Process for the catalytic synthesis of 2,5-dimethylol tetrahydrofuran from 5-hydroxymethylfurfural

Abstract

The present disclosure provides a method for catalyzing 5-hydroxymethylfurfural to synthesize 2,5-dihydroxymethyltetrahydrofuran, which comprises: dissolving 5-hydroxymethylfurfural and alkaline substance in formaldehyde solution, adding a ruthenium and zinc oxide composite catalyst, and obtaining a reaction solution; mixing the reaction solution and placing it in a sealed reaction container; then introducing nitrogen into the reaction container; and in the nitrogen atmosphere, using the ruthenium and zinc oxide composite catalyst to catalyze the decomposition of formaldehyde to generate hydrogen in situ under alkaline conditions, so that 5-hydroxymethylfurfural undergoes a hydrogenation reaction to obtain 2,5-dihydroxymethyltetrahydrofuran.

Description

Technical Field

[0001] This disclosure relates to the field of organic synthesis technology, specifically to a method for catalytic synthesis of 2,5-dihydroxymethyltetrahydrofuran from 5-hydroxymethylfurfural. Background Technology

[0002] 2,5-Dihydroxymethyl-tetrahydrofuran (DHMTHF) exhibits excellent stability and good solubility, making it superior in chemical reactions. DHMTHF possesses a rigid furan ring and symmetrical hydroxyl functional groups, allowing it to be further converted into high-value-added bio-based platform derivatives. Furthermore, DHMTHF shows broad application prospects in the development of bio-based polyesters. Currently, DHMTHF is widely used in packaging, agriculture, and chemical industries, for example, as an insecticide, surfactant, stabilizer, lubricant, decolorizing agent, and plasticizer. Its high-value-added characteristics and the environmentally friendly synthesis method through selective hydrogenation make it a promising candidate for applications in chemical engineering and materials science.

[0003] 5-Hydroxymethylfurfural (5-HMF), as one of the most promising biomass-based platform molecules, can be converted into various high-value-added derivatives such as 2,5-furandicarboxylic acid (FDCA), 2,5-furandiethanol (DHMF), 2,5-dihydroxymethyltetrahydrofuran (DHMTHF), 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furancarboxylic acid, and 2,5-dimethylfuran through reactions such as oxidation, hydrogenation, and etherification. Currently, the synthesis of DHMTHF mainly relies on the catalytic hydrogenation of 5-hydroxymethylfurfural. In related technologies, those skilled in the art have explored various catalytic methods to achieve this process, including the use of noble metal catalysts, non-noble metal catalysts, and ionic liquids. However, these catalytic methods require high hydrogen pressure and stringent catalyst requirements, leading to increased costs and complex processes. Meanwhile, with the promotion of green chemistry concepts, more environmentally friendly and economical synthesis methods are constantly being explored. With its unique properties and wide range of applications, DHMTHF is becoming a research hotspot and is expected to achieve more breakthroughs and innovations in the future.

[0004] Therefore, in order to further reduce the demand for high-pressure equipment in hydrogenation reactions and ensure the safety of hydrogen use under high temperature and high pressure, those skilled in the art urgently need to find a catalyst with high catalytic activity and selectivity to develop a safe, low-cost, and simple synthesis method for DHMTHF, and optimize the synthesis efficiency and purity of DHMTHF. Summary of the Invention

[0005] In view of the above, in order to solve at least one technical problem mentioned in the related art and other aspects, this disclosure proposes a method for catalytic synthesis of 2,5-dihydroxymethyltetrahydrofuran from 5-hydroxymethylfurfural. The method includes: dissolving 5-hydroxymethylfurfural and an alkaline substance in formaldehyde solution, adding a ruthenium and zinc oxide composite catalyst (hereinafter referred to as ruthenium / zinc oxide composite catalyst or Ru / ZnO catalyst), mixing the resulting reaction solution and placing it in a sealed reaction vessel; then introducing nitrogen gas into the reaction vessel, and under the nitrogen atmosphere, using the ruthenium / zinc oxide composite catalyst under alkaline conditions to catalyze the in-situ decomposition of formaldehyde to generate hydrogen gas, thereby causing 5-hydroxymethylfurfural to undergo a hydrogenation reaction to obtain 2,5-dihydroxymethyltetrahydrofuran.

[0006] According to embodiments of this disclosure, the alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate; the concentration of formaldehyde in the formaldehyde solution is 1-5 mol / L; and the mass molar ratio of the alkaline substance to formaldehyde is (0.5-2):1.

[0007] According to embodiments of this disclosure, the mass ratio of the ruthenium / zinc oxide composite catalyst to 5-hydroxymethylfurfural is (0.1-1):1.

[0008] According to embodiments of this disclosure, in the hydrogenation reaction, the reaction pressure is 0.05–0.1 MPa, the reaction temperature is 150–200 °C, and the reaction time is 1–24 h.

[0009] According to embodiments of this disclosure, the ruthenium / zinc oxide composite catalyst has a mesoporous structure, with ruthenium serving as the catalytic center dispersed on the surface of the zinc oxide particle support.

[0010] According to embodiments of this disclosure, the ruthenium loading is 2-10%, and the pore size of the mesoporous structure is 20-30 nm.

[0011] According to embodiments of this disclosure, the ruthenium / zinc oxide composite catalyst is obtained through the following steps: dissolving zinc salt and ruthenium salt in water to obtain a reactant solution; adding an alkaline precipitant to the reactant solution to carry out a precipitation reaction, making the pH of the reactant solution greater than 10; aging, filtering, washing, and drying the obtained precipitate to obtain a precipitate powder; calcining the precipitate powder in an air atmosphere to obtain a precursor powder; and thermally reducing the precursor powder in a mixed atmosphere of hydrogen and nitrogen to obtain the ruthenium / zinc oxide composite catalyst.

[0012] According to embodiments of this disclosure, the zinc salt includes any one of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate; the ruthenium salt includes ruthenium chloride or ruthenium acetate; the molar ratio of zinc salt to soluble ruthenium salt is (0.05-0.2):1; and the alkaline precipitant includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0013] According to embodiments of this disclosure, the aging treatment temperature is 20–30°C, and the aging treatment time is 12–24 hours.

[0014] According to embodiments of this disclosure, the calcination temperature is 200–500°C, and the calcination time is 1–10 h.

[0015] According to embodiments of this disclosure, during the thermal reduction process, the reaction temperature is 100–300°C, the reaction time is 1–10 h, and the volume fraction of hydrogen in the mixed atmosphere is 10%–50%.

[0016] According to embodiments of this disclosure, a method for catalytically preparing 2,5-dihydroxymethyltetrahydrofuran from 5-hydroxymethylfurfural is proposed. This method does not require the additional introduction of hydrogen gas above standard pressure. Under the action of a ruthenium / zinc oxide composite catalyst, toxic and harmful formaldehyde is converted into a clean hydrogen donor and reaction solvent, and 2,5-dihydroxymethyltetrahydrofuran is prepared under mild conditions. The preparation process is simple to operate, has high catalytic selectivity, and the yield, purity, and stability of the product 2,5-dihydroxymethyltetrahydrofuran are high. This not only conforms to the concept of sustainable development but also improves the safety of the reaction. Attached Figure Description

[0017] Figure 1 This is a flowchart of the preparation method for synthesizing 2,5-dihydroxymethyltetrahydrofuran by catalytic synthesis of 5-hydroxymethylfurfural in the embodiments of this disclosure;

[0018] Figure 2 This is a flowchart illustrating the preparation method of the ruthenium / zinc oxide composite catalyst in this embodiment of the present disclosure;

[0019] Figure 3 The specific surface area (BET plot) of the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure is shown.

[0020] Figure 4 This is the Raman spectrum of the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure;

[0021] Figure 5 The images shown are X-ray photoelectron spectroscopy (XPS) images of the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure. Among them, a is the XPS test image of the ruthenium / zinc oxide composite catalyst, b is the XPS test image of oxygen, c is the XPS test image of ruthenium, and d is the XPS test image of zinc.

[0022] Figure 6 This is the X-ray diffraction (XRD) pattern of the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0024] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this disclosure.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0026] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0027] Similarly, to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present disclosure. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0029] 5-Hydroxymethylfurfural (5-HMF) can be hydrogenated to 2,5-furandimethylethanol (DHMF), and DHMF can be further hydrogenated to 2,5-dihydroxymethyltetrahydrofuran (DHMTHF). Therefore, DHMTHF is a derivative of 5-HMF obtained through deep hydrogenation and is a low-toxicity, highly stable, and biodegradable bio-based solvent. However, because 5-HMF contains hydroxyl and aldehyde active groups, it is prone to ring-opening and degradation side reactions during selective hydrogenation, which poses a certain challenge to the selective reduction of 5-HMF to prepare DHMTHF.

[0030] In related technologies, the conversion of 5-HMF to DHMTHF inevitably requires the introduction of high-pressure hydrogen gas to achieve the conversion, which places extremely high demands on the pressure resistance of the equipment and the safety of the reaction. Meanwhile, existing catalysts have various problems, such as complex preparation methods, poor selectivity, and large catalyst requirements, which in turn lead to low yields and low purity of the target product DHMTHF.

[0031] As used in this disclosure, the term "high-pressure hydrogen" refers to a hydrogen atmosphere at a pressure higher than one standard atmosphere.

[0032] This disclosure describes a process in which formaldehyde is introduced as a solvent and hydrogen donor in the conversion of 5-HMF to DHMTHF. A novel ruthenium / zinc oxide composite catalyst is designed to catalyze the production of hydrogen from formaldehyde and to selectively hydrogenate 5-HMF, thereby completing the conversion of 5-HMF to DHMTHF.

[0033] Figure 1 This is a flowchart of the preparation method for synthesizing 2,5-dihydroxymethyltetrahydrofuran by catalytic synthesis of 5-hydroxymethylfurfural in the embodiments of this disclosure.

[0034] This disclosure presents a method for catalytically synthesizing 2,5-dihydroxymethyltetrahydrofuran from 5-hydroxymethylfurfural, such as... Figure 1 As shown, the method includes the following steps S101 to S102:

[0035] Step S101: Dissolve 5-hydroxymethylfurfural and an alkaline substance in formaldehyde solution, add ruthenium and zinc oxide composite catalyst, mix the resulting reaction solution and place it in a sealed reaction container;

[0036] Step S102: Nitrogen gas is introduced into the reaction vessel. Under the nitrogen atmosphere, ruthenium and zinc oxide composite catalysts are used under alkaline conditions to catalyze the in-situ decomposition of formaldehyde to produce hydrogen gas, which causes 5-hydroxymethylfurfural to undergo a hydrogenation reaction to obtain 2,5-dihydroxymethyltetrahydrofuran.

[0037] According to embodiments of this disclosure, a method for catalytically preparing 2,5-dihydroxymethyltetrahydrofuran from 5-hydroxymethylfurfural is proposed. This method does not require the additional introduction of hydrogen gas above standard pressure. Under the action of a ruthenium and zinc oxide composite catalyst (hereinafter referred to as a ruthenium / zinc oxide composite catalyst or Ru / ZnO catalyst), toxic and harmful formaldehyde is converted into a clean hydrogen donor and reaction solvent, and 2,5-dihydroxymethyltetrahydrofuran is prepared under mild conditions. The preparation process is simple to operate, has high catalytic selectivity, and the yield, purity, and stability of the product 2,5-dihydroxymethyltetrahydrofuran are high. This not only conforms to the concept of sustainable development but also improves the safety of the reaction.

[0038] The reaction formula for preparing DHMTHF from 5-HMF is as follows (1):

[0039]

[0040] During hydrogenation, 5-hydroxymethylfurfural first generates furan-diethanol intermediate, and then further hydrogenates to obtain tetrahydrofuran-diethanol. The hydrogenation of the aldehyde double bond is faster than that of the unsaturated furan ring, thus yielding 2,5-dihydroxymethyltetrahydrofuran.

[0041] According to embodiments of this disclosure, the alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate; the concentration of formaldehyde in the formaldehyde solution is 1-5 mol / L; and the mass molar ratio of the alkaline substance to formaldehyde is (0.5-2):1.

[0042] According to embodiments of this disclosure, the mass ratio of the ruthenium / zinc oxide composite catalyst to 5-hydroxymethylfurfural is (0.1-1):1.

[0043] According to embodiments of this disclosure, in the hydrogenation reaction, the reaction pressure is 0.05–0.1 MPa, the reaction temperature is 150–200 °C, and the reaction time is 1–24 h.

[0044] According to embodiments of this disclosure, no additional high-pressure hydrogen gas is required in the hydrogenation reaction, which reduces the requirements for reaction conditions compared to related technologies and improves the safety of the reaction.

[0045] According to embodiments of this disclosure, the ruthenium / zinc oxide composite catalyst has a mesoporous structure, with ruthenium serving as the catalytic center dispersed on the surface of the zinc oxide particle support.

[0046] According to embodiments of this disclosure, the Ru / ZnO catalyst has a mesoporous structure with a large contact area. Elemental ruthenium serves as the active center, dispersed on the surface of porous zinc oxide particles, constituting a heterogeneous composite catalyst. Elemental ruthenium catalyzes the in-situ decomposition of formaldehyde to generate hydrogen, and also activates the generated hydrogen. Zinc oxide acts as a support, preventing the aggregation of elemental ruthenium to maintain the high activity of the heterogeneous composite catalyst. Simultaneously, it can form hydrogen bonds with the aldehyde groups in 5-hydroxymethylfurfural, which is beneficial for ruthenium-catalyzed hydrogenation of 5-hydroxymethylfurfural.

[0047] According to embodiments of this disclosure, the ruthenium loading is 2-10%, and the pore size of the mesoporous structure is 20-30 nm.

[0048] According to embodiments of this disclosure, the catalyst loading and the amount of catalyst used have no effect on the amount of hydrogen produced. The formaldehyde concentration and the concentration of alkaline substances affect the hydrogen production from formaldehyde: when the concentration of alkaline substances is low, the hydrogen production activity is relatively low, and when the concentration of sodium hydroxide is too high, the amount of hydrogen produced decreases.

[0049] Figure 2 This is a flowchart illustrating the preparation method of the ruthenium / zinc oxide composite catalyst in this embodiment.

[0050] According to embodiments of this disclosure, the preparation method of the ruthenium / zinc oxide composite catalyst is as follows: Figure 2 As shown, the process includes the following steps S201 to S205:

[0051] Step S201: Dissolve zinc salt and ruthenium salt in water to obtain a reactant solution;

[0052] Step S202: Add an alkaline precipitant to the reactant solution to carry out a precipitation reaction, so that the pH of the reactant solution is greater than 10;

[0053] Step S203: The obtained precipitate is aged, filtered, washed and dried to obtain precipitate powder;

[0054] Step S204: Calcining the precipitate powder in air atmosphere to obtain precursor powder;

[0055] Step S205: In a mixed atmosphere of hydrogen and nitrogen, the precursor powder is thermally reduced to obtain a ruthenium / zinc oxide composite catalyst.

[0056] According to embodiments of this disclosure, zinc salt and ruthenium salt are first co-dissolved, and a mixed precipitate of ruthenium hydroxide and zinc hydroxide is prepared by co-precipitation under the action of an alkaline precipitant. Then, the mixed precipitate is calcined to convert ruthenium hydroxide and zinc hydroxide into ruthenium oxide and zinc oxide, thereby strengthening the interaction between ruthenium and zinc to enhance the composite catalytic performance. Finally, the ruthenium oxide is heated in a stable atmosphere to reduce ruthenium oxide to elemental ruthenium, thus obtaining a ruthenium / zinc oxide composite catalyst.

[0057] According to embodiments of this disclosure, the zinc salt includes any one of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate; the ruthenium salt includes ruthenium chloride or ruthenium acetate; the molar ratio of the zinc salt to the soluble ruthenium salt is (0.05-0.2):1, for example, it can be 0.05:1, 0.1:1, 0.15:1, or 0.2:1; the alkaline precipitant includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0058] According to embodiments of this disclosure, the alkaline precipitant used in the preparation of the Ru / ZnO catalyst may be the same as or different from the alkaline substance selected in the catalytic synthesis of 2,5-dihydroxymethyltetrahydrofuran from 5-hydroxymethylfurfural.

[0059] According to embodiments of this disclosure, the alkaline precipitant added to the reactant solution in step S201 reacts with the dissolved ruthenium and zinc salts to generate hydroxide precipitates and soluble sodium or potassium salts. Therefore, the precipitate obtained in step S202 needs to be washed to remove impurities for subsequent processing.

[0060] According to an embodiment of this disclosure, in step S203, the drying temperature is 70–100°C, and the drying time is 8–12 hours. After drying, the precipitate needs to be ground uniformly to obtain precipitate powder, and then subjected to subsequent calcination to ensure the uniformity of calcination.

[0061] According to an embodiment of this disclosure, in step S203, the aging treatment temperature is 20-30°C, and the aging treatment time is 12-24 hours.

[0062] According to embodiments of this disclosure, the precipitate obtained in step S202 can be aged to form uniformly sized precipitate particles, and the impurities that were not cleaned properly can be transferred into the solution, resulting in a more stable structure for the precipitate.

[0063] According to an embodiment of this disclosure, in step S204, the calcination temperature is 200–500°C, and the calcination time is 1–10 h.

[0064] According to embodiments of this disclosure, the calcination process removes residual volatile components from the precursor powder, allowing the precursor powder to transform into catalyst components in an air atmosphere. This is a prerequisite for the Ru / ZnO catalyst to exhibit excellent catalytic performance.

[0065] According to embodiments of this disclosure, after calcination, the precursor solid needs to be ground uniformly before thermal reduction sintering to ensure the uniformity of thermal reduction sintering.

[0066] According to embodiments of this disclosure, during the thermal reduction process, the reaction temperature is 100–300°C, the reaction time is 1–10 h, and the volume fraction of hydrogen in the mixed atmosphere is 10%–50%.

[0067] According to embodiments of this disclosure, the purpose of thermal reduction treatment is to reduce ruthenium oxide to elemental ruthenium, that is, to convert oxidized ruthenium to a reduced state, exhibiting an active metallic state, while zinc oxide is not reduced under these conditions because the reduction temperature has not been reached.

[0068] It should be noted that the described embodiments are merely some, not all, of the embodiments disclosed herein. Other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are all within the scope of protection of this disclosure.

[0069] Example 1-1: Preparation of 5% Ru / ZnO catalyst

[0070] RuCl3·3H2O (2.58 g, 0.009894 mol) and ZnCl2 (31.82 g, 0.2334 mol) were dissolved in 400 mL of deionized water to prepare a salt solution, which served as the reactant solution. The reactant solution was black, and its pH was measured to be 2.3 using a pH meter.

[0071] Dissolve 20g of NaOH in 500mL of water to prepare a 1mol / L NaOH solution as a precipitant. Under stirring, slowly add the precipitant dropwise into the reactant solution to precipitate the product, making the pH of the solution greater than 10. The pH is measured to be 11-12 by a pH meter.

[0072] After precipitation, continue stirring and aging overnight. After aging, filter and wash the precipitate until neutral. The mass of the precipitate after washing is 144.2g. Dry the washed precipitate at 80℃ for 12h. The mass of the dried precipitate powder is 23.8g.

[0073] The dried precipitate powder was calcined in a tube furnace at 300°C for 2 hours in air atmosphere, and the solid mass of the precursor powder obtained after calcination was 20.1 g.

[0074] The calcined precursor powder was reduced in a tube furnace at 200°C for 3 hours under a 10% H2 / N2 mixed atmosphere to obtain a 5% Ru / ZnO catalyst with a mass of 19.1 g.

[0075] The structure of the 5% Ru / ZnO catalyst prepared in Example 1-1 was characterized as follows:

[0076] Figure 3 This is a BET plot showing the specific surface area of ​​the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure.

[0077] like Figure 3 As shown, the BET results indicate that the specific surface area of ​​the 5% Ru / ZnO catalyst prepared in Example 1-1 is 4.2097 m². 2 / g, with an average pore diameter (4V / A by BET) of 25.4nm, exhibiting a mesoporous structure. The suitable pore size is conducive to the adsorption of substrates and the separation of products.

[0078] Figure 4 This is the Raman spectrum of the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure.

[0079] like Figure 4 As shown, the Raman spectrum of the 5% Ru / ZnO catalyst prepared in Example 1-1 at 324 cm⁻¹ is... -1 and 431cm -1 The Raman band at this location was assigned to ZnO with a wurtzite (hexagonal) structure, belonging to the P63mc space group, at 574 cm⁻¹. -1 The Raman peak of Eg is shown at [location], corresponding to RuO2 in the Ru / ZnO sample.

[0080] Figure 5 The images show the X-ray photoelectron spectroscopy (XPS) spectra of the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure, where a is the XPS test pattern of the ruthenium / zinc oxide composite catalyst, b is the XPS test pattern of oxygen, c is the XPS test pattern of ruthenium, and d is the XPS test pattern of zinc.

[0081] like Figure 5 As shown, the 5% Ru / ZnO catalyst prepared in Example 1-1 clearly shows the presence of Ru, Zn and O elements, indicating the composition of the catalyst.

[0082] Figure 6 This is the X-ray diffraction (XRD) pattern of the ruthenium / zinc oxide composite catalyst prepared in Example 1-1 of this disclosure.

[0083] like Figure 6 As shown, all diffraction peaks of the 5% Ru / ZnO catalyst prepared in Example 1-1 can be attributed to the hexagonal wurtzite structure of ZnO (JCPDS Card 36-1451). No changes in the XRD peaks corresponding to RuO2 and the ZnO crystal structure were observed, indicating that Ru has good dispersion on the zinc oxide support, which is more conducive to the oxidation reaction.

[0084] The above analysis shows that the 5% Ru / ZnO catalyst prepared in Example 1-1 of this disclosure has a mesoporous structure and contains both Ru and ZnO. Due to the high dispersion of Ru, no obvious Ru-derived peaks were observed on XRD. The highly dispersed active Ru has a positive effect on the activity of the Ru / ZnO catalyst and the selectivity of the target product DHMTHF.

[0085] Examples 1-2: Preparation of 3% Ru / ZnO catalyst

[0086] The specific preparation method is the same as in Example 1-1, except that the amount of RuCl3·3H2O used is 1.55g and the amount of ZnCl2 used is 32.49g.

[0087] Examples 1-3: Preparation of 7% Ru / ZnO catalyst

[0088] The specific preparation method is the same as in Example 1-1, except that the amount of RuCl3·3H2O used is 3.62g and the amount of ZnCl2 used is 31.15g.

[0089] Examples 1-4: Preparation of 9% Ru / ZnO catalyst

[0090] The specific preparation method is the same as in Example 1-1, except that the amount of RuCl3·3H2O used is 4.66g and the amount of ZnCl2 used is 30.48g.

[0091] Examples 1-5: Preparation of 5% Ru / ZnO catalyst

[0092] The specific preparation method is the same as in Example 1-1. The difference from Example 1-1 is that, when the precursor powder is reduced to obtain the Ru / ZnO catalyst, the reaction conditions are that the calcined precursor powder is reduced in a tube furnace at 200°C for 2 hours under a 10% H2 / N2 mixed atmosphere.

[0093] Examples 1-6: Preparation of 5% Ru / ZnO catalyst

[0094] The specific preparation method is the same as in Example 1-1. The difference from Example 1-1 is that, when processing the precursor powder by calcining the precipitate powder, the reaction conditions are to calcine the dried precipitate in an air atmosphere at 300°C for 5 hours; when processing the precursor powder by reducing it to obtain the Ru / ZnO catalyst, the reaction conditions are to reduce the calcined precursor powder in a tube furnace at 200°C for 5 hours in a 10% H2 / N2 mixed gas atmosphere.

[0095] Examples 1-7: Preparation of 5% Ru / ZnO catalyst

[0096] The specific preparation method is the same as in Example 1-1. The difference from Example 1-1 is that, when processing the precursor powder by calcining the precipitate powder, the reaction conditions are to calcine the dried precipitate in an air atmosphere at 400°C for 2 hours; when processing the precursor powder by reducing it to obtain the Ru / ZnO catalyst, the reaction conditions are to reduce the calcined precursor powder in a tube furnace at 300°C for 3 hours in a 10% H2 / N2 mixed gas atmosphere.

[0097] Example 2-1: Synthesis of DHMTHF

[0098] 5-HMF (2g, 15.9mmol) and sodium hydroxide (2.4g, 0.06mol) were dissolved in 20mL of formaldehyde solution (formaldehyde concentration was 3mol / L), and then 2g of the 5% Ru / ZnO catalyst prepared in Example 1-1 was added.

[0099] After the reaction solutions are mixed, they are placed in a sealed reactor. Nitrogen gas is introduced to fully purge the air from the reactor, and the reaction is carried out at 170°C for 6 hours in an N2 atmosphere with a pressure of 0.05 MPa. After the reaction is complete, the mixture is cooled, the air is vented, and the reaction solution is removed.

[0100] The reaction solution was sampled and tested under the following conditions:

[0101] The chromatographic column was Analytical Technology OV-1701, 30m × 0.32mm × 1.8μm; the injection port temperature was 240℃, and the detector temperature was 260℃; the temperature program was: initial temperature 80℃, hold for 2 min, increase to 250℃ at 20℃ / min, hold for 5 min; the carrier gas flow rate was 2mL / min, and the split ratio was 20:1.

[0102] Liquid chromatography analysis showed that the yield of DHMTHF was 93.8% and the purity was 98.1%.

[0103] Example 2-2: Synthesis of DHMTHF

[0104] The specific preparation method is the same as in Example 2-1, except that sodium hydroxide is replaced with potassium carbonate (8.30 g, 0.06 mol).

[0105] Test results showed that the yield of DHMTHF was 54.3% and the purity was 97.3%.

[0106] Example 2-3: Synthesis of DHMTHF

[0107] The specific preparation method is the same as in Example 2-1, except that sodium hydroxide is replaced with potassium hydroxide (3.37g, 0.06mol).

[0108] Test results showed that the yield of DHMTHF was 85.6% and the purity was 97.6%.

[0109] Examples 2-4: Synthesis of DHMTHF

[0110] The specific preparation method is the same as in Example 2-1. The difference from Example 2-1 is that the 5% Ru / ZnO catalyst prepared in Example 1-1 is replaced with the 3% Ru / ZnO catalyst prepared in Example 1-2.

[0111] Test results showed that the yield of DHMTHF was 75.3% and the purity was 98.4%.

[0112] Examples 2-5: Synthesis of DHMTHF

[0113] The specific preparation method is the same as in Example 2-1. The difference from Example 2-1 is that the 5% Ru / ZnO catalyst prepared in Example 1-1 is replaced with the 7% Ru / ZnO catalyst prepared in Example 1-3.

[0114] Test results showed that the yield of DHMTHF was 90.1% and the purity was 97.9%.

[0115] Examples 2-6: Synthesis of DHMTHF

[0116] The specific preparation method is the same as in Example 2-1. The difference from Example 2-1 is that the 5% Ru / ZnO catalyst prepared in Example 1-1 is replaced with the 9% Ru / ZnO catalyst prepared in Example 1-4.

[0117] Test results showed that the yield of DHMTHF was 82.3% and the purity was 98.5%.

[0118] Examples 2-7: Synthesis of DHMTHF

[0119] The specific preparation method is the same as in Example 2-1, except that the formaldehyde concentration of 3 mol / L is replaced with 2 mol / L.

[0120] Test results showed that the yield of DHMTHF was 82.1% and the purity was 98.0%.

[0121] Examples 2-8: Synthesis of DHMTHF

[0122] The specific preparation method is the same as in Example 2-1, except that the formaldehyde concentration of 3 mol / L is replaced with 4 mol / L.

[0123] Test results showed that the yield of DHMTHF was 89.3% and the purity was 97.6%.

[0124] Examples 2-9: Synthesis of DHMTHF

[0125] The specific preparation method is the same as in Example 2-1, except that the formaldehyde concentration of 3 mol / L is replaced with 5 mol / L.

[0126] Test results showed that the yield of DHMTHF was 78.4% and the purity was 96.6%.

[0127] Examples 2-10: Synthesis of DHMTHF

[0128] The specific preparation method is the same as in Example 2-1, except that the molar amount of sodium hydroxide is replaced with 0.03 mol, which corresponds to a mass of 1.2 g.

[0129] Test results showed that the yield of DHMTHF was 99.1% and the purity was 98.5%.

[0130] Example 2-11: Synthesis of DHMTHF

[0131] The specific preparation method is the same as in Example 2-1, except that the molar amount of sodium hydroxide is replaced with 0.10 mol, which corresponds to a mass of 4 g.

[0132] Test results showed that the yield of DHMTHF was 83.3% and the purity was 97.4%.

[0133] Example 2-12: Synthesis of DHMTHF

[0134] The specific preparation method is the same as in Example 2-1, except that the molar amount of sodium hydroxide is replaced with 0.12 mol, which corresponds to a mass of 4.8 g.

[0135] Test results showed that the yield of DHMTHF was 75.6% and the purity was 98.1%.

[0136] Example 2-13: Synthesis of DHMTHF

[0137] The specific preparation method is the same as in Example 2-1, except that the mass of the 5% Ru / ZnO catalyst is replaced with 0.8g.

[0138] Test results showed that the yield of DHMTHF was 74.3% and the purity was 97.9%.

[0139] Example 2-14: Synthesis of DHMTHF

[0140] The specific preparation method is the same as in Example 2-1, except that the mass of the 5% Ru / ZnO catalyst is replaced with 1.2g.

[0141] Test results showed that the yield of DHMTHF was 80.1% and the purity was 98.2%.

[0142] Example 2-15: Synthesis of DHMTHF

[0143] The specific preparation method is the same as in Example 2-1, except that the mass of the 5% Ru / ZnO catalyst is replaced with 1.6g.

[0144] Test results showed that the yield of DHMTHF was 91.8% and the purity was 98.4%.

[0145] Example 2-16: Synthesis of DHMTHF

[0146] The specific preparation method is the same as in Example 2-1, except that the reaction temperature is replaced with 160℃.

[0147] Test results showed that the yield of DHMTHF was 86.5% and the purity was 99.1%.

[0148] Example 2-17: Synthesis of DHMTHF

[0149] The specific preparation method is the same as in Example 2-1, except that the reaction temperature is replaced with 180℃.

[0150] Test results showed that the yield of DHMTHF was 94.8% and the purity was 97.6%.

[0151] Example 2-18: Synthesis of DHMTHF

[0152] The specific preparation method is the same as in Example 2-1, except that the reaction temperature is replaced with 190℃.

[0153] Test results showed that the yield of DHMTHF was 85.6% and the purity was 96.8%.

[0154] Example 2-19: Synthesis of DHMTHF

[0155] The specific preparation method is the same as in Example 2-1, except that the reaction time is replaced with 3 hours.

[0156] Test results showed that the yield of DHMTHF was 78.6% and the purity was 96.9%.

[0157] Examples 2-20: Synthesis of DHMTHF

[0158] The specific preparation method is the same as in Example 2-1, except that the reaction time is replaced with 7 hours.

[0159] Test results showed that the yield of DHMTHF was 94.0% and the purity was 97.8%.

[0160] Example 2-21: Synthesis of DHMTHF

[0161] The specific preparation method is the same as in Example 2-1, except that the reaction time is replaced with 10 hours.

[0162] Test results showed that the yield of DHMTHF was 79.1% and the purity was 97.5%.

[0163] Example 2-22: Synthesis of DHMTHF

[0164] The specific preparation method is the same as in Example 2-1. The difference from Example 2-1 is that the 5% Ru / ZnO catalyst prepared in Example 1-1 is replaced with the 5% Ru / ZnO catalyst prepared in Example 1-5.

[0165] Test results showed that the yield of DHMTHF was 79.3% and the purity was 97.8%.

[0166] Example 2-23: Synthesis of DHMTHF

[0167] The specific preparation method is the same as in Example 2-1. The difference from Example 2-1 is that the 5% Ru / ZnO catalyst prepared in Example 1-1 is replaced with the 5% Ru / ZnO catalyst prepared in Example 1-6.

[0168] Test results showed that the yield of DHMTHF was 94.1% and the purity was 98.2%.

[0169] Example 2-24: Synthesis of DHMTHF

[0170] The specific preparation method is the same as in Example 2-1. The difference from Example 2-1 is that the 5% Ru / ZnO catalyst prepared in Example 1-1 is replaced with the 5% Ru / ZnO catalyst prepared in Example 1-7.

[0171] Test results showed that the yield of DHMTHF was 92.0% and the purity was 98.0%.

[0172] The above examples demonstrate that the 5% Ru / ZnO catalyst exhibits high catalytic activity and selectivity in the preparation of DHMTH from 5-HMF, and can also catalyze the production of hydrogen from formaldehyde under alkaline conditions. By altering reaction conditions, such as reaction temperature, time, and catalyst dosage, the yield of DHMTH can be further improved. Simultaneously, the hydrogen production can be adjusted by rationally controlling the formaldehyde concentration and alkaline content. This provides new ideas and directions for those skilled in the art to obtain higher yields of DHMTH.

[0173] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for catalytic synthesis of 2,5-dihydroxymethyltetrahydrofuran from 5-hydroxymethylfurfural, comprising: 5-hydroxymethylfurfural and an alkaline substance were dissolved in formaldehyde solution, and a composite catalyst of ruthenium and zinc oxide was added. The resulting reaction solution was mixed and placed in a sealed reaction container. Nitrogen gas is introduced into the reaction vessel. Under alkaline conditions, the ruthenium and zinc oxide composite catalyst is used to catalyze the in-situ decomposition of formaldehyde to produce hydrogen gas, thereby causing the 5-hydroxymethylfurfural to undergo a hydrogenation reaction to obtain 2,5-dihydroxymethyltetrahydrofuran. The alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate; the formaldehyde concentration in the formaldehyde solution is 1–5 mol / L; and the mass molar ratio of the alkaline substance to the formaldehyde is (0.5–2):

1. The ruthenium and zinc oxide composite catalyst is obtained through the following steps: Zinc salt and ruthenium salt are dissolved in water to obtain a reaction solution; An alkaline precipitant is added to the reactant solution to carry out a precipitation reaction, so that the pH of the reactant solution is greater than 10; The obtained precipitate was aged, filtered, washed, and dried to obtain precipitate powder. The precipitate powder was calcined in air to obtain precursor powder. In a mixed atmosphere of hydrogen and nitrogen, the precursor powder is thermally reduced to obtain the ruthenium and zinc oxide composite catalyst, wherein the ruthenium loading in the ruthenium and zinc oxide composite catalyst is 2-10%.

2. The method according to claim 1, wherein, The mass ratio of the ruthenium and zinc oxide composite catalyst to the 5-hydroxymethylfurfural is (0.1-1):

1.

3. The method according to claim 1, wherein, In the hydrogenation reaction, the reaction pressure is 0.05–0.1 MPa, the reaction temperature is 150–200 °C, and the reaction time is 1–24 h.

4. The method according to claim 1, wherein, The ruthenium and zinc oxide composite catalyst has a mesoporous structure, with ruthenium acting as a catalytic center dispersed on the surface of the zinc oxide particle support.

5. The method according to claim 4, wherein, The pore size of the mesoporous structure is 20–30 nm.

6. The method according to claim 1, wherein, The zinc salt includes any one of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate; The ruthenium salt includes ruthenium chloride or ruthenium acetate; The alkaline precipitant includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

7. The method according to claim 1, wherein, The aging treatment temperature is 20–30°C, and the aging treatment time is 12–24 hours. The calcination temperature is 200–500℃, and the calcination time is 1–10 h.

8. The method according to claim 1, wherein, During the thermal reduction process, the reaction temperature is 100–300°C and the reaction time is 1–10 h; the volume fraction of hydrogen in the mixed atmosphere is 10%–50%.

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