Method for preparing furfuryl alcohol by catalyzing xylose through inorganic metal molten salt hydrate

Abstract

The invention discloses a method for preparing furfuryl alcohol based on catalysis of xylose by an inorganic metal molten salt hydrate, and belongs to the technical field of biomass catalytic conversion. According to the method, isopropanol is used as a green hydrogen donor, an inorganic metal molten salt hydrate is used as a high-efficiency catalyst, and a one-step catalytic conversion system without participation of hydrogen is constructed by combining the synergistic regulation effect of an auxiliary agent and a solvent. In the system, xylose can be efficiently converted into furfuryl alcohol, and the yield reaches 88% or above. Compared with a traditional hydrogenation process, the method has the advantages that high-pressure hydrogen can be prevented from being used, and the process safety is remarkably improved; the catalyst is low in cost, good in stability and mild in reaction condition (the temperature is 160-200 DEG C, and normal pressure); the method is simple in process flow, easy in product separation and suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention relates to a method for preparing furfuryl alcohol from xylose by catalyzing an inorganic metal molten salt hydrate, and belongs to the technical field of furfuryl alcohol preparation. Background Art

[0002] Lignocellulosic biomass is Earth's most abundant renewable carbon resource, and the targeted conversion of its components (cellulose, hemicellulose, and lignin) is considered an important pathway to replace petroleum-based chemicals. Hemicellulose, a major component of lignocellulosic biomass, and its hydrolysis product, xylose, are key platform molecules for the synthesis of high-value-added chemicals. Furfuryl alcohol, a key green chemical derived primarily from the deep processing of xylose and furfural, is widely used in the production of resins, fuel additives, and pharmaceutical intermediates.

[0003] Typically, furfuryl alcohol is produced through a two-step process: xylose is dehydrated with acid to produce furfural, which is then catalyzed by precious metals (such as Pd / C or Ru / Al2O3) to produce the target product, furfuryl alcohol. However, this process has drawbacks such as lengthy procedures, high energy consumption, and significant hydrogen storage risks. Especially when high-pressure hydrogen is used, equipment safety requirements are stringent, and the cost of precious metal catalysts exceeds 40% of the total cost. CN 106810516 A discloses a method for producing furfuryl alcohol by hydrogenating furfural. However, the direct use of hydrogen in the hydrogenation process increases safety risks.

[0004] Inorganic molten salt hydrate (MSH), as an emerging non-traditional solvent system, exhibits unique advantages in biomass conversion reactions. MSH can release acid-base active sites in situ at high temperatures. By adjusting its composition and structure, the reaction microenvironment can be precisely controlled, thereby improving the selectivity of the target product and the reaction efficiency. Our research has found that isopropanol can act as a hydrogen source in the catalytic reaction during the xylose conversion process. Studies have shown that urea / choline chloride-based deep eutectic solvents (DES) can form directional hydrogen bonds with the hydroxyl groups of xylose through the amino groups of the urea molecule, promoting C-O bond cleavage and cyclodehydration. Therefore, if the directional activation effect of DES can be combined with the hydrogen-donating capacity of isopropanol to construct a "dehydration-hydrogenation" tandem catalytic system, it is expected to achieve efficient conversion of xylose to furfuryl alcohol in a "one-step" manner. This avoids the risks associated with the direct use of H2, simplifies product separation, and significantly improves product yield. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing furfuryl alcohol from xylose by catalyzing an inorganic metal molten salt hydrate. The method does not directly use H2. Instead, isopropanol is used as a hydrogen donor, an inorganic metal molten salt hydrate is used as a catalyst, and an organic combination of an auxiliary agent and a solvent is combined to achieve the preparation of furfuryl alcohol from xylose in a one-step process in a constructed catalytic reaction system.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A method for preparing furfuryl alcohol by catalyzing xylose with an inorganic metal molten salt hydrate comprises the following steps:

[0008] (1) constructing a catalytic reaction system: taking an inorganic metal molten salt hydrate, a hydrogen source, an auxiliary agent, and a solvent and mixing them in proportion to obtain a uniform catalytic reaction system;

[0009] (2) One-step synthesis of furfuryl alcohol: Add biomass raw materials to the above catalytic reaction system, place it in a pressure-resistant reaction vessel, stir and react at 160-200°C for 1-6 hours, and quickly cool after the reaction is completed to obtain furfuryl alcohol.

[0010] Preferably, the inorganic metal molten salt hydrate is MCl x ·One or more of 3-5H2O, wherein M is Zn, Ca, Al, Sn or Cr, and x=2-4.

[0011] Preferably, the hydrogen source is isopropanol.

[0012] Preferably, the auxiliary agent is one or more of urea or choline chloride.

[0013] Preferably, the solvent is one of isopropyl alcohol, N,N-dimethylformamide, dimethyl sulfoxide, and methyl isobutyl ketone.

[0014] Preferably, the biomass raw material is one or more of xylose, hemicellulose or xylooligosaccharides.

[0015] Preferably, the usage ratio of the biomass raw material, the inorganic metal molten salt hydrate, the hydrogen source, the auxiliary agent and the solvent is 0.1-0.2 g: 5-10 g: 2-5 mL: 0.1-0.5 g: 5-10 mL.

[0016] Preferably, the reaction temperature in step (2) is 170° C. and the reaction time is 5 h.

[0017] The inorganic metal molten salt hydrate in the present invention undergoes metal hydrolysis in water as the temperature increases, releasing acid-base active centers in situ. The released acid-base sites catalyze the dehydration and hydrogenation of xylose. Isopropyl alcohol acts as a hydrogen donor in the reaction. Auxiliary agents such as urea or choline chloride can regulate the reaction process and inhibit side reactions (polymerization), thereby increasing the yield of the target product. The above raw materials, when used in optimal proportions and under optimal process conditions, increase the yield of the furfuryl alcohol product.

[0018] Compared with the prior art, the present invention has the following beneficial effects: the present invention uses an inorganic metal molten salt hydrate as a homogeneous catalyst, thereby avoiding coking and deactivation of a heterogeneous catalyst and increasing its service life; introduces isopropyl alcohol as a hydrogen source, thereby eliminating the dangers caused by the original use of hydrogen and high pressure and simplifying process conditions; uses an amine auxiliary agent, thereby suppressing the occurrence of side reactions and improving product selectivity by regulating intermediate products; and the raw materials are mixed in an optimal ratio to form a highly efficient catalytic reaction system, significantly improving the yield of the target product furfuryl alcohol. Under one-pot conditions, the yield of furfuryl alcohol is increased from the original approximately 60% to more than 88%. When the optimal ratio of the raw materials is exceeded, side reactions increase and the yield of furfuryl alcohol is significantly affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The product furfuryl alcohol obtained in Example 2 of the present invention is 13 C-NMR spectrum;

[0020] Figure 2 2 is the mass spectrum of the product furfuryl alcohol obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0022] Example 1

[0023] Weigh 5.0g of CaCl2·4H2O, 4mL of isopropanol, 0.3g of urea, and 5mL of methyl isobutyl ketone and thoroughly stir to combine. Add 0.1g of xylose and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 170°C for 5 hours. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product of 93.2%.

[0024] Example 2

[0025] Weigh 3.0g of CaCl2·4H2O, 3.0g of AlCl3·5H2O, 3mL of isopropyl alcohol, 0.2g of choline chloride, and 5mL of methyl isobutyl ketone (MIBK) and thoroughly stir. Add 0.1g of xylose and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 200°C for 1 hour. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product of 91.5%.

[0026] Example 3

[0027] Weigh 5.0g of SnCl2·5H2O, 3.0g of AlCl3·5H2O, 3mL of isopropyl alcohol, 0.1g of urea, and 10mL of DMF and thoroughly stir. Add 0.2g of hemicellulose and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 200°C for 2 hours. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product of 92.3%.

[0028] Example 4

[0029] Weigh 10.0g of AlCl3·5H2O, 5mL of isopropyl alcohol, 0.5g of choline chloride, and 10mL of dimethyl sulfoxide (DMSO) and stir thoroughly. Add 0.2g of xylo-oligosaccharide and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 160°C for 6 hours. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product yield of 90.4%.

[0030] Example 5

[0031] Weigh 8.0 g of CrCl₃·5H₂O, 4 mL of isopropanol, 0.5 g of urea, and 8 mL of DMF and stir thoroughly. Add 0.1 g of xylose and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 180°C for 6 hours. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product of 89.6%.

[0032] Example 6

[0033] Weigh 4.0g of ZnCl2·3H2O, 3.0g of CaCl2·4H2O, 8mL of isopropyl alcohol, and 0.3g of choline chloride and thoroughly stir to combine. Add 0.15g of hemicellulose and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 190°C for 3 hours. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product of 91.1%.

[0034] Example 7

[0035] Weigh 6.0g of SnCl2·5H2O, 3mL of isopropyl alcohol, 0.4g of choline chloride, and 6mL of dimethyl sulfoxide and stir thoroughly. Add 0.15g of xylo-oligosaccharide and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 180°C for 4 hours. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product yield of 88.3%.

[0036] Comparative Example 1

[0037] Weigh 3.0g of CaCl2·4H2O, 3.0g of AlCl3·5H2O, 3mL of isopropanol, and 5mL of methyl isobutyl ketone (MIBK) and thoroughly stir. Add 0.15g of xylose and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 200°C for 1 hour. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product of 66.4%.

[0038] This comparative example 1 is the same as Example 2 except that choline chloride is not contained. From the above results, it can be seen that in the absence of an auxiliary agent, side reactions increase and the yield of furfuryl alcohol decreases significantly.

[0039] Comparative Example 2

[0040] Weigh 3.0g of CaCl2·4H2O, 3.0g of AlCl3·5H2O, 3mL of isopropyl alcohol, 0.05g of choline chloride, and 5mL of methyl isobutyl ketone (MIBK) and thoroughly stir. Add 0.1g of xylose and stir thoroughly. Transfer the mixture to a pressure-resistant microreactor and stir at 200°C for 1 hour. After the reaction is complete, cool rapidly. The sample composition is determined by gas chromatography-mass spectrometry and liquid chromatography, yielding a calculated product of 70.1%.

[0041] It should be noted that the above embodiments are only some of the preferred embodiments of the present invention, and not all of them. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

Claims

1. A method for preparing furfuryl alcohol from xylose catalyzed by an inorganic metal molten salt hydrate, characterized in that: It includes the following steps: (1) constructing a catalytic reaction system: taking an inorganic metal molten salt hydrate, a hydrogen source, an auxiliary agent, and a solvent and mixing them in proportion to obtain a uniform catalytic reaction system; (2) One-step synthesis of furfuryl alcohol: add biomass raw materials to the above catalytic reaction system, place it in a pressure-resistant reaction vessel, stir and react at 160-200°C for 1-6 hours, and quickly cool after the reaction is completed. Furfuryl alcohol is obtained after separation.

2. The method for preparing furfuryl alcohol from xylose by catalysis of an inorganic metal molten salt hydrate according to claim 1, wherein The inorganic metal molten salt hydrate is MCl x ·One or more of 3-5H2O, wherein M is a combination of one or more of Zn, Ca, Al, Sn or Cr, and x=2-4.

3. The method for preparing furfuryl alcohol from xylose by catalysis of inorganic metal molten salt hydrate according to claim 1, wherein The hydrogen source is isopropanol.

4. The method for preparing furfuryl alcohol from xylose by catalysis of inorganic metal molten salt hydrate according to claim 1, wherein The auxiliary agent is one or more of urea or choline chloride.

5. The method for preparing furfuryl alcohol from xylose by catalysis of inorganic metal molten salt hydrate according to claim 1, wherein The solvent is one of isopropyl alcohol, N,N-dimethylformamide, dimethyl sulfoxide and methyl isobutyl ketone.

6. The method for preparing furfuryl alcohol from xylose by catalysis of an inorganic metal molten salt hydrate according to claim 1, wherein The biomass raw material is one or more of xylose, hemicellulose or xylooligosaccharides.

7. The method for preparing furfuryl alcohol from xylose by catalysis of an inorganic metal molten salt hydrate according to claim 1, wherein The usage ratio of the biomass raw material, the inorganic metal molten salt hydrate, the hydrogen source, the auxiliary agent and the solvent is 0.1-0.2 g: 5-10 g: 2-5 mL: 0.1-0.5 g: 5-10 mL.

8. The method for preparing furfuryl alcohol from xylose by catalysis of an inorganic metal molten salt hydrate according to claim 1, wherein The reaction temperature in step (2) is 170° C. and the reaction time is 5 h.

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