Method for producing high-purity 2,5-furandimethanol by catalyzing furfuryl alcohol by using aprotic acid catalyst

Abstract

The present invention belongs to the field of furyl biomass chemicals and materials. Disclosed is a method for producing high-purity 2,5-furandimethanol by catalyzing furfuryl alcohol by using an aprotic acid catalyst. The method comprises: adding a modified zeolite catalyst, furfuryl alcohol and a hydroxymethylation reagent into an aprotic solvent, introducing nitrogen thereto to perform a reaction, and after the reaction is finished, filtering same, separating a solid phase from a liquid phase, subjecting the liquid phase to rotary evaporation to recover the solvent, then continuously heating same, and collecting a solid, namely, high-purity 2,5-furandimethanol, wherein the modified zeolite catalyst is obtained by subjecting β-zeolite to a dealumination treatment, and then introducing a transition metal element as a Lewis acid active site into the zeolite by means of a solid-solid ion exchange method. The modified zeolite of the present invention is used as the aprotic acid catalyst, and in contrast to the problems of poor target product selectivity and separation caused by related side reactions of a protonic acid catalyst, can achieve high selectivity of the target product, such that the synthesis process and separation and purification process are simple, the raw material cost is low, and the green chemical development concept is satisfied.

Description

A method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol using a proton-free acid catalyst Technical Field

[0001] The invention belongs to the field of furan-based biomass chemicals and materials, and particularly relates to a method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a proton-free acid catalyst. Background Art

[0002] 2,5-Furan dimethanol (BHMF), an aromatic furandiol primarily derived from 5-hydroxymethylfurfural (HMF), is an important monomer for the synthesis of aromatic polyesters, replacing petroleum-based diols. It has a wide range of applications in the synthesis of ethers, polymers, resins, and adhesives. Currently, the main factor limiting BHMF's application is its high cost: industrial production of HMF primarily relies on the dehydration of fructose catalyzed by inorganic acids, while cheaper glucose processes remain under investigation. Furthermore, the reduction and derivatization of HMF require high selectivity for both C=O and C=C bonds, posing significant challenges for catalysts and catalytic processes. In contrast, the furfural industry has achieved economies of scale, with over 65% of its production capacity dedicated to furfuryl alcohol applications. This makes the direct production of BHMF via the hydroxymethylation of furfuryl alcohol a highly cost-effective strategy.

[0003] The earliest attempts to produce BHMF from furfuryl alcohol can be traced back to Laszlo-Hedwig et al. (Polymer Science USSR, 1983, 25:228-236). By mimicking the acidic polymerization process of phenolic resin, they used formaldehyde as a hydroxymethylation agent to convert furfuryl alcohol into BHMF in an acidic environment. However, compared with the hydroxymethylation of phenol, highly reactive furfuryl alcohol undergoes severe self-polymerization in acidic environments, especially in aqueous solutions, resulting in lower BHMF selectivity. Furthermore, side reactions initiated by the ring-opening of the furan structure in strong acidic environments are another major factor contributing to the low BHMF selectivity. To address these issues, researchers have conducted several studies: using high-silica hydrophobic mordenite as a replacement for inorganic acid to achieve higher BHMF selectivity at low FAl concentrations; using polyoxymethylene to replace formaldehyde solution to mitigate the side reactions caused by the introduction of formaldehyde into the aqueous phase; and protecting the active hydroxyl groups of furfuryl alcohol prior to hydroxymethylation to reduce associated side reactions. Even so, there are still some problems that need to be solved: the reaction energy barrier of the C-H bond on the aromatic ring is too high, the self-polymerization problem after protonation of free formaldehyde, product selectivity and subsequent separation problems caused by by-products such as humic acid.

[0004] Therefore, it is urgent to provide a method for preparing high-purity BHMF with high selectivity, simple separation, reduced side reactions and simple process. Technical issues

[0005] In view of the above-mentioned problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol using a proton-free acid catalyst, which is used to address the problems of severe side reactions, poor selectivity, complex separation and high cost in the current preparation of 2,5-furan dimethanol. Technical Solutions

[0006] In order to solve the above problems, the technical solution adopted in the present invention is as follows:

[0007] A method for producing high-purity 2,5-furandimethanol from furfuryl alcohol using a protonic acid catalyst comprises the following steps: adding a modified zeolite catalyst, furfuryl alcohol, and a hydroxymethylation agent to an aprotic solvent, introducing nitrogen gas for reaction, filtering after the reaction, separating the solid and liquid phases, rotary evaporating the liquid phase to recover the solvent, and then heating the liquid phase to collect the solid, thereby obtaining the high-purity 2,5-furandimethanol; wherein the modified zeolite catalyst is obtained by introducing a transition metal element into the β-zeolite through a solid-solid ion exchange method after dealumination treatment with concentrated nitric acid.

[0008] Furthermore, the transition metal element is one or more of manganese, cobalt and tin.

[0009] Furthermore, the transition metal is manganese.

[0010] Furthermore, the hydroxymethylation agent is one or a mixture of formaldehyde, trioxymethylene and paraformaldehyde.

[0011] Furthermore, the aprotic solvent is one or a mixture of tetrahydrofuran, 1,4-dioxane and methyl acetate.

[0012] Furthermore, the molar ratio of furfuryl alcohol to the hydroxymethylation agent is 1:1-9.

[0013] Furthermore, the amount of furfuryl alcohol added is 1-10% of the volume of the aprotic solvent, and the amount of the modified zeolite catalyst added is 1-20% of the total solvent mass.

[0014] Furthermore, the reaction temperature is 80-140° C., and the reaction time is 1-12 hours.

[0015] Further, the specific steps are as follows:

[0016] 1) The β-zeolite is placed in concentrated nitric acid for dealumination at a boiling temperature for 8 hours, then washed with water until neutral, dried, and mechanically ground to introduce exogenous ions, i.e., transition metal elements. The catalyst is then calcined at a high temperature and cooled to obtain a modified zeolite catalyst. The molar ratio of SiO2 to Al2O3 in the β-zeolite is 30:1.

[0017] 2) Furfuryl alcohol and a hydroxymethylation agent are added to an aprotic solvent at a molar ratio of 1:1-9, and a catalyst is added at a rate of 1-20% of the total mass of the solvent. The reaction is carried out under nitrogen as a protective gas at a temperature of 80-140°C for 1-12 hours. The amount of furfuryl alcohol added is 1-10% of the volume of the aprotic solvent.

[0018] 3) After the reaction is completed, the reaction system is filtered to separate the solid and liquid. The solid, i.e., the catalyst, is washed with a washing solution and dried before being regenerated. The liquid is subjected to rotary evaporation at 40-80°C to separate the solvent and continue to heat to 100°C to remove trace amounts of the furfuryl alcohol substrate. The collected solid is high-purity 2,5-furan dimethanol.

[0019] Furthermore, in step 3), the washing liquid is one or a mixture of methanol, ethanol and acetone.

[0020] FIG1 is a schematic diagram of converting furfuryl alcohol into high-purity 2,5-furan dimethanol under the catalysis of a proton-free acid catalyst. Beneficial effects

[0021] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0022] (1) The catalyst used in the present invention is a non-protonic acid catalyst, which is characterized by relying on Lewis acid active sites to complete the hydroxymethylation process, thereby reducing protonic acid-related side reactions.

[0023] (2) The catalytic pathway of the present invention is different from the proton acid forming hydroxymethyl cations and then disorderly attacking furfuryl alcohol to complete hydroxymethylation. The proton-free acid catalyst of the present invention not only promotes the hydroxymethyl cations but also assists them in anchoring to the reaction position of furfuryl alcohol, thereby achieving the targeted completion of the hydroxymethylation reaction and reducing the side reactions associated with the electrophilic reagent.

[0024] (3) The low by-product content and high selectivity for BHMF of the present invention allow the reaction solution and catalyst to be recovered by simple distillation, simplifying the product separation and reagent recovery process.

[0025] (4) The synthesis process and separation and purification process of the present invention are simple, the catalyst can be recycled and reused, and the cost of raw materials is reduced, which is in line with the development concept of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic diagram of the conversion of furfuryl alcohol into high-purity 2,5-furan dimethanol under the catalysis of a proton-free acid catalyst according to the present invention;

[0027] FIG2 is a gas chromatography-mass spectrometry time chart of the reaction solution prepared in the present invention;

[0028] FIG3 is a mass spectrum corresponding to the BHMF product peak in FIG1 of the present invention;

[0029] FIG4 is a gas chromatography-mass spectrometry time chart of the product prepared in Comparative Example 1 of the present invention. Best Mode for Carrying Out the Invention

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] The selectivity, yield and purity of BHMF prepared in the following examples were calculated according to the following formula:

[0032] The selectivity of BHMF (S BHMF ) is calculated as follows:

[0033]

[0034] Among them, m0 is the mass of furfuryl alcohol substrate; m1 is the mass of remaining furfuryl alcohol substrate; m3 is the mass of chromatographically pure BHMF; M 糠醇 is the molar molecular mass of furfuryl alcohol; M BHMF is the molar molecular mass of BHMF.

[0035] BHMF yield Y BHMF The calculation formula is as follows:

[0036]

[0037] Wherein, m2 is the mass of the absolute dry product; m0 is the mass of the furfuryl alcohol substrate; M 糠醇 is the molar molecular mass of furfuryl alcohol; M BHMF is the molar molecular mass of BHMF.

[0038] The purity of BHMF (P BHMF ) is calculated as follows:

[0039]

[0040] Wherein, m3 is the chromatographic mass of BHMF; m2 is the mass of the absolute dry product.

[0041] The purity of BHMF prepared in the following examples was determined by chromatographic purity and tested according to the following steps:

[0042] 0.1 g (dry equivalent) of the product was placed in a beaker and dissolved in tetrahydrofuran. The mixture was cooled to room temperature and the volume was adjusted to 100 mL. The mixture was filtered through a 0.22 µm organic syringe filter and used to determine the BHMF concentration. Analysis was performed using a gas chromatograph (Shimadzu, GC-2010 Plus) equipped with a highly polar column (DB-WAXetr). Chromatographically pure n-dodecane was used as an internal reference. The test conditions were: a temperature range of 40–280°C, a heating rate of 5°C / min from 40–150°C and a heating rate of 2°C / min from 150–280°C. The precise BHMF content in the product was determined by comparing the internal reference with a pre-established BHMF standard curve, which was then calculated as the chromatographic purity of the sample.

[0043] Formaldehyde (37 wt % aqueous solution), trioxymethylene (AR), paraformaldehyde (95%), tetrahydrofuran (AR), 1,4-dioxane (99.5%), and methyl acetate (99%) used in the following examples were purchased from Shanghai Macklin. Example 1

[0044] 1. Preparation of modified zeolite catalyst

[0045] β-zeolite (the molar ratio of SiO2 to Al2O3 is 30:1) is placed in concentrated nitric acid (mass fraction is 68%) and dealuminated under boiling conditions for 8 hours. The product is then washed with water until neutral, dried at 105°C, and mechanically ground with cobalt nitrate in an amount equivalent to the amount of aluminum removed. The product is then placed in a tubular furnace and treated at 600°C under nitrogen protection for 4 hours. The product is then placed in a muffle furnace and kept warm at 600°C for 4 hours. The product after cooling is the prepared modified zeolite catalyst.

[0046] 2. Preparation of BHMF

[0047] Furfuryl alcohol and formaldehyde solution (calculated as formaldehyde monomer molar equivalent) are added to tetrahydrofuran in a molar ratio of 1:3, wherein the furfuryl alcohol accounts for 2% of the volume of tetrahydrofuran. At the same time, a modified zeolite catalyst equivalent to 5% of the total solvent mass is added. The air in the device is evacuated with nitrogen, and the reaction is stirred at 100°C for 4 hours. After the reaction is completed, the solid and liquid phases are separated using a filtration device. The solid is washed three times with ethanol and then dried to recover the catalyst. The drying temperature is 105°C. The liquid is used to recover the solvent using a rotary evaporator at 60°C, and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals are collected to obtain BHMF. Example 2

[0048] Preparation of BHMF

[0049] Furfuryl alcohol and formaldehyde solution (calculated as formaldehyde monomer molar equivalent) were added to tetrahydrofuran in a molar ratio of 1:9, wherein the furfuryl alcohol accounted for 5% of the volume of the tetrahydrofuran. A modified zeolite catalyst (modified zeolite catalyst prepared by the method of Example 1) equivalent to 10% of the total solvent mass was added. The air in the apparatus was purged with nitrogen, and the reaction was stirred at 80°C for 8 hours. After the reaction was completed, the solid and liquid phases were separated using a filtration device. The solid was washed three times with ethanol and then dried to recover the catalyst at 105°C. The liquid was used to recover the solvent using a rotary evaporator at 60°C. The temperature was further raised to 100°C to remove trace amounts of the furfuryl alcohol substrate, and the remaining crystals were collected to obtain BHMF. Example 3

[0050] Preparation of BHMF

[0051] Furfuryl alcohol and trioxymethylene (calculated as formaldehyde monomer molar equivalent) were added to tetrahydrofuran in a molar ratio of 1:9, wherein the furfuryl alcohol accounted for 5% of the volume of the tetrahydrofuran. A modified zeolite catalyst (modified zeolite catalyst prepared by the method of Example 1) equivalent to 10% of the total solvent mass was added. The air in the apparatus was purged with nitrogen, and the reaction was stirred at 100°C for 4 hours. After the reaction was completed, the solid and liquid phases were separated using a filtration device, the solid was washed three times with acetone, and then dried to recover the catalyst at a drying temperature of 105°C. The liquid was used to recover the solvent using a rotary evaporator at 60°C, and the temperature was further raised to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals were collected to obtain BHMF. Example 4

[0052] Preparation of BHMF

[0053] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) were added to methyl acetate in a molar ratio of 1:3, wherein the furfuryl alcohol accounted for 5% by volume of tetrahydrofuran. A modified zeolite catalyst (prepared by the method of Example 1) equivalent to 10% by mass of the total solvent was added. The air in the apparatus was purged with nitrogen, and the reaction was stirred at 100°C for 8 hours. After the reaction was completed, the solid and liquid phases were separated using a filtration device. The solid was washed three times with methanol and then dried to recover the catalyst at 105°C. The liquid was used to recover the solvent using a rotary evaporator at 60°C. The temperature was further raised to 100°C to remove trace amounts of the furfuryl alcohol substrate, and the remaining crystals were collected to obtain BHMF. Example 5

[0054] 1. Preparation of modified zeolite catalyst

[0055] β-zeolite (the molar ratio of SiO2 to Al2O3 is 30:1) is placed in concentrated nitric acid (mass fraction is 68%) and dealuminated at boiling temperature for 8 hours. The product is then washed with water until neutral, dried at 105°C, and mechanically ground with manganese nitrate in an amount equivalent to the molar amount of the removed aluminum element. The product is then placed in a muffle furnace and kept at 600°C for 4 hours. The product after cooling is the prepared modified zeolite catalyst.

[0056] 2. Preparation of BHMF

[0057] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) are added to methyl acetate in a molar ratio of 1:9, wherein the volume of furfuryl alcohol is 5% of the volume of tetrahydrofuran. A modified zeolite catalyst equivalent to 10% of the total solvent mass is added at the same time. The air in the device is evacuated with nitrogen, and the reaction is stirred at 120°C for 8 hours. After the reaction is completed, the solid and liquid phases are separated using a filtration device. The solid is washed three times with ethanol and then dried to recover the catalyst at a drying temperature of 105°C. The liquid is used to recover the solvent using a rotary evaporator at 60°C, and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals are collected to obtain BHMF. Example 6

[0058] Preparation of BHMF

[0059] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) were added to methyl acetate in a molar ratio of 1:6, wherein the furfuryl alcohol accounted for 10% by volume of tetrahydrofuran. A modified zeolite catalyst (prepared by the method of Example 5) equivalent to 20% by mass of the total solvent was added. The air in the apparatus was purged with nitrogen, and the reaction was stirred at 120°C for 8 hours. After the reaction was completed, the solid and liquid phases were separated using a filtration device. The solid was washed three times with ethanol and then dried to recover the catalyst at 105°C. The liquid was used to recover the solvent using a rotary evaporator at 60°C. The temperature was further raised to 100°C to remove trace amounts of the furfuryl alcohol substrate, and the remaining crystals were collected to obtain BHMF. Example 7

[0060] Preparation of BHMF

[0061] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) were added to 1,4-dioxane in a molar ratio of 1:9, wherein the furfuryl alcohol was 1% by volume of tetrahydrofuran. A modified zeolite catalyst (modified zeolite catalyst prepared by the method of Example 5) equivalent to 5% by mass of the total solvent was added, and the mixture was stirred and reacted at 110°C for 4 hours. After the reaction was completed, the solid and liquid phases were separated using a filtration device. The solid was washed three times with ethanol and then dried to recover the catalyst at a drying temperature of 105°C. The liquid was used to recover the solvent using a rotary evaporator at 60°C, and the temperature was further raised to 100°C to remove trace amounts of the furfuryl alcohol substrate. The remaining crystals were collected to obtain BHMF. Example 8

[0062] 1. Preparation of modified zeolite catalyst

[0063] β-zeolite (the molar ratio of SiO2 to Al2O3 is 30:1) is placed in concentrated nitric acid (mass fraction is 68%) and dealuminated under boiling conditions for 8 hours. The product is then washed with water until neutral, dried at 105°C, and mechanically ground with manganese nitrate in an amount equivalent to the amount of aluminum removed. The product is then placed in a tubular furnace and treated at 600°C under nitrogen protection for 4 hours. The product is then placed in a muffle furnace and kept warm at 600°C for 4 hours. The product after cooling is the prepared modified zeolite catalyst.

[0064] 2. Preparation of BHMF

[0065] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) are added to 1,4-dioxane in a molar ratio of 1:9, wherein the furfuryl alcohol is 1% by volume of tetrahydrofuran. At the same time, a modified zeolite catalyst equivalent to 5% by mass of the total solvent is added. The air in the device is evacuated with nitrogen, and the reaction is stirred at 110°C for 12 hours. After the reaction is completed, the solid and liquid phases are separated using a filtration device. The solid is washed three times with ethanol and then dried to recover the catalyst at a drying temperature of 105°C. The liquid is used to recover the solvent using a rotary evaporator at 80°C, and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals are collected to obtain BHMF. Example 9

[0066] 1. Preparation of modified zeolite catalyst

[0067] β-zeolite (the molar ratio of SiO2 to Al2O3 is 30:1) is placed in concentrated nitric acid (mass fraction is 68%) and dealuminated at boiling state for 8 hours, washed with water until neutral, dried at 105°C, and then mechanically ground with tin nitrate in an amount equivalent to the dealuminized element. The product is then placed in a tubular furnace at 600°C under nitrogen protection for 4 hours, and then placed in a muffle furnace at 600°C for 4 hours. The product after cooling is the prepared modified zeolite catalyst.

[0068] 2. Preparation of BHMF

[0069] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) were added to 1,4-dioxane in a molar ratio of 1:9, wherein the furfuryl alcohol was 1% by volume of tetrahydrofuran. A modified zeolite catalyst equivalent to 5% by mass of the total solvent was also added. Nitrogen was used to evacuate the air in the apparatus, and the reaction was stirred at 80°C for 12 hours. After the reaction was completed, the solid and liquid phases were separated using a filtration device. The solid was washed three times with acetone and then dried to recover the catalyst at 105°C. The liquid was used to recover the solvent using a rotary evaporator at 60°C, and the temperature was continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals were collected to obtain BHMF.

[0070] Comparative Example 1

[0071] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) are added to 1,4-dioxane in a molar ratio of 1:9, wherein the furfuryl alcohol is 5% by volume of tetrahydrofuran. At the same time, acetic acid equivalent to 5% of the total solvent volume is added as a catalyst. The air in the apparatus is purged with nitrogen, and the reaction is stirred at 110°C for 6 hours. After the reaction is completed, the solvent and acetic acid are recovered using a rotary evaporator at 80°C, and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals are collected to obtain BHMF.

[0072] Comparative Example 2

[0073] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) are added to 1,4-dioxane in a molar ratio of 1:9, wherein the volume of furfuryl alcohol is 1% of the volume of tetrahydrofuran. At the same time, an unmodified β-zeolite catalyst (the molar ratio of SiO2 to Al2O3 is 30:1) equivalent to 20% of the total solvent mass is added. The air in the device is purged with nitrogen, and the reaction is stirred at 110°C for 6 hours. After the reaction is completed, the reaction is filtered, and the solid is washed three times with acetone and then dried to recover the catalyst at a drying temperature of 105°C. The liquid is used to recover the solvent using a rotary evaporator at 60°C, and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals are collected to obtain BHMF.

[0074] Comparative Example 3

[0075] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) are added to 1,4-dioxane in a molar ratio of 1:9, wherein the furfuryl alcohol is 1% by volume of tetrahydrofuran. At the same time, a zeolite (H-ZSM-5, SiO2 to Al2O3 molar ratio of 18:1) catalyst equivalent to 20% of the total solvent mass is added. The air in the device is purged with nitrogen, and the reaction is stirred at 110°C for 6 hours. After the reaction is completed, the reaction is filtered, and the solid is washed three times with acetone and then dried to recover the catalyst at a drying temperature of 105°C. The liquid is used to recover the solvent using a rotary evaporator at 60°C, and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals are collected to obtain BHMF.

[0076] Comparative Example 4

[0077] Furfuryl alcohol and paraformaldehyde (calculated as formaldehyde monomer molar equivalent) are added to 1,4-dioxane in a molar ratio of 1:9, wherein the furfuryl alcohol is 1% by volume of tetrahydrofuran. At the same time, a zeolite (H-SAPO-11, with a molar ratio of SiO2, Al2O3 and P2O5 of 0.63:1:0.82) catalyst equivalent to 20% of the total solvent mass is added. The air in the apparatus is purged with nitrogen, and the reaction is stirred at 110°C for 6 hours. After the reaction is completed, the reaction is filtered, and the solid is washed three times with acetone and then dried to recover the catalyst at a drying temperature of 105°C. The liquid is used to recover the solvent using a rotary evaporator at 60°C, and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The remaining crystals are collected to obtain BHMF.

[0078] The yields and conversion rates of the BHMF products prepared in Examples 1 to 9 of the present invention and Comparative Examples 1 to 4 are shown in Table 1 below.

[0079] Table 1 BHMF product yield and product conversion rate prepared in Examples 1 to 9 and Comparative Examples 1 to 4

[0080]

[0081] Table 1 shows the BHMF product yields and product conversion rates prepared in Examples 1-9 and Comparative Examples 1-4. As can be seen from the table, the temperature and time of the catalytic reaction affect the progress and selectivity of the hydroxymethylation reaction. Generally, increasing the substrate concentration is detrimental to improving the selectivity of the reaction, while increasing the amount of catalyst used can accelerate the reaction process. Compared to protic acid catalysts such as Comparative Example 1, the BHMF produced by protic acid-free catalysts has higher purity and is more conducive to catalyst recovery, thereby ensuring the purity of the target product and efficient separation and recovery. Furthermore, the silicon-aluminum ratio affects the number of ion exchanges. A high silicon-aluminum ratio results in relatively fewer active sites, but the catalyst is usually in excess during use, resulting in significant differences in catalytic performance. Among the different single-metal-modified zeolite catalysts, the manganese-modified zeolite catalyst performed the best. In Comparative Examples 1-4, although the furfuryl alcohol conversion was high, the BHMF yield and purity were low, failing to meet the requirements for use.

[0082] FIG2 is a gas chromatography-mass spectrometry time diagram of the reaction solution prepared in the present invention. As can be seen from the figure, 3.185 min, 19.289 min and 20.805 min represent the solvent peak, the internal reference peak and the BHMF product peak, respectively, and no obvious other by-product peaks are found.

[0083] FIG3 is a mass spectrum corresponding to the BHMF product peak in FIG1 of the present invention. As can be seen from the figure, the product at this position is identified as BHMF based on comparison with the standard spectrum library.

[0084] Figure 4 is a gas chromatography-mass spectrometry time chart of the product prepared in Comparative Example 1 of the present invention. As can be seen from the figure, excluding the solvent, substrate, and product peaks, the time spectrum under the experimental conditions shows a large number of miscellaneous peaks within the time range. These miscellaneous peaks usually correspond to by-products such as acid polymerization and hydrolysis of the furfuryl alcohol substrate, which bring difficulties to the subsequent separation and purification.

Claims

1. A method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst, characterized in that: A modified zeolite catalyst, furfuryl alcohol and a hydroxymethylation agent are added to a non-protonic solvent, and nitrogen is introduced to react. After the reaction is completed, the reaction is filtered to separate the solid and liquid phases. The liquid phase is rotary evaporated to recover the solvent and then the temperature is continued to rise to collect the solid, which is high-purity 2,5-furan dimethanol. The modified zeolite catalyst is obtained by introducing the transition metal element into the β-zeolite through a solid-solid ion exchange method after the β-zeolite is dealuminated with concentrated nitric acid.

2. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 1, characterized in that: The transition metal element is one or more of manganese, cobalt and tin.

3. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 2, characterized in that: The transition metal is manganese.

4. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 1, characterized in that: The hydroxymethylation agent is one or a mixture of formaldehyde, trioxymethylene and polyformaldehyde.

5. The method for producing high-purity 2,5-furan dimethanol by using a protonic acid catalyst to catalyze furfuryl alcohol according to claim 1, characterized in that: The aprotic solvent is one of tetrahydrofuran, 1,4-dioxane and methyl acetate or a mixture of several of them.

6. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 1, characterized in that: The molar ratio of furfuryl alcohol to the hydroxymethylation agent is 1:1-9.

7. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 1, characterized in that: The amount of furfuryl alcohol added is 1-10% of the volume of the aprotic solvent, and the amount of the modified zeolite catalyst added is 1-20% of the total solvent mass.

8. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 1, characterized in that: The reaction temperature is 80-140° C., and the reaction time is 1-12 hours.

9. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 1, characterized in that: The specific steps are as follows: 1) The β-zeolite is placed in concentrated nitric acid for dealumination under boiling conditions for 8 hours, then washed with water until neutral, dried, and then introduced with exogenous ions, i.e. transition metal elements, by mechanical grinding, and then calcined at high temperature and cooled to finally obtain a modified zeolite catalyst; wherein the molar ratio of SiO2 to Al2O3 in the β-zeolite is 30:1; 2) Add furfuryl alcohol and hydroxymethylation agent into a non-protic solvent at a molar ratio of 1:1-9, and add 1-20% of the total mass of the total solvent as catalyst, and react for 1-12 hours under nitrogen as protective gas and temperature of 80-140°C; wherein, the amount of furfuryl alcohol added is 1-10% of the volume of the aprotic solvent; 3) After the reaction is completed, the solid and liquid in the reaction system are separated by filtration. The solid, i.e., the catalyst, is washed and dried with a washing solution and then regenerated. The liquid is subjected to rotary evaporation to separate the solvent at 40-80°C and the temperature is continued to rise to 100°C to remove trace amounts of furfuryl alcohol substrate. The collected solid is high-purity 2,5-furan dimethanol.

10. The method for producing high-purity 2,5-furan dimethanol by catalyzing furfuryl alcohol with a protonic acid catalyst according to claim 9, characterized in that: In step 3), the washing liquid is one or a mixture of methanol, ethanol and acetone.

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