Transition metal oxide solid acid and application thereof in preparation of 5-hydroxymethylfurfural

Abstract

The invention provides transition metal oxide solid acid H < 1-x > Ta < 1-x > Mo < 1 + x > O < 6 > and application of the transition metal oxide solid acid to preparation of 5-hydroxymethylfurfural. According to the transition metal oxide solid acid H < 1-x > Ta < 1-x > Mo < 1 + x > O < 6 > disclosed by the invention, interlayer acid sites can be effectively utilized, and phosphoric acid modified on the surface of a layered structure can also provide acid sites, so that the catalytic activity and selectivity are improved. When the 5-hydroxymethylfurfural HMF is prepared from a sugar raw material in a water-acetone green cosolvent system as a catalyst, the HMF is easy to extract in the cosolvent system after the reaction is completed, and compared with a high-boiling-point solvent DMF (Dimethyl Formamide) reaction system which is used as a catalyst HTAWO6, the product separation method is simpler, and the product loss can be remarkably reduced. In addition, compared with the condition that the catalyst HTAWO6 can only catalyze disaccharide to prepare furfural, the solid acid catalyst disclosed by the invention is obviously wider in catalytic substrate range.

Description

Technical Field

[0001] The present invention relates to the field of catalytic chemistry, and in particular to a transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 (-0.3≤x≤0.3) and its application in the preparation of 5-hydroxymethylfurfural. Background Art

[0002] Due to the great concern of the society for sustainable development and environmental issues (such as carbon dioxide and sulfur dioxide emissions), the preparation of bio-based fuels or important chemicals from renewable biomass resources can not only alleviate the crisis of the increasing depletion of fossil resources, but also provide an innovative source of power for people to develop new materials based on the unique structural characteristics of bio-based chemicals. 5-Hydroxymethylfurfural (HMF), as a platform compound for cellulose hydrolysis, contains a variety of chemical groups and can undergo a variety of chemical reactions, such as hydrogenation, oxidative dehydrogenation, esterification, halogenation, polymerization, hydrolysis, etc., which are used to synthesize a variety of important compounds and new polymer materials, including medicines, resin plastics, diesel fuel additives, etc. Therefore, HMF is a bridge between green biomass resources and important chemicals or fuels derived from biomass. The research and development of green and efficient HMF preparation catalytic systems is of great significance for the implementation of relevant strategic tasks.

[0003] The polysaccharides used to prepare HMF mainly include inulin, lignocellulose, starch, etc., which have the advantages of wide sources and low prices. However, the literature reports that the reaction conditions of polysaccharide raw materials are harsh, there are many by-products, and the yield is low. Current research mainly focuses on monosaccharides as raw materials. Compared with fructose, it is more economical to prepare HMF directly from glucose. Therefore, the study of the efficient conversion of glucose to prepare HMF is a current hot topic. Patent document CN 106810517 A discloses that the HMF yield is about 60% in a continuous extraction process using glucose as a raw material and an extractant continuously passing through the reaction phase; Patent document CN 113351253 A discloses the use of high-boiling point DMSO as a solvent, and the reaction-extraction flash evaporation method is used to obtain an HMF yield of more than 80%; Jason P. Hallet et al. used CrCl 3 6H 2 O catalyzes the hydrolysis of fructose in ionic liquids to prepare HMF with a yield of up to 96% [ACSSustainable Chem. Eng. 2014, 2, 978-981]. However, the above process still has problems such as the large amount of ionic liquids and high-boiling point solvents and complex operation methods, which limits the industrial development of HMF.

[0004] The pathway for catalyzing glucose to prepare HMF is roughly as follows: glucose is isomerized to fructose under the action of catalysts such as alkaline enzymes and Lewis acids, and fructose is then cyclized to form HMF under the action of Bronsted acid. This process usually requires a high reaction temperature, and the simultaneous occurrence of glucose isomerization and cyclization reactions leads to more side reactions. Therefore, it is much more difficult to prepare HMF using glucose as a raw material than fructose. Solid acid catalysts have the advantages of high catalytic activity, easy separation, and reusability, and are green catalysts advocated in the 21st century. Among them, transition metal oxides have the advantages of heat resistance and two acidic sites, and show good application prospects in the reaction of catalyzing sugar hydrolysis to prepare HMF. For example, the nanosheet HTaWO prepared by J. Zhong et al. according to traditional methods 6 Solid acid catalyzes fructose dehydration in DMSO, with an HMF yield of 67% [Journal of Energy Chemistry. 2017, 26, 147-15]. However, its interlayer acid sites cannot be fully utilized, resulting in low catalytic activity and waste. Summary of the invention

[0005] The present invention can prepare transition metal oxide solid acid H by high energy ball milling and phosphoric acid stripping. 1-x Ta 1-x Mo 1+x O 6 As a catalyst, it has good catalytic activity in the reaction of preparing 5-hydroxymethylfurfural HMF using glucose and fructose as raw materials and a low boiling point solvent system. It can overcome the problems of using high boiling point solvents in the prior art in the HMF synthesis system of hexose, which leads to difficulty in separating HMF, long preparation cycle of layered solid acid, and inability of interlayer acid sites to contact with substrates.

[0006] A transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 , wherein -0.3≤x≤0.3, is prepared by the following method:

[0007] a) The raw material Li 2 CO 3 、 2 O 5 、MoO 3 After mixing, calcination is performed to obtain the precursor Li 1-x Ta 1-x Mo 1+x O 6 ;

[0008] b) the precursor Li obtained in step a) 1-x Ta 1-x Mo 1+x O6 ball milling;

[0009] c) the precursor Li after ball milling in step b) 1-x Ta 1-x Mo 1+x O 6 Join H 3 PO 4 Aqueous solution, or H 3 PO 4 Mix with other inorganic acids and heat with stirring.

[0010] According to an embodiment of the present invention, the method further comprises step d), wherein step d) comprises: centrifuging the mixed solution obtained in step c), washing it, and then freeze-drying it to obtain a transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 .

[0011] According to an embodiment of the present invention, the raw material Li in step a) 2 CO 3 、 2 O 5 、MoO 3 The molar ratio is 1:1:2 to 0.7:0.7:1.3.

[0012] According to an embodiment of the present invention, in step a), the calcination is performed at 500-900° C. for 1-50 h.

[0013] According to an embodiment of the present invention, a high energy ball mill is used for ball milling in step b).

[0014] According to an embodiment of the present invention, the small balls used in the ball milling in step b) are mixed with the catalyst precursor Li 1-x Ta 1-x Mo 1+x O 6 The mass ratio is (20~2):1.

[0015] According to an embodiment of the present invention, the ball milling speed in step b) is 400-1000 r / min.

[0016] According to an embodiment of the present invention, the size of the zirconium oxide balls used in the high-energy ball mill in step b) is 1-10 mm, the number of cycles is 2-10 times, and each cycle includes: ball milling for 1 minute and resting for 5-10 minutes, and ball milling 10 times.

[0017] According to an embodiment of the present invention, in step c), the inorganic acid is HCl, HNO 3 or H 2 SO4 ;

[0018] According to an embodiment of the present invention, in step c), H 3 PO 4 The aqueous solution concentration or H 3 PO 4 The concentration of the mixed acid in the mixed solution with other inorganic acids is 0.5-5 mol / L, for example 1-3 mol / L.

[0019] According to an embodiment of the present invention, in step c), when H 3 PO 4 When mixed with other inorganic acids, H 3 PO 4 The molar ratio to other inorganic acids is 1:1 to 1:5, for example 1:1 to 1:3.

[0020] According to an embodiment of the present invention, in step c), the temperature of heating and stirring is 50-150° C., and the heating time is 2-50 h.

[0021] According to an embodiment of the present invention, the H 1-x Ta 1-x Mo 1+x O 6 It has a layered structure.

[0022] According to an embodiment of the present invention, the H 1-x Ta 1-x Mo 1+x O 6 HTaMoO 6 .

[0023] According to an embodiment of the present invention, the transition metal oxide solid acid H is prepared by the following method: 1-x Ta 1-x Mo 1+ x O 6 :

[0024] In step a1), the raw material Li 2 CO 3 、 2 O 5 、MoO 3 The catalyst precursor Li is obtained by weighing the catalyst according to the stoichiometric ratio of 1:1:2 to 0.7:0.7:1.3, grinding and mixing by wet method, and calcining the solid powder at 550-850°C for 2-48h after the solvent evaporates. 1- x Ta 1-x Mo 1+x O 6 ;

[0025] In step b1), the catalyst precursor Li obtained in step a1) is 1-x Ta 1-x Mo 1+x O 6 Ball milling; small balls and catalyst precursor Li 1-x Ta 1-x Mo 1+x O 6 The mass ratio is (10-5):1, the ball milling speed is 500-800r / min, the size of the zirconia balls is 2-5mm, the number of cycles is 2-6 times, 1 cycle: ball milling for 1min, rest for 5-10min, and ball milling 10 times.

[0026] For example, first use 5mm zirconia balls and 500r / min for 2 cycles of ball milling, then use 2mm zirconia balls and 500r / min for 2 cycles of ball milling;

[0027] In step c1), the heating temperature is 60-140°C, the mechanical stirring speed is 800-1400r / min, and the reaction time is 12-24h;

[0028] In step d1), the mixed solution is cooled to room temperature and then allowed to stand for 1-24 hours, centrifuged at a speed of 800-1000 r, and then the supernatant is removed, washed with distilled water, and freeze-dried to obtain a transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 .

[0029] The present invention also provides the transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 The invention relates to a catalyst for preparing furfural from hexose (e.g. fructose, glucose), sugar composed of two or more hexose units (e.g. sucrose, cellobiose, inulin, cellulose, starch) or xylose.

[0030] The present invention also provides a method for preparing 5-hydroxymethylfurfural, comprising: 1-x Ta 1-x Mo 1+x O 6 The sugar raw material is catalyzed in the presence of; the sugar raw material is selected from hexose (e.g., fructose, glucose), sugar composed of two or more hexose units (e.g., sucrose, cellobiose, inulin, cellulose, starch) or xylose.

[0031] According to an embodiment of the present invention, the reaction is carried out, for example, by the following steps:

[0032] In a closed autoclave, the sugar raw material is mixed with the solvent, and a transition metal oxide solid acid H is added to the mixture. 1-x Ta 1-x Mo 1+x O 6 Acts as a catalyst to heat the reaction.

[0033] According to an embodiment of the present invention, the concentration of the sugar raw material may be 0.033-0.16 mol / L, for example 0.05 mol / L;

[0034] According to an embodiment of the present invention, the reaction temperature may be 120-150°C, for example, fructose may be dehydrated at 120°C; and the glucose system may be reacted at 130°C.

[0035] According to an embodiment of the present invention, the reaction time is within 1-6 hours, for example, the reaction time of the fructose system at 120°C is 1.5-3 hours, and the reaction time of the glucose system at 130°C is 5 hours;

[0036] According to an embodiment of the present invention, the solvent in the reaction can be selected from a mixed solvent consisting of tetrahydrofuran, acetone, γ-valerolactone and water, or a mixed system further consisting of an ionic liquid (such as [BMIM]Br or [BMIM]Cl).

[0037] According to an embodiment of the present invention, inorganic salts, such as NaCl, KCl, etc., may be added to the reaction system to form a two-phase system of salt-water / organic solvent, thereby accelerating the reaction rate and improving the reaction selectivity and yield.

[0038] According to an embodiment of the present invention, a transition metal oxide solid acid H is added to the reaction. 1-x Ta 1-x Mo 1+x O 6 The mass ratio of fructose to sugar raw material can be 1:1-4:1. For example, 25 mg of fructose can be added with 25 mg or 45 mg of transition metal oxide solid acid H. 1-x Ta 1-x Mo 1+x O 6 catalyst.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) Compared with the traditional method for preparing transition metal oxide solid acid, the preparation method of the present invention is simple, has a short cycle, and does not require the participation of a large amount of volatile strong acid;

[0041] (2) The transition metal oxide solid acid H of the present invention 1-x Ta 1-x Mo1+x O 6 Not only can the interlayer acidic sites be effectively utilized, but the phosphoric acid modified on the surface of the layered structure can also provide acidic sites, thereby improving the catalytic activity and selectivity;

[0042] (3) The present invention uses transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 As a catalyst, sugar raw materials were used to prepare HMF in a water-acetone green co-solvent system. After the reaction was completed, HMF was easily extracted from the co-solvent system. Compared with the catalyst HTaWO 6 Using the high boiling point solvent DMSO reaction system, the product separation method is simpler and can significantly reduce product loss;

[0043] (4) The present invention uses transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 As a catalyst, it can catalyze the production of furfural from a variety of sugar raw materials, such as hexose (e.g., fructose, glucose), sugars consisting of two or more hexose units (e.g., sucrose, cellobiose, inulin, cellulose, starch), or xylose. 6 It can only catalyze disaccharides to produce furfural. The substrate range of the present invention is significantly wider.

[0044] (5) The catalyst of the present invention is insoluble in the reaction system and can be easily recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The catalyst precursor prepared by calcination in Example 1 (calcined) and the LiTaMoO after ball milling 6 (Ball milling), catalyst HTaMoO 6 (Exfoliation) SEM image.

[0046] Figure 2 The catalyst precursor prepared by calcination in Example 1 and the LiTaMoO 6 , stripped catalyst HTaMoO 6 Powder diffraction pattern (calcined refers to calcined LiTaMoO 6 ; Ball milling refers to the calcined LiTaMoO 6 After ball milling, exfoliation refers to the above calcined and ball milled LiTaMoO 6 Then, it is exfoliated into a thin layer structure HTaMoO by auxiliary liquid phase such as phosphoric acid. 6 powder diffraction pattern). DETAILED DESCRIPTION

[0047] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0048] Example 1

[0049] Weigh 1.000g Li 2 CO 3 , 5.996g Ta 2 O 5 、3.908g MoO 3 , add 5 ml of acetone to disperse the solid powder, and grind it in a mortar until the solvent is completely evaporated. Use a muffle furnace to calcine at 600 °C for 24 h with a heating rate of 5 °C / min to obtain a catalyst precursor LiTaMoO with a layered bulk structure. 6 . Weigh 4g of catalyst precursor and add 40g of 5mm zirconium oxide balls. Mill at 500r / min for 2 cycles (mill for 1 minute, rest for 5 minutes). Take out the 5mm balls and add 40g of 2mm zirconium oxide balls. Mill at 500r / min for 2 cycles. At the end of each cycle, scrape the solids on the ball mill and grind them before the next ball milling. Weigh 1g of the ball-milled catalyst precursor and disperse it in 150mL of 2.5mol / L H 3 PO 4 The aqueous solution was heated to 100°C in an oil bath and mechanically stirred at a speed of 1000 r / min for 12 h. After the reaction was completed, the mixture was allowed to stand for 12 h, centrifuged at a speed of 10000 r / min for 10 min, washed once with distilled water, and the obtained solid was freeze-dried to prepare HTaMoO 6 .

[0050] Example 2

[0051] The difference between Example 2 and Example 1 is that: 1.000 g Li 2 CO 3 , 5.996g Ta 2 O 5 3.629g MoO 3 , 5 mL of acetone was added to disperse the solid powder, and the solid powder was ground using a mortar until the solvent was completely evaporated. Other details were the same as in Example 1.

[0052] Example 3

[0053] The difference between Example 2 and Example 1 is that the ball milling speed is 800 r / min and the stripping temperature is 80° C. The other parts are the same as those in Example 1.

[0054] Example 4

[0055] The difference between Example 4 and Example 3 is that in Example 4, H is used for stripping. 2 SO 4 :H 3 PO 4 =0.5:1.5 (mol / mol) mixed solution. Others are the same as in Example 3.

[0056] Example 5

[0057] The difference between Example 5 and Example 3 is that HNO is used during stripping. 3 :H 3 PO 4 =0.5:1.5 (mol / mol) mixed solution. Others are the same as in Example 3.

[0058] Comparative Example 1

[0059] Jiawei Zhong et al. 2 CO 3 With metal oxide (Ta 2 O 5 and WO 3 ) were mixed in a stoichiometric ratio of 1:1:2, ground and calcined in a muffle furnace at 800 °C for 24 h. 3 The aqueous solution was shaken for 1 week for proton exchange, and HNO was replaced twice during the reaction. 3 The solution was centrifuged and washed with distilled water and dried at 50°C. Then 25 wt% tetrabutylammonium hydroxide solution was added to the aqueous solution containing the protonated catalyst precursor and shaken for 1 week. The supernatant was collected by centrifugation and 1 mol / L HNO 3 The aqueous solution was adjusted to an acidic pH, and the aggregated nanosheet catalyst was collected by centrifugation, washed with distilled water and dried at 50 °C to prepare the catalyst HTaWO 6 .

[0060] Catalytic performance test:

[0061] (1) Preparation of HMF by catalytic dehydration of fructose using the catalyst prepared in Examples 1-5:

[0062] Weigh 25 mg of fructose, HTaMoO 6 25 mg of catalyst was added to 2.5 ml of H 2 The mixture was placed in a high-pressure reactor, sealed and placed in a heating furnace heated to 120°C for 3 hours. After the reaction, the reactor was placed in ice water and quickly cooled to room temperature. HMF was obtained after centrifugation.

[0063] The same operation was used in Comparative Example 1, except that 2.5 mL of DMSO was used as the reaction solvent.

[0064] (2) Preparation of HMF by catalytic dehydration of fructose using the catalyst prepared in Example 1-2:

[0065] According to the method of (1), 2.5 mL of ionic liquid-acetone (v / v, 1:6) mixed solution was used as the reaction solvent, and the reaction time was 1 h.

[0066] (3) Preparation of HMF by catalytic dehydration of glucose using the catalyst prepared in Example 1:

[0067] According to the method of (1), glucose was used as the substrate, the reaction temperature was set to 130°C, and the reaction time was 5 h.

[0068] The same operation was used in Comparative Example 1, except that 2.5 mL of DMSO was used as the reaction solvent.

[0069] After the mixed system was diluted 10 times with water, it was determined by Shimadzu high performance liquid chromatography (HPLC) using an Aminex HPX-87H column (300x7.8 mm) and a UV detector and a differential detector. The specific parameters of the process are as follows:

[0070] The mobile phase flow rate was 0.6 mL / min, the UV detection wavelength was 320 nm, the column temperature was 35 °C, and the mobile phase was 0.005 MH 2 SO 4 HMF and raw sugar were detected by UV detector and differential detector respectively, and the conversion rate of raw sugar and the yield of HMF were calculated based on the standard curves of standard solutions of HMF and raw sugar with different concentrations. The conversion rate of raw hexose and the yield of product HMF were summarized in Table 1 after liquid chromatography detection:

[0071] Table 1

[0072]

[0073] The above results show that the catalyst HTaMoO prepared by the present invention 6 The yield of HMF is as high as 86% when catalyzing fructose dehydration with a small amount of ionic liquid as an auxiliary agent. The conversion rate of glucose in the water-acetone system is 97% and the yield of HMF is 44%. 6 With glucose as substrate, the yield of HMF is only 2%. By comparing the above examples with the comparative examples, the desired thin layer catalyst HTaMoO can be prepared by ball milling-stripping. 6, which can overcome the disadvantage that the interlayer acid sites of traditional transition metal oxide solid acid cannot be fully utilized, and has good selectivity and high yield in monosaccharide system. The catalyst prepared by the present invention has good universality and can be applied to the dehydration of various sugars such as sucrose, cellobiose, inulin, etc. to prepare HMF, and can also be applied to catalyze the hydrolysis of xylose to prepare furfural, with a yield of 40%.

[0074] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 ,in ，- 0.3≤x≤0.3, characterized in that it is prepared by a method comprising the following steps: a) The raw material Li 2 CO 3 、 2 O 5 、MoO 3 After mixing, calcination is performed to obtain the precursor Li 1-x Ta 1-x Mo 1+x O 6 ; b) the precursor Li obtained in step a) 1-x Ta 1-x Mo 1+x O 6 ball milling; c) the precursor Li after ball milling in step b) 1-x Ta 1-x Mo 1+x O 6 Join H 3 PO 4 Aqueous solution, or H 3 PO 4 Mix with other inorganic acids and heat with stirring.

2. The transition metal oxide solid acid H according to claim 1 1-x Ta 1-x Mo 1+x O 6 , It is characterized in that The method further comprises step d), wherein step d) comprises: centrifuging the mixed solution obtained in step c), washing it and then freeze-drying it to obtain a transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 .

3. The transition metal oxide solid acid H according to claim 1 or 2 1-x Ta 1-x Mo 1+x O 6 , It is characterized in that In step a), the raw material Li 2 CO 3 、 2 O 5 、MoO 3 The molar ratio is 1:1:2 to 0.7:0.7:1.3; Preferably, in step a), the calcination is performed at 500-900° C. for 1-50 h.

4. The transition metal oxide solid acid H according to any one of claims 1 to 3 1-x Ta 1-x Mo 1+x O 6 , It is characterized in that In step b), high energy ball mill is used for ball milling; Preferably, the balls used in the ball milling in step b) are the same as the catalyst precursor Li 1-x Ta 1-x Mo 1+x O 6 The mass ratio is (20~2):

1. Preferably, in step b), the ball milling speed is 400-1000 r / min; Preferably, the size of the zirconium oxide balls used in the high-energy ball mill in step b) is 1-10 mm, the number of cycles is 2-10 times, and each cycle includes: ball milling for 1 min, resting for 5-10 min, and ball milling 10 times.

5. The transition metal oxide solid acid H according to any one of claims 1 to 4 1-x Ta 1-x Mo 1+x O 6 , It is characterized in that In step c), the inorganic acid is HCl, HNO 3 or H 2 SO 4 ; Preferably, in step c), H 3 PO 4 The concentration of aqueous solution is 0.5-5mol / L; Preferably, H 3 PO 4 The mixed acid concentration in the mixed solution with other inorganic acids is 0.5-5 mol / L; Preferably, in step c), when H is used 3 PO 4 When mixed with other inorganic acids, H 3 PO 4 The molar ratio with other inorganic acids is 1:1 to 1:5; Preferably, in step c), the temperature of heating and stirring is 50-150°C.

6. The transition metal oxide solid acid H according to any one of claims 1 to 5 1-x Ta 1-x Mo 1+x O 6 , It is characterized in that The H 1-x Ta 1-x Mo 1+x O 6 HTaMoO 6 ; Preferably, the transition metal oxide solid acid H is prepared by a method comprising the following steps: 1-x Ta 1-x Mo 1+x O 6 : In step a1), the raw material Li 2 CO 3 、 2 O 5 、MoO 3 The mixture is weighed according to a molar ratio of 1:1:2 to 0.7:0.7:1.3, wet-grinded and mixed, and the solid powder after the solvent is evaporated is calcined at 550-850°C for 2-48h to obtain the catalyst precursor Li 1-x Ta 1- x Mo 1+x O 6 ; In step b1), the catalyst precursor Li obtained in step a1) is 1-x Ta 1-x Mo 1+x O 6 Ball milling; small balls and catalyst precursor Li 1-x Ta 1-x Mo 1+x O 6 The mass ratio is (10-5):1, the ball milling speed is 500-800r / min, the size of the zirconium oxide ball is 2-5mm, the number of cycles is 2-6 times, 1 cycle: ball milling for 1min, rest for 5-10min, ball milling 10 times; In step c1), the heating temperature is 60-140°C, the mechanical stirring speed is 800-1400r / min, and the reaction time is 12-24h; In step d1), the mixed solution is cooled to room temperature and then allowed to stand for 1-24 hours, centrifuged at a speed of 800-1000 r, and then the supernatant is removed, washed with distilled water, and freeze-dried to obtain a transition metal oxide solid acid H 1-x Ta 1-x Mo 1+x O 6 .

7. The transition metal oxide solid acid H according to any one of claims 1 to 6 1-x Ta 1-x Mo 1+x O 6 The invention relates to a catalyst for preparing furfural from hexose (e.g. fructose, glucose), sugar composed of two or more hexose units (e.g. sucrose, cellobiose, inulin, cellulose, starch) or xylose.

8. A method for preparing 5-hydroxymethylfurfural, It is characterized in that The method comprises: adding the transition metal oxide solid acid H according to any one of claims 1 to 6 1-x Ta 1-x Mo 1+x O 6 A catalytic dehydration reaction is carried out on a sugar raw material in the presence of , wherein the sugar raw material is selected from hexose (such as fructose, glucose), a sugar composed of two or more hexose units (such as sucrose, cellobiose, inulin, cellulose, starch) or xylose.

9. The method according to claim 8, It is characterized in that The reaction is carried out using the following steps: In a closed autoclave, a sugar raw material is mixed with a solvent, and a transition metal oxide solid acid H according to any one of claims 1 to 6 is added to the mixture. 1-x Ta 1-x Mo 1+x O 6 Acts as a catalyst to heat the reaction.

10. The method according to claim 9, It is characterized in that The concentration of sugar raw materials is 0.033-0.16 mol / L; Preferably, a transition metal oxide solid acid H is added to the reaction 1-x Ta 1-x Mo 1+x O 6 The mass ratio with the sugar raw material is 1:1-4:1; Preferably, the reaction temperature is 120-150°C.

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