Processes and catalysts for production of 5-hydroxymethylfurfural

Abstract

The present invention relates to processes and catalysts for production of 5- hydroxymethylfurfural. In particular, the present invention concerns a γ-alumina-supported sulfone group catalyst; a method of preparing said catalyst, use of said catalyst functioning as a co-catalyst in combination with a catalyst, and a method of producing 5-hydroxymethylfurfural. Additionally, polysulfone materials can serve as a catalyst or co-catalyst in a manner similar to the γ-alumina-supported sulfone group. In one form, a γ-alumina-supported sulfone group catalyst is provided including: sulfone groups grafted on a γ-alumina support, wherein the sulfone groups are grafted using electron beam irradiation.

Description

PROCESSES AND CATALYSTS FOR PRODUCTION OF 5-HYDROXYMETHYLFURFURALTECHNICAL FIELD

[0001] The present invention relates to aluminium complex catalysts with immobilised sulfone groups on solid surfaces for the Lewis acid-catalysed production of 5- hydroxymethylfurfural from hexose sugars.BACKGROUND

[0002] 5-hydroxymethylfurfural (5-HMF) is a vital platform chemical for producing high-value biochemicals including 2,5-furandicarboxylic acid (FDCA), a priority chemical for establishing the “green” chemical industry and a monomer in the production of biodegradable polymers.

[0003] One of the most challenging reactions in this context is the conversion of industrial sugars, such as glucose and fructose, into 5-HMF. Converting sugars to 5-HMF has been described as an essential process for establishing the future green chemical industry.

[0004] Typically, to produce 5-HMF from sugars, aluminium salts are employed as a Lewis acid catalyst for sugar conversion. However, to achieve a reasonable yield of 5-HMF, thermal catalysis of sugars with aluminium salts must proceed at a relatively high temperature e.g., between 130°C and 170°C.

[0005] Conducting the reactions at high temperatures often leads to undesired side reactions which may produce large molecular weight by-products such as humic substances. The formation of such substances can not only waste the feedstock sugar but also deactivate catalysts and cause difficulty in subsequent product separation.

[0006] Furthermore, a Bronsted acid is also generally necessary to achieve adequate 5- HMF yield. Bronsted acids, such as hydrochloric acid, increase the cost of the operation, require specialist equipment and training, and create a potential health and safety concern for chemists.

[0007] Clearly, there is a need for a safe and effective method of producing 5-HMF from sugar reactants.

[0008] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.SUMMARY OF INVENTION

[0009] Embodiments of the present invention provide processes and catalysts for production of 5-hydroxymethylfurfural, which may at least partially address one or more of the problems or deficiencies mentioned above or which may provide the public with a useful or commercial choice.

[0010] According to a first aspect of the present invention, there is provided a y-alumina- supported sulfone group catalyst including: sulfone groups grafted on a y-alumina support; and wherein the sulfone groups are grafted using electron beam irradiation.

[0011] Preferably, the y-alumina-supported sulfone group catalyst will function as a cocatalyst. In such embodiments, it is envisaged that aluminium ions are a preferred catalyst for interaction with the y-alumina-supported sulfone group co-catalyst.

[0012] In some embodiments, polysulfone materials such as, for e.g., polyether sulfone, may be used as catalyst and / or co-catalyst.

[0013] The skilled addressee will appreciate that the quantity of sulfone groups grafted on the y-alumina support may vary. In this regard, the density of sulfone groups grafted on the y- alumina support may be varied depending on the number and type of sulfone groups and the number and type of y-alumina support.

[0014] Supports with alternate phases of aluminium oxide may be provided. For example, the support may include a, q, 5, 0, or p alumina. The skilled addressee will appreciate that y- alumina support is preferred due to its high surface area.

[0015] In some embodiments, the y-alumina support is a solid support. In such embodiments, the solid support may be any one of a particle, film and / or coating.

[0016] In some embodiments, the sulfone groups may be grafted on the y-alumina support with a linker. The linker may be of any suitable length.

[0017] According to a second aspect of the invention, there is provided a method of preparing a y-alumina-supported sulfone group catalyst including: providing a y-alumina support; and grafting sulfone groups on the y-alumina support using electron beam irradiation to produce the y-alumina-supported sulfone group catalyst.

[0018] In some embodiments, the grafting may use 4-vinylbenzenesulfonic acid sodium salt as a sulfone group precursor.

[0019] In some embodiments, Fourier-transform infrared spectroscopy may be used to confirm successful grafting of the sulfone groups on a surface of the y-alumina support.

[0020] In some embodiments, silica may be used as a support material in the preparation of a silica-supported sulfone group catalyst. However, the skilled addressee will appreciate that in such embodiments, dissolved silica may affect catalyst performance and product separation. Accordingly, reduced catalyst performance and product separation may need to be accounted for by use of alternate or additional reactants and / or catalysts where the sulfone group catalyst is silica supported.

[0021] In other embodiments, alternate metal oxides may be used as a support material in the preparation of the supported sulfone group catalyst. The skilled addressee will appreciate that where silica or alternate metal oxides are used as support materials, the dissolved species may require treatment to reduce environmental impact.

[0022] According to a third aspect of the invention, there is provided use of a y-alumina- supported sulfone group catalyst for production of 5-hydroxymethylfurfural including: providing a solution including a sugar reactant and an aluminium salt dissolved in a solvent; combining the solution with the y-alumina-supported sulfone group catalyst; and dehydrating the sugar reactant in the solution to produce the 5-hydroxymethylfurfural at a controlled temperature of between about 60°C and about 120°C.

[0023] According to a fourth aspect of the invention, there is provided a method of producing 5- hyd roxym ethylfurfural i ncl ud i ng : dispersing a y-alumina-supported sulfone group catalyst in a solution including a sugar reactant and an aluminium salt dissolved in a solvent; and dehydrating the sugar reactant in the solution to produce the 5-hydroxymethylfurfural at a controlled temperature of between about 60°C and about 120°C.

[0024] In some embodiments, the sulfone groups grafted on a surface of a y-alumina support may coordinate with aluminium ions from the aluminium salt to form aluminium ion complexes on the y-alumina support.

[0025] In some embodiments, the sugar reactant may coordinate with the aluminium ion complexes on the y-alumina support.

[0026] In some embodiments the use of y-alumina-supported sulfone group catalyst for production of 5-hydroxymethylfurfural and / or the method of producing 5-hydroxymethylfurfural is undertaken without light irradiation.

[0027] In alternate embodiments, the use of y-alumina-supported sulfone group catalyst for production of 5-hydroxymethylfurfural and / or the method of producing 5-hydroxymethylfurfural is undertaken under light irradiation, such as, e.g., sunlight, simulated sunlight, ultraviolet light, and / or visible light.

[0028] In some embodiments, the use of y-alumina-supported sulfone group catalyst for production of 5-hydroxymethylfurfural and / or the method of producing 5-hydroxymethylfurfural is undertaken in atmospheric conditions.

[0029] In other embodiments, the use of y-alumina-supported sulfone group catalyst for production of 5-hydroxymethylfurfural and / or the method of producing 5-hydroxymethylfurfural is undertaken in an inert atmosphere, preferably a nitrogen atmosphere.

[0030] The sugar reactant may be any suitable monosaccharide, disaccharide and / or polysaccharide, preferably a monosaccharide or a disaccharide, most preferably glucose. For example, the sugar reactant may be glucose, fructose, sucrose, mannose, maltose, sorbose, and combinations thereof.

[0031] In some embodiments, commercial sucrose and mannose are particularly preferred due to their high conversion efficiency to 5-hydroxymethylfurfural. A person skilled in the art will appreciate that industry-grade glucose is widely available and inexpensive thereby making it an economical reactant.

[0032] Any suitable aluminium salt may be used. It will be understood that the aluminium salt may provide aluminium cations to function as a catalyst in the reaction. For example, the aluminium salt may be aluminium chloride, aluminium sulphate, potassium aluminium sulphate, aluminium hydroxide, and / or aluminium nitrate.

[0033] In preferred embodiments, the aluminium salt is hydrated. For example, the aluminium salt may include aluminium sulphate octadeca hydrate, potassium alum, aluminium nitrate nonahydrate, and / or aluminium chloride hexahydrate, preferably aluminium nitrate nonahydrate.

[0034] Any suitable solvent may be used. The solvent may be an organic or an inorganic solvent, preferably an organic solvent. The solvent may be toluene, acetonitrile, methanol, methyl isobutyl ketone (MIBK), isopropyl acetate (IProAC) and / or dimethyl sulfoxide. In someembodiments, the solvent may be water. Preferably, the solvent is dimethyl sulfoxide (DMSO).

[0035] The skilled addressee will appreciate that DMSO participates in the formation of an intermediate in the dehydration process which may accelerate production of 5- hydroxymethylfurfural.

[0036] Preferably, the controlled temperature is between about 70°C and about 110°C, more preferably between about 80°C and about 100°C. For scale-up processes, the controlled temperature is most preferably about 110°C.

[0037] The y-alumina-supported sulfone group catalyst may advantageously be reused for future reactions. For example, the y-alumina-supported sulfone group catalyst may be filtered out of the solution and reused for future reactions. The skilled addressee will appreciate that there may be a decrease in yield of 5-hydroxymethylfurfural with each recycle of the y-alumina- supported sulfone group catalyst.

[0038] The y-alumina-supported sulfone group catalyst may be used with a variety of sugar substrates. In addition to glucose and fructose, the catalyst system has demonstrated high catalytic activity for converting commercial sucrose, mannose, maltose and sorbose into 5- hydroxymethylfurfural. Commercial sucrose and mannose were particularly easily converted into 5-hydroxymethylfurfural, exhibiting conversion efficiencies comparable to or exceeding those of glucose.

[0039] Indeed, the skilled addressee will appreciate that it may be beneficial to replenish the aluminium salt in future reactions due to its use in a solution and possible loss in separation post reaction. In this regard, even if the decrease in yield of 5-hydroxymethylfurfural with each recycle of the y-alumina-supported sulfone group catalyst is minimal and may allow the reaction to proceed with reasonably high yield, it may still be advantageous to replenish the aluminium salt.

[0040] In some embodiments, the y-alumina-supported sulfone group catalyst may be treated to enable reuse of the y-alumina. Typically, such treatment may be undertaken after many reuses and a substantial loss of function. The treatment may involve using electron beam irradiation. Preferably, the treatment is substantially the same as the procedure for grafting sulfone groups using electron beam irradiation, noting however that a smaller quantity of sulfone group precursor will be required for treatment.

[0041] In alternate embodiments, the treatment may involve cleaving the sulfone group and replacing the sulfone group with an alternate group.

[0042] In some embodiments, the process may be extended to an integrated two-step method for production of 2,5-furandicarboxylic acid (FDCA) from sugars. In such embodiments, following conversion of the sugar reactant to 5-hydroxymethylfurfural, the y-alumina-supported sulfone group catalyst is removed from the reaction system by filtration.

[0043] Water and an oxidation catalyst, such as platinum-copper bimetallic nanoparticles supported on magnesium oxide, may then be added to the system for aerobic oxidation of 5- hydroxymethylfurfural to 2,5-furandicarboxylic acid. The water content significantly influences the oxidation process. When the volume ratio of water to DMSO is approximately 19:1 , over 90% of 5-hydroxymethylfurfural can be converted to 2,5-furandicarboxylic acid.

[0044] The 2,5-furandicarboxylic acid product can be readily separated from the reaction mixture. The water may then be evaporated, leaving DMSO solvent that can be reused for subsequent sugar conversion reactions. This integrated two-step method advantageously reduces the environmental impact of DMSO solvent through recycling and provides a streamlined route from sugars to 2,5-furandicarboxylic acid.

[0045] Advantageously, the aluminium cations from the aluminium salt dissolved in the solvent may complex with the y-alumina-supported sulfone group to form immobilised complexes. Reactant sugar molecules may coordinate with the Aluminium ions of the immobilised complexes. These immobilised complexes may exhibit improved catalytic performance when compared to aluminium salt alone thereby enabling increased efficiency of isomerisation of the coordinated sugar molecules and hydrolysis of aluminium ions and in turn enabling higher yields of 5-hydroxymethylfurfural to be produced at lower temperatures and without the need for additional Bronsted acid. This in turn results in safer reaction conditions. Furthermore, the production of 5-hydroxymethylfurfural may occur in ambient conditions including in the presence of moisture. Additionally, the y-alumina-supported sulfone group catalyst may be recycled for use in future reactions without significantly impairing efficacy of the Y-alumina-supported sulfone group catalyst. For example, the spent y-alumina-supported sulfone group catalyst may advantageously be regenerated via electron beam irradiation treatment. A further advantage of sulfone groups grafted y-alumina is that they do not introduce impurities that may affect catalyst performance, product separation, or result in negative environmental impact. Trace dissolved aluminium ions may become catalysts.

[0046] The process is scalable to industrially relevant conditions. Scale-up experiments have demonstrated successful glucose-to-5-hydroxymethylfurfural conversion at both increased reaction volumes and elevated substrate concentrations. At constant sugar concentration (1.8 wt.%), increasing the reaction volume had minimal effect on yield.

[0047] When substrate concentration was increased to industrially relevant levels (15-18 wt.%), the process maintained acceptable yields. Specifically, raising substrate concentration from 1.8 wt.% to 18 wt.% resulted in yields of approximately 67% for glucose and 57% for fructose. These yields, while lower than those at dilute concentrations, remain commercially viable for industrial applications.

[0048] At high sugar concentrations, 5-hydroxymethylfurfural formation proceeds most rapidly during the initial reaction period, with approximately 60% yield achieved within the first 5 hours, after which the reaction rate decreases.

[0049] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0050] The reference to any prior art in this specification is not and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.BRIEF DESCRIPTION OF DRAWINGS

[0051] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[0052] Figure 1 is a reaction overview of y-alumina-supported sulfone groups functioning as a co-catalyst in an aluminium ion and sugar solution according to an embodiment of the present invention;

[0053] Figure 2 is a flow chart showing steps in a method of preparing a y-alumina- supported sulfone group catalyst according to an embodiment of the present invention;

[0054] Figure 3 is a flow chart showing steps in use of a y-alumina-supported sulfone group co-catalyst for production of 5-hydroxymethylfurfural according to an embodiment of the present invention;

[0055] Figure 4 is a flow chart showing steps in a method of producing 5- hydroxymethylfurfural according to an embodiment of the present invention;

[0056] Figure 5 is an overview of a reaction set up of the method of Figure 3 and / or 4;

[0057] Figure 6 is a chart showing 5-hydroxymethylfurfural yield with different reaction systems;

[0058] Figure 7 is a chart showing 5-hydroxymethylfurfural yield with different cycles of use of the y-alumina-supported sulfone group co-catalyst;

[0059] Figure 8 is a chart showing 5-hydroxymethylfurfural yield from various sugar substrates; and

[0060] Figure 9 is a chart showing 5-hydroxymethylfurfural yield at different sugar concentrations and reaction scales.DETAILED DESCRIPTION

[0061] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as would be commonly understood by those of ordinary skill in the art to which this invention belongs.

[0062] Figure 1 is a reaction overview (100) of y-alumina-supported sulfone groups, functioning as a co-catalyst in an aluminium ion and sugar solution for the production of production of 5-hydroxymethylfurfural. The aluminium ions are functioning as the catalyst.

[0063] Broadly, the reaction involves a y-alumina-support (101) linked to sulfone groups (102), forming a y-alumina-supported sulfone group co-catalyst (108) which is placed in a solution containing aluminium ions (103) and sugar reactants (104). In this instance, the sugar reactants (104) are glucose. The aluminium ions (103) are from an aluminium salt dissolved in a solvent.

[0064] The oxygen (105) of the y-alumina-support (101) links with the sulfone groups (102) via a linker. The oxygen (105) of the y-alumina-support (101) may link with the sulfone groups (102) in any suitable manner.

[0065] As illustrated, carbon chain (106) may be of any suitable length. Likewise, each of the sulfone groups (102) may have any suitable end group (107). In this manner, it will be understood that the link and end group may vary depending on reactants and conditions.

[0066] Under appropriate reaction conditions, the sulfone groups (102) associated with the Y-alumina-support (101) complexes with the aluminium ions (103) and solvent molecules. This complexing improves catalytic performance thereby enabling increased efficiency of isomerisation of the sugar reactants (104) and hydrolysis of the aluminium ions (103) and in turn enabling high yield production of 5-hydroxymethylfurfural to occur in safer reaction conditions.

[0067] Components of the reaction overview referred to in Figure 1 will now be described in further detail.

[0068] Figure 2 is a flow chart (200) showing steps in a method of preparing a y-alumina- supported sulfone group catalyst according to an embodiment of the present invention. The y- alumina-supported sulfone group catalyst may be the same as feature 108 described in Figure 1 (in which regard the catalyst will function as a co-catalyst), or it may be different, preferably the same.

[0069] At step 201 , there is provided a y-alumina support.

[0070] At step 202, sulfone groups are grafted on the y-alumina support using electron beam irradiation to produce a y-alumina-supported sulfone group catalyst.

[0071] Preferably, the electron beam irradiation is undertaken for a period between 1 and 20 seconds, most preferably for a period of 10 seconds.

[0072] Advantageously, electron beam irradiation is environmentally friendly as there are no chemical residues. Additionally, electron beam irradiation is energy efficient and does not involve radioactive isotopes making it a much safer alternative to traditional chemical methods of grafting.

[0073] In preferred embodiments, the grafting of the sulfone groups is achieved using 4- vinylbenzenesulfonic acid sodium salt as a sulfone group precursor.

[0074] In preferred embodiments, the y-alumina support is a solid support. The solid support may be any one of a particle, film and / or coating.

[0075] The sulfone groups may be grafted on the y-alumina support with a linker. The linker may be any suitable type. In embodiments such as those illustrated by Figure 1 , the linker may be formed by the interaction with the oxygens of the y-alumina support with the sulfone groups.

[0076] In some embodiments, silica may be used as a support material in the preparation of the Y-alumina-supported sulfone group catalyst.

[0077] Preferably, a checking step is provided whereby Fourier-transform infrared spectroscopy is used to confirm successful grafting of the sulfone groups on a surface of the y- alumina support. In this manner, the formation of the y-alumina-supported sulfone group catalyst (108) may be confirmed.

[0078] Figure 3 is a flow chart (300) showing steps in use of a y-alumina-supported sulfonegroup co-catalyst and aluminium cation catalyst for production of 5-hydroxymethylfurfural according to an embodiment of the present invention.

[0079] At step 301 , a solution including a sugar reactant and an aluminium salt dissolved in a solvent is provided.

[0080] The sugar reactant may be any suitable monosaccharide, disaccharide and / or polysaccharide, preferably a monosaccharide or a disaccharide, most preferably glucose.

[0081] Any suitable aluminium salt may be used as the catalyst. For example, the aluminium salt may be aluminium chloride, aluminium sulphate, potassium aluminium sulphate, aluminium hydroxide, and / or aluminium nitrate, preferably aluminium nitrate.

[0082] In preferred embodiments, the aluminium salt is hydrated. For example, the aluminium salt may include aluminium sulphate octadeca hydrate, potassium alum, aluminium nitrate nonahydrate, and / or aluminium chloride hexahydrate, preferably aluminium nitrate nonahydrate.

[0083] Any suitable solvent may be used. The solvent may be an organic or an inorganic solvent, preferably an organic solvent. The solvent may be toluene, acetonitrile, methanol, methyl isobutyl ketone (MIBK), isopropyl acetate (IProAC), and / or dimethyl sulfoxide. In some embodiments, the solvent may be water. Most preferably, the solvent is dimethyl sulfoxide (DMSO).

[0084] At step 302, the solution is combined with the y-alumina-supported sulfone group co-catalyst. The y-alumina-supported sulfone group co-catalyst may be the same as feature 108 described in Figure 1 or may be different, preferably the same.

[0085] The solution and y-alumina-supported sulfone group co-catalyst may be combined in any suitable manner. Preferably, they are combined in a reaction container. Most preferably, a glass tube.

[0086] Aluminium cations from the aluminium salt dissolved in the solvent complexes with the y-alumina-supported sulfone group to form immobilised complexes. Reactant sugar molecules may coordinate with the aluminium ions of the immobilised complexes.

[0087] Typically, the reaction container is sealed. Preferably, a rubber septum cap is used to seal the reaction container.

[0088] Preferably, the combined y-alumina-supported sulfone group co-catalyst and sugarreactant and aluminium salt dissolved in a solvent are purged with an inert gas, preferably nitrogen.

[0089] At step 303, the sugar reactant is dehydrated in the solution to produce the 5- hydroxymethylfurfural at a controlled temperature of between about 60°C and about 120°C, preferably between about 70°C and about 110°C, more preferably between about 80°C and about 100°C, most preferably at about 90°C.

[0090] The combined y-alumina-supported sulfone group co-catalyst and sugar reactant and aluminium salt dissolved in a solvent may be stirred, preferably with a magnetic stirrer.

[0091] The y-alumina-supported sulfone group co-catalyst may be recovered and reused for future reactions. For example, the y-alumina-supported sulfone group co-catalyst may be filtered out of the solution and reused for future reactions. The aluminium ions may be precipitated as aluminium hydrate by adjusting the pH to 5 and separated by filtration. It will be understood that the pH will be adjusted up to 5. The recovered precipitate may then be readily dissolved in dilute acid (e.g., dilute HNO3) yielding an AI(NOs)3 solution, which may be reused as a catalyst.

[0092] The skilled addressee will appreciate that there may be a decrease in the yield of 5- hydroxymethylfurfural with each recycle of the y-alumina-supported sulfone group co-catalyst.

[0093] In some embodiments, the y-alumina-supported sulfone group co-catalyst may be treated before it is reused for future reactions. The treatment may include electron beam irradiation.

[0094] In some embodiments, use of a y-alumina-supported sulfone group co-catalyst for production of 5-hydroxymethylfurfural may occur in the absence or presence of light irradiation. The inventors have found that sunlight as a source of light irradiation enhances the isomerization and dehydration processes at moderate temperatures (i.e. , below 100°C). Advantageously, the use of sunlight may further facilitate a more energy efficient process (when compared to artificial light sources).

[0095] Figure 4 is a flow chart (400) showing steps in a method of producing 5- hydroxymethylfurfural.

[0096] At step 401, y-alumina-supported sulfone groups, functioning as a co-catalyst, are dispersed in a solution including a sugar reactant and an aluminium salt dissolved in a solvent.

[0097] At step 402, the sugar reactant is dehydrated in the solution to produce the 5-hydroxymethylfurfural at a controlled temperature of between about 60°C and about 120°C.

[0098] Preferably, the co-catalyst and the solution are the same as those described with reference to the earlier figures.

[0099] Figure 5 is an overview of a reaction set-up (500) of the method of Figure 3 and / or Figure 4.

[0100] The co-catalyst is dispersed in a solution including a sugar reactant and an aluminium salt dissolved in a solvent provided in a reaction container (not visible).

[0101] Aluminium foil (501) is wrapped around the reaction container to block light irradiation. The reaction container may then be placed in water bath (502). The reaction container and the water bath (502) are then heated atop heat source (503) and stirred continuously using a magnetic stirrer.

[0102] In some embodiments, the sulfone groups described in Figures 1 to 6 may comprise polysulfone materials such as, for e.g., polyether sulfone. In such embodiments, it will be understood that the reactions may proceed in largely the same manner as described in Figures 1 to 6.

[0103] Figure 6 is a chart (600) showing 5-hydroxymethylfurfural yield with different reaction systems.

[0104] As illustrated, there is a notably higher yield (-92%) when under the following reaction conditions: 0.04 mmol AI(NO3)3'9H2O, 0.2 mmol glucose, 10 mg co-catalyst of the grafted Y-AI2O3 in 2 ml DMSO, 90°C, 20 h.

[0105] Figure 7 is a chart (700) showing 5-hydroxymethylfurfural yield with different cycles of reuse of the y-alumina-supported sulfone group when functioning as a co-catalyst.

[0106] Following the reaction, the y-alumina-supported sulfone group co-catalyst can be recovered by filtration and reused. As illustrated by Figure 7, there is a slight reduction in 5- hydroxymethylfurfural yield with each reuse of the y-alumina-supported sulfone group co- catalyst.

[0107] Figure 8 is a chart (800) showing 5-hydroxymethylfurfural yield from various sugar substrates.

[0108] Various sugar substrates were tested under identical reaction conditions at 110°C for 20 hours. As illustrated, in addition to glucose and fructose, commercial sucrose andmannose demonstrated particularly high conversion to 5-hydroxymethylfurfural, with yields comparable to or exceeding those obtained from glucose. Maltose and sorbose also showed good catalytic activity with the y-alumina-supported sulfone group co-catalyst system.

[0109] Figure 9 is a chart (900) showing 5-hydroxymethylfurfural yield at different sugar concentrations and reaction scales.

[0110] Scale-up experiments demonstrated successful conversion at both increased reaction volumes and elevated substrate concentrations. As illustrated, at constant sugar concentration (1.8 wt.%), increasing the reaction volume from 2 ml to 60 ml had minimal effect on 5-hydroxymethylfurfural yield. When substrate concentration was increased to industrially relevant levels (18 wt.%), yields of approximately 67% for glucose and 57% for fructose were achieved, demonstrating the scalability of the process to commercial concentrations.

[0111] In the present specification and claims (if any), the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0112] Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0113] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

[0114] The following non-limiting examples further illustrate the present invention.EXAMPLESExample 1. A method of preparing a y-alumina-supported sulfone group co-catalyst.

[0115] The y-alumina-supported sulfone group catalyst was prepared by combining the y-alumina-support (aluminium oxide) and 4-vinylbenzenesulfonic acid sodium salt. It is understood that 4-vinylbenzenesulfonic acid sodium salt is a sulfone group precursor.

[0116] Electron beam irradiation was employed to graft the sulfone group to the y-alumina- support forming the y-alumina-supported sulfone group catalyst.

[0117] Fourier-transform infrared spectra were employed to confirm the successful grafting of the sulfone group to the y-alumina-support. The Fourier-transform infrared spectra indicate the presence of sulfonate groups on the y-alumina-support.Example 2. A method of producing 5-hydroxymethylfurfural.

[0118] The reactants 0.04 mmol AI(NO3)3'9H2O, 0.2 mmol glucose, 10 mg y-alumina- supported sulfone group co-catalyst in 2 ml DMSO were added to a reaction chamber. A glass tube with aluminium foil wrapping was used as the reaction chamber. The skilled addressee will appreciate that the aluminium foil was used to prevent interference from light irradiation.

[0119] After adding the above reactants, the glass tube was purged with nitrogen for 1-2 minutes to create an inert atmosphere.

[0120] After purging with nitrogen, the glass tube was sealed with a rubber septum cap.

[0121] The tube was placed on a magnetic stirrer and stirred at a controlled reaction temperature of about 90°C for about 20 hours.

[0122] The reaction was undertaken in darkness.

[0123] The reaction resulted in a 92% 5-hydroxymethylfurfural yield.

[0124] Under the same reaction conditions, dehydration of sucrose resulted in a 93% 5- hydroxymethylfurfural yield.

[0125] Under the same reaction conditions, dehydration of fructose resulted in a 97% 5- hydroxymethylfurfural yield.Example 3. Substrate scope for 5-hydroxymethylfurfural production.

[0126] Various sugar substrates including maltose, sorbose, mannose, and commercial sucrose were tested under identical reaction conditions. The reaction conditions were: 110°C, 20 h, 36 mg substrate, 0.04 mmol AI(NO3)3'9H20, 10 mg y-alumina-supported sulfone group cocatalyst, 2 ml DMSO and 350 rpm, with nitrogen purging for 2 minutes.

[0127] Commercial sucrose and mannose demonstrated particularly high conversion to 5- hydroxymethylfurfural, with yields comparable to or exceeding those obtained from glucose and fructose.Example 4. Scale-up of 5-hydroxymethylfurfural production.

[0128] Scale-up experiments were conducted using two approaches: (1) increased reaction volume at constant sugar concentration (1.8 wt.%), and (2) increased substrate concentration (up to 18 wt.%) to simulate industrial conditions.

[0129] For the larger volume approach, 1.08 g of substrate was processed with 300 mg of co-catalyst, 450 mg of AI(NO3)3'9H2O, 60 mL of DMSO at 110°C for 20 hours with nitrogen purging for 2 minutes. Increasing the reaction volume at constant concentration had minimal effect on 5-hydroxymethylfurfural yield.

[0130] For the higher concentration approach, substrate concentration was raised to 18 wt.%. Under these conditions, 5-hydroxymethylfurfural yields of 67% for glucose and 57% for fructose were achieved. For fructose, 112.5 mg of AI(NO3)3'9H2O was used instead of 450 mg. At high sugar concentrations, 5-hydroxymethylfurfural formation reached approximately 60% yield within the first 5 hours.Example 5. Integrated two-step conversion of glucose to 2,5-furandicarboxylic acid.

[0131] Following glucose conversion to 5-hydroxymethylfurfural using the y-alumina- supported sulfone group co-catalyst, the co-catalyst was removed by filtration.

[0132] Water and platinum-copper bimetallic nanoparticles supported on magnesium oxide were added to the system for aerobic oxidation of 5-hydroxymethylfurfural to 2,5- furandicarboxylic acid. With a water to DMSO volume ratio of 19:1 , over 90% of 5- hydroxymethylfurfural was converted to 2,5-furandicarboxylic acid.

[0133] The 2,5-furandicarboxylic acid was separated, and water was evaporated leaving DMSO for reuse in subsequent glucose conversion reactions.

Claims

CLAIMS1. A Y-alumina-supported sulfone group catalyst including: sulfone groups grafted on a v-alumina support, wherein the sulfone groups are grafted using electron beam irradiation.

2. The catalyst of claim 1 , wherein the y-alumina support is a solid support.

3. The catalyst of claim 2, wherein the solid support is any one of a particle, film and coating.

4. The catalyst of any one of claims 1 to 3, wherein the sulfone groups are grafted on the Y-alumina support with a linker.

5. A method of preparing a y-alumina-supported sulfone group catalyst including: providing a y-alumina support; and grafting sulfone groups on the y-alumina support using electron beam irradiation to produce the y-alumina-supported sulfone group catalyst.

6. The method of claim 5, wherein the grafting uses 4-vinylbenzenesulfonic acid sodium salt as a sulfone group precursor.

7. The method of claim 5 or claim 6, wherein Fourier-transform infrared spectroscopy is used to confirm successful grafting of the sulfone groups on a surface of the y-alumina support.

8. Use of a Y-alum'na-suPPortecl sulfone group catalyst for production of 5- hydroxymethylfurfural including: providing a solution including a sugar reactant and an aluminium salt dissolved in a solvent; combining the solution with the y-alumina-supported sulfone group catalyst; and dehydrating the sugar reactant in the solution to produce the 5-hydroxymethylfurfural at a controlled temperature of between about 60°C and about 120°C.

9. A method of producing 5-hydroxymethylfurfural including: dispersing a y-alumina-supported sulfone group catalyst in a solution including a sugar reactant and an aluminium salt dissolved in a solvent; and dehydrating the sugar reactant in the solution to produce the 5-hydroxymethylfurfural at a controlled temperature of between about 60°C and about 120°C.

10. The method of claim 9, wherein y-alumina-supported sulfone group catalyst includessulfone groups grafted on a surface of a y-alumina support, and wherein the sulfone groups coordinate with aluminium ions from the aluminium salt to form aluminium ion complexes on the y-alumina support.

11. The method of claim 10, wherein the sugar reactant coordinates with the aluminium ion complexes on the y-alumina support.

12. The method of any one of claims 9 to 11, wherein the sugar reactant is selected from glucose, fructose, sucrose, mannose, maltose, and sorbose.

13. The method of any one of claims 9 to 12, wherein the solution comprises the sugar reactant at a concentration of at least 15 wt.%.

14. A method of producing 2,5-furandicarboxylic acid including:(a) producing 5-hydroxymethylfurfural according to the method of claim 9;(b) removing the y-alumina-supported sulfone group catalyst from the solution;(c) adding water and an oxidation catalyst to the solution; and(d) oxidizing the 5-hydroxymethylfurfural to produce 2,5-furandicarboxylic acid.

15. The method of claim 14, wherein the oxidation catalyst comprises platinum-copper bimetallic nanoparticles supported on magnesium oxide.

16. The method of claim 14 or claim 15, wherein the volume ratio of water to DMSO is approximately 19:1.

17. The method of any one of claims 9 to 13, further comprising: recovering the y-alumina-supported sulfone group catalyst by filtration after production of 5-hydroxymethylfurfural; and reusing the recovered y-alumina-supported sulfone group catalyst in a subsequent reaction.

18. The method of claim 17, further including treating the recovered y-alumina-supported sulfone group catalyst with electron beam irradiation to regenerate catalytic activity.

19. The method of any one of claims 9 to 13, wherein the dehydration is conducted under light irradiation selected from sunlight, simulated sunlight, ultraviolet light, and visible light at a temperature below 100°C.

20. The method of claim 14, further including: separating the 2,5-furandicarboxylic acid from the reaction mixture;evaporating water from the reaction mixture; and reusing the recovered dimethyl sulfoxide in a subsequent production of 5- hydroxymethylfurfural.

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