The invention relates to a preparation method of furan-2-acrolein and 2, 2apos; preparation method of-dimethyldifuran

Abstract

The invention belongs to the field of organic synthesis, and relates to a preparation method of furan-2-acrolein and 2, 2 '-dimethyldifuran, which specifically comprises the following steps: filling furfural, ethanol, hydrogen peroxide, sodium carbonate and a noble metal supported cerium dioxide catalyst into a high-pressure reaction kettle, sealing, reacting at 130-170 DEG C for 4-8 hours, and cooling to room temperature to obtain furan-2-acrolein and 2, 2'-dimethyldifuran. Adding a 2, 2 '-dimethyl difuran solution; the preparation method has the advantages of easily available raw materials and simple preparation; compared with polyvinyl alcohol and vinylpyrrolidone organic stabilizers in the prior art, the precious metal supported cerium dioxide catalyst is adopted, no extra organic reagent is needed, the synthesis method is simple, and operation is convenient; reaction conditions are mild, consumed time is short, only a sealed reaction kettle is needed, equipment is simple, and operation is easy; and the higher conversion rate of furfural and the yield of furan-2-acrolein and 2, 2 '-dimethyldifuran are obtained.

Description

Technical Field

[0001] The present invention belongs to the field of organic synthesis, and particularly relates to a method for preparing furan-2-acrolein and 2,2'-dimethyl difuran. Background Art

[0002] In recent years, the gradual depletion of fossil fuels has led to the search for and development of alternative energy sources, fuels, and organic compounds, which are widely used in a variety of application fields. Among them, biomass is a resource from which energy and chemicals can be obtained, and this resource shows the greatest potential to replace fossil resources in the medium and long term. Biomass platform compounds can achieve the growth of intermolecular carbon chains through condensation, and synthesize high-value carbon fuel precursors and chemicals. As one of the most valuable biomass-based furan compounds, furfural can be used to prepare various high-value chemicals through catalytic reaction processes. Among them, furfural can be used to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) through an oxidative coupling reaction, so as to obtain high-quality fuels and achieve the effective catalytic conversion of furfural, and promote the efficient utilization of biomass energy.

[0003] Currently, in industry, the direct oxidation of furfural is carried out through the Cannizzaro reaction. In this reaction, furfural undergoes a disproportionation reaction to produce the corresponding alcohol (furfuryl alcohol) and carboxylic acid (furfuroic acid). However, the maximum yield of F2A obtained from this reaction is limited to 50%. Although the use of strong oxidants can promote the reaction, these oxidants are harmful to health, and will accumulate inside the instrument, increasing the cleaning cost, and will also cause environmental pollution, which does not conform to the development concept of green chemistry. Therefore, it is necessary to find oxidants that are harmless to the environment.

[0004] Therefore, whether it is possible to provide a method for preparing furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) that is safer, more environmentally friendly, and has higher reaction efficiency has become one of the problems to be solved urgently in this field. Summary of the Invention

[0005] To solve the problems in the prior art that the yields of preparing furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) from furfural are relatively low, the reaction steps are numerous, and strong oxidants need to be used, causing environmental pollution, the present invention provides a method for preparing furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) from furfural, ethanol and hydrogen peroxide. A noble metal supported cerium dioxide is used as a catalyst. Furfural, ethanol, sodium carbonate and hydrogen peroxide are heated and reacted under the action of the catalyst to obtain furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM). By oxidative coupling of furfural and ethanol, the growth of the carbon chain between molecules is realized to prepare furan-2-acrolein and 2,2'-dimethyl difuran, providing a brand-new reaction route. Furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) can be prepared with a special catalyst and mild conditions. The noble metal supported cerium dioxide catalyst adopted has high reaction activity, is simple to prepare, and the preparation process is safe and environmentally friendly, having good industrialization prospects.

[0006] In this application, the role of hydrogen peroxide is to oxidize ethanol to generate acetaldehyde, which is more conducive to the condensation reaction with furfural. The role of sodium carbonate is to remove the α-H in furfural, which is more conducive to the progress of the reaction. These two together with the noble metal supported cerium dioxide catalyst act together to promote the occurrence of this reaction.

[0007] The preparation method of furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) provided by the present invention is specifically as follows: Furfural, ethanol, hydrogen peroxide, sodium carbonate and the catalyst are loaded into a high-pressure reaction kettle and sealed, and reacted at 130-170 °C for 4-8 h, and cooled to room temperature to obtain a furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) solution; the catalyst is a noble metal supported cerium dioxide catalyst.

[0008] Preferably, the furfural, ethanol, hydrogen peroxide, sodium carbonate and the catalyst are added in a ratio of 0.086 mL: 6 mL: 2 mL: 0.1 g: 0.05 g.

[0009] Preferably, the furfural, ethanol, hydrogen peroxide, sodium carbonate and the catalyst are reacted at 130-160 °C after being loaded into the high-pressure reaction kettle and sealed; as a further preference, the reaction is stirred at 500-700 rpm during the process.

[0010] Preferably, the noble metal of the noble metal supported cerium dioxide catalyst is one of Au, Pt, Pd, and the preparation method of the noble metal supported cerium dioxide catalyst is: Dissolve cerium dioxide in deionized water, add an aqueous solution of a noble metal, stir at room temperature for 0.5 - 2 h, then add a certain amount of sodium hydroxide to adjust the pH to 9 - 10, stir at room temperature for 0.5 - 2 h, and then add a sodium borohydride solution, stir at room temperature for 1 - 3 h, and obtain a noble metal-loaded cerium dioxide catalyst through filtration, washing, and drying; the cerium dioxide is dissolved in water at a ratio of 1 g:150 mL; the molar ratio of sodium borohydride to the solute of the aqueous solution of the noble metal is 15:1.

[0011] As a further preference, the aqueous solution of the noble metal is an AuCl 3 solution, the content of Au in the aqueous solution of the noble metal is 2.4 mg / mL, and the mass ratio of cerium dioxide to Au in the aqueous solution of the noble metal is 1:0.01.

[0012] As a further preference, the aqueous solution of the noble metal is a PtCl 4 solution, the content of Pt in the aqueous solution of the noble metal is 0.285 mg / mL, and the mass ratio of cerium dioxide to Pt in the aqueous solution of the noble metal is 1:0.01.

[0013] As a further preference, the aqueous solution of the noble metal is a PdCl 2 solution, the content of Pd in the aqueous solution of the noble metal is 0.3 mg / mL, and the mass ratio of cerium dioxide to Pd in the aqueous solution of the noble metal is 1:0.01.

[0014] As a preference, the cerium dioxide is rod-shaped cerium dioxide, and the preparation method of the rod-shaped cerium dioxide is as follows: Dropwise add a cerium nitrate solution into a sodium hydroxide solution to form a flocculent substance. After the dropping is completed, stir for 30 min, then add the solution into a hydrothermal reaction kettle, control the temperature at 100 - 120 °C for reaction for 12 - 14 h, cool to room temperature and take out, then perform suction filtration to obtain a precipitate. Wash the precipitate repeatedly with deionized water until the pH of the washing solution is neutral, dry and grind to obtain a precursor of rod-shaped cerium dioxide (R-CeO 2 ), and calcine the precursor at 450 °C for 3 h - 5 h to obtain rod-shaped cerium dioxide; In the above preparation method, the concentration of the cerium nitrate solution is 0.4 mol / L, the concentration of the sodium hydroxide solution is 4 - 9 mol / L, and the molar ratio of cerium nitrate to sodium hydroxide is 1:30.

[0015] As a preference, the cerium dioxide is nano-particle cerium dioxide, and the preparation method of the nano-particle cerium dioxide is as follows: The cerium nitrate solution was added dropwise into the sodium hydroxide solution to form a flocculent substance. After the addition was completed, it was stirred for 30 min. The mixed solution was added to a hydrothermal reactor, and the reaction was carried out at a temperature of 100 - 120 °C for 12 - 14 h. After cooling to room temperature, it was taken out, and then suction filtration was carried out to obtain a precipitate. The precipitate was repeatedly washed with deionized water until the pH of the washing solution was neutral, and after drying, it was ground to obtain a precursor of nano-sized cerium dioxide (P-CeO 2 ). The precursor was calcined at 450 °C for 3 h - 5 h to obtain nano-sized cerium dioxide; wherein the concentration of the cerium nitrate solution was 0.4 mol / L, the concentration of the sodium hydroxide solution was 0.1 - 0.4 mol / L, and the molar ratio of cerium nitrate to sodium hydroxide was 1:1.

[0016] In this solution, the noble metal-loaded cerium dioxide catalyst was used in the reaction of furfural and ethanol, and the following beneficial effects were obtained: 1) In the present invention, noble metal-loaded cerium dioxide is used as a catalyst, with furfural and ethanol as the main raw materials, for the preparation of furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM). The raw materials are easily available and the preparation is simple; 2) Compared with the prior art which uses polyvinyl alcohol and vinylpyrrolidone as organic stabilizers, the noble metal-loaded cerium dioxide catalyst used in the present invention has no additional organic reagents, and the synthesis method is relatively simple and the operation is convenient; 3) The reaction conditions of the present invention are mild, and the time-consuming is short, only a sealed reaction kettle is required. The equipment is simple and the operation is easy; 4) In the present invention, the conversion rate of furfural and the yields of furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) can reach as high as 96.7%, 65.2% and 33.4% respectively, which are significantly better than the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 XRD patterns of gold (Au)-loaded cerium dioxide (1 wt% Au / CeO 2 ) catalysts with different morphologies for Example 3 and Example 6. The figure includes Au-loaded rod-shaped cerium dioxide (R-CeO 2 ) and nano-sized cerium dioxide (P-CeO 2 ) catalysts; Figure 2 Gas chromatogram of the reaction solution in Example 9; Figure 3 Mass spectrum of furfural in Example 9, with a gas-phase retention time of 5.19; Figure 4 Mass spectrum of furan-2-acrolein (F2A) in Example 9, with a gas-phase retention time of 8.24; Figure 5 Mass spectrum of 2,2'-dimethyl difuran (DFM) in Example 9, with a gas-phase retention time of 11.00. Detailed implementation manners

[0018] The above content of the present invention will be further described in detail below through specific implementation manners in the form of examples, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. All technologies implemented based on the above content of the present invention belong to the scope of the present invention. Unless otherwise specified, conventional existing technologies are used in the following examples.

[0019] Substances and reagents used in the following examples are all general commercially available products unless otherwise specified.

[0020] Example 1 Preparation method of rod-shaped cerium dioxide (R-CeO 2 ), the specific steps are as follows: (1) Weigh 4.34 g of Ce(NO 3 ) 3 •6H 2 O (0.01 mol) and dissolve it in 25 mL of deionized water, stir at room temperature for 10 min to obtain solution A; (2) Weigh 12 g of sodium hydroxide and dissolve it in 50 mL of deionized water, stir at room temperature for 10 min to obtain solution B; (3) Drop solution A into solution B drop by drop, stir at room temperature for 30 min, then transfer it to a 100 mL reaction kettle and react at 110 °C for 12 h. After the reaction is completed, cool it to room temperature, filter the product to obtain a precipitate, and wash the precipitate repeatedly with deionized water (at least three times) until the pH of the filtrate is 7. The obtained precipitate is dried in an oven at 80 °C for 6 h and then ground to obtain the product R-CeO 2 precursor; (4) Calcinate the precursor at 450 °C for 3 h to obtain the required R-CeO 2 .

[0021] Example 2 Preparation method of nano-particle cerium dioxide (P-CeO 2 ), the specific steps are as follows: (1) Weigh 4.34 g of Ce(NO 3 ) 3 •6H 2 O (0.01 mol) and dissolve it in 25 mL of deionized water, stir at room temperature for 10 min to obtain solution A; (2) Weigh 0.4 g of sodium hydroxide and dissolve it in 50 mL of deionized water, stir at room temperature for 10 min to obtain solution B; (3) Slowly add solution A drop by drop into solution B. After stirring at room temperature for 30 min, transfer it to a 100 mL autoclave and react at 110 °C for 12 h. After the reaction is completed, cool it to room temperature, filter the product to obtain a precipitate. Wash the precipitate repeatedly with deionized water (at least three times) until the pH of the filtrate is 7. Dry the obtained precipitate in an oven at 80 °C overnight and then grind it to obtain the product P-CeO 2 Precursor; (4) Calcinate at 450 °C for 3 h to obtain the required P-CeO 2 .

[0022] Example 3 Method for preparing 1 wt% gold-loaded rod-shaped cerium oxide catalyst (Au / R-CeO 2 ) is as follows: (1) Prepare an AuCl 3 solution with an Au concentration of 2.4 mg / mL and a 0.01 mol / L AgNO 3 solution; (2) Take 1 g of R-CeO 2 prepared in Example 1 and dissolve it in 150 mL of deionized water. Add 4.2 mL of the AuCl 3 solution prepared in step (1) (AuCl 3 is 5.08×10 -5 mol) to it. Stir at room temperature for 1 h at a rotation speed of 500 r / min. Then add 0.1 mol / L sodium hydroxide solution to adjust the pH to 9, stir again for 1 h at a rotation speed of 500 r / min, and quickly add 10 mL of freshly prepared NaBH 4 solution (NaBH 4 is 7.62×10 -4 mol), where the molar ratio of NaBH 4 to AuCl 3 is 15:1. Keep the rotation speed unchanged, then stir for 2 h, filter to obtain the solid, and then wash the solid with deionized water until there is no Cl - in the filtrate. After that, collect the sample and put it into an oven to dry at 60 °C for 4 h to obtain Au / R-CeO 2 . Its XRD pattern is as shown in Figure 1 . It can be seen that the gold-loaded rod-shaped cerium oxide catalyst is successfully synthesized in this example. No diffraction peak of Au is detected, indicating that the Au particles are small and evenly dispersed, and no stabilizer is required.

[0023] The judgment method for no Cl - is as follows: Take 1 mL of the filtrate and add 0.05 mL of the 0.01 mol / L AgNO prepared in step (1) to it.3 solution and observe whether a white precipitate is formed. If no white precipitate is formed, it indicates that Cl - has been cleaned thoroughly.

[0024] Example 4 Method for preparing 1 wt% platinum-loaded rod-shaped cerium oxide catalyst (Pt / R-CeO 2 ), which is the same as the method in Example 3 as a whole, except that in step (1), no AuCl 3 solution is prepared, but a PtCl 4 solution with a Pt concentration of 0.285 mg / mL is prepared. In step (2), 35.1 mL of the above-mentioned PtCl 4 solution (PtCl 4 is 5.13×10 -5 mol) and 10 mL of NaBH 4 solution (NaBH 4 is 7.70×10 -4 mol) are added. Other steps are the same as those in Example 3.

[0025] Example 5 Method for preparing 1 wt% palladium-loaded rod-shaped cerium oxide catalyst (Pd / R-CeO 2 ), which is the same as the method in Example 3 as a whole, except that in step (1), no AuCl 3 solution is prepared, but a PdCl 2 solution with a Pd concentration of 0.3 mg / mL is prepared. In step (2), 33.3 mL of the above-mentioned PdCl 2 solution (PdCl 2 is 9.40×10 -5 mol) and 10 mL of NaBH 4 solution (NaBH 4 is 1.41×10 -3 mol) are added. Other steps are the same as those in Example 3.

[0026] Example 6 Method for preparing gold-loaded nanoparticle-shaped cerium oxide catalyst (Au / P-CeO 2 ), which is the same as the method in Example 3 as a whole, except that in step (2), instead of using the R-CeO 2 prepared in Example 1, the P-CeO 2 prepared in Example 2 is used. Other steps are the same as those in Example 3, and its XRD pattern is as shown in Figure 1As shown, it can also be seen that the gold-loaded nano-sized cerium dioxide catalyst was successfully synthesized in this example, and no diffraction peak of Au was detected, indicating that the Au particles are small and evenly dispersed, and no stabilizer is required.

[0027] Example 7 Method for preparing platinum-loaded nano-sized cerium dioxide catalyst (Pt / P-CeO 2 ), which generally adopts the same method as in Example 4, except that in step (2), R-CeO prepared in Example 1 is not used. 2 , but P-CeO prepared in Example 2 is used. 2 , and the other steps are the same as in Example 4.

[0028] Example 8 Method for preparing palladium-loaded nano-sized cerium dioxide catalyst (Pd / P-CeO 2 ), which generally adopts the same method as in Example 5, except that in step (2), R-CeO prepared in Example 1 is not used. 2 , but P-CeO prepared in Example 2 is used. 2 , and the other steps are the same as in Example 5.

[0029] Example 9 Using the Au / P-CeO 2 prepared in Example 6 as a catalyst, furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) are prepared from furfural and ethanol, and the specific method is as follows: Put 0.086 mL of furfural, 6 mL of ethanol, 2.0 mL of hydrogen peroxide, 0.1 g of sodium carbonate and 0.05 g of Au / P-CeO 2 catalyst into a stainless steel autoclave with a polytetrafluoroethylene liner, and under the stirring condition of 500 r / min, heat to 130 °C and react for 6 h, and cool to room temperature to obtain a solution of furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM).

[0030] The reaction products in Example 9 were analyzed and detected by gas chromatography and liquid chromatography-mass spectrometry respectively, and the results are as Figures 2 - 5 shown, and the results show that furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) were finally obtained.

[0031] Example 10 Using the Au / P-CeO 2As a catalyst, furfural and ethanol were used to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), and the same method as in Example 9 was used, except that the temperature for heating the reaction in the reaction kettle was 150 °C.

[0032] Example 11 Using the Au / P-CeO prepared in Example 6 2 As a catalyst, furfural and ethanol were used to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), and the same method as in Example 9 was used, except that the temperature for heating the reaction in the reaction kettle was 170 °C.

[0033] Experimental Example 1 After filtering with a 0.22 μm organic nylon 6 filter, a GC2030 gas chromatograph equipped with a hydrogen flame ionization detector (separating the reaction mixture using an FFAP gas chromatographic capillary column (30 m × 0.32 mm × 0.25 μm)) was used to measure the conversion rates and yields of furfural, furan-2-acrolein (F2A), and 2,2'-dimethyl difuran (DFM) in Examples 9-11, and the results are shown in Table 1.

[0034] Table 1 Conversion rates and yields of F2A and DFM at different reaction temperatures in Examples 9-11 Example 9 Example 10 Example 11 Catalyst <![CDATA[Au / P-CeO 2 > <![CDATA[Au / P-CeO 2 > <![CDATA[Au / P-CeO 2 > Reaction temperature 130℃ 150℃ 170℃ Furfural conversion rate 96.7% 90.1% 92.5% F2A yield 57.5% 65.2% 55.2% DFM yield 33.4% 20.2% 30.5% As can be seen from Table 1, the above Au / P-CeO 2 catalyst has good catalytic activity for catalytically converting furfural to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), can obtain the target products without extra products, has good selectivity, a relatively high furfural conversion rate, a relatively high yield of furan-2-acrolein (F2A), and a general yield of 2,2'-dimethyl difuran (DFM). Among them, when the reaction temperature is 130 °C, the performance of Au / P-CeO 2 is the best.

[0035] Example 12 Using the Pt / R-CeO prepared in Example 4 2 as a catalyst, furfural and ethanol were used to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM). The overall method was the same as in Example 9, except that the Pt / R-CeO in Example 4 2 was used to replace the Au / P-CeO in Example 6 2 , and the other steps were the same as in Example 9.

[0036] Example 13 Using the Pt / R-CeO prepared in Example 4 2As a catalyst, furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) were prepared using furfural and ethanol, and the same method as in Example 12 was used, with the only difference being that the temperature for heating the reaction in the reaction kettle was 150 °C.

[0037] Example 14 Using the Pt / R-CeO prepared in Example 4 2 As a catalyst, furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) were prepared using furfural and ethanol, and the same method as in Example 12 was used, with the only difference being that the temperature for heating the reaction in the reaction kettle was 160 °C.

[0038] Experimental Example 2 After filtering with a 0.22 μm organic nylon 6 filter, a GC2030 gas chromatograph equipped with a flame ionization detector (separating the reaction mixture using an FFAP gas chromatographic capillary column (30 m × 0.32 mm × 0.25 μm)) was used to measure the conversion rates and yields of furfural, furan-2-acrolein (F2A), and 2,2'-dimethyl difuran (DFM) in Examples 12 - 14, and the results are shown in Table 2.

[0039] Table 2 Conversion rates and yields of F2A and DFM at different reaction temperatures in Examples 12 - 14 Example 12 Example 13 Example 14 Catalyst <![CDATA[Pt / R-CeO 2 > <![CDATA[Pt / R-CeO 2 > <![CDATA[Pt / R-CeO 2 > Reaction temperature 130℃ 150℃ 160℃ Furfural conversion rate 75.5% 68.4% 59.1% F2A yield 64.5% 55.9% 36.1% DFM yield 10.9% 12.5% 12.4% As can be seen from Table 2, the Pt / R-CeO 2 catalyst of the present invention has good catalytic activity for catalytically converting furfural to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), a relatively high furfural conversion rate, a relatively high yield of furan-2-acrolein (F2A), and a relatively low yield of 2,2'-dimethyl difuran (DFM). Among them, when the reaction temperature is 130 °C, the performance of Pt / R-CeO 2 is the best.

[0040] Example 15 Using the Pd / R-CeO prepared in Example 5 2 as a catalyst, furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) were prepared using furfural and ethanol. The overall method was the same as in Example 9, with the difference being that the Pd / R-CeO of Example 5 2 was used to replace the Au / P-CeO of Example 6 2 , and the other steps were the same as in Example 9.

[0041] Example 16 Using the Pd / R-CeO prepared in Example 5 2As a catalyst, furfural and ethanol were used to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), and the same method as in Example 15 was used, except that the temperature for heating the reaction in the reaction kettle was 150 °C.

[0042] Example 17 Using the Pd / R-CeO prepared in Example 5 2 As a catalyst, furfural and ethanol were used to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), and the same method as in Example 15 was used, except that the temperature for heating the reaction in the reaction kettle was 160 °C.

[0043] Experimental Example 3 A 0.22 μm organic nylon 6 filter was used, and a GC 2030 gas chromatograph equipped with a hydrogen flame ionization detector (separating the reaction mixture using a SH-5 gas chromatographic capillary column (30 m × 0.32 mm × 0.25 μm)) was used to measure the conversion rates and yields of furfural, furan-2-acrolein (F2A), and 2,2'-dimethyl difuran (DFM) in Examples 15 - 17. The results are shown in Table 3.

[0044] Table 3 Conversion rates and yields of F2A and DFM at different reaction temperatures in Examples 15 - 17 Example 15 Example 16 Example 17 Catalyst <![CDATA[Pd / R-CeO 2 > <![CDATA[Pd / R-CeO 2 > <![CDATA[Pd / R-CeO 2 > Reaction temperature 130℃ 150℃ 160℃ Furfural conversion rate 72.7% 79.6% 70.8% F2A yield 62.6% 62.2% 54.8% DFM yield 10.2% 17.3% 8.8% As can be seen from Table 3, the Pd / R-CeO 2 catalyst of the present invention has good catalytic activity for the catalytic conversion of furfural to prepare furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), a relatively high furfural conversion rate, and a relatively high yield of furan-2-acrolein (F2A). Among them, when the reaction temperature is 150 °C, the performance of the Pd / R-CeO 2 catalyst is the best.

[0045] Experimental Example 4 The cyclic stability of the Au / P-CeO 2 catalyst in Example 6 was tested.

[0046] The catalyst that had undergone one catalytic reaction (reaction conditions: temperature 150 °C, reaction time 6 h, i.e., the reaction conditions in Example 10) was collected. The catalyst was washed with 150 - 200 mL of water and 50 - 100 mL of ethanol respectively, and dried in a vacuum oven at 60 °C for 12 h, and named M-1 (1 is the number of reaction times). The following steps were repeated: 0.086 mL of furfural, 6 mL of ethanol, 2.0 mL of hydrogen peroxide, 0.1 g of sodium carbonate and 0.05 g of M-1 catalyst were loaded into a stainless-steel autoclave with a polytetrafluoroethylene liner, mixed evenly, and under the stirring condition of 500 r / min, heated to 150 °C respectively and reacted for 6 hours, then cooled to room temperature to obtain a solution of furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM).

[0047] After obtaining the above solution, the operations of catalyst collection, water washing, alcohol washing and vacuum drying were carried out again. The above-mentioned reaction and catalyst recovery treatment were repeated. The treatment was repeated five times in total to obtain M-5.

[0048] The system after the fifth reaction of M-5 was filtered through a 0.22 μm organic nylon 6 filter, and a GC 2030 gas chromatograph equipped with a flame ionization detector (using a SH-5 gas chromatographic capillary column (30 m×0.32 mm×0.25 μm) to separate the reaction mixture) was used to determine the conversion rates and yields of furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM). The results showed that the conversion rate of furfural was 90%, and the yields of furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM) were 63.3% and 19.6% respectively. It can be seen that the catalyst still showed excellent catalytic performance after 5 cycles.

[0049] Comparative example Furan-2-acrolein and 2,2'-dimethyl difuran were prepared according to the method described in the literature (Oxidative condensation / esterification of furfural with ethanol using preformed Au colloidal nanoparticles. Molecular Catalysis, 2022, 528:112438). The oxidative condensation reaction was carried out in a batch reactor, and the reactor was placed in a temperature control module and carried out under magnetic stirring.

[0050] In a typical experiment, a mixture of 0.05 g of polyvinyl alcohol-stabilized gold-loaded activated carbon catalyst (Au / AC PVA), 6 ml of ethanol (as alcohol), 0.086 ml of furfural, 0.10 g of sodium carbonate and 0.02 ml of o-xylene (as internal standard) was loaded into the reactor and sealed. First, N 2 was introduced into the reactor to remove the gas, and then O 2 was introduced into the reactor again to make the partial pressure of O 2 in the reactor 0.6 MPa. The ratio of furfural:ethanol:Na 2 CO3 The molar ratio was 1:98.8:0.9, and the reaction was carried out at 150 °C for 6 h. After the reaction, it was cooled to room temperature. After microfiltration, the catalyst was separated from the liquid. The liquid phase was analyzed by a gas chromatograph (Shimadzu GC, model 14A). The gas chromatograph was equipped with a flame ionization detector and a TBR-14 capillary column. The results showed that the conversion rate of furfural was 82%, the yield of furan-2-acrolein (F2A) was 47%, and the yield of 2,2'-dimethyl difuran (DFM) was 28%.

[0051] In the data of this application, Au / P-CeO 2 When the reaction was carried out at 130 °C for 6 h, the conversion rate of furfural reached 96.7%, the yield of furan-2-acrolein (F2A) was 57.5%, and the yield of 2,2'-dimethyl difuran (DFM) was 33.4%; Pt / R-CeO 2 When the reaction was carried out at 130 °C for 6 h, the yield of furan-2-acrolein (F2A) was 64.5%; Pd / R-CeO 2 When the reaction was carried out at 130 °C, the conversion rate of furfural reached 72.7%, and the yield of furan-2-acrolein (F2A) reached 62.6%, both of which were significantly higher than those of the comparative examples.

[0052] In addition, in the present invention, hydrogen peroxide is used as an oxidant to oxidize ethanol, and the used oxidant is mild and environmentally friendly; while in the comparative example, a certain partial pressure of oxygen is introduced into the reaction kettle, and the process is cumbersome and requires high equipment requirements.

[0053] It can be seen that the noble metal-supported cerium dioxide catalysts with different morphologies in the present invention can well obtain furan-2-acrolein (F2A) and 2,2'-dimethyl difuran (DFM), and the by-product of this catalytic reaction system is only water, and the preparation of the catalyst does not require additional organic stability, which is green and environmentally friendly.

[0054] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification. The description of the above embodiments can be used to help understand the principle and method of the present invention. However, the above embodiments are not unique and should not be construed as a limitation of the present invention. At the same time, for those of ordinary skill in the art, according to the principle and method of the present invention, flexible changes can be made in the specific implementation manner and application scope.

Claims

1. A method for preparing furan-2-propenal and 2,2'-dimethyldifuran, characterized in that: Furfural, ethanol, hydrogen peroxide, sodium carbonate and a catalyst are placed in a high-pressure reactor and sealed, reacted at 130-170° C. for 4-8 hours, and cooled to room temperature to obtain furan-2-propenal and 2,2'-dimethyldifuran solution, wherein the catalyst is a noble metal-supported cerium dioxide catalyst, and the noble metal is one of Au, Pt and Pd.

2. The preparation method according to claim 1, characterized in that: The furfural, ethanol, hydrogen peroxide, sodium carbonate and catalyst were added in a ratio of 0.086 mL:6 mL:2 mL:0.1 g:0.05 g.

3. The preparation method according to claim 1 or 2, characterized in that: The furfural, ethanol, hydrogen peroxide, sodium carbonate and catalyst are placed in a high-pressure reactor and sealed to react at 130-160° C.; during the reaction, the reactor is stirred at 500-700 rpm.

4. The preparation method according to claim 1, characterized in that: The preparation method of the noble metal-supported cerium dioxide catalyst is as follows: Dissolve cerium dioxide in deionized water, add a noble metal aqueous solution, then add a certain amount of sodium hydroxide to adjust the pH to 9-10, then add sodium borohydride solution, filter, wash and dry to obtain a noble metal-loaded cerium dioxide catalyst; the cerium dioxide and water are dissolved in a ratio of 1 g:150 mL; the molar ratio of the sodium borohydride to the noble metal aqueous solution solute is 15:

1.

5. The preparation method according to claim 1 or 4, characterized in that: The mass ratio of the cerium dioxide to the noble metal in the noble metal aqueous solution is 1:0.

01.

6. The preparation method according to claim 5, characterized in that: The noble metal is Au, and the cerium dioxide is nano-particle cerium dioxide.

7. The preparation method according to claim 4, characterized in that: The preparation method of cerium dioxide is as follows: dripping cerium nitrate solution into sodium hydroxide solution drop by drop to form flocs, stirring for 30 minutes after dripping, then adding the solution into a hydrothermal reactor, controlling the temperature at 100-120°C to react for 12-14 hours, cooling to room temperature, taking out, and then filtering to obtain a precipitate, repeatedly washing the precipitate with deionized water until the pH of the washing liquid is neutral, drying and grinding to obtain a precursor of cerium dioxide, and calcining the precursor at 450°C for 3h-5h to obtain cerium dioxide.

8. The preparation method according to claim 7, characterized in that: When the cerium dioxide is rod-shaped, the concentration of the cerium nitrate solution is 0.4 mol / L, the concentration of the sodium hydroxide solution is 4-9 mol / L, and the molar ratio of cerium nitrate to sodium hydroxide is 1:

30.

9. The preparation method according to claim 7, characterized in that: When the cerium dioxide is nano-particulate cerium dioxide, the concentration of the cerium nitrate solution is 0.4 mol / L, the concentration of the sodium hydroxide solution is 0.1-0.4 mol / L, and the molar ratio of cerium nitrate to sodium hydroxide is 1:1.

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