown, the yield of ribose was 20.7%, and the conversion rate of arabinose was 39.3%.

[0019] The formulas for calculating conversion rate and yield in the above application examples are as follows: Monosaccharide conversion rate (%) = (initial concentration of monosaccharide - concentration of monosaccharide after reaction) / initial concentration of monosaccharide × 100%; Rare sugar yield (%) = Rare sugar production (mol) / Initial monosaccharide addition (mol) × 100%.

[0020] In summary, the molybdenum-based biomass-based heterogeneous catalyst prepared in the embodiments of the present invention can catalyze the epimerization of common monosaccharides such as glucose, xylose, and arabinose under mild conditions in a pure aqueous phase without pH adjustment, and generate rare monosaccharides such as mannose, lythose, and ribose with high selectivity, of which the selectivity for mannose can reach more than 98%.

[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a molybdenum-based biomass-based heterogeneous catalyst, characterized in that, Includes the following steps: Step S1: Dissolve deacetylated chitosan in a dilute glacial acetic acid solution, and simultaneously add phosphomolybdic acid solution dropwise while continuously stirring to obtain a gel suspension of chitosan cross-linked with phosphomolybdic acid; the mass-to-volume ratio of the deacetylated chitosan, the dilute glacial acetic acid solution, and the phosphomolybdic acid solution is 1:60:20 (g:mL:mL), the volume fraction of the dilute glacial acetic acid solution is 1%-2%, and the molar concentration of the phosphomolybdic acid solution is 0.05 mol / L-0.1 mol / L; Step S2: The gel suspension obtained in step S1 is subjected to solvothermal stirring at 50°C for 12 h to obtain the precursor. Step S3: Wash the precursor obtained in step S2 with ultrapure water and dry it to obtain a molybdenum-based biomass-based heterogeneous catalyst.

2. The preparation method of the molybdenum-based biomass-based heterogeneous catalyst according to claim 1, characterized in that, In S1, the stirring rate is 700 rpm and the time is 3-6 hours.

3. The preparation method of the molybdenum-based biomass-based heterogeneous catalyst according to claim 1, characterized in that, In step S3, the specific cleaning process is as follows: the precursor obtained in step S2 is mixed with ultrapure water, magnetically stirred at 300-500 rpm for 5-10 min, and centrifuged at 10000 rpm for 3 min; the cleaning is performed 1-2 times.

4. The preparation method of the molybdenum-based biomass-based heterogeneous catalyst according to claim 1, characterized in that, In S3, the drying temperature is 60 °C and the time is 12 h.

5. A molybdenum-based biomass-based heterogeneous catalyst, characterized in that, It is prepared using the preparation method described in any one of claims 1-4.

6. The application of the molybdenum-based biomass-based heterogeneous catalyst as described in claim 5 in the catalytic production of rare sugars from common monosaccharides.

7. The application according to claim 6, characterized in that, When the common monosaccharide is glucose, the rare sugar is mannose; when the common monosaccharide is xylose, the rare sugar is lysol; when the common monosaccharide is arabinose, the rare sugar is ribose.

8. The application according to claim 6, characterized in that, The process includes the following steps: adding the molybdenum-based biomass-based heterogeneous catalyst and common monosaccharide as described in claim 5 into water, heating and stirring to react, taking out the upper liquid after the reaction, filtering it with a filter membrane, taking the filtered solution, and separating it to obtain the rare sugar.

9. The application according to claim 6, characterized in that, The mass ratio of the molybdenum-based biomass-based heterogeneous catalyst to ordinary monosaccharide is 1:(2-25); the stirring reaction temperature is 110℃, the time is 10-40 min, and the stirring speed is 600 rpm.

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