Process for the preparation of furan acid compounds

Abstract

The application provides a preparation method of a furfuryl acid compound and belongs to the technical field of chemical synthesis. The preparation method of the furfuryl acid compound comprises the following steps: mixing a furfuryl alcohol compound, lye and a noble metal supported catalyst, and performing an oxidation reaction under an oxygen atmosphere to obtain a furfuryl acid compound. The application adjusts the pH value of a reaction system by adding lye, which is helpful to promote the oxidation reaction. Under the catalysis of the noble metal supported catalyst, oxygen molecules are activated and adsorbed to the surface of the catalyst to form active oxygen molecules, which are reacted with aldehyde groups in the furfuryl alcohol compound to oxidize the aldehyde groups into carboxylic acid groups. The reaction process of the application is simple and has a high yield.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method for preparing furoic acid compounds. Background Technology

[0002] Biomass resources are widely distributed in nature, possessing advantages such as abundant reserves, renewability, green origin, and environmental friendliness. Through the targeted conversion of biomass resources, some important biomass "platform molecules" can be obtained first, and then further converted to produce a series of high-value-added chemicals. Among these biomass "platform molecules," 5-hydroxymethylfurfural's furan ring has a structure similar to an aromatic ring, exhibiting aromatic ring characteristics. Further conversion based on 5-hydroxymethylfurfural yields aromatic polymer monomers.

[0003] Furoic acid compounds, as polymer monomers, can be used to prepare polyester materials for automotive glass, lamps, and adhesives. Currently, the preparation of furoic acid compounds mainly uses potassium permanganate, sodium hypochlorite, etc. for oxidation, but the reaction is relatively vigorous and difficult to control, resulting in a low reaction yield. Summary of the Invention

[0004] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a method for preparing a furoic acid compound.

[0005] According to one aspect of the present invention, a method for preparing a furoic acid compound is provided, comprising: mixing a furfural compound, an alkaline solution and a noble metal supported catalyst, and carrying out an oxidation reaction under an oxygen atmosphere to prepare a furoic acid compound.

[0006] According to embodiments of the present invention, the furfural compound includes 5,5-oxydimethylene-2-furfural; the furoic acid compound includes 5,5-oxydimethylene-2-furic acid.

[0007] According to an embodiment of the present invention, the alkaline solution comprises an aqueous solution of sodium hydroxide, and the concentration of the alkaline solution is 0.2~2.0 mol / L, preferably 1.5~2.0 mol / L.

[0008] According to an embodiment of the present invention, the mass ratio of water to furfural compound is (20~100):1.

[0009] According to an embodiment of the present invention, the noble metal supported catalyst includes a noble metal and a support, wherein the noble metal is supported on the support; the noble metal is ruthenium, iridium or palladium, preferably ruthenium.

[0010] According to embodiments of the present invention, the carrier includes at least one selected from hydroxyapatite, zirconium dioxide, aluminum oxide, and magnesium oxide.

[0011] According to an embodiment of the present invention, the loading of noble metal in the noble metal supported catalyst is 1~8 wt%.

[0012] According to an embodiment of the present invention, the noble metal supported catalyst is prepared by mixing and stirring a noble metal precursor solution with a support, drying the mixture, and then subjecting it to a heating reduction treatment under a hydrogen atmosphere to obtain the noble metal supported catalyst; preferably, the heating reduction treatment temperature is 300~600℃.

[0013] According to an embodiment of the present invention, the mass ratio of furfural compound to noble metal supported catalyst is (5~20):1, preferably (5~10):1.

[0014] According to an embodiment of the present invention, the pressure of the oxidation reaction is 0.2~3MPa, preferably 1.5~3MPa; the temperature of the oxidation reaction is 80~140℃; and the time of the oxidation reaction is 2~8h.

[0015] According to embodiments of the present invention, by adding an alkaline solution, the pH value of the reaction system is increased, creating alkaline conditions for the oxidation reaction and facilitating its progress. Under the action of a noble metal-supported catalyst, oxygen molecules are activated and adsorbed onto the surface of the catalyst to form reactive oxygen molecules. Furfural compounds are adsorbed on the catalyst surface, causing the aldehyde groups in the furfural compounds to react with the reactive oxygen molecules and be oxidized to carboxylic acid groups. The addition of the noble metal-supported catalyst helps to weaken the alkaline conditions, reducing the requirement for an alkaline environment in this oxidation reaction. The preparation method of the present invention is simple to operate, yields a high amount of furfural compounds, and uses oxygen as an oxidant to oxidize furfural compounds, reducing environmental pollution. This method has broad industrial application prospects. Attached Figure Description

[0016] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0017] Figure 1 The 1H NMR spectrum of 5,5-oxybismethylene-2-furfural prepared in Example 1 of this invention is shown. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0020] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0021] In related technologies, potassium permanganate or sodium hypochlorite are often used to prepare furoic acid compounds through oxidation. However, the reaction is vigorous and difficult to control, and the reaction yield is low, which can easily cause environmental pollution.

[0022] In realizing the concept of this invention, it was discovered that by adding an alkaline solution to provide an alkaline environment and promote the oxidation reaction, the noble metal supported catalyst helps to activate oxygen molecules and react with the aldehyde group in furfural compounds to generate furoic acid compounds, thereby simplifying the operation steps, making the reaction more gradual, and obtaining a higher yield.

[0023] Specifically, according to one aspect of the present invention, a method for preparing a furoic acid compound is provided, comprising: mixing a furfural compound, an alkaline solution and a noble metal supported catalyst, and carrying out an oxidation reaction under an oxygen atmosphere to prepare a furoic acid compound.

[0024] According to embodiments of the present invention, the pH value of the reaction system is increased by adding an alkaline solution, creating an alkaline environment for the oxidation reaction and facilitating its progress. Under the action of a noble metal-supported catalyst, oxygen molecules are activated and adsorbed onto the surface of the catalyst to form reactive oxygen molecules. Furfural compounds are adsorbed on the catalyst surface, causing the aldehyde groups in the furfural compounds to react with the reactive oxygen molecules and be oxidized to carboxylic acid groups. The addition of the noble metal-supported catalyst helps to weaken the alkaline conditions, reducing the requirement for an alkaline environment in this oxidation reaction. The preparation method of the present invention is simple to operate, yields a high amount of furfural compounds, and uses oxygen as an oxidant to oxidize furfural compounds, reducing environmental pollution. This method has broad industrial application prospects. Furthermore, the oxygen oxidation method used in this invention is relatively green and environmentally friendly; the oxidation effect is good, and the obtained products are relatively easy to recycle.

[0025] According to embodiments of the present invention, the furfural compound includes 5,5-oxydimethylene-2-furfural; the furoic acid compound includes 5,5-oxydimethylene-2-furic acid. 5-Hydroxymethylfurfural undergoes a self-etherification reaction to obtain 5,5-oxydimethylene-2-furic acid with a difuran ring linked by an ether bond in the middle, with aldehyde groups at both ends. The aldehyde groups can be converted to carboxyl groups through oxidation, thus preparing 5,5-oxydimethylene-2-furic acid. Due to the presence of the intermediate ether bond, although the initial decomposition temperature of the prepared 5,5-oxydimethylene-2-furic acid is slightly lower, its thermal stability is sufficient to serve as a substitute for polyethylene 2,5-furandicarboxylate (PEF), and it can be used in automotive glass, lighting fixtures, and adhesives, etc. Using the method of the present invention can promote the industrial production of difurandiic acid containing ether bonds.

[0026] According to an embodiment of the present invention, after the obtained product is filtered, 37% hydrochloric acid is added dropwise and stirred until the pH is less than 1, so that the solid precipitates out. The reaction solution is then allowed to stand overnight at 2-8°C to allow the product to precipitate completely. After filtration and drying, the product is then recrystallized and purified to obtain pure furoic acid compound.

[0027] According to embodiments of the present invention, the prepared 5,5-oxydimethylene-2-furfural acid with two furan rings is composed of two furan rings linked by ether bonds, and has better thermal stability than monomers with a single furan ring, and can be used to prepare highly heat-resistant flexible furan polyesters.

[0028] According to embodiments of the present invention, the alkaline solution comprises an aqueous sodium hydroxide solution with a concentration of 0.2~2.0 mol / L, for example, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 1.8 mol / L, or 2 mol / L, preferably 1.5~2.0 mol / L. The aqueous sodium hydroxide solution provides an alkaline environment, promoting electron transfer and thus facilitating the oxidation reaction, while also increasing the reaction rate and product selectivity. The addition of the aqueous sodium hydroxide solution also helps to activate oxygen molecules into reactive oxygen molecules, making it easier for oxygen to react with furfural compounds. The addition of a noble metal-supported catalyst to the aqueous sodium hydroxide solution helps to improve the dispersibility of the noble metal-supported catalyst, thereby increasing its activity and reaction efficiency. Using a strong alkaline solution as a solvent can prevent the adsorption of carboxylic acid groups on the noble metal-supported catalyst, thus preventing deactivation of the noble metal-supported catalyst during the reaction.

[0029] According to embodiments of the present invention, a noble metal-supported catalyst comprises a noble metal and a support, wherein the noble metal is supported on the support; the noble metal is ruthenium, iridium, or palladium, preferably ruthenium. The noble metal-supported catalyst exhibits high catalytic activity, promoting the transfer of electrons from furfural compounds to reactive oxygen molecules, accelerating the oxidation reaction, and reducing side reactions, thus contributing to improved reaction rate and selectivity in the preparation of furfural compounds. The noble metal-supported catalyst has a long service life, good chemical and thermal stability, is not easily deactivated, and is easily recyclable, allowing for repeated use in multiple oxidation reaction cycles, which helps reduce catalytic costs. Supporting the noble metal on the support improves the dispersion of the noble metal, increases the effective surface area of ​​the noble metal-supported catalyst, thereby improving catalytic efficiency. The use of noble metal-supported catalysts helps reduce the consumption of noble metals and reduce environmental impact, facilitating industrial production. Furthermore, ruthenium is used because, while possessing high catalytic activity and selectivity, it has a lower cost compared to iridium and palladium, and has broad application prospects.

[0030] According to embodiments of the present invention, the support comprises at least one selected from hydroxyapatite (HAP), zirconium dioxide, alumina, and magnesium oxide, preferably hydroxyapatite. The aforementioned support possesses high thermal and chemical stability, which helps to protect the noble metal and reduce its deactivation under alkaline conditions. The aforementioned support has a large specific surface area, which facilitates the uniform dispersion of the noble metal and improves catalytic efficiency. The interaction between the aforementioned support and the noble metal promotes the transfer of electrons from furfural compounds to reactive oxygen molecules, thereby accelerating the oxidation reaction. The aforementioned support helps protect the noble metal, reducing its physical and chemical damage during the oxidation process and extending its service life. After a reaction stage is completed, the aforementioned support can be recovered from the product through filtration or other methods; the presence of the aforementioned support helps to assist in the separation and reuse of the noble metal. Furthermore, using the aforementioned support can reduce the amount of noble metal used, lower costs, and facilitate industrial application.

[0031] According to embodiments of the present invention, the noble metal ruthenium and the aforementioned metal oxide support can mutually promote dispersion, which is beneficial to the adsorption of oxygen and the activation of oxygen molecules, thereby promoting the oxidation reaction.

[0032] According to embodiments of the present invention, a noble metal supported catalyst is prepared by mixing and stirring a noble metal precursor solution with a support, drying the mixture, and then subjecting it to a heating reduction treatment under a hydrogen atmosphere to obtain the noble metal supported catalyst. The noble metal precursor solution includes at least one of a ruthenium salt solution or hydrate, an iridium salt solution or hydrate, or a palladium salt solution or hydrate, preferably ruthenium trichloride hydrate. The noble metal ions in the precursor solution bind to the active sites on the support surface through physical adsorption or chemical adsorption. Stirring helps to achieve uniform dispersion of the noble metal precursor on the support, ensuring a uniform distribution of active sites on the catalyst and thus improving catalytic efficiency. Drying helps to remove moisture from the mixture, allowing the precursor solution to form a stable load on the support. During the drying process, the precursor solution may undergo hydrolysis or polymerization to form noble metal oxides or noble metal hydroxides. Heating in a hydrogen atmosphere helps hydrogen atoms in the gas adsorb onto the noble metal oxides or hydroxides on the support surface. This allows the hydrogen atoms to undergo a reduction reaction with the noble metal ions in the oxides or hydroxides, resulting in a high dispersion of the noble metal atoms on the support surface, forming active sites. The interaction between the support and the noble metal helps enhance the stability of the noble metal particles, reducing their aggregation and growth during the reaction process, thereby maintaining the long-term stability and activity of the noble metal supported catalyst.

[0033] Specifically, noble metal supported catalysts can be prepared using an impregnation method. Taking water and ruthenium trichloride as an example, the preparation process is as follows: First, the support is calcined in a muffle furnace at 350-450℃ for 3-5 hours. Ruthenium trichloride is dissolved in water and sonicated for 30 minutes to prepare a 250 mL ruthenium trichloride aqueous solution (1 mg / mL). Then, 1 g of support is added to a 100 mL flask, followed by a certain amount of ruthenium trichloride aqueous solution to obtain aqueous solutions with different ruthenium concentrations. After rotary evaporation, the solutions are dried in an oven at 100-120℃ for 10-16 hours, and then reduced in a hydrogen atmosphere for a certain period of time to obtain the ruthenium-based supported catalyst sample.

[0034] According to an embodiment of the present invention, the ruthenium-based supported catalyst sample needs to be ground to reduce the particle size before use, so as to increase the contact area of ​​the oxidation reaction and thus improve the reaction rate.

[0035] Preferably, the temperature for the heat reduction treatment is 300~600℃, for example, 400℃ or 500℃. Using this temperature range helps prevent the precious metal particles from sintering at excessively high temperatures, resulting in a more uniform distribution of active sites, maintaining high dispersion of the precious metal particles, and improving the selectivity for subsequent catalytic reactions. This temperature also allows for better control of the growth of the precious metal particles, preventing excessively large particles from reducing catalytic activity. Furthermore, this temperature helps ensure the cleanliness of the precious metal surface, removing impurities or oxide layers.

[0036] According to embodiments of the present invention, the loading of noble metal in the noble metal supported catalyst is 1-8 wt%, for example, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt%, preferably 3-5 wt%. Since noble metals are relatively expensive, using the above loading range helps reduce the preparation cost of the noble metal supported catalyst. Furthermore, the lower noble metal content helps improve its dispersion on the support, forming more and more uniform active sites, thereby improving catalytic efficiency. Due to the relatively low noble metal content, the aggregation and sintering of noble metal particles on the support are reduced, which helps maintain the long-term stability of the noble metal supported catalyst.

[0037] According to embodiments of the present invention, the mass ratio of water to furfural compound is (20~100):1, for example, it can be 30:1, 40:1, 50:1, 60:1, 70:1, 80:1 or 90:1, preferably (50~70):1. Water, as a solvent, can dissolve sodium hydroxide, forming a uniform alkaline environment. The above-mentioned mass ratio of water helps to participate in the oxygen activation process, promoting the oxidation reaction. The above-mentioned mass ratio of water helps to better dissolve furfural compound, increases the contact area in the reaction process, and improves the oxidation reaction rate; and the addition of water helps to dilute the reaction system, avoiding the formation of side reactions due to excessively rapid reaction.

[0038] According to embodiments of the present invention, the mass ratio of furfural compound to noble metal supported catalyst is (5~20):1, for example, it can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 18:1 or 20:1, preferably (15~20):1. The above-mentioned ratio of noble metal supported catalyst helps ensure sufficient catalytic active sites and reduces excessive oxidation or other side reactions of furfural compound during the reaction process, thereby improving the reaction rate, reaction selectivity and conversion rate. By controlling the mass ratio of furfural compound to noble metal supported catalyst, the utilization rate of the catalyst can be improved, waste can be reduced, and costs can be lowered. It also facilitates better recovery of the catalyst, thereby achieving recycling.

[0039] According to embodiments of the present invention, the pressure of the oxidation reaction is 0.2~3 MPa, for example, 0.1 MPa, 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa or 3 MPa, preferably 1.5~3 MPa. The temperature of the oxidation reaction is 80~140℃, for example, 90℃, 100℃, 110℃, 120℃ or 130℃, preferably 120~140℃. The time of the oxidation reaction is 2~8 h, for example, 3 h, 4 h, 5 h, 6 h or 7 h, preferably 4~6 h. During the relevant experiments of the present invention, it was found that when the parameters of the oxidation reaction are within the above ranges, the conversion rate and reaction yield of the furoic acid compound can be improved.

[0040] According to embodiments of the present invention, the oxidation reaction can be carried out, for example, in a reaction vessel, which facilitates heating and pressurization.

[0041] According to embodiments of the present invention, the preparation process of the present invention enables the efficient preparation of 5,5-oxydimethylene-2-furfural from 5,5-oxydimethylene-2-furfural through oxidation. The conversion rate of the raw material 5,5-oxydimethylene-2-furfural can reach 100%, ensuring complete consumption. The yield of 5,5-oxydimethylene-2-furfural can reach over 97%, demonstrating promising application prospects. Furthermore, the reaction process is green and pollution-free, without generating harmful substances, exhibiting good oxidation efficiency, and the obtained product is easy to process. The noble metal supported catalyst used in this invention is suitable for industrial production, especially the ruthenium-based supported catalyst, which is inexpensive, readily available, and recyclable, showing broad application prospects.

[0042] The present invention will be further illustrated below through embodiments, accompanying drawings, and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0043] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this invention is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods. The reaction vessel used is a high-temperature, high-pressure reactor.

[0044] Example 1:

[0045] Preparation of ruthenium-based supported catalyst 1:

[0046] Hydroxyapatite was first calcined in a muffle furnace at 400℃ for 4 hours. Ruthenium trichloride was dissolved in water and sonicated for 30 minutes to prepare a 250 mL ruthenium trichloride aqueous solution (concentration 1 mg / mL). Then, 1 g of hydroxyapatite was added to a 100 mL flask, followed by a certain amount of ruthenium trichloride aqueous solution to obtain a ruthenium salt solution. After rotary evaporation, the solution was dried in an oven at 100~120℃ for 12±2 hours, and then reduced in a hydrogen atmosphere at 450℃ to obtain a 3 wt% ruthenium-based supported catalyst 1.

[0047] Preparation of 5,5-oxybismethylene-2-furfural:

[0048] 0.2 g of 5,5-oxydimethylene-2-furfural (OBMF), ruthenium-based supported catalyst 1, and NaOH aqueous solution were mixed and added to a high-temperature and high-pressure reactor. O2 was introduced at 0.1 MPa, and the reaction was carried out at 120 °C for 4 h to obtain reaction solution 1.

[0049] After filtration, 37% hydrochloric acid was added dropwise and stirred until the pH was less than 1, causing the solid to precipitate. The reaction solution 1 was then allowed to stand overnight at 2-8°C to allow the product to precipitate completely. After filtration and drying, the product was then purified by recrystallization to obtain 5,5-oxydimethylene-2-furfural acid with a yield of 85.7%.

[0050] Figure 1 The 1H NMR spectrum of 5,5-oxydimethylene-2-furfuric acid prepared in Example 1 of this invention is shown. Figure 1 As shown, this confirms that 5,5-oxybismethylene-2-furfural acid can be prepared using this method.

[0051] Examples 2 to 7:

[0052] The preparation process of Examples 2 to 7 is basically the same as that of Example 1. The difference is that the reaction parameters are changed according to Table 1 below, including adjusting the pressure of oxygen to 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa and 3.0 MPa respectively. The yields obtained are shown in Table 1 below.

[0053] Examples 8 to 10:

[0054] The preparation process of Examples 8 to 10 is basically the same as that of Example 5. The difference is that the reaction parameters are changed according to Table 1 below, including adjusting the reaction temperature to 80℃, 100℃ and 140℃ respectively. The yields obtained are shown in Table 1 below.

[0055] Examples 11 to 13:

[0056] The preparation processes of Examples 11 to 13 are basically the same as those of Example 5, except that the reaction parameters are changed according to Table 1 below, including adjusting the reaction time to 2h, 6h and 8h respectively, and the yields obtained are shown in Table 1 below.

[0057] Examples 14-16:

[0058] The preparation processes of Examples 14 to 16 are basically the same as those of Example 5, except that the reaction parameters are changed according to Table 1 below, including adjusting the mass ratio of OBMF to catalyst to 5, 10, and 15 respectively. The yields obtained are shown in Table 1 below.

[0059] Examples 17-20:

[0060] The preparation process of Examples 17 to 20 is basically the same as that of Example 5, except that the reaction parameters are changed according to Table 1 below, including adjusting the concentration of NaOH aqueous solution to 0.2 mol / L, 0.5 mol / L, 1.5 mol / L and 2 mol / L respectively, and the yields obtained are shown in Table 1 below.

[0061] Examples 21-23:

[0062] The preparation processes of Examples 21 to 23 are basically the same as those of Example 5, except that the reaction parameters are changed according to Table 1 below, including adjusting the catalyst support to zirconium trioxide, alumina, and magnesium oxide respectively. The yields obtained are shown in Table 1 below.

[0063] Examples 24-29:

[0064] The preparation process of Examples 24 to 29 is basically the same as that of Example 5. The difference is that the reaction parameters are changed according to Table 1 below, including adjusting the loading of ruthenium catalyst to 1wt%, 2wt%, 4wt%, 5wt%, 8wt%, and 10wt% respectively. The yields obtained are shown in Table 1 below.

[0065] Examples 30-33:

[0066] The preparation process of Examples 24 to 29 is basically the same as that of Example 5. The difference is that the reaction parameters are changed according to Table 1 below, including adjusting the mass ratio of water to OBMF to 20, 30, 60 and 80 respectively. The yields obtained are shown in Table 1 below.

[0067] Examples 34-38:

[0068] The catalyst after the reaction in Example 5 was washed, dried, calcined, and reused. Examples 34 to 38 corresponded to the first to the fifth reuse, and the product yields are shown in Table 1 below.

[0069] Table 1. Reaction parameters and yields for the preparation of 5,5-oxydimethylene-2-furfural acid in Examples 1-33

[0070]

[0071]

[0072] A comparison of Examples 1 through 33 shows that the yields of 5,5-oxydimethylene-2-furonic acid prepared in Examples 5 and 12 are both 97.8%, representing the highest yield. In other words, the best yield of 5,5-oxydimethylene-2-furonic acid is achieved when the mass ratio of OBMF to catalyst is 20, the concentration of sodium hydroxide aqueous solution is 1 mol / L, the mass ratio of water to OBMF is 50, the oxygen pressure is 2.0 MPa, the reaction temperature is 120°C, the reaction time is 4 h, the catalyst support is hydroxyapatite, and the ruthenium loading in the ruthenium-based supported catalyst is 3 wt%. Examples 34 through 38 demonstrate that the catalyst can be recycled and reused after washing, drying, and calcination, thus saving costs.

[0073] Comparative Example 1:

[0074] The oxidation of 5,5-oxydimethylene-2-furfural was carried out in a reactor using a ruthenium-carbon catalyst.

[0075] 0.2 g of 5,5-oxydimethylene-2-furfural, 0.01 g of catalyst (commercial catalyst, ruthenium carbon catalyst with a loading of 5% wt), and 10 mL of 1.0 mol / L NaOH aqueous solution were mixed and added to a high-temperature and high-pressure reactor. O2 was introduced at 2.0 MPa and the reaction was carried out at 120 °C for 4 h to obtain reaction solution 1'. After post-treatment, high-purity 5,5-oxydimethylene-2-furfural monomer was obtained. The molar yield of the product was calculated to be 89.5%.

[0076] The comparison between Examples 1-33 and Comparative Example 1 shows that by using the preparation method of the present invention, the selectivity and product yield in the reaction process can be greatly improved, and it is expected to achieve the mass industrial production of 5,5-oxydimethylene-2-furfural.

[0077] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a furoic acid compound, comprising: The furfural compound, alkaline solution, and noble metal supported catalyst are mixed and oxidized under an oxygen atmosphere to prepare the furoic acid compound. The noble metal supported catalyst includes a noble metal and a support, wherein the noble metal is supported on the support, the noble metal is ruthenium, and the support is hydroxyapatite; The oxidation reaction is carried out at a pressure of 1.5~3.0 MPa, at a temperature of 120~130℃, and for a duration of 4~6 hours. The noble metal supported catalyst was prepared by the following method: After mixing and stirring the noble metal precursor solution with the support and drying it, the solution was subjected to heating and reduction treatment under a hydrogen atmosphere to obtain the noble metal supported catalyst. The heating reduction temperature is 400~500℃; the furfural compound is 5,5-oxydimethylene-2-furfural; the furoic acid compound is 5,5-oxydimethylene-2-furic acid.

2. The preparation method according to claim 1, wherein, The alkaline solution comprises an aqueous solution of sodium hydroxide, and the concentration of the alkaline solution is 0.2~2.0 mol / L.

3. The preparation method according to claim 2, wherein, The concentration of the alkaline solution is 1.5~2.0 mol / L.

4. The preparation method according to claim 2, wherein, The mass ratio of water to the furfural compound is (20~100):

1.

5. The preparation method according to claim 1, wherein, The loading of noble metals in the noble metal supported catalyst is 1~8 wt%.

6. The preparation method according to claim 1, wherein, The mass ratio of the furfural compound to the noble metal supported catalyst is (5~20):

1.

7. The preparation method according to claim 6, wherein, The mass ratio of the furfural compound to the noble metal supported catalyst is (15~20):1.

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