Method for preparing furfuryl alkyl ether through furfural reduction etherification

Abstract

The invention discloses a method for preparing furfuryl alkyl ether through furfural reduction etherification. A catalyst adopted by the method comprises metal Ni, titanium oxide and silicon oxide. The mass content of metal Ni in the catalyst is 4-15 wt%, the mass content of titanium oxide is 20-40 wt%, and the balance is silicon oxide. The preparation method of the catalyst comprises the following steps: synthesizing titanium oxide modified SiO2 by dipping SiO2 with a titanium precursor, and then loading cheap metal Ni on the titanium oxide modified SiO2. The catalyst is applied to a reaction for preparing furfuryl alkyl ether through furfural reduction etherification, and under mild reaction conditions, the catalyst shows high catalytic activity and has high selectivity on furfuryl alkyl ether. The method for preparing furfuryl alkyl ether through furfural reduction etherification has the advantages of being simple in process and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of catalysis, and specifically relates to a method for the reduction and etherification of furfural to produce furfural alkyl ethers. Background Technology

[0002] In recent decades, with the continuous depletion of fossil fuels and the resulting increasingly serious environmental problems, utilizing clean and renewable energy sources to replace fossil fuels in the production of fuels and chemicals has become an important production development strategy and research hotspot in today's society. Among these, lignocellulosic biomass (such as grain crop residues), which is widely available, abundant, and inexpensive, is a key renewable resource for research. It can be processed into functional platform molecules through fermentation or chemical methods, and these platform molecules can then be further processed into fuels and chemicals. Furfural is an important lignocellulosic biomass-derived platform molecule, which can be obtained through large-scale hydrolysis processes, with an annual output of approximately 300,000 tons. Furfural and alcohols can react catalytically to produce furfuryl alkyl ethers. Furfural alkyl ethers are characterized by high stability, high octane number, and high cetane number, and are considered a promising biofuel or gasoline additive. The production of furfuryl alkyl ethers from furfural has been recognized as an important pathway for the effective utilization of biomass derivatives.

[0003] Currently, reported methods for producing furfural alkyl ethers include two-step and one-step methods. Most literature reports a two-step process, involving the conversion of furfural to furfuryl alcohol via hydrogenation, followed by the etherification of furfuryl alcohol with ethanol over a solid acid catalyst to produce furfural alkyl ethers. However, the two-step process is complex, requires significant equipment investment, and is costly, hindering industrialization. To overcome these drawbacks, a one-step reductive etherification method for furfural alkyl ethers has been a focus of research in recent years. Currently reported one-step furfural alkyl ether production processes are mainly conducted under hydrogen conditions in a heterogeneous metal-acid catalytic system containing both hydrogenation and Brønsted acid sites. The heterogeneous metal-acid catalytic systems reported for this type of reaction are primarily Pd-based catalyst systems. Wang et al. studied the reductive etherification of furfural to prepare furfural ethyl ether using a Pd / C catalyst at 60 °C and 0.3 MPa H2 pressure, achieving a furfural ethyl ether yield of up to 81% (Green Chem. 2018, 20, 2110). However, the cost of precious metal catalysts limits their industrial application, and carbon supports suffer from low mechanical strength, difficulty in particle forming, and challenges in catalyst recovery and regeneration after reaction. In contrast, using inexpensive metals as active components to replace precious metals can reduce catalyst costs, while metal oxides as supports can improve catalyst stability and recovery rates due to their higher mechanical strength, melting point, and calcination resistance. Therefore, developing catalyst systems combining inexpensive metals and metal oxides for the reductive etherification of furfural is a significant research direction, but related reports are currently scarce. Summary of the Invention

[0004] Based on the above research, one objective of this invention is to provide a catalyst for the reductive etherification of furfural to produce furfuryl alkyl ethers. This catalyst is prepared by synthesizing titanium oxide-modified SiO2 through impregnation of a titanium precursor, followed by loading inexpensive metal Ni onto the titanium oxide-modified SiO2. The titanium oxide modification enhances the acidity of the catalyst and suppresses the hydrogenation ability of metallic Ni, thereby inhibiting the formation of byproduct hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol) in the reductive etherification reaction of furfural and improving the selectivity for furfuryl alkyl ethers.

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

[0006] The catalyst provided by this invention for the reduction and etherification of furfural to produce furfural alkyl ethers comprises metallic Ni, titanium oxide, and silicon oxide; wherein the mass content of metallic Ni in the catalyst is 4-15 wt%, the mass content of titanium oxide is 20-40 wt%, and the remainder is silicon oxide.

[0007] Preferably, the catalyst contains 5-11 wt% Ni and 25-35 wt% titanium oxide.

[0008] More preferably, the catalyst contains 6-9 wt% Ni and 28-32 wt% titanium oxide.

[0009] The second objective of this invention is to provide a method for preparing the above-mentioned catalyst for furfural reduction etherification to furfuryl alkyl ether. This method is simple to operate, easy to industrialize, and the catalyst obtained exhibits high activity and selectivity in the furfural reduction etherification to furfuryl alkyl ether reaction.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] A method for preparing a catalyst for the reduction etherification of furfural to produce furfural alkyl ethers includes the following steps:

[0012] (1) Add SiO2 support to a water / ethanol mixed solution, adjust the pH to 9-12 with ammonia water, and stir to obtain SiO2 suspension;

[0013] (2) Mix Ti precursor, acetylacetone and ethanol, and stir until homogeneous to obtain Ti precursor solution;

[0014] (3) Under stirring conditions, the Ti precursor solution was added dropwise to the SiO2 suspension, and then stirred for 4-8 hours to obtain a Ti-SiO2 mixed solution;

[0015] (4) The Ti-SiO2 mixed solution was obtained by rotary evaporation to obtain a solid sample, and then the solid sample was dried and calcined to obtain a titanium oxide modified SiO2 support;

[0016] (5) Add titanium oxide modified SiO2 support to Ni salt solution, stir thoroughly, and then obtain NiO / TiO2-SiO2 catalyst by rotary evaporation, drying and calcination.

[0017] (6) The NiO / TiO2-SiO2 catalyst was reduced in H2 atmosphere at 400-600℃ for 1-5 hours to obtain Ni / TiO2-SiO2 catalyst.

[0018] In step (1), the volume ratio of water to ethanol in the water / ethanol mixed solution is 3-10:1; the mass concentration of ammonia is 10-30wt%; and the concentration of SiO2 in the SiO2 suspension is 0.01-0.08g / mL.

[0019] In step (2), the Ti precursor includes one or two of isopropyl titanate and tetrabutyl titanate; the molar ratio of acetylacetone to Ti precursor is 2-5:1; and the volume ratio of acetylacetone to ethanol is 1:2-7.

[0020] In step (4), the roasting temperature is 450-550℃ and the roasting time is 3-6 hours.

[0021] In step (5), the Ni salt includes one or more of nickel nitrate, nickel chloride, and nickel acetate; the calcination temperature is 450-550℃, and the calcination time is 3-6 hours.

[0022] Preferably, in step (1), the pH is 10-11; the volume ratio of water to ethanol in the water / ethanol mixed solution is 5-8:1; the mass concentration of ammonia is 25-28 wt%; and the concentration of SiO2 in the SiO2 suspension is 0.03-0.05 g / mL.

[0023] Preferably, in step (2), the Ti precursor is isopropyl titanate; the molar ratio of acetylacetone to Ti precursor is 3:1; and the volume ratio of acetylacetone to ethanol is 1:2-5.

[0024] Preferably, the stirring time in step (3) is 6-7 hours.

[0025] Preferably, the roasting temperature in step (4) is 500°C and the roasting time is 4-5 hours.

[0026] Preferably, in step (5), the salt of Ni is nickel nitrate; the calcination temperature is 450-500℃, and the calcination time is 4-5 hours.

[0027] A third objective of this invention is to provide a method for the reduction and etherification of furfural to produce furfuryl alkyl ethers. This method uses the aforementioned catalyst to carry out the reduction and etherification reaction of furfural in an alcohol solvent. The method can obtain a high yield of furfuryl alkyl ethers under mild conditions.

[0028] To achieve the above objectives, the technical solution of the present invention is as follows:

[0029] A method for preparing furfural-based alkyl ethers by reduction etherification is characterized by using a closed reactor, employing an alcohol as a solvent, and using hydrogen as a hydrogen source to carry out the reaction. The alcohol is selected from at least one of methanol, ethanol, propanol, and butanol; the mass ratio of alcohol to furfural is 5-30:1; and the mass ratio of catalyst to furfural is 0.1-0.5:1.

[0030] In the method for preparing furfural-based alkyl ethers by reduction etherification, the reaction temperature is 110-200℃; the reaction time is 2-8 hours; and the hydrogen pressure is 2-6 MPa.

[0031] Preferably, in the method for reducing furfural to produce furfural alkyl ether, the mass ratio of alcohol to furfural is 10-25:1; the mass ratio of catalyst to furfural is 0.2-0.4:1; the reaction temperature is 130-150℃; the reaction time is 4-5 hours; and the hydrogen pressure is 3-5 MPa.

[0032] Compared with the prior art, the beneficial effects of the present invention include:

[0033] (1) The catalyst provided by the present invention is inexpensive and the preparation method of the catalyst is simple, and it can be used for large-scale industrial catalyst synthesis.

[0034] (2) This invention employs a method of modifying SiO2 support with titanium oxide, which improves the acidity of commonly used SiO2 support in industry. Furthermore, the interaction between titanium oxide and metallic Ni suppresses the hydrogenation capacity of metallic Ni, thereby inhibiting the formation of hydrogenation byproducts. The catalyst provided by this invention exhibits high activity and selectivity in the furfural reduction etherification reaction to produce furfuryl alkyl ethers.

[0035] (3) The method for one-step synthesis of furfural alkyl ethers provided by the present invention has mild reaction conditions, is easy to operate, and is easy to scale up, meeting the requirements of large-scale industrial production. Detailed Implementation

[0036] The present invention will now be described in detail with reference to embodiments. Unless otherwise specified, all figures appearing in this specification and claims are subject to certain experimental errors due to the standard deviation of measurement techniques. These embodiments do not limit the scope of the present invention.

[0037] Example 1

[0038] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 4.45g of isopropyl titanate, 4.70g of acetylacetone, and 20mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.045 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 5 wt% and a TiO2 loading of 20 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 2 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 1.

[0039] Example 2

[0040] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 28% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.045 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 5 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 2 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 1.

[0041] Example 3

[0042] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 25% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 11.86g of isopropyl titanate, 12.54g of acetylacetone, and 40mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.045 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 5 wt% and a TiO2 loading of 40 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 2 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 1.

[0043] Comparative Example 1

[0044] 5 g of SiO2 support was added to 100 mL of a 0.045 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to finally obtain a Ni / SiO2 catalyst with a Ni loading of 5 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 2 hours. After the reaction was completed, the reactor was cooled to room temperature and then depressurized. Octyl alcohol was added to the reactor as an internal standard at a concentration of 0.015 g / mL. The liquid product was detected by gas chromatography, and the reaction results are listed in Table 1.

[0045] Comparative Example 2

[0046] 3.5 g of SiO2 support and 1.5 g of nano-anatase TiO2 were mixed and ground for 30 minutes to obtain a physically mixed support TiO2@SiO2. 5 g of TiO2@SiO2 was added to 100 mL of a 0.045 mol / L nickel nitrate aqueous solution, stirred thoroughly, and then the solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, and then calcined in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2@SiO2 catalyst. 0.25 g of the prepared NiO / TiO2@SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to finally obtain a Ni / TiO2@SiO2 catalyst with a Ni loading of 5 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. The reaction vessel was purged with nitrogen three times, then with pure H2 three times, and finally purged with H2 to 3 MPa. The reaction vessel was heated to 130°C and maintained for 2 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 1.

[0047] Table 1

[0048]

[0049] Table 1 shows the test results of the reductive etherification reaction of furfural in ethanol in Examples 1-3 and Comparative Examples 1-2. As can be seen from Table 1, under reaction conditions of 130℃ and 3 MPa H2, the Ni / TiO2-SiO2 catalyst of this invention exhibits higher selectivity for furfuryl ethyl ether compared to the Ni / SiO2 catalyst (Comparative Example 1), indicating that the strategy of adding titanium dioxide modification provided by this invention is beneficial to improving the selectivity of furfuryl alkyl ethers. Compared to the Ni / TiO2@SiO2 catalyst using a physical mixed support of TiO2 and SiO2 (Comparative Example 2), the Ni / TiO2-SiO2 catalyst of this invention exhibits higher selectivity for furfuryl ethyl ether, indicating that the method for preparing the titanium dioxide-modified SiO2 support provided by this invention is beneficial to improving the selectivity of furfuryl alkyl ethers. The results in Table 1 indicate that the catalyst preparation method provided by this invention is beneficial to reducing the overall selectivity of the by-product hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol) and promoting the formation of furfuryl alkyl ethers.

[0050] Example 4

[0051] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 28% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 5.37g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.054 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 6 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 2.

[0052] Example 5

[0053] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 28% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 13.43g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.054 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 6 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 2.

[0054] Comparative Example 3

[0055] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 28% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate was mixed with 30mL ethanol and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2-1 mixed solution. The Ti-SiO2-1 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.054 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2-1 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to finally obtain a Ni / TiO2-SiO2-1 catalyst with a Ni loading of 6 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reaction vessel was heated to 130°C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 2.

[0056] Example 6

[0057] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 28% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 9.13g of tetrabutyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.054 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 6 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 3 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 2.

[0058] Example 7

[0059] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 28% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.62g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.054 mol / L nickel acetate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 6 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 3 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 2.

[0060] Comparative Example 4

[0061] 5 g of SiO2 was added to a mixed solution of 145 mL of water and 20 mL of ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 28% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 5.09 g of titanium tetrachloride, 8.06 g of acetylacetone, and 30 mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100 °C for 12 hours, and then calcined in a muffle furnace at 500 °C for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.054 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 500 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 6 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 3 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 2.

[0062] Table 2

[0063]

[0064]

[0065] Table 2 shows the test results of the reduction etherification reaction of furfural in ethanol in Examples 4-7 and Comparative Examples 3-4. As can be seen from Table 2, for the Ni / TiO2-SiO2 catalyst described in this invention, when the molar ratio of acetylacetone to isopropyl titanate is between 2 and 5:1, the catalyst exhibits high activity in the reduction etherification of furfural to furfuryl alkyl ether, significantly higher than that of the Ni / TiO2-SiO2 catalyst without the addition of acetylacetone (Comparative Example 3). Furthermore, for the preparation method of the catalyst described in this invention, when using tetrabutyl titanate as a Ti precursor and nickel acetate as a Ni salt, the prepared Ni / TiO2-SiO2 catalyst still exhibits high activity in the reduction etherification of furfural to furfuryl alkyl ether, significantly higher than that of the Ni / TiO2-SiO2 catalyst prepared using titanium tetrachloride as a Ti precursor (Comparative Example 4). The above results indicate that the raw materials and methods for preparing the catalyst provided in this invention are beneficial for the conversion of furfural to furfuryl alkyl ether.

[0066] Example 8

[0067] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 27% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.035 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 4 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 3.

[0068] Example 9

[0069] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 27% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.084 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 3.

[0070] Example 10

[0071] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.15 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 15 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 3.

[0072] Comparative Example 5

[0073] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.078 mol / L copper nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a CuO / TiO2-SiO2 catalyst. 0.25 g of the prepared CuO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Cu / TiO2-SiO2 catalyst with a Cu loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 3.

[0074] Comparative Example 6

[0075] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.084 mol / L cobalt nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a CoO / TiO2-SiO2 catalyst. 0.25 g of the prepared CoO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Co / TiO2-SiO2 catalyst with a Co loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 3.

[0076] Table 3

[0077]

[0078]

[0079] Table 3 shows the test results of the reductive etherification reaction of furfural in ethanol in Examples 8-10 and Comparative Examples 5-6. As can be seen from Table 3, under the reaction conditions of 130°C, 3 MPa H2, the Ni / TiO2-SiO2 catalyst of this invention exhibits high activity for the conversion of furfural to furfuryl ethyl ether in the range of 4-15 wt% Ni loading. Furthermore, the results in Table 3 indicate that, under the same metal loading, the yield of furfuryl ethyl ether on the Ni / TiO2-SiO2 catalyst provided by this invention is significantly higher than that on the copper-based catalyst (Comparative Example 5) and the cobalt-based catalyst (Comparative Example 6), indicating that the catalyst composition provided by this invention is favorable for the conversion of furfural to furfuryl alkyl ether.

[0080] Example 11

[0081] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.084 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 4 MPa. The reactor was heated to 120 °C and maintained for 3 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 4.

[0082] Example 12

[0083] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.084 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 4 MPa. The reactor was heated to 160 °C and maintained for 3 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 4.

[0084] Example 13

[0085] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.084 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of ethanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 5 MPa. The reactor was heated to 200 °C and maintained for 3 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 4.

[0086] Example 14

[0087] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.084 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of n-propanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 4.

[0088] Example 15

[0089] 5g of SiO2 was added to a mixed solution of 145mL water and 20mL ethanol, stirred until homogeneous, and the pH was adjusted to 10 with ammonia solution containing 26% ammonia by mass. Stirring continued to obtain a SiO2 suspension. 7.63g of isopropyl titanate, 8.06g of acetylacetone, and 30mL of ethanol were mixed and stirred until homogeneous to obtain a Ti precursor solution. Under stirring conditions, the Ti precursor solution was slowly added dropwise to the SiO2 suspension, and the mixture was stirred for 6 hours to obtain a Ti-SiO2 mixed solution. The Ti-SiO2 mixed solution was rotary evaporated to obtain a solid sample, which was then dried in an oven at 100℃ for 12 hours, and then calcined in a muffle furnace at 500℃ for 4 hours to obtain a titanium oxide-modified SiO2 support. 5 g of titanium oxide-modified SiO2 support was added to 100 mL of a 0.084 mol / L nickel nitrate aqueous solution. After thorough stirring, a solid sample was obtained by rotary evaporation. The solid sample was then dried in an oven at 110 °C for 12 hours, followed by calcination in a muffle furnace at 450 °C for 4 hours to obtain a NiO / TiO2-SiO2 catalyst. 0.25 g of the prepared NiO / TiO2-SiO2 catalyst was treated at 550 °C for 1 hour in a pure H2 atmosphere to obtain a Ni / TiO2-SiO2 catalyst with a Ni loading of 9 wt% and a TiO2 loading of 30 wt%. The reduced catalyst was placed in a 70 mL mechanically stirred batch reactor (closed reactor), and 25 mL of n-butanol and 1.0 g of furfural were added. The reactor was then sealed. Nitrogen gas was purged into the reactor three times, followed by pure H2 purging three times, and finally H2 was introduced to 3 MPa. The reactor was heated to 130 °C and maintained for 4 hours. After the reaction was complete, the reaction vessel was cooled to room temperature and then depressurized. Octyl alcohol was added to the vessel as an internal standard at a concentration of 0.015 g / mL. The liquid products were detected by gas chromatography, and the reaction results are listed in Table 4.

[0090] Table 4

[0091]

[0092]

[0093] Table 4 shows the test results of the reductive etherification reaction of furfural in alcohols in Examples 11-15. As can be seen from Table 4, the Ni / TiO2-SiO2 catalyst described in this invention exhibits high activity for the conversion of furfural to furfuryl ethyl ether within a reaction temperature range of 120-200℃. Furthermore, the Ni / TiO2-SiO2 catalyst described in this invention exhibits high activity for the reductive etherification reaction of furfural with different alcohols. The results in Table 4 indicate that the method for the reductive etherification of furfural to furfuryl alkyl ethers provided by this invention is advantageous for obtaining high yields of furfuryl alkyl ethers.

[0094] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing furfural-based etherification to furfuryl alkyl ethers, characterized in that, The catalyst used in the method comprises metallic Ni, titanium oxide, and silicon oxide; in the catalyst, the mass content of Ni is 4-15 wt% (preferably 5-11 wt%, more preferably 6-9 wt%), the mass content of titanium oxide is 20-40 wt% (preferably 25-35 wt%, more preferably 28-32 wt%), and the remainder is silicon oxide.

2. The method according to claim 1, characterized in that, The specific preparation process of the catalyst used in the method includes the following steps: (1) Add SiO2 support to a water / ethanol mixed solution, adjust the pH to 9-12 (preferably 10-11) with ammonia water, and stir to obtain SiO2 suspension; (2) Mix Ti precursor, acetylacetone and ethanol, and stir until homogeneous to obtain Ti precursor solution; (3) Under stirring conditions, the Ti precursor solution is added dropwise to the SiO2 suspension, and then stirred for 4-8 hours (preferably 6-7 hours) to obtain a Ti-SiO2 mixed solution; (4) The Ti-SiO2 mixed solution was obtained by rotary evaporation to obtain a solid sample, and then the solid sample was dried and calcined to obtain a titanium oxide modified SiO2 support; (5) Add titanium oxide modified SiO2 support to Ni salt solution, stir thoroughly, and then obtain NiO / TiO2-SiO2 catalyst by rotary evaporation, drying and calcination. (6) The NiO / TiO2-SiO2 catalyst is reduced in H2 atmosphere at a temperature of 400-600℃ (preferably 450-550℃) for 1-5 hours (preferably 1-3 hours) to obtain the Ni / TiO2-SiO2 catalyst.

3. The method as described in claim 2, characterized in that, In step (1), the volume ratio of water to ethanol in the water / ethanol mixed solution is 3-10:1 (preferably 5-8:1), the mass concentration of ammonia is 10-30wt% (preferably 25-28wt%), and the concentration of SiO2 in the SiO2 suspension is 0.01-0.08g / mL (preferably 0.03-0.05g / mL).

4. The method as described in claim 2, characterized in that, In step (2), the Ti precursor includes one or two of isopropyl titanate and tetrabutyl titanate; the molar ratio of acetylacetone to Ti precursor is 2-5:1 (preferably 3:1); the volume ratio of acetylacetone to ethanol is 1:2-7 (preferably 1:4-5).

5. The method as described in claim 2, characterized in that, In step (4), the calcination temperature is 450-550℃ (preferably 500℃) and the time is 3-6 hours (preferably 4-5 hours).

6. The method as described in claim 2, characterized in that, In step (5), the Ni salt includes one or more of nickel nitrate, nickel chloride, and nickel acetate; the calcination temperature is 450-550℃ (preferably 450-500℃), and the calcination time is 3-6 hours (preferably 4-5 hours).

7. The method according to any one of claims 1-6, characterized in that, A closed-loop reactor was used to carry out the reaction of furfural reduction etherification to produce furfural alkyl ethers, with alcohols as solvents and hydrogen as the hydrogen source. The alcohol is selected from at least one or more of methanol, ethanol, propanol, and butanol; the mass ratio of the alcohol to furfural is 5-30:1 (preferably 10-25:1); the mass ratio of the catalyst to furfural is 0.1-0.5:1 (preferably 0.2-0.4:1).

8. The method as described in claim 7, characterized in that, The reaction temperature is 110-200℃ (preferably 130-150℃); the reaction time is 2-8 hours (preferably 4-5 hours); and the hydrogen pressure is 2-6 MPa (preferably 3-5 MPa).

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