Process and system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid

Abstract

A process for continuously producing 5-hydroxymethylfurfural and 2,5-furandicarboxylic acid is disclosed, which comprises: (1) a step of intramolecularly dehydrating fructose-based carbohydrate in a two-phase reaction medium containing a polar organic solvent and an aqueous solution of a quaternary ammonium halide salt in the presence of a protonic acid catalyst to produce an organic phase containing 5-hydroxymethylfurfural; and (2) a step of adding water to the organic phase containing 5-hydroxymethylfurfural obtained in step (1), and oxidizing the 5-hydroxymethylfurfural in the presence of an oxidation catalyst and oxygen gas to produce 2,5-furandicarboxylic acid. This process can continuously produce 5-hydroxymethylfurfural and 2,5-furandicarboxylic acid starting from a fructose-based carbohydrate, and can avoid the separation and purification of 5-hydroxymethylfurfural in the process of producing 2,5-furandicarboxylic acid, and has the advantages of being simple, generating and discharging three types of waste, and being environmentally friendly.

Description

Detailed description of the invention

[0001] [Technical Field] This application relates to the preparation of oxygen-containing organic compounds, and more particularly to a process and system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid.

[0002] [Technical background] Due to the renewable nature and wide range of available sources of biomass, research into preparing fuels and fine chemicals from biomass using chemical catalysts has become an important research route for the utilization and conversion of biomass. Sugar compounds, represented by glucose and fructose, are important components of biomass resources. Starting from sugar compounds, new platform compounds and intermediates are prepared through chemical processes. Further conversion can effectively replace chemical products obtained from fossil resources, thereby effectively mitigating the energy crisis and environmental problems caused by the current heavy use of fossil resources. In recent years, 5-hydroxymethylfurfural (HMF), a product obtained by dehydrating hexose, has been recognized as an important bio-based furan compound. This compound and its derivatives can be further converted into various fine chemicals, and applications in polymer monomers, furan pharmaceutical intermediates, agrochemicals, or other fields are expected. Therefore, developing an efficient process for preparing HMF using sugar compounds is an important challenge for the effective utilization of biological resources. On the other hand, 2,5-franzicarboxylic acid (FDCA) can be obtained by catalytic oxidation of HMF. FDCA is used in the synthesis of bio-based polymer materials and can effectively improve heat resistance and mechanical properties. FDCA is considered an ideal substitute for terephthalic acid (PTA), a petroleum-derived monomer, and can be widely used in the synthesis of bio-based polymers such as polyesters, polyamides, and epoxy resins. Therefore, developing a synthesis process for 2,5-franzicarboxylic acid has significant application value and is important for the sustainable use of biomass.

[0003] HMF can be prepared from glucose or fructose. Compared to glucose, the fructose route does not require isomerization and only requires intramolecular dehydration of fructose under a protonic acid catalyst to obtain the desired product. The reaction rate is fast and the product yield is high. The fructose route is currently a hot research topic in HMF preparation processes. Research has shown that in order to improve HMF production yield and realize large-scale HMF production as soon as possible, it is urgent to establish a two-phase solvent system suitable for liquid acid catalysts and realize continuous HMF production technology. However, general liquid acid catalysts have high solubility in water and organic solvents, making it difficult to separate the reaction medium from the product. Therefore, it is necessary to establish an effective process for recovering the liquid acid catalyst by appropriate means while improving the yield and purity of the desired product, and to enhance the effective separation and integrated utilization of other by-products and impurities to reduce the environmental impact. In addition, attention should be paid to reaction factors other than catalysts and organic solvents, such as the role of salt compounds in improving HMF yield and overcoming inhibitory factors that existing reaction factors have on HMF yield.

[0004] On the other hand, in processes for preparing FDCA by selective oxidation of HMF, researchers often add alkaline compounds to the reaction process because FDCA has low solubility in water (<1g / 100mL water, 100°C). This generates soluble salt compounds of FDCA along with the FDCA product, thus improving the unidirectional processing capacity of the process. However, the FDCA salt compounds obtained in these processes cannot be directly used in polymer production or other processes and must be acidified (pH≒1) to be converted back to the FDCA product. This undoubtedly complicates the entire FDCA production process and reduces its environmental friendliness. CN108779088A discloses a process for preparing FDCA by oxidizing HMF in one or two steps without introducing alkaline compounds. This process effectively improves the solubility of FDCA by using a mixed solvent of water and an organic solvent. The catalyst used in this process is a supported metal catalyst, with metal components being Pt and Au, and the specific surface area of ​​the support being 20m². 2 / g~500m 2 The price range is limited to 1 / g. Due to the high price of Pt and Au (approximately 300 yuan / g to 400 yuan / g), the overall process cost is relatively high, making it difficult to apply in practice. CN111039906A realizes a method for preparing FDCA by oxidizing HMF in a mixed solvent of water and organic solvents by doping the surface of a carbon-based support with nitrogen. However, in this method, the process of doping the support with nitrogen is relatively complex, and consequently the cost of preparing the catalyst is high, making it also difficult to apply in practice.

[0005] Therefore, in order to solve the above problems in existing technologies, there is an urgent need to provide a simple, inexpensive, and green process for synthesizing 2,5-franzicarboxylic acid.

[0006] Please note that the information disclosed in the "Technical Background" section above is intended solely to enhance understanding of the background of this application, and therefore may contain information about existing technology already known to those skilled in the art.

[0007] [Summary of the Invention] One object of this application is to provide a process and system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid. This process can continuously produce 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid starting from a fructose-based carbohydrate, avoids the separation and purification of 5-hydroxymethylfurfural in the process of producing 2,5-franzicarboxylic acid, and has advantages such as being simple, generating and discharging three types of waste, and being environmentally friendly.

[0008] Another object of this application is to provide a process for producing 2,5-franzicarboxylic acid from 5-hydroxymethylfurfural, which avoids the complex processes of introducing alkali compounds and the resulting acidification treatments in conventional processes. At the same time, this process can use a Ru-based catalyst supported on a carbon-containing support with a high specific surface area as the oxidation catalyst. The catalyst preparation method is simple and inexpensive, the reaction process is green and concise, and the FDCA yield is high.

[0009] To achieve the above objective, in one embodiment, the present application provides a process for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid: (1) In a two-liquid-phase reaction medium comprising a polar organic solvent and an aqueous solution of a quaternary ammonium halide, a fructose-based carbohydrate is subjected to intramolecular dehydration in the presence of a proton acid catalyst to produce an organic phase containing 5-hydroxymethylfurfural; and (2) Add water to the organic phase containing 5-hydroxymethylfurfural obtained in step (1), and in the presence of an oxidation catalyst and oxygen gas, oxidize 5-hydroxymethylfurfural to produce 2,5-franzicarboxylic acid; The protonic acid catalyst is selected from hydrochloric acid, sulfuric acid, sulfonic acid, phosphoric acid, sulfamic acid, or a combination thereof; The oxidation catalyst comprises a support and an active metal component supported on the support, the active metal component comprising a noble metal selected from Ru, Pt, Pd, Au, or a combination thereof. Provide the process.

[0010] In another embodiment, this application relates to a process for producing 2,5-franzicarboxylic acid, comprising the following steps: The step of oxidizing 5-hydroxymethylfurfural in a mixed solvent containing an organic solvent and water, in the presence of an oxidation catalyst and oxygen gas, to produce 2,5-franzicarboxylic acid; The organic solvent is an aprotic polar organic solvent that is miscible with water. The oxidation catalyst comprises a support and an active metal component supported on the support, and the support is 1000 m 2 / g~2000m 2 It is activated carbon with a specific surface area of ​​ / g, and the active metal component contains Ru. Provide the process.

[0011] In yet another embodiment, the present application provides a reaction system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid. The system comprises a dehydration reaction unit, a phase separation unit and an oxidation reaction unit, wherein the dehydration reaction unit has an inlet and an outlet, the phase separation unit has an inlet, an aqueous phase outlet and an organic phase outlet, and the oxidation reaction unit has an inlet and an outlet, the outlet of the dehydration reaction unit is connected to the inlet of the phase separation unit, the aqueous phase outlet of the phase separation unit is connected to the inlet of the dehydration reaction unit, and the organic phase outlet of the phase separation unit is connected to the inlet of the oxidation reaction unit. A fructose-based carbohydrate is dehydrated in a dehydration reaction unit in the presence of a protonic acid catalyst in a two-phase reaction medium containing a polar organic solvent and an aqueous solution of a quaternary ammonium halide to produce a two-phase stream containing 5-hydroxymethylfurfural. The two-phase stream is then separated in a phase separation unit to produce an aqueous phase containing an acid catalyst and an organic phase containing 5-hydroxymethylfurfural. The aqueous phase containing the acid catalyst is returned to the dehydration reaction unit, and the organic phase containing 5-hydroxymethylfurfural is oxidized in an oxidation reaction unit to produce a stream containing 2,5-franzicarboxylic acid.

[0012] The process and system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid according to this application has one or more of the following advantages: 1. The catalyst and organic solvent used facilitate the large-scale production of 5-hydroxymethylfurfural (HMF); 2. By adjusting the solubility of HMF and the acid catalyst in the two-phase solution, after the dehydration reaction, HMF and the acid catalyst are retained in the organic and aqueous phases, respectively, solving the difficult problem of separating the liquid acid catalyst from the reaction medium and the target product, significantly simplifying the catalyst separation operation, and enabling continuous operation of the reaction; 3. During the dehydration reaction, in-situ separation of HMF and the acid catalyst is achieved, reducing the amount of acid in the HMF in the organic phase and avoiding the decomposition of HMF caused by the presence of the acid catalyst during high-temperature in-situ extraction of HMF; 4. By using the organic phase containing HMF directly as a raw material to produce 2,5-franzicarboxylic acid (FDCA), intermediate separation and purification processes are avoided, simplifying the FDCA production process. In the oxidation reaction for preparing 5-FDCA, by using a mixed solvent formed from an organic solution and water, the solubility of FDCA can be increased, the introduction of an alkali compound can be avoided, and the formation of an FDCA salt product can also be avoided. Since a solution containing FDCA can be directly obtained and FDCA can be obtained after separating and purifying the solution, the process flow is greatly simplified. At the same time, the situation where a large amount of waste acid and waste water are generated by the acidification process is avoided. 6. The Ru-based catalyst supported on a carbon-containing material having a high specific surface area can be used in the oxidation reaction step of the process of the present application. The preparation process of this catalyst is simple, less expensive, and favorable for large-scale production, and has good prospects for industrial application.

[0013] [Brief Description of the Drawings] The accompanying drawings, which form a part of this specification, are provided to provide a further understanding of the present application and should not be considered as limiting. The present application can be interpreted by referring to the drawings in combination with the following detailed description. In the drawings: FIG. 1 is a schematic flowchart of a preferred embodiment of the reaction system of the present application.

[0014] [Detailed Description of the Invention] Hereinafter, specific embodiments of the present application will be described in detail in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are only intended to illustrate and explain the present application and are not intended to limit the present application.

[0015] Any specific numerical value (including the endpoints of a numerical range) disclosed in this specification is not limited to the exact value of the number, but is understood to further cover values close to the exact value, for example, all possible values within ±5% of the exact value. Further, for the disclosed numerical ranges, one or more new numerical ranges can be obtained by any combination between the endpoint values of the range, between one endpoint value of the range and one specific point value within the range, and between any two specific point values within the range. These new numerical ranges are also regarded as specifically disclosed in this specification.

[0016] Unless otherwise specified, the terms used in this specification have the same meaning as generally understood by those skilled in the art. If a term is defined in this specification and its definition is different from the general understanding in the art, the definition in this specification shall prevail.

[0017] In this application, the term "sulfonic acid" refers to a group of strongly acidic organic compounds formed by connecting a sulfonic group (-SO3H) to a hydrocarbyl, having the general formula R-SO3H, where R is an alkyl or aryl, especially C1~C 12 alkyl or C6~C 12 hydrocarbyl such as aryl, and the alkyl group and aryl group can also optionally have substituents such as hydroxyl.

[0018] In this application, the term "low-boiling polar organic solvent" refers to a polar organic solvent having a boiling point close to that of water or lower than that of water (for example, having a boiling point of less than 110 °C at atmospheric pressure).

[0019] In this application, the term "quaternary ammonium halide salt" has the meaning generally understood in the art, and in particular, refers to a compound having the general formula R4NX, where each group R is independently a hydrocarbyl such as C1~C 12 hydrocarbyl, and X is a halogen such as fluorine, chlorine, bromine, or iodine. Optionally, the hydrocarbyl R may also have substituents such as hydroxyl and halogen.

[0020] In this application, the term "hydrocarbyl" has the meaning commonly understood in the art, and in particular refers to a group formed by removing a hydrogen atom from a hydrocarbon compound that may be saturated or unsaturated, including various aliphatic, alicyclic, and aromatic hydrocarbyls such as methyl, ethyl, propyl, butyl, allyl, cyclohexyl, and phenyl.

[0021] In this application, unless expressly stated otherwise, any problems or matters not described herein shall be governed by those known in the art without modification. Furthermore, any embodiment described herein may be freely combined with one or more other embodiments described herein, and any technical solution or technical idea thus formed shall be deemed to be part of the original disclosure or content of this application and shall not be deemed to be novel matter not disclosed or anticipated herein, unless a person skilled in the art would consider the combination to be obviously unreasonable.

[0022] All patent and non-patent documents referred to herein, including but not limited to textbooks and journal articles, are incorporated in their entirety by reference.

[0023] As described above, in the first embodiment, the present application is a process for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid: (1) In a two-liquid-phase reaction medium comprising a polar organic solvent and an aqueous solution of a quaternary ammonium halide, a fructose-based carbohydrate is subjected to intramolecular dehydration in the presence of a proton acid catalyst to produce an organic phase containing 5-hydroxymethylfurfural; and (2) The present invention provides a process comprising the step of adding water to the organic phase containing 5-hydroxymethylfurfural obtained in step (1), and oxidizing 5-hydroxymethylfurfural in the presence of an oxidation catalyst and oxygen gas to produce 2,5-frangic carboxylic acid.

[0024] In a preferred embodiment, in step (1), the fructose-based carbohydrate is selected from purified fructose, crude fructose, polyfructose, fructose syrup, fructose dextrose syrup, or a combination thereof.

[0025] In a preferred embodiment, in step (1), the quaternary ammonium halide salt is a quaternary ammonium halide salt having an unsubstituted C1-C 12 hydrocarbyl, a quaternary ammonium halide salt having a C1-C 12 hydrocarbyl substituted with hydroxy or halogen, or a combination thereof, more preferably selected from an unsubstituted C1-C6 hydrocarbyltrimethylammonium halide, a C1-C6 hydrocarbyltrimethylammonium halide substituted with hydroxy or halogen, or a combination thereof, still more preferably selected from an unsubstituted C1-C4 hydrocarbyltrimethylammonium chloride, an unsubstituted C1-C4 hydrocarbyltrimethylammonium bromide, a C1-C4 hydrocarbyltrimethylammonium chloride substituted with hydroxy or halogen, a C1-C4 hydrocarbyltrimethylammonium bromide substituted with hydroxy or halogen, or a combination thereof. Particularly preferred is that the quaternary ammonium halide salt is selected from tetramethylammonium chloride, tetramethylammonium bromide, choline chloride, chlorocholine chloride (chlormequat chloride), allyltrimethylammonium chloride, butyltrimethylammonium chloride, or a combination thereof, still more preferably selected from tetramethylammonium chloride, choline chloride, chlorocholine chloride, or a combination thereof.

[0026] In a preferred embodiment, in step (1), the polar organic solvent is a water-miscible aprotic polar organic solvent, preferably selected from acetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, or a combination thereof, and more preferably 1,4-dioxane.

[0027] Suitable proton acid catalysts for the processes of this application may be inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, sulfamic acid, and nitric acid; or organic acids such as aliphatic carboxylic acids (acetic acid, propionic acid, etc.), sulfonic acid, and sulfinic acid; preferably selected from hydrochloric acid, sulfuric acid, sulfonic acid, phosphoric acid, sulfamic acid, or a combination thereof, more preferably selected from sulfamic acid, sulfuric acid, and sulfonic acid, and particularly preferably selected from sulfuric acid and sulfonic acid. When sulfamic acid, sulfuric acid, and sulfonic acid are used as proton acid catalysts in the processes of this application, higher catalyst recovery rates can be achieved. In particularly preferred embodiments, the sulfonic acid is selected from benzenesulfonic acid, methylsulfonic acid, or a combination thereof, and more preferably methylsulfonic acid.

[0028] According to this application, in step (1), the proton acid catalyst can establish a stronger hydrogen bonding network with water in the presence of the specific organic solvent used. Therefore, the catalyst is soluble in aqueous solution of quaternary ammonium halide but insoluble in the organic solvent. Consequently, after the reaction is complete and the organic solvent and the aqueous solution of quaternary ammonium halide separate, the acid catalyst is substantially retained in the lower layer of aqueous solution of quaternary ammonium halide and separated in situ from the upper layer of the target product. At this point, the aqueous phase solution is a mixed aqueous solution of quaternary ammonium halide and liquid acid, and there is no need to further separate the quaternary ammonium halide from the acid catalyst; it can be recovered directly by liquid separation. After decolorization, it can be reused as is. The small amount of acid catalyst remaining in the organic phase can be neutralized by adding an equal amount of alkali. The resulting salt precipitates from the organic phase and can be filtered directly without affecting solvent recovery. In this way, the difficult problem of separating the liquid acid catalyst from the target product is solved, and the continuous production of 5-hydroxymethylfurfural can be achieved.

[0029] In a preferred embodiment, step (1) further comprises phase separation of the dehydration reaction product to obtain an aqueous phase containing an acid catalyst and an organic phase containing 5-hydroxymethylfurfural. According to this application, in step (1), when the fructose-based carbohydrate is dehydrated to prepare the target product, 5-hydroxymethylfurfural is extracted into the organic solvent in real time. Therefore, after the reaction is complete and the organic solvent and the aqueous solution of the quaternary ammonium halide have phase-separated, 5-hydroxymethylfurfural is present in the upper organic solvent. At the same time, the upper organic solvent is brown in color because by-products and impurities such as humic acid generated during the reaction remain in the organic phase. As a specific example, the phase separation process of a two-liquid-phase reaction system of a dehydration reaction includes a system in which, after the reaction is complete and stirring is stopped, the organic solvent and the aqueous solution of the quaternary ammonium halide immediately separate into an upper and lower phase due to the salting-out effect of the quaternary ammonium halide. Here, the upper phase is the organic solvent and the lower phase is the aqueous solution of the quaternary ammonium halide, and a clear phase interface exists between the two phases. These two phases can be separated by conventional processes, such as syringe extraction, separation funnel separation, or other conventional processes in the art for separating and removing the two phases.

[0030] In some more preferred embodiments, in step (1), after phase separation, a portion of the organic phase containing 5-hydroxymethylfurfural is decolorized and separated and purified to obtain 5-hydroxymethylfurfural. Preferably, the decolorization treatment can be carried out by activated carbon adsorption, and the separation and purification process may include vacuum distillation of the decolorized 5-hydroxymethylfurfural solution, followed by crystallization or recrystallization, followed by freeze-drying. Furthermore, the process of the present application may also include calcining the activated carbon that has adsorbed impurities at a high temperature to restore the adsorption capacity of the activated carbon.

[0031] In a preferred embodiment, in step (1), the mass ratio of the fructose-based carbohydrate to the reaction medium is 1:1 to 1000, preferably 1:2 to 100, more preferably 1:5 to 20, and the reaction system is a two-liquid-phase reaction medium consisting of a polar organic solvent and an aqueous solution of a quaternary ammonium halide.

[0032] In a preferred embodiment, in step (1), the mass ratio of the fructose-based carbohydrate to the quaternary ammonium halogenated salt is 1:0.1 to 10, preferably 1:1 to 5.

[0033] In a preferred embodiment, in step (1), the ratio of the volume of the quaternary ammonium halide aqueous solution to the total volume of the reaction medium is 5% to 50%, preferably 10% to 35%.

[0034] In a preferred embodiment, in step (1), the concentration of the proton acid catalyst in the aqueous phase of the reaction medium is 0.02 g / mL to 0.5 g / mL, preferably 0.03 g / mL to 0.1 g / mL, based on the mass of the proton acid.

[0035] In a preferred embodiment, step (1) includes the following conditions for the dehydration reaction: a reaction temperature of 80°C to 200°C, preferably 100°C to 150°C; and a reaction time of 0.1 hours to 12 hours, preferably 0.1 hours to 1 hour.

[0036] According to this application, the reactor used for the dehydration reaction in step (1) can be a thick-walled pressure vessel, a stainless steel reactor with polytetrafluoroethylene (PTFE) lining, and other reactors commonly used in the art. To facilitate observation of the phase interface between the aqueous and organic phases and to further facilitate the two-phase separation operation, the reactor is preferably a thick-walled pressure vessel.

[0037] According to this application, the organic phase containing 5-hydroxymethylfurfural obtained in step (1) has a relatively high content of 5-hydroxymethylfurfural and a relatively low content of impurities, and therefore can be used directly as a raw material for producing 2,5-franzicarboxylic acid for the oxidation reaction described in step (2) in the presence of an oxidation catalyst and oxygen gas, without undergoing a separation and purification process.

[0038] In a preferred embodiment, the oxidation reaction in step (2) is carried out without the presence of an alkali.

[0039] According to this application, the oxidation catalyst used in step (2) is a supported metal catalyst, which preferably comprises a support and an active metal component supported on the support. The active metal component comprises a noble metal selected from Ru, Pt, Pd, Au, or a combination thereof, and preferably Ru. In a preferred embodiment, the active metal component of the oxidation catalyst is Ru, or a combination of Ru and one or more selected from Pt, Pd, and Au. For example, the active metal component may be a combination of Ru and one or more selected from Pt, Pd, and Au, and the mass content of Ru is 5% to 100%, preferably 20% to 100%, more preferably 40% to 100%, even more preferably 50% to 100%, and particularly preferably 60% to 100%, based on the total mass of the active metal component.

[0040] In preferred embodiments, the content of the active metal component in the oxidation catalyst is 0.25% to 30%, preferably 1% to 20%, more preferably 5% to 15%, based on the total mass of the carrier, and particularly preferably the Ru content is 5% to 15%.

[0041] In preferred embodiments, the carrier is a carbon-containing material, preferably selected from activated carbon, carbon nanotubes, graphene, graphene oxide, or a combination thereof, and more preferably activated carbon. In even more preferred embodiments, the carrier is 1000 m 2 / g~2000m 2 / g, preferably 1000m 2 / g~1500m2 The activated carbon has a specific surface area of ​​1 / g; more preferably, the activated carbon has a pore size of about 1 nm to 5 nm. The inventors of this application have found that a high specific surface area (1000 m²) is difficult to predict. 2 / g~2000m 2 We found that using a Ru-based catalyst supported on a carbon-containing material (such as activated carbon) with a specific surface area (1000 m²) is more suitable for the HMF oxidation reaction process for preparing FDCA in a mixed solvent consisting of water and an organic solvent under alkali-free conditions. 2 / g~2000m 2 Activated carbon having ( / g) can be used as a carrier without treatment with an alkaline nitrogen-containing compound, and as a result, a Ru-based catalyst with excellent performance can be obtained, simplifying the catalyst preparation process and reducing costs. Therefore, the oxidation catalyst used in this application is preferably one that is substantially free of nitrogen elements, for example, one in which the nitrogen element content is less than 0.01% of the catalyst weight.

[0042] According to this application, oxidation catalysts can be prepared according to existing processes such as isococcal impregnation processes, intensive wetting impregnation processes, ion exchange processes, deposition and precipitation processes, or vacuum impregnation processes. For example, in some specific embodiments, after depositing an active metal component on a support, the resulting solid powder is dried in an oven at a temperature of 100°C to 140°C for about 6 to 24 hours, the resulting catalyst precursor is first calcined in nitrogen gas at a temperature of 300°C to 800°C for a certain period of time, and then reduced in a reducing atmosphere (such as H2, or a mixed atmosphere of H2 and N2) at a temperature of 200°C to 500°C for about 6 to 24 hours to obtain an oxidation catalyst. The oxidation catalyst preparation process used in this application is simple, inexpensive, easily scalable to large-scale production, and has good prospects for industrial application.

[0043] In a preferred embodiment, in step (2), the mass ratio of the organic phase containing 5-hydroxymethylfurfural to water is 5:1 to 0.5:1, preferably 3:1 to 1:1.

[0044] In a preferred embodiment, in step (2), the oxidation catalyst is used in such an amount that the molar ratio of the active metal component in the oxidation catalyst to 5-hydroxymethylfurfural is 1:1 to 1000, preferably 1:5 to 500, and more preferably 1:5 to 250.

[0045] In a preferred embodiment, in step (2), the conditions for the oxidation reaction include a reaction temperature of 50°C to 170°C, preferably 90°C to 150°C, and an oxygen gas partial pressure of 0.2 MPa to 4 MPa, preferably 1 MPa to 3 MPa, and more preferably the oxidation reaction is carried out in an oxygen gas atmosphere, an air atmosphere, or a mixed atmosphere of oxygen gas and nitrogen gas.

[0046] In a preferred embodiment, step (2) further comprises separating and purifying the product of the 2,5-franzicarboxylic acid solution obtained from the oxidation reaction to obtain 2,5-franzicarboxylic acid. More preferably, the separation and purification process comprises subjecting the solution containing 2,5-franzicarboxylic acid to vacuum distillation, with a distillation temperature of 30°C to 100°C, preferably 30°C to 50°C, and a distillation time of 1 hour to 10 hours, preferably 2 hours to 4 hours; or, the separation and purification process comprises subjecting the solution containing 2,5-franzicarboxylic acid to crystallization or recrystallization, with a crystallization temperature of -10°C to 30°C, preferably 0°C to 20°C, and a crystallization time of 1 hour to 24 hours, preferably 5 hours to 10 hours. Even more preferably, the purification process further comprises a process of drying the product after distillation or crystallization, the drying process preferably being freeze-drying. The drying time is 3 hours to 24 hours, preferably 18 hours to 24 hours.

[0047] In a second embodiment, the present application relates to a process for producing 2,5-franzicarboxylic acid, comprising the following steps: The step of oxidizing 5-hydroxymethylfurfural in a mixed solvent containing an organic solvent and water, in the presence of an oxidation catalyst and oxygen gas, to produce 2,5-franzicarboxylic acid; The oxidation catalyst comprises a support and an active metal component supported on the support, and the support is 1000 m 2 / g~2000m 2 / g, preferably 1000m 2 / g~1500m 2 Activated carbon having a specific surface area of ​​ / g, and the active metal component includes Ru. Provide the process.

[0048] In a preferred embodiment, the oxidation reaction of the process of this application is carried out without the presence of an alkali.

[0049] In preferred embodiments, the organic solvent used is a water-miscible aprotic polar organic solvent, preferably selected from acetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, dimethyl sulfoxide, or a combination thereof, more preferably 1,4-dioxane; In the oxidation reaction of the processes of the first and second embodiments of this application, on the one hand, the mixed solvent formed from the organic solvent in the raw materials and the added water can increase the solubility of the 2,5-franzicarboxylic acid product, thereby avoiding the introduction of alkali compounds and the generation of salt products. Since the solution containing 2,5-franzicarboxylic acid can be obtained directly, and then the 2,5-franzicarboxylic acid can be obtained after separation and purification of the solution, the product post-treatment step is simplified, and the generation of large amounts of waste acid and wastewater in the subsequent acidification process can be avoided. On the other hand, the price of the active metal Ru used as the oxidation catalyst is significantly lower than that of metals such as Pt or Au. At the same time, the catalyst can be prepared by a simple process from commercially available activated carbon and metal precursors, and the FDCA yield is also high (over 90%). Compared with the disclosed process, the process of this application greatly simplifies the process flow and reduces costs. The reaction process is green and simple, and the FDCA yield is high. This is an FDCA preparation process with great industrial potential.

[0050] In preferred embodiments, the active metal component of the oxidation catalyst is Ru, or a combination of Ru and one or more selected from Pt, Pd, and Au. For example, the active metal component may be Ru, or a combination of Ru and one or more selected from Pt, Pd, and Au, with the mass content of Ru being 40% to 100%, preferably 50% to 100%, and more preferably 60% to 100%, based on the total mass of the active metal component. According to the second aspect of this application, other features of the oxidation catalyst may be those described in the first aspect of this application and will not be described again here.

[0051] In a preferred embodiment, the mixed solvent consists of an organic solvent and water. More preferably, the mass ratio of the organic solvent to water in the mixed solvent is 5:1 to 0.5:1, preferably 3:1 to 1:1.

[0052] In a preferred embodiment, in the solution formed from 5-hydroxymethylfurfural and the mixed solvent, the mass percentage of 5-hydroxymethylfurfural is 0.1% to 30%, preferably 0.5% to 20%, and more preferably 1% to 10%.

[0053] In preferred embodiments, the oxidation catalyst is used in such an amount that the molar ratio of the active metal component in the oxidation catalyst to 5-hydroxymethylfurfural is 1:1 to 1000, preferably 1:5 to 500, and more preferably 1:5 to 250.

[0054] In preferred embodiments, the oxidation reaction conditions include a reaction temperature of 50°C to 170°C, preferably 90°C to 150°C, and an oxygen gas partial pressure of 0.2 MPa to 4 MPa, preferably 1 MPa to 3 MPa. More preferably, the oxidation reaction is carried out in an oxygen gas atmosphere, an air atmosphere, or a mixed atmosphere of oxygen gas and nitrogen gas.

[0055] In a third aspect, the present application provides a reaction system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid. The system comprises a dehydration reaction unit, a phase separation unit and an oxidation reaction unit, wherein the dehydration reaction unit has an inlet and an outlet, the phase separation unit has an inlet, an aqueous phase outlet and an organic phase outlet, and the oxidation reaction unit has an inlet and an outlet, the outlet of the dehydration reaction unit is connected to the inlet of the phase separation unit, the aqueous phase outlet of the phase separation unit is connected to the inlet of the dehydration reaction unit, and the organic phase outlet of the phase separation unit is connected to the inlet of the oxidation reaction unit. A fructose-based carbohydrate is dehydrated in a dehydration reaction unit in the presence of a protonic acid catalyst in a two-phase reaction medium containing a polar organic solvent and an aqueous solution of a quaternary ammonium halide to produce a two-phase stream containing 5-hydroxymethylfurfural. The two-phase stream is then separated in a phase separation unit to produce an aqueous phase containing an acid catalyst and an organic phase containing 5-hydroxymethylfurfural. The aqueous phase containing the acid catalyst is returned to the dehydration reaction unit, and the organic phase containing 5-hydroxymethylfurfural is oxidized in an oxidation reaction unit to produce a stream containing 2,5-franzicarboxylic acid.

[0056] In a preferred embodiment, the dehydration reaction unit includes a dehydration reactor selected from a slurry bed, a bubbling bed, a shell and tube reactor, or a combination thereof.

[0057] In a preferred embodiment, the oxidation reaction unit includes an oxidation reactor selected from a slurry bed, a fixed bed, a bubbling bed, or a combination thereof.

[0058] In a preferred embodiment, the phase separation unit includes a phase separation tank and the like.

[0059] In a preferred embodiment, the reaction system further comprises a purification unit and a drying unit, wherein a stream containing 2,5-franzicarboxylic acid from the oxidation reaction unit is processed in the purification unit and the drying unit to obtain a product of 2,5-franzicarboxylic acid.

[0060] In a more preferred embodiment, the purification unit may be a distillation separation unit, and the separation apparatus may be a vacuum distillation column or a molecular distiller; the purification unit may also be a crystallization separation unit, and the separation apparatus may be a fluidized bed, a tubular continuous crystallizer or a precipitation crystallizer, etc.; the purification unit may also be an adsorption separation unit, and the separation apparatus may be an activated carbon adsorption column.

[0061] In a more preferred embodiment, the drying unit includes a dryer selected from a spray dryer, a fluidized bed dryer, an air dryer, a box dryer, or a combination thereof.

[0062] In a preferred embodiment, the reaction system further comprises a decolorization and purification unit and a freeze-drying unit, wherein a portion of the organic phase containing 5-hydroxymethylfurfural from the phase separation unit is processed in the decolorization and purification unit and the freeze-drying unit to obtain a 5-hydroxymethylfurfural product. Particularly preferably, the decolorization and purification unit includes an activated carbon adsorption column, a vacuum distillation column and a crystallizer, and the freeze-drying unit includes a freeze-dryer.

[0063] In a preferred embodiment, the reaction system of this application may include an activated carbon furnace and a corresponding exhaust gas absorber.

[0064] Preferred embodiments of the reaction system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid of this application are described in detail below with reference to the accompanying drawings.

[0065] As shown in Figure 1, the reaction system comprises a dehydration unit, a phase separation unit, an oxidation unit, a purification unit, and a drying unit. A fructose-based carbohydrate raw material is subjected to intramolecular dehydration in the dehydration unit in the presence of a protonic acid catalyst in a two-phase reaction medium containing a polar organic solvent and an aqueous solution of a quaternary ammonium halide to produce a two-phase stream containing 5-hydroxymethylfurfural. The two-phase stream is separated in the phase separation unit to produce an aqueous phase containing an acid catalyst and an organic phase containing 5-hydroxymethylfurfural. The aqueous phase containing the acid catalyst is returned to the dehydration unit. The organic phase containing 5-hydroxymethylfurfural is oxidized in the oxidation unit to produce a solution containing 2,5-franzicarboxylic acid. This solution containing 2,5-franzicarboxylic acid is separated and / or purified in the purification unit and then dried in the drying unit to obtain the 2,5-franzicarboxylic acid product.

[0066] In a preferred embodiment, this application provides the following technical solution: A process for the continuous production of 1,5-hydroxymethylfurfural and 2,5-franzicarboxylic acid: (1) In a two-phase reaction system consisting of a low-boiling polar organic solvent and an aqueous solution of a quaternary ammonium halide, a fructose-based carbohydrate is subjected to intramolecular dehydration in a reactor under the catalytic action of a strongly acidic liquid acid catalyst containing a sulfonic acid group; after the reaction is complete, the reaction system is separated into an aqueous phase and an organic phase containing 5-hydroxymethylfurfural; and (2) Using the organic phase containing 5-hydroxymethylfurfural from step (1) as a raw material, water is added, and the 5-hydroxymethylfurfural is oxidized in a reactor in the presence of an oxidation catalyst and oxygen gas to produce a solution containing 2,5-franzicarboxylic acid, which is then separated and purified to obtain 2,5-franzicarboxylic acid; Oxidation catalysts are supported metal catalysts.

[0067] 2. The process described in item 1, wherein in step (1), the fructose-based carbohydrate is one of the following: refined fructose, crude fructose, polyfructose, fructose syrup, and fructose dextrose syrup.

[0068] 3. The process described in item 1, wherein in step (1), the liquid acid catalyst is selected from sulfuric acid, methylsulfonic acid, or a combination thereof.

[0069] 4. In step (1), the quaternary ammonium halide salt is C1-C 12 Hydrocarbyl quaternary ammonium halide salts, and C1-C substituted with hydroxyl or halogen 12 The process according to item 1, wherein the salt is selected from hydrocarbyl halogenated quaternary ammonium salts, preferably one or more C1-C6 hydrocarbyl trimethylammonium halides and C1-C6 hydrocarbyl trimethylammonium halides substituted with hydroxyl or halogen, and more preferably one or more C1-C4 hydrocarbyl trimethylammonium chloride or bromide and C1-C4 hydrocarbyl trimethylammonium chloride or bromide substituted with hydroxyl or halogen.

[0070] 5. The process according to item 1, wherein in step (1), the quaternary ammonium halide is one of tetramethylammonium chloride, collinchloride, and chlorocolinchloride.

[0071] 6. The process according to item 1, wherein in step (1), the polar organic solvent is one or two of acetone, tetrahydrofuran, 1,4-dioxane, and acetonitrile, preferably 1,4-dioxane.

[0072] 7. The process described in item 1, wherein in step (1), the mass ratio of the fructose-based carbohydrate to the reaction system is 1:1 to 1000, preferably 1:2 to 100, more preferably 1:5 to 20, where the reaction system refers to the sum of the polar organic solvent and the aqueous solution of the quaternary ammonium halide.

[0073] 8. The process according to item 1, wherein in step (1), the aqueous solution of a quaternary ammonium halide constitutes 5% to 50%, preferably 10% to 35%, of the total volume of the reaction system.

[0074] 9. The process according to item 1, wherein in step (1), the concentration of the liquid acid catalyst in the aqueous phase is 0.02 g / mL to 0.5 g / mL, preferably 0.03 g / mL to 0.1 g / mL.

[0075] 10. The process according to item 1, wherein in step (1), the temperature of the dehydration reaction is 80°C to 200°C, preferably 100°C to 150°C; and the duration of the dehydration reaction is 0.1 hours to 12 hours, preferably 0.1 hours to 1 hour.

[0076] 11. The process according to item 1, wherein in step (2), the supported metal catalyst comprises a carrier and a metal supported on the carrier, and the metal is Ru, or a combination of Ru and one or more of Pt, Pd, or Au.

[0077] 12. The process according to item 11, wherein in step (2), the mass content of Ru in the combination consisting of Ru and one or more of Pt, Pd or Au is 5% to 95%, preferably 20% to 90%, more preferably 40% to 80%.

[0078] 13. The process according to item 11, wherein in step (2), the metal is supported in the supported metal catalyst in an amount of 0.25% to 30%, preferably 1% to 20%, more preferably 5% to 15%, based on the total mass of the support.

[0079] 14. The process according to item 11, wherein in step (2), the support is selected from a carbon-containing material comprising one or more of activated carbon, carbon nanotubes, graphene, and graphene oxide, and is preferably activated carbon.

[0080] 15. If the carrier in step (2) is activated carbon, the activated carbon is 1000m 2 / g~1500m 2 The process described in item 14, having a specific surface area of ​​ / g.

[0081] 16. The process according to item 1, wherein in step (2), the mass ratio of the organic phase containing 5-hydroxymethylfurfural to water is 5:1 to 0.5:1, preferably 3:1 to 1:1.

[0082] 17. The process according to item 1, wherein in step (2), the molar ratio of the metal in the supported metal catalyst to 5-hydroxymethylfurfural is 1:1 to 1000, preferably 1:5 to 500, and more preferably 1:5 to 250.

[0083] 18. In step (2), the oxygen gas is derived from pure oxygen, air, or a mixed gas consisting of oxygen gas and nitrogen gas, and the oxygen gas has a partial pressure of 0.2 MPa to 4 MPa, preferably 1 MPa to 3 MPa, the process as described in item 1.

[0084] 19. The process according to item 1, wherein in step (2), the reaction temperature of the oxidation reaction is 50°C to 170°C, preferably 90°C to 150°C.

[0085] 20. A reaction system for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid, comprising a dehydration reaction unit, a phase separation unit, an oxidation reaction unit, a separation and purification unit, and a drying unit.

[0086] 21. The reaction system according to item 20, wherein a fructose-based carbohydrate is dehydrated in a dehydration reaction unit to prepare 5-hydroxymethylfurfural, the dehydration reactor is a slurry bed, a bubbling bed, or a shell and tube reactor, and after the reaction is complete, the two-liquid-phase reaction system is supplied to a phase separation unit for automatic phase separation.

[0087] 22. The reaction system according to item 20, wherein an organic phase containing 5-hydroxymethylfurfural, separated from a phase separation unit, is supplied to a reactor of an oxidation reaction unit, and the oxidation reactor is a slurry bed, a fixed bed, or a bubbling bed.

[0088] 23. The reaction system according to item 20, wherein the reaction solution containing 2,5-franzicarboxylic acid obtained from the oxidation reaction unit is passed through a separation and purification unit and a drying unit to obtain the product of 2,5-franzicarboxylic acid.

[0089] 24. The reaction system described in item 20, wherein the reactor of the separation and purification unit is selected from a vacuum distillation column, molecular distillation apparatus, fluidized bed, tubular continuous crystallizer, or precipitation crystallizer.

[0090] 25. The reaction system according to item 20, wherein the organic phase containing 5-hydroxymethylfurfural, separated from the phase separation unit, is partially supplied to a decolorization and purification unit and a freeze-drying unit to obtain the product of 2,5-franzicarboxylic acid.

[0091] 26. The reaction system according to item 25, wherein the decolorization and purification unit includes an activated carbon adsorption column, a vacuum distillation column, and a crystallization apparatus, and the freeze-drying unit includes a freeze-dryer.

[0092] [Examples] Unless otherwise noted, the experimental methods used in the following examples and comparative examples are conventional methods.

[0093] The materials and reagents used in the following examples and comparative examples can be obtained from commercially available sources unless otherwise specified, and their purity is analytical purity grade. The source of 5-hydroxymethylfurfural is Beijing Innochem Science and Technology Co. Ltd.; the sources of activated carbon are Beijing Dali Hongye Technology Co. Ltd. (analytically pure, hereinafter referred to as "Dali Hongye"), Calgon Carbon (Suzhou) Co. Ltd. (brand: OVC 4x8, 107C), and Cabot (China) Investment Co. Ltd. (brand: VXC72); methylsulfonic acid and sulfamic acid were purchased from China Sinopharm Chemical Reagent Co. Ltd.; and tetramethylammonium chloride was purchased from Beijing Innochem Science and Technology Co. Ltd.

[0094] In the following examples and comparative examples, high-performance liquid chromatography was used to analyze and calculate the conversion rate of the reaction substrate, as well as the selectivity, yield, and purity of the target product in the reaction process.

[0095] [Preparation Examples 1-6] The oxidation catalyst 10% Ru / C was prepared by the intensive wet impregnation method: An aqueous RuCl3 solution containing 0.1 g of Ru and 10.0 mL of deionized water were mixed and stirred uniformly. Then, 1.0 g of activated carbon support was added to the mixed solution. Impregnation was carried out at room temperature for 10 hours with stirring. The water was evaporated and the mixture was dried. The resulting solid was then placed in an oven at 110°C and dried for 12 hours to obtain a catalyst precursor. The Ru loading amount was 10 (mass)%. The precursor prepared in the above steps was placed in a quartz tube and first calcined in nitrogen at 500°C for 4 hours, and then reduced in 20% H2 + N2 at 500°C for 3 hours to produce catalyst C1 with a Ru / C loading of 10%.

[0096] Different catalysts C2 to C6 were prepared by supporting varying amounts of Ru on various commercially available activated carbon powders or particles using the same method. The compositions and specific surface areas of these catalysts are shown in Table I-1 below.

[0097] [Preparation Examples 7-11] The oxidation catalyst 10%Ru-5%Pt / C was prepared by the intensive wet impregnation method: An aqueous solution of RuCl3 containing 0.1 g of Ru, an aqueous solution of H2PtCl6 containing 0.05 g of Pt, and 10.0 mL of deionized water were mixed and stirred uniformly. Then, 1.0 g of activated carbon support was added to the mixed solution. Impregnation was carried out at room temperature for 10 hours with stirring. The water was evaporated and the mixture was dried. The resulting solid was then placed in an oven at 110°C and dried for 12 hours to obtain a catalyst precursor. The loading amount of Ru was 10 (mass)% and the loading amount of Pt was 5 (mass)%. The precursor prepared in the above steps was placed in a quartz tube and first calcined in nitrogen at 500°C for 4 hours, and then reduced in 20% H2 + N2 at 500°C for 3 hours to produce catalyst C7 with a loading of 10% Ru-5% Pt / C.

[0098] Different catalysts C8-C11 were prepared by supporting various amounts of Ru and Pt / Pd / Au on various commercially available activated carbon powders or particles using the same method. The compositions and specific surface areas of these catalysts are shown in Table I-1 below.

[0099] [Preparation Examples 8-12] Following the procedure of Preparation Example 1, different catalysts D1 to D5 were prepared by supporting various amounts of Pt or Au on various commercially available activated carbon powders or particles. The compositions and specific surface areas of these catalysts are shown in Table I-3 below.

[0100] [Preparation Examples 13-14] Different catalysts D6-D7 were prepared by supporting various amounts of Ru on commercially available silica (SiO2) or zirconia (ZrO2) powder or particles according to the procedure of Preparation Example 1. The compositions and specific surface areas of these catalysts are shown in Table I-4 below.

[0101] [Preparation Examples 15-16] Different catalysts D8-D9 were prepared by supporting various amounts of Ru on activated carbon powder or particles treated with an alkaline nitrogen-containing compound, according to the methods reported in Preparation Examples 1-2 of Patent CN111039906A. The compositions and specific surface areas of these catalysts are shown in Table I-5 below.

[0102] [Examples I-1 to I-4] This example is used to illustrate the synthesis process of 2,5-franzicarboxylic acid according to this application.

[0103] A 50 mL high-pressure reactor was filled with 0.5 g of 5-hydroxymethylfurfural, 0.2 g of 10% Ru / C oxidation catalysts C1-C4 obtained in Preparation Examples 1-4, and a mixed solvent consisting of 10 g of water and 1,4-dioxane (mass ratio of water to 1,4-dioxane = 1:1). After sealing the reactor, 1 MPa of oxygen was added to replace any remaining air inside. This was repeated three times, and then 1 MPa of oxygen was added to the reactor. The reactor was placed on a heating furnace and heated to a reaction temperature of 100°C. The reaction was carried out for 10 hours at a rotation speed of 700 rpm under stirring. After the reaction was complete, the reactor was removed from the heating furnace and cooled to room temperature. The filtration was performed, and the filtration cake was washed with the same mixed solvent as the reaction solvent, and the final volume was adjusted to 100 mL. A liquid sample was taken for high-performance liquid chromatography analysis. The reaction results are shown in Table I-1.

[0104] [Examples I-5 to I-6] The Ru / C catalysts C5-C6, supported on Dali Hongye activated carbon obtained in Preparation Examples 5-6, were used as oxidation catalysts. The experiment was carried out according to the method of Example I-1, except that the amount of Ru supported in the oxidation catalyst was set to 5% or 15%. The reaction results are shown in Table I-1.

[0105] [Examples I-7 to I-8] The experiment was conducted according to the method of Example I-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst, and the oxygen pressure was set to 2 MPa or 3 MPa. The reaction results are shown in Table I-1.

[0106] [Examples I-9 to I-10] The experiment was conducted according to the method of Example I-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst, and the reaction temperature was set to 120°C or 140°C. The reaction results are shown in Table I-1.

[0107] [Examples I-11 to I-15] The experiment was carried out according to the method of Example I-1, except that catalysts C7-C11 supported on Dali Hongye activated carbon obtained in Preparation Examples 7-11 were used as oxidation catalysts. The reaction results are shown in Table I-1.

[0108] [Table 1]

[0109] From the data in Table I-1, we can see the following: 1. The specific surface area of ​​the activated carbon support for the Ru / C oxidation catalyst had a significant impact on the catalyst activity and the yield of FDCA. 2 When the value exceeded 1 / g, the FDCA yield reached over 90%. 2. The amount of Ru supported in the Ru / C oxidation catalyst affects the catalyst performance; however, when the support amount was in the range of 5% to 15%, the FDCA yield was over 90%. 3. Oxygen gas partial pressure and reaction temperature also affect the performance of the Ru / C oxidation catalyst. If the oxygen gas partial pressure and reaction temperature are too high, the FDCA yield may decrease; and 4. Oxidation catalysts consisting of Ru and Pt / Pd / Au supported on activated carbon also showed relatively good catalytic performance under the conditions investigated in this application.

[0110] [Examples I-16 to I-17] The experiment was carried out according to the method of Example I-1, except that the oxidation catalyst used was 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1, and the reaction solvent was either a mixed solvent composed of water and tetrahydrofuran (mass ratio of water to tetrahydrofuran = 1:1) or a mixed solvent composed of water and dimethyl sulfoxide (mass ratio of water to dimethyl sulfoxide = 1:1). The reaction results are shown in Table I-2.

[0111] [Examples I-18 to I-19] The experiment was carried out according to the method of Example I-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst, and the reaction solvent was a mixed solvent consisting of water and 1,4-dioxane (mass ratio of water to 1,4-dioxane = 1:2 or 1:3). The reaction results are shown in Table I-2.

[0112] [Examples I-20 to I-21] The experiment was carried out according to the method of Example I-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst, and the total mass of the reaction solvent was 5 g or 20 g. The reaction results are shown in Table I-2.

[0113] [Table 2]

[0114] The data in Table I-2 shows that the HMF oxidation reaction process for preparing FDCA can be effectively achieved by using water and solvents consisting of 1,4-dioxane, tetrahydrofuran, or dimethyl sulfoxide in different mass ratios within the limited scope of this application. The total amount of solvent added affects the performance of the catalyst. Increasing the total amount of solvent added, i.e., decreasing the concentration of 5-hydroxymethylfurfural, will contribute to an increase in the yield of FDCA, but will also correspondingly decrease the unidirectional processing capacity of this process.

[0115] [Examples I-22 to I-26] The experiment was conducted according to the method of Example I-1, except that catalysts D1-D5, prepared in Preparation Examples 8-12, which consisted of activated carbon supported with Pt, Pd, or Au, were used as oxidation catalysts. The reaction results are shown in Table I-3.

[0116] [Table 3]

[0117] As can be seen from the data in Table I-3, within the limited scope of this application, oxidation catalysts in which Pt, Pd, or Au were supported individually on activated carbon all showed significantly lower catalytic performance compared to the Ru / C oxidation catalyst. Therefore, it can be seen that the Ru / C oxidation catalyst supported on a carbon-containing material with a high specific surface area according to this application has a special catalytic effect on the reaction of oxidizing HMF to FDCA.

[0118] [Examples I-27 to I-28] The experiment was conducted according to the method of Example I-1, except that catalysts D6-D7, prepared in Preparation Examples 13-14, consisting of Ru supported on SiO2 or ZrO2, were used as oxidation catalysts. The reaction results are shown in Table I-4.

[0119] [Table 4]

[0120] From the data in Table I-4, it can be seen that, within the limited scope of this application, oxidation catalysts with Ru supported on SiO2 or ZrO2 all exhibited significantly lower catalytic performance than the Ru / C oxidation catalyst used in this application.

[0121] [Examples I-29 to I-30] The experiment was conducted according to the method of Example I-1, except that catalysts D8-D9, prepared in Preparation Examples 15-16, which consisted of activated carbon treated with an alkaline nitrogen-containing compound and supported with Ru, were used as oxidation catalysts. The reaction results are shown in Table I-5.

[0122] [Table 5]

[0123] A comparison of the data in Tables I-1 and I-5 shows that the catalytic performance of the Ru / C oxidation catalyst supported on activated carbon with a high specific surface area used in this application is equivalent to that of the catalyst in which Ru is supported on activated carbon treated with an alkaline nitrogen-containing compound, as reported in Patent CN111039906A. However, the catalyst used in this application does not require treatment with an alkaline nitrogen-containing compound, making it simpler to prepare and suitable for large-scale applications.

[0124] [Comparative Examples I-1 to I-4] The experiment was carried out according to the method of Example I-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst, and the reaction solvent was pure water, pure 1,4-dioxane, pure tetrahydrofuran, or pure dimethyl sulfoxide. The reaction results are shown in Table I-4.

[0125] [Table 6]

[0126] The data in Table I-4 shows that pure water, or 1,4-dioxane, tetrahydrofuran, or dimethyl sulfoxide solvents alone, cannot effectively dissolve the FDCA produced in the reaction. As a result, the small amount of FDCA produced in the reaction adheres to the surface of the oxidation catalyst, contaminating the catalytic active site, and consequently significantly reducing the activity of the oxidation catalyst and the yield of FDCA.

[0127] [Example II-1] This example illustrates a dehydration reaction step for synthesizing HMF according to this application using a sulfuric acid catalyst.

[0128] 0.5 g of fructose, 0.06 g of sulfuric acid, 1.5 g of water, 8.5 g of 1,4-dioxane, and 0.5 g of tetramethylammonium chloride were added to a 15 mL pressure vessel. After heating a multi-channel heater to 110 °C, the pressure vessel was placed on the multi-channel heater and stirred at a rotation speed of 600 r / min for 25 minutes. After the reaction was complete, the pressure vessel was removed from the multi-channel heater and allowed to cool naturally to room temperature. The reaction mixture was separated into an aqueous phase and an organic phase containing 5-hydroxymethylfurfural through a phase separator. These two phases were analyzed using high-performance liquid chromatography to determine the conversion rate of fructose and the yield of HMF. The yield of HMF and the corresponding conversion rate of fructose, as well as the inclusion rate of HMF in the upper organic phase (i.e., the ratio of HMF in the organic phase to the total amount of HMF) are shown in Table II-1.

[0129] After the reaction was complete, the reaction solution was quickly separated into two phases, and the lower layer, an aqueous solution of organic quaternary ammonium salt, was removed using a phase separator. The aqueous solution of organic quaternary ammonium salt contained an acid catalyst. The acid catalyst content in the aqueous phase was measured by alkaline titration, and the recovery rate of the acid catalyst in the aqueous phase (i.e., the ratio of the amount of acid catalyst in the aqueous phase to the amount of acid catalyst supplied) was calculated based on the amount of catalyst supplied. The corresponding reaction results are shown in Table II-1.

[0130] [Example II-2] This example illustrates a dehydration reaction step for synthesizing HMF according to this application using a sulfuric acid catalyst.

[0131] The reaction was carried out according to Example II-1, except that the supply of tetramethylammonium chloride was increased to 1.5 g. The corresponding reaction results are shown in Table II-1.

[0132] [Example II-3] This example illustrates a dehydration reaction step for synthesizing HMF according to this application using a sulfuric acid catalyst.

[0133] The reaction was carried out according to Example II-1, except that the supply of tetramethylammonium chloride was increased to 2.5 g. The corresponding reaction results are shown in Table II-1.

[0134] After the reaction was complete, the reaction solution was quickly separated into two phases. The lower aqueous phase solution was removed using a phase separator and immediately used for the next cycle test. The results of the cycle test are shown in Table II-2.

[0135] [Example II-4] This example illustrates a dehydration reaction step for synthesizing HMF according to this application using a methylsulfonic acid catalyst.

[0136] The reaction was carried out according to Example II-1, except that the sulfuric acid catalyst was replaced with a methylsulfonic acid catalyst and the catalyst supply was increased to 0.2 g. The corresponding reaction results are shown in Table II-1.

[0137] [Example II-5] This example illustrates a dehydration reaction step for synthesizing HMF according to this application using a methylsulfonic acid catalyst.

[0138] The reaction was carried out according to Example II-2, except that the sulfuric acid catalyst was replaced with a methylsulfonic acid catalyst and the catalyst supply was increased to 0.2 g. The corresponding reaction results are shown in Table II-1.

[0139] [Example II-6] This example illustrates a dehydration reaction step for synthesizing HMF according to this application using a methylsulfonic acid catalyst.

[0140] The reaction was carried out according to Example II-3, except that the sulfuric acid catalyst was replaced with a methylsulfonic acid catalyst and the catalyst supply was increased to 0.2 g. The corresponding reaction results are shown in Table II-1.

[0141] [Example II-7] The reaction was carried out according to Example II-1, except that the supply of tetramethylammonium chloride was increased to 3.0 g. The corresponding reaction results are shown in Table II-1.

[0142] [Example II-8] The reaction was carried out according to Example II-6, except that the supply of tetramethylammonium chloride was increased to 3.0 g. The corresponding reaction results are shown in Table II-1.

[0143] [Example II-9] This example illustrates a dehydration reaction step for synthesizing HMF according to this application using a sulfamic acid catalyst.

[0144] The reaction was carried out according to Example II-1, except that the sulfuric acid catalyst was replaced with an equimolar amount of sulfamic acid catalyst. The corresponding reaction results are shown in Table II-1.

[0145] [Comparative Example II-1] The reaction was carried out according to Example II-1, except that tetramethylammonium chloride was replaced with equimolar amounts of sodium chloride. The corresponding reaction results are shown in Table II-1.

[0146] [Comparative Example II-2] The reaction was carried out according to Example II-2, except that tetramethylammonium chloride was replaced with equimolar amounts of sodium chloride. The corresponding reaction results are shown in Table II-1.

[0147] [Comparative Example II-3] The reaction was carried out according to Example II-3, except that tetramethylammonium chloride was replaced with equimolar amounts of sodium chloride. The corresponding reaction results are shown in Table II-1.

[0148] [Table 7]

[0149] [Table 8]

[0150] Comparing the results of Examples II-1 to II-3 and Example II-7, it can be seen that after adding tetramethylammonium chloride to the reaction system, the HMF yield gradually increases as the supply of tetramethylammonium chloride increases, and when the supply increases from 2.5 g to 3.0 g, the HMF yield remains essentially unchanged. Considering both the HMF yield and the manufacturing cost, the preferred mass ratio of fructose to tetramethylammonium chloride is 1:1 to 5.

[0151] Comparing the results of Examples II-4 to II-6 and Example II-8, it was observed that after replacing the catalyst with methylsulfonic acid, the HMF yield tended to change with the supply of tetramethylammonium chloride, while the preferred mass ratio of fructose to tetramethylammonium chloride remained unchanged.

[0152] Comparing the results of Examples II-1, II-4, and II-9, it can be seen that, under the same reaction conditions, the yield of HMF is lower when sulfamic acid is used as a catalyst than when sulfuric acid or methylsulfonic acid is used as a catalyst. This is because sulfamic acid produces more humic acid as a byproduct. Therefore, sulfuric acid and methylsulfonic acid are more preferred catalysts compared to sulfamic acid.

[0153] The results in Table II-2 show that in Example II-3, after the reaction was complete, the lower aqueous solvent of the two-phase system was removed and the mixture was immediately used for the next cycle test. After six consecutive cycles, the fructose conversion rate remained above 99.0% without any significant decrease. The HMF yield decreased slightly after four cycles, falling to 87.2% in the fifth cycle and 86.8% in the sixth cycle, indicating that the aqueous solution after phase separation had excellent recovery performance.

[0154] Comparing the results of Comparative Examples II-1 to II-3, it can be seen that when the salt compound used in the reaction system is the inorganic salt sodium chloride, although a two-phase system can still be formed, the yield of HMF does not increase even when the supply of sodium chloride increases. This indicates that, unlike organic quaternary ammonium chloride salts, ordinary inorganic chloride salts do not have the effect of promoting HMF production. Furthermore, at the same salt concentration, the HMF yield for organic quaternary ammonium salts was higher than that for inorganic chloride salts, indicating that the cations of organic quaternary ammonium salts promote HMF production more than metal cations.

[0155] [Examples III-1 to III-4] This example is used to illustrate the synthesis process of 2,5-franzicarboxylic acid using the product obtained in Example II-1 as a starting material.

[0156] In a 50 mL high-pressure reactor, 5 g of the organic phase containing 5-hydroxymethylfurfural obtained in Example II-1, 0.2 g of the 10% Ru / C oxidation catalysts C1-C4 obtained in Preparation Examples 1-4, and 5 g of water were added (mass ratio of water to organic phase = 1:1). After sealing the reactor, 1 MPa of oxygen was added to replace any remaining air inside the reactor. This was repeated three times, and then 1 MPa of oxygen was added to the reactor. The reactor was placed in a heating furnace and heated to a reaction temperature of 100°C. The reaction was carried out for 10 hours under stirring at a rotation speed of 700 rpm. After the reaction was complete, the reactor was removed from the heating furnace and cooled to room temperature. The filtration was performed, and the filtration cake was washed with the same mixed solvent as the reaction solvent, and the final volume was adjusted to 100 mL. A liquid sample was taken for high-performance liquid chromatography analysis. The reaction results are shown in Table III-1.

[0157] [Examples III-5 to III-6] The Ru / C catalysts C5-C6, supported on Dali Hongye activated carbon obtained in Preparation Examples 5-6, were used as oxidation catalysts. The experiment was conducted according to the method of Example III-1, except that the amount of Ru supported in the oxidation catalyst was set to 5% or 15%. The reaction results are shown in Table III-1.

[0158] [Examples III-7 to III-8] The experiment was conducted according to the method of Example III-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst, and the oxygen pressure was set to 2 MPa or 3 MPa. The reaction results are shown in Table III-1.

[0159] [Examples III-9 to III-10] The experiment was conducted according to the method of Example III-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst, and the reaction temperature was set to 120°C or 140°C. The reaction results are shown in Table III-1.

[0160] [Examples III-11 to III-15] The experiment was carried out according to the method of Example III-1, except that catalysts C7-C11 supported on Dali Hongye activated carbon obtained in Preparation Examples 7-11 were used as oxidation catalysts. The reaction results are shown in Table III-1.

[0161] [Table 9]

[0162] Comparing the data in Table III-1 and Table I-1, it can be seen that by directly using the reaction product containing 5-hydroxymethylfurfural obtained from the dehydration reaction step of this application as a raw material in the oxidation reaction step, substantially equivalent reaction results can be obtained compared to using pure 5-hydroxymethylfurfural as a raw material. Therefore, it has been demonstrated that the process of this application can continuously produce 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid from fructose-based carbohydrates and has a high raw material conversion rate and a high product yield.

[0163] [Examples III-16 to III-20] The experiment was conducted according to the method of Example III-1, except that catalysts D1-D5, prepared in Preparation Examples 8-12, which consisted of activated carbon supported with Pt, Pd, or Au, were used as oxidation catalysts. The reaction results are shown in Table III-2.

[0164] [Table 10]

[0165] From the data in Table III-2, similar to the data shown in Table I-3, within the limited scope of this application, oxidation catalysts in which Pt, Pd, or Au were individually supported on activated carbon all showed significantly lower catalytic performance than the Ru / C oxidation catalyst. Therefore, it can be seen that the Ru / C oxidation catalyst supported on a carbon-containing material with a high specific surface area according to this application has a special catalytic effect on the reaction of oxidizing HMF to FDCA.

[0166] [Comparative Example III-1] The experiment was carried out according to the method of Example III-1, except that the 10% Ru / C catalyst C1 supported on Dali Hongye activated carbon obtained in Preparation Example 1 was used as the oxidation catalyst without the addition of water. After the reaction, the conversion rate of HMF was 14%, and the yield of FDCA was 3%.

[0167] As can be seen from Comparative Example III-1, without the addition of water, the organic solvent alone could not effectively dissolve the FDCA produced in the reaction. As a result, the small amount of FDCA produced in the reaction adhered to the surface of the oxidation catalyst, contaminating the catalytic active site, and consequently, the activity of the oxidation catalyst and the yield of FDCA were significantly reduced.

[0168] Preferred embodiments of this application have been described in detail above. However, this application is not limited to the specific details of the embodiments described above. Various simple modifications can be made to the technical solutions of this application within the scope of the technical idea of ​​this application. All of these simple modifications are covered by the protection of this application.

[0169] Furthermore, it should be noted that each of the specific technical features described in the above-mentioned specific embodiments can be combined. These combinations can be carried out in any suitable manner without contradiction. To avoid unnecessary repetition, various possible combinations are not described further in this application.

[0170] Furthermore, any combination of the various different embodiments of this application is possible, as long as it does not contradict the spirit of this application, and such combinations should also be considered part of the disclosures of this application. [Brief explanation of the drawing]

[0171] [Figure 1] This is a schematic flowchart of a preferred embodiment of the reaction system of this application.

Claims

1. A process for the continuous production of 5-hydroxymethylfurfural and 2,5-franzicarboxylic acid, comprising the following steps: (1) In a two-phase reaction medium comprising a polar organic solvent and an aqueous solution of a quaternary ammonium halide, a fructose-based carbohydrate is subjected to intramolecular dehydration in the presence of a protonic acid catalyst to produce a two-phase stream containing 5-hydroxymethylfurfural, and the two-phase stream is phase-separated to produce an aqueous phase containing the protonic acid catalyst and an organic phase containing 5-hydroxymethylfurfural; and (2) Add water to the organic phase containing 5-hydroxymethylfurfural obtained in step (1), and in the presence of an oxidation catalyst and oxygen gas, oxidize the 5-hydroxymethylfurfural to produce 2,5-franzicarboxylic acid; The proton acid catalyst is selected from hydrochloric acid, sulfuric acid, sulfonic acid, phosphoric acid, sulfamic acid, or a combination thereof; The oxidation catalyst comprises a carrier and an active metal component supported on the carrier. The carrier is activated carbon having a specific surface area of ​​1000 m² / g to 2000 m² / g, and the activated metal component contains Ru, in a process.

2. The protonate catalyst is selected from sulfamic acid, sulfuric acid and sulfonic acid; and / or The carrier is activated carbon having a specific surface area of ​​1000 m² / g to 1500 m² / g; and / or The process according to claim 1, wherein the active metal component is Ru, or a combination of Ru and one or more selected from Pt, Pd, and Au.

3. The process according to claim 1 or 2, wherein the fructose-based carbohydrate in step (1) is selected from refined fructose, crude fructose, polyfructose, fructose syrup, fructose dextrose syrup, or a combination thereof.

4. The process according to claim 1 or 2, wherein the sulfonic acid is selected from methylsulfonic acid, benzenesulfonic acid, or a combination thereof.

5. In step (1), the quaternary ammonium halide salt is optionally substituted with hydroxyl or halogen. １ ~C １２ The process according to claim 1 or 2, selected from quaternary ammonium halide salts having hydrocarbyl.

6. The process according to claim 5, wherein in step (1), the quaternary ammonium halogenated salt is selected from tetramethylammonium chloride, tetramethylammonium bromide, collinchloride, chlorocolinchloride, allyltrimethylammonium chloride, butyltrimethylammonium chloride, or a combination thereof.

7. The process according to claim 1 or 2, wherein in step (1), the polar organic solvent is an aprotic polar organic solvent that is miscible with water.

8. The process according to claim 7, wherein in step (1), the polar organic solvent is selected from acetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, or a combination thereof.

9. Step (1) described above has the following characteristics: The mass ratio of the fructose-based carbohydrate to the reaction medium is 1:1 to 1000, and the reaction medium is a two-liquid-phase reaction medium composed of the polar organic solvent and the aqueous solution of the quaternary ammonium halide salt; The ratio of the volume of the quaternary ammonium halide aqueous solution to the total volume of the reaction medium is 5% to 50%; Based on the mass of the protonic acid, the concentration of the protonic acid catalyst in the aqueous phase of the reaction medium is 0.02 g / mL to 0.5 g / mL; and The conditions for the dehydration reaction include: a reaction temperature of 80°C to 200°C; and a reaction time of 0.1 hours to 12 hours. The process according to claim 1 or 2, comprising one or more of the above.

10. The oxidation catalyst in step (2) has the following characteristics: The mass content of Ru is 5% to 100% based on the total mass of the aforementioned active metal components; The content of the active metal component in the oxidation catalyst is 0.25% to 30% based on the total mass of the carrier. The process according to claim 1 or 2, comprising one or more of the above.

11. The oxidation catalyst of step (2) has the following characteristics: The mass content of Ru is 50% to 100% based on the total mass of the aforementioned active metal components; Based on the total mass of the support, the Ru content in the oxidation catalyst is 5% to 15%. The process according to claim 10, comprising one or more of the above.

12. Step (2) has the following characteristics: The mass ratio of the organic phase containing 5-hydroxymethylfurfural to water is 5:1 to 0.5:1; The oxidation catalyst is used in such an amount that the molar ratio of the active metal component in the oxidation catalyst to 5-hydroxymethylfurfural is 1:1 to 1000; The oxidation reaction is carried out under an oxygen gas atmosphere, an air atmosphere, or a mixed atmosphere of oxygen gas and nitrogen gas; and The conditions for the oxidation reaction include: a reaction temperature of 50°C to 170°C, and an oxygen gas partial pressure of 0.2 MPa to 4 MPa. The process according to claim 1 or 2, comprising one or more of the above.

13. A process for producing 2,5-franzicarboxylic acid, comprising the following steps: The step of oxidizing 5-hydroxymethylfurfural in a mixed solvent containing an organic solvent and water, in the presence of an oxidation catalyst and oxygen gas, to produce 2,5-franzicarboxylic acid; The aforementioned organic solvent is a non-protic polar organic solvent that is miscible with water; The oxidation catalyst comprises a carrier and an active metal component supported on the carrier, and the carrier is 1000 m ２ / g to 2000m ２ A process comprising activated carbon having a specific surface area of ​​1 / g, wherein the activated metal component includes Ru.

14. The organic solvent is selected from acetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, dimethyl sulfoxide, or a combination thereof; and / or The carrier is activated carbon having a specific surface area of ​​1000 m² / g to 1500 m² / g; and / or The active metal component is Ru, or a combination of Ru and one or more selected from Pt, Pd, and Au. The process according to claim 13.

15. The mass content of Ru is 40% to 100% based on the total mass of the active metal component; The process according to claim 13 or 14, wherein the content of the active metal component in the oxidation catalyst is 0.25% to 30% based on the total mass of the carrier.

16. The mass content of Ru is 60% to 100% based on the total mass of the active metal component; The process according to claim 15, wherein the Ru content in the oxidation catalyst is 5% to 15% based on the total mass of the support.

17. The following features: The mixed solvent consists of the organic solvent and water, and the mass ratio of the organic solvent to water is 5:1 to 0.5:1; In the solution formed from the 5-hydroxymethylfurfural and the mixed solvent, the mass proportion of the 5-hydroxymethylfurfural is 0.1% to 30%; The oxidation catalyst is used in such an amount that the molar ratio of the active metal component in the oxidation catalyst to 5-hydroxymethylfurfural is 1:1 to 1000; The conditions for the oxidation reaction include: a reaction temperature of 50°C to 170°C, and an oxygen gas partial pressure of 0.2 MPa to 4 MPa; and The oxidation reaction is carried out under an oxygen gas atmosphere, an air atmosphere, or a mixed atmosphere of oxygen gas and nitrogen gas. The process according to claim 13 or 14, comprising one or more of the above.

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