A process for the preparation of furfuryl alcohol by transfer hydrogenation of furfural

Abstract

The application discloses a method for preparing furfuryl alcohol by furfural transfer hydrogenation. The active components Zr and Mg of the magnetic catalyst come from corresponding non-noble metal salt solution, and Fe is selected from oxides. The catalyst is prepared by a coprecipitation method. The method takes furfuryl alcohol as raw material, commercial isopropyl alcohol as hydrogen source and solvent, and carries out a closed reaction at 160-210 DEG C for 3-7 h under the stirring rate of 500 rpm, and then is cooled to room temperature to obtain the furfuryl alcohol. Under the optimal conditions, the conversion rate of furfuryl alcohol is 99.13%, and the yield of furfuryl alcohol is 92.50%. The catalyst preparation method is simple, low in price and good in cycle stability, the catalytic system is green and efficient, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a method for preparing furfuryl alcohol from furfural by transfer hydrogenation, and more specifically to a method for preparing furfuryl alcohol by liquid-phase transfer hydrogenation of furfural using a metal oxide magnetic catalyst. Background Technology

[0002] With the continuous exploitation and extensive use of fossil resources, the deterioration of the ecological environment and the depletion of fossil resources are becoming increasingly apparent, making the development of renewable and clean energy to replace traditional energy sources an inevitable trend. Among numerous renewable resources, biomass resources have the advantages of wide availability, abundant reserves, and low price. It is the only renewable organic carbon resource in nature and can be converted into various fuels and high-value-added chemicals. Furfural is one of the most promising bio-based platform compounds. The application of furfural mainly focuses on its hydrogenation. Its hydrogenation reduction product, furfuryl alcohol, is an important chemical raw material widely used in the synthesis of rubber, resins, pesticides, fragrances, and casting adhesives. It can also be used to synthesize important intermediates such as lysine, vitamin C, lubricants, and dispersants.

[0003] Currently, in industrial production, furfural is mainly hydrogenated to furfuryl alcohol using Cu-Cr catalysts. However, this catalyst requires harsh reaction conditions, posing safety risks. Furthermore, the catalytic reaction easily generates highly toxic Cr compounds, resulting in significant pollution, which contradicts the principles of green and sustainable development. Additionally, catalyst separation is costly, and the coke formed from the reaction substrate adhering to the catalytic active sites during the reaction can lead to rapid catalyst deactivation. Therefore, the preparation of catalysts with excellent stability and easy separation is particularly important. Summary of the Invention

[0004] The purpose of this invention is to overcome the deficiencies of the prior art and provide a method for preparing furfuryl alcohol from furfural by transfer hydrogenation.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] The method for preparing furfuryl alcohol from furfural by transfer hydrogenation specifically includes: loading furfural, magnetic catalyst and solvent into a high-pressure reactor, mixing them evenly and sealing them, and carrying out a closed reaction at 160-210℃ for 3-7 hours with a stirring rate of 500 rpm, and then cooling to room temperature to obtain furfuryl alcohol. The cooled solution is then detected by gas chromatography and gas chromatography-mass spectrometry.

[0007] The preparation method of the above-mentioned magnetic catalyst includes the following steps: Dissolve the active metal zirconium precursor and the active metal magnesium precursor in an appropriate amount of deionized water at room temperature, then add an appropriate amount of Fe3O4 particles and sonicate for 30-60 minutes. Subsequently, under magnetic stirring, slowly add ammonia water until complete precipitation, then stir for another 5-8 hours. Collect the precipitate using a vacuum filter and wash the collected solid with pure water until the pH of the aqueous layer is approximately neutral. Place the washed solid in an oven and dry it at 80°C for 6 hours. Remove the solid, cool it to room temperature, grind it thoroughly in a mortar, and pass it through a 100-mesh sieve. Finally, calcine the solid in a tube furnace at 360-400°C for 3-4 hours to obtain the magnetic catalyst. The active metal of the magnetic catalyst is composed of Zr, Mg, and Fe, and the molar ratio of Zr, Mg, and Fe3O4 in the catalyst is 7:1:0.5-2, preferably 7:1:1.

[0008] In a preferred embodiment of the present invention, the mass ratio of the magnetic catalyst to furfural is 0.05-0.4g:0.384g, preferably 0.2g:0.384g, the ratio of furfural to solvent is 4mmol:20mL, the reaction temperature is 160-210℃, preferably 180-200℃, and the reaction time is 3-7h, preferably 4-6h.

[0009] In a preferred embodiment of the present invention, the calcination operation in the tubular furnace is carried out by calcining at 360-400°C for 3-4 hours in the tubular furnace, preferably by calcining at 400°C in a nitrogen-filled tubular furnace for 4 hours.

[0010] In a preferred embodiment of the present invention, the molar ratio of the active zirconium precursor, the active magnesium precursor, and the Fe3O4 particles, based on Zr, Mg, and Fe3O4, is 7:1:0.5-2, and more preferably 7:1:1.

[0011] In a preferred embodiment of the present invention, the active zirconium precursor is ZrOCl2·8H2O; and the active magnesium precursor is Mg(NO3)2·6H2O.

[0012] In a preferred embodiment of the present invention, the solvent is methanol, ethanol, isopropanol, sec-butanol, n-butanol, and tert-butanol is preferably isopropanol. Isopropanol serves as both a hydrogen source and a solvent.

[0013] The beneficial effects of this invention are:

[0014] 1. The materials used in this invention are simple and readily available, the preparation method is simple, the preparation cost is low, and the economy is strong.

[0015] 2. The magnetic catalyst used in this invention has high magnetic saturation strength and is easily separated by a magnet, thus simplifying the separation process and significantly reducing the cost of catalyst separation in industrial production.

[0016] 3. This invention uses isopropanol as a solvent and hydrogen donor, which does not require the participation of external hydrogen and does not require the introduction of other gases to provide high pressure. The reaction system is relatively simple and safe, which is beneficial to the separation and purification of the product.

[0017] 4. In the prepared catalytic hydrogenation materials, acid-base centers play a crucial role. The characteristic of this approach is that it prepares a magnetic zirconium-based catalyst with high catalytic activity through a simple precipitation method, which contains abundant acid-base centers (unsaturated Zr). 4+ -O 2- The catalyst contains acid-base pairs and strong Lewis base centers (MgO), while the doped Fe3O4 also contains abundant strong Lewis acid centers. This scheme adjusts the number of acid-base sites in the catalyst by adjusting the molar ratio of Zr, Mg, and Fe3O4 metals, thereby optimizing its catalytic activity. Furthermore, the magnetic iron-containing catalyst enables efficient catalyst recovery. Attached Figure Description

[0018] Figure 1 XRD patterns of ZrMg@Fe3O4 catalysts with different metal ratios. Detailed Implementation

[0019] The invention is further illustrated with examples. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products. Specific implementation examples are as follows:

[0020] Examples 1-5

[0021] Accurately weigh 0.125 mol Mg(NO3)2·6H2O and 0.875 mol ZrOCl2·8H2O, dissolve them in 100 mL of deionized water at room temperature to prepare a 1 mol / L mixed solution. Then, weigh 0.125 mol Fe3O4 particles and disperse them in the mixed solution, and sonicate for 30 min. Under magnetic stirring, slowly add excess ammonia water to the above mixture until precipitation is complete, followed by vigorous stirring for 5 h. Collect the precipitate using a vacuum filter, and wash the collected solid with pure water until the pH of the aqueous layer is approximately neutral. Place the washed solid in an oven and dry it at 80 °C for 6 h. Remove the solid, cool it to room temperature, grind it thoroughly in a mortar, and pass it through a 100-mesh sieve. Finally, calcine the solid in a tube furnace at 400 °C for 4 h under nitrogen atmosphere to obtain the corresponding magnetic catalyst, which is stored in a desiccator for later use.

[0022] Add 0.384 g of furfural and 20 mL of isopropanol to a 100 mL high-pressure reactor, then add 0.2 g of magnetic catalyst (ZrMg@Fe3O4, with a molar ratio of active metals Zr, Mg, and Fe3O4 of 7:1:1). After replacing the air in the reactor with nitrogen three to four times, seal the reactor and stir at 500 rpm. Heat to 190 °C and maintain for 3, 4, 5, 6, and 7 hours respectively. After the reaction is completed and cooled to room temperature, the reaction mixture is magnetically separated. Take the supernatant and prepare standard solutions of furfural, furfuryl alcohol, etc. Quantitative analysis is performed using gas chromatography, and qualitative analysis is performed using gas chromatography-mass spectrometry. The results are listed in Table 1, serial numbers 1-5.

[0023] The effect of reaction time on catalytic activity was investigated. At 190℃ and a reaction time of 3 h, the FF conversion was 88.86% and the FFA yield was 72.61%. Similarly, when the reaction time was extended to 5 h, the FF conversion increased to 99.13% and the FFA yield increased to 92.50%. This indicates that extending the reaction time improves catalytic efficiency. However, when the reaction time was extended to 7 h at 190℃, the FFA yield slightly decreased to 79.07%. After a longer reaction time, the FFA product underwent etherification condensation to form difurfuryl ether (DFE), and the formation of 2-acetylfuran and isopropyl ether also increased significantly, leading to a decrease in the yield of the target product, FFA. Therefore, the optimal reaction time is 5 h.

[0024] Examples 6-9

[0025] The corresponding magnetic catalysts were prepared according to the methods in Examples 1-5 for later use.

[0026] Add 0.384 g of furfural and 20 mL of isopropanol to a 100 mL high-pressure reactor, then add 0.2 g of magnetic catalyst (ZrMg@Fe3O4, with a molar ratio of active metals Zr, Mg, and Fe3O4 of 7:1:1). After replacing the air in the reactor with nitrogen three to four times, seal the reactor and stir at 500 rpm. Heat to 160, 180, 200, and 210 °C respectively and maintain for 5 h. After the reaction is completed and cooled to room temperature, the reaction mixture is magnetically separated. Take the supernatant and prepare standard solutions of furfural and furfuryl alcohol. Perform quantitative analysis using gas chromatography and qualitative analysis using gas chromatography-mass spectrometry. The results are listed in Table 1, numbers 6-9.

[0027] The effect of reaction temperature on catalytic activity was investigated. At 160℃ for 5 h, the FF conversion was 69.11% and the FFA yield was 55.10%. However, at 190℃ for 5 h (Example 3), the FF conversion increased to 99.13% and the FFA yield increased to 92.50%. This indicates that increasing the reaction temperature significantly promotes substrate conversion and product formation. When the reaction temperature was increased to 200℃, the conversion remained almost unchanged, but the yield decreased significantly. This is because at high temperatures, the product FFA is more prone to etherification and condensation to form DFE, leading to a decrease in the yield of the target product FFA. Therefore, the optimal reaction temperature is 190℃.

[0028] Examples 10-13

[0029] The corresponding magnetic catalysts were prepared according to the methods in Examples 1-5 for later use.

[0030] Add 0.384 g of furfural and 20 mL of isopropanol to a 100 mL high-pressure reactor, then add 0.05 / 0.1 / 0.3 / 0.4 g of magnetic catalyst (ZrMg@Fe3O4, with a molar ratio of active metals Zr, Mg, and Fe3O4 of 7:1:1). Replace the air in the reactor with nitrogen three to four times, then seal the reactor and stir at 500 rpm. Heat to 190 °C and maintain for 5 h. After the reaction is completed and cooled to room temperature, magnetically separate the reaction mixture and take the supernatant. Prepare standard solutions of furfural and furfuryl alcohol, etc. Quantitative analysis is performed using gas chromatography, and qualitative analysis is performed using gas chromatography-mass spectrometry. The results are listed in Table 1, serial numbers 10-13.

[0031] The effect of catalyst dosage on catalytic activity was investigated. Since the hydrogenation of FF to FFA requires catalytic sites, both FF conversion and FFA yield increased with increasing catalyst dosage. When the catalyst dosage was 0.2 g (Example 3), the FF conversion reached 99.13% and the FFA yield reached 92.50%. Further increasing the catalyst dosage to 0.3 g resulted in a continued increase in conversion to nearly 100%, but the FFA yield decreased significantly, and the amount of byproducts in the reaction system increased. When the dosage increased to 400 mg, the conversion also declined sharply, the yield decreased, and the amount of byproducts in the reaction system continued to increase. Therefore, the optimal catalyst dosage was 200 mg.

[0032] Examples 14-18

[0033] The corresponding magnetic catalysts were prepared according to the methods in Examples 1-5 for later use.

[0034] Add 0.384 g of furfural and 20 mL of solvent (methanol, ethanol, n-butanol, sec-butanol, and tert-butanol, respectively) to a 100 mL high-pressure reactor, then add 0.2 g of magnetic catalyst (ZrMg@Fe3O4, with a molar ratio of active metals Zr, Mg, and Fe3O4 of 7:1:1). After replacing the air in the reactor with nitrogen three to four times, seal the reactor, stir at 500 rpm, heat to 190 °C and maintain for 5 h, then stop the reaction and cool to room temperature. Magnetically separate the reaction mixture, take the supernatant, and prepare standard solutions of furfural, furfuryl alcohol, etc. Quantitative analysis is performed using gas chromatography, and qualitative analysis is performed using gas chromatography-mass spectrometry. The results are listed in Table 1, serial numbers 14-18.

[0035] Examples 19-20

[0036] Accurately weigh 0.125 mol of Mg(NO3)2·6H2O and 0.875 mol of ZrOCl2·8H2O, and dissolve them in 100 mL of deionized water at room temperature. Then, weigh 0.0625 mol and 0.25 mol of Fe3O4 particles respectively and disperse them in the prepared solution, followed by sonication for 30 min. Subsequently, ammonia water is slowly added dropwise under magnetic stirring until precipitation is complete, followed by vigorous stirring for 5 h. The precipitate is collected by vacuum filtration, and the collected solid is washed with pure water until the pH of the aqueous layer is approximately neutral. The washed solid is placed in an oven and dried at 80 °C for 6 h. The solid is removed, cooled to room temperature, and thoroughly ground in a mortar and sieved through a 100-mesh sieve. Finally, the solid is calcined in a tube furnace under nitrogen at 400 °C for 4 h to obtain magnetic catalysts with different metal molar ratios.

[0037] Add 0.384 g of furfural and 20 mL of isopropanol to a 100 mL high-pressure reactor, then add 0.2 g of magnetic catalyst (ZrMg@Fe3O4, with a molar ratio of active metals Zr, Mg, and Fe3O4 of 7:1:0.5 or 7:1:2). Replace the air in the reactor with nitrogen three to four times, then seal the reactor and stir at 500 rpm. Heat to 190 °C and maintain for 5 h. After the reaction is completed and cooled to room temperature, magnetically separate the reaction mixture, take the supernatant, and prepare standard solutions of furfural, furfuryl alcohol, etc. Quantitative analysis is performed using gas chromatography, and qualitative analysis is performed using gas chromatography-mass spectrometry. The results are listed in Table 1, serial numbers 19-20.

[0038] The effect of different metal molar ratios on catalytic activity was investigated. When n(Zr):n(Mg) = 7:1, the conversion rate of FF and the yield of the target product FFA showed a trend of first increasing and then decreasing with the continuous introduction of Fe3O4, reaching the maximum at a metal molar ratio of 7:1:1 (Example 3). Therefore, the optimal molar ratio n(Zr):n(Mg):n(Fe3O4) for this magnetic ZrMg@Fe3O4 material is 7:1:1.

[0039] Examples 21-23

[0040] Add 0.384 g of furfural and 20 mL of isopropanol to a 100 mL high-pressure reactor, followed by 0.2 g of catalyst (ZrO2, MgO, and Fe3O4, respectively). Replace the air in the reactor with nitrogen three to four times, then seal the reactor and stir at 500 rpm. Heat to 190 °C and maintain for 5 h. After the reaction is completed and cooled to room temperature, the reaction mixture is magnetically separated. Take the supernatant and prepare standard solutions of furfural, furfural alcohol, etc. Quantitative analysis is performed using gas chromatography, and qualitative analysis is performed using gas chromatography-mass spectrometry. The results are listed in Table 1, serial numbers 21-23.

[0041] Examples 24-34

[0042] Zr7Mg1O x For example: Accurately weigh 0.125 mol of Mg(NO3)2·6H2O and 0.875 mol of ZrOCl2·8H2O, dissolve them in 100 mL of deionized water at room temperature, and add 0 Fe3O4 particles. Then, under magnetic stirring, slowly add ammonia water until precipitation is complete, followed by vigorous stirring for 5 hours. Collect the precipitate using a vacuum filter and wash the collected solid with pure water until the pH of the water layer is approximately neutral. Place the washed solid in an oven and dry it at 80°C for 6 hours. Remove the solid, cool it to room temperature, grind it thoroughly in a mortar and pestle, and then pass it through a 100-mesh sieve. Finally, calcine the solid in a tube furnace at 400°C under air for 4 hours to obtain the corresponding ZrMgO. x Catalysts (by adjusting the amounts of Mg(NO3)2·6H2O and ZrOCl2·8H2O added, catalysts with active metal Zr and Mg molar ratios of 7:1, 14:1, 21:1, 35:1 and 70:1 were prepared).

[0043] Taking ZrO2@Fe3O4 (1:1) as an example: Accurately weigh 0.0125 mol ZrOCl2·8H2O and dissolve it in 12.5 mL of deionized water at room temperature to prepare a 1 mol / L mixed solution. Then, weigh 0.0125 mol Fe3O4 particles and disperse them in the prepared solution, and sonicate for 30 min. Subsequently, under magnetic stirring, slowly add excess ammonia water until the solution is completely precipitated, and then stir vigorously for 5 h. Collect the precipitate through a vacuum filter and wash the collected solid with pure water until the pH of the aqueous layer is approximately neutral. Place the washed solid in an oven and dry it at 80℃ for 6 h. Remove the solid, cool it to room temperature, grind it thoroughly in a mortar and pestle, and then pass it through a 100-mesh sieve. Finally, the solid was calcined in a tube furnace at 400°C for 4 hours under nitrogen to obtain the corresponding ZrO2@Fe3O4 (by adjusting the amount of ZrOCl2·8H2O and Fe3O4 added, catalysts with active metal Zr:Fe3O4 ratios of 1:1, 7:1 and 1:3 were prepared).

[0044] Taking MgO@Fe3O4 (1:1) as an example: Accurately weigh 0.0125 mol of Mg(NO3)2·6H2O and dissolve it in 12.5 mL of deionized water at room temperature to prepare a 1 mol / L mixed solution. Then, weigh 0.0125 mol of Fe3O4 particles and disperse them in the prepared solution, and sonicate for 30 min. Subsequently, under magnetic stirring, slowly add excess ammonia water until the solution is completely precipitated, and then stir vigorously for 5 h. Collect the precipitate through a vacuum filter and wash the collected solid with pure water until the pH of the aqueous layer is approximately neutral. Place the washed solid in an oven and dry it at 80℃ for 6 h. Remove the solid, cool it to room temperature, grind it thoroughly in a mortar and pestle, and then pass it through a 100-mesh sieve. Finally, the solid was calcined in a tube furnace at 400°C for 4 hours under nitrogen to obtain the corresponding MgO@Fe3O4 (by adjusting the amount of Mg(NO3)2·6H2O and Fe3O4 added, catalysts with active metal Mg:Fe3O4 ratios of 1:1, 2:1 and 1:2 were prepared).

[0045] Add 0.384 g of furfural and 20 mL of isopropanol to a 100 mL high-pressure reactor, then add 0.2 g of catalyst. Replace the air in the reactor with nitrogen three to four times, then seal the reactor and stir at 500 rpm. Heat to 190 °C and maintain for 5 h. After the reaction is finished, cool to room temperature and magnetically separate the reaction mixture. Take the supernatant and prepare standard solutions of furfural, furfuryl alcohol, etc. Quantitative analysis is performed using gas chromatography, and qualitative analysis is performed using gas chromatography-mass spectrometry. The results are listed in Table 1, serial numbers 24-34.

[0046] Examples 35-40

[0047] The corresponding magnetic catalysts were prepared according to the methods in Examples 1-5 for later use.

[0048] 0.384 g of furfural and 20 mL of isopropanol were added to a 100 mL high-pressure reactor, followed by 0.2 g of magnetic catalyst (ZrMg@Fe3O4, with a molar ratio of active metals Zr, Mg, and Fe3O4 of 7:1:1). The reactor was purged with nitrogen three to four times, then sealed. The mixture was stirred at 500 rpm and heated to 190 °C for 5 hours. After the reaction was completed and cooled to room temperature, the reaction mixture was magnetically separated and dried at 80 °C for 2 hours. The mixture was then reused for five cycles. For the final cycle, the catalyst was regenerated by calcining the recovered catalyst in a tube furnace at 400 °C under a nitrogen atmosphere for 4 hours, followed by a repeat experiment. The supernatant was used to prepare standard solutions of furfural and furfuryl alcohol. Quantitative analysis was performed using gas chromatography, and qualitative analysis was performed using gas chromatography-mass spectrometry (GC-MS). The results are listed in Table 1, numbers 35-40. The first to fifth cycles correspond to Examples 35-39, respectively.

[0049] The reusability of the catalyst was investigated. The reusability of the ZrMg@Fe3O4 (7:1:1) catalyst was explored under the selected optimal reaction conditions (190℃, 5h, and 200mg). After each test, the catalyst was separated from the reaction mixture using an external magnet, dried at 80℃ for 2h, and directly used for the next test. Over five consecutive uses, the catalytic activity of ZrMg@Fe3O4 (7:1:1) continuously decreased, with both FF conversion and FFA yield showing a certain decline. After the fifth cycle, the FF conversion decreased to 73.11%, and the FFA yield decreased to 62.50%. Before the sixth cycle, the catalyst was calcined in a tube furnace at 400℃ for 4h, and then the catalytic reaction was carried out again. The results showed that the FF conversion recovered to 90.71%, and the FFA yield recovered to 78.41%, indicating that the catalyst exhibited excellent stability after calcination.

[0050] Table 1. Detection results of Examples 1–40

[0051]

[0052]

[0053] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing furfural alcohol by transfer hydrogenation, characterized in that: Furfural, magnetic catalyst and isopropanol are loaded into a high-pressure reactor, mixed evenly and sealed. The mixture is stirred at 500 rpm and reacted in a closed environment at 160-210℃ for 3-7 hours. The mixture is then cooled to room temperature to obtain furfural alcohol. The preparation method of the magnetic catalyst includes the following steps: dissolving an active zirconium metal precursor and an active magnesium metal precursor in an appropriate amount of deionized water at room temperature, then adding an appropriate amount of Fe3O4 particles, and sonicating for 30-60 min; subsequently, slowly adding ammonia water dropwise under magnetic stirring until complete precipitation, and then stirring for 5-8 h, collecting the precipitate through a vacuum filter, and washing the collected solid with pure water until the pH of the water layer is neutral; placing the washed solid in an oven, drying at 80℃ for 6 h, cooling to room temperature, and grinding thoroughly with a mortar and pestle and passing through a 100-mesh sieve; finally, calcining the solid in a tube furnace at 360-400℃ for 3-4 h to obtain the magnetic catalyst; wherein, the molar ratio of the active zirconium metal precursor, the active magnesium metal precursor, and the Fe3O4 particles, based on Zr, Mg, and Fe3O4, is 7:1:0.5-2.

2. The method as described in claim 1, characterized in that: The ratio of furfural to isopropanol is 4 mmol: 20 mL.

3. The method as described in claim 1, characterized in that: The active zirconium precursor is ZrOCl2·8H2O; the active magnesium precursor is Mg(NO3)2·6H2O.

4. The method as described in claim 1, characterized in that: The mass ratio of the magnetic catalyst to furfural is 0.05-0.4 g : 0.384 g.

5. The method as described in claim 1, characterized in that: The calcination was carried out in a tube furnace at 400°C with nitrogen gas for 4 hours.

Images