Cu-nb bifunctional catalyst, preparation method and application thereof in preparation of 2-mf by hydrodeoxygenation of furfural

Abstract

This invention discloses a Cu-Nb bifunctional catalyst, its preparation method, and its application in the hydrodeoxygenation of furfural to 2-MF, belonging to the field of biomass resource catalytic conversion technology. The bifunctional catalyst includes a support and an active metal component loaded on the support; the active metal component includes Cu and Nb; the support is a mesoporous molecular sieve MCM-41. In application, the catalyst is reduced and activated under a hydrogen atmosphere, and then mixed with a mixed feedstock containing furfural and alcohol hydrogen donors for gas-phase hydrodeoxygenation to obtain 2-methylfuran. By introducing Nb as a promoter, a strongly interacting Nb-O-Cu interface is formed with Cu, synergistically modulating the hydrogenation activity and surface acidity of the catalyst, thereby achieving near 100% conversion of furfural at a low temperature and atmospheric pressure of 160℃, with a 2-MF yield of 92.41%, and stable performance after 240 hours of continuous operation. This method features mild reaction conditions, high selectivity, long catalyst lifetime, and simple process, making it suitable for the green and continuous preparation of bio-based fuels.

Description

Technical Field

[0001] This invention belongs to the field of biomass resource catalytic conversion technology, specifically relating to a Cu-Nb bifunctional catalyst, its preparation method, and its application in furfural hydrodeoxygenation to 2-MF. Background Technology

[0002] 2-Methylfuran (2-MF) is an excellent fuel additive with high octane number and energy density, and its bio-based synthetic route has attracted much attention. The production of 2-MF from furfural via hydrodeoxygenation is one of the most feasible routes. This process involves a series of reactions: the hydrogenation of furfural to obtain the intermediate furfuryl alcohol, followed by deoxygenation to obtain 2-MF. This requires extremely high synergistic effects of catalyst hydrogenation activity and controllable acidity.

[0003] Copper-based catalysts have been extensively studied due to their excellent selectivity for carbonyl hydrogenation. However, single copper catalysts (such as Cu / SiO2, Cu / Al2O3) generally suffer from insufficient deoxidation capacity, with the reaction easily stopping at the furfuryl alcohol intermediate. Furthermore, achieving deep deoxidation often requires high reaction temperatures (≥200℃), leading to exacerbated side reactions such as over-hydrogenation and ring-opening. The catalysts are also prone to sintering and carbon deposition, resulting in poor stability. To overcome these shortcomings, introducing a second metal promoter to construct bifunctional catalysts is a major technological direction.

[0004] In existing technologies, the selection of additives and their effects vary significantly. For example, while the noble metal Re (CN108970601A) can improve performance, it is costly; non-noble metal additives such as W and Mg have been studied, but breakthroughs have not been achieved in terms of overall performance in low-temperature activity, 2-MF selectivity, and long-term stability. In particular, how to achieve a synergistic improvement in the three key performance indicators of "high activity at low temperatures," "high selectivity for target products," and "stable operation over long periods" through precise additive design, without significantly increasing costs, remains a pressing technical challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a Cu-Nb bifunctional catalyst, its preparation method, and its application in the hydrodeoxygenation of furfural to produce 2-MF, thereby solving the problems in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: A Cu-Nb bifunctional catalyst includes a support and an active metal component supported on the support; the active metal component includes Cu and Nb; the support is a mesoporous molecular sieve MCM-41.

[0007] Furthermore, based on the total mass of the catalyst, the loading of Cu is 3wt% to 10wt%, and the loading of Nb is 3wt%.

[0008] Furthermore, the specific surface area of ​​the mesoporous molecular sieve MCM-41 is 600 m². 2 / g~1200m 2 / g, with a pore size distribution range of 2nm~4nm.

[0009] The preparation method of the above-mentioned Cu-Nb bifunctional catalyst includes the following steps: The mesoporous molecular sieve MCM-41 was dried to obtain a pre-dried carrier. Copper and niobium compounds are dissolved separately in alcohol solvents or mixed alcohol solvents to form precursor solutions. The niobium compound is preferably niobium pentachloride; to suppress its rapid hydrolysis, it is preferably first dissolved in anhydrous ethanol solvent before being mixed with the copper precursor solution to obtain a uniformly dispersed mixed metal precursor solution. The mixed metal precursor solution is loaded onto the pre-dried support using an equal-volume impregnation method to obtain the impregnated mesoporous molecular sieve MCM-41. The impregnated mesoporous molecular sieve MCM-41 was subjected to aging, drying and calcination in sequence to obtain the Cu-Nb bifunctional catalyst.

[0010] Furthermore, the calcination is carried out in an air atmosphere at a temperature of 500°C.

[0011] The above-mentioned Cu-Nb bifunctional catalyst is used in the preparation of 2-methylfuran from furfural.

[0012] A method for preparing 2-methylfuran from biomass-derived furfural includes the following steps: The above Cu-Nb bifunctional catalyst was reduced and activated under a hydrogen atmosphere to obtain the activated catalyst. A mixed feedstock containing furfural and alcohol hydrogen donors is mixed with the activated catalyst and subjected to a gas-phase hydrodeoxygenation reaction to obtain 2-methylfuran.

[0013] Furthermore, the hydrogen donor for the alcohol is isopropanol.

[0014] Furthermore, the temperature of the gas-phase hydrogenation deoxygenation reaction is 150℃~170℃.

[0015] Furthermore, the temperature of the gas-phase hydrogenation deoxygenation reaction is 160°C.

[0016] The beneficial effects of this invention are: 1. This invention creatively introduces the transition metal niobium (Nb) as a co-catalyst into a copper-based catalyst system. The introduction of niobium is not a simple physical mixing process, but rather a strong Nb-O-Cu interfacial bond formed with the silicon framework and copper species. At the electronic level, this strong interaction effectively stabilizes the highly dispersed Cu⁺ active centers crucial for hydrogenation. At the surface acidity level, the Nb co-catalyst selectively creates numerous medium-to-strong acid sites on the catalyst surface, promoting the dehydration step. This allows this approach to overcome the technical bottleneck of traditional copper-based catalysts, which suffer from incomplete reactions at low temperatures and decreased selectivity at high temperatures leading to side reactions. Under extreme temperature and low-temperature atmospheric pressure conditions of 160℃, near-100% complete conversion of furfural can be achieved, with a yield of the target product 2-MF reaching 92.41%. Compared to other co-catalysts such as Re, W, and Mg, the Nb co-catalyst exhibits unexpectedly superior overall performance. 2. This invention strictly limits the selection of materials with a specific surface area between 600 m². 2 / g to 1200m 2 MCM-41, a mesoporous molecular sieve with a pore size between 2 nm and 4 nm, was used as a support. The high specific surface area and regular mesoporous structure of MCM-41 showed a unique compatibility with the Cu-Nb active component. The introduction of Nb further stabilized and optimized the mesoporous pore walls, forming a more unobstructed pore system, providing an optimal platform for the full dispersion of active centers, efficient mass transfer of reactant molecules, and the ideal spatial arrangement of active-acidic sites. Experiments showed that when the exact same Cu-Nb active component was loaded onto other supports (such as microporous HZSM-5 molecular sieve), the 2-MF yield dropped significantly to 61.44%, fully demonstrating the irreplaceable role and outstanding substantial effect of using MCM-41 as a support for achieving efficient directional transformation.

[0017] 3. This invention applies the prepared Cu-Nb / MCM-41 bifunctional catalyst to a fixed-bed continuous flow gas-phase hydrodeoxygenation process. The catalyst particles exhibit a locally enriched structure of active components, forming high-density active microregions. The Nb promoter maintains a stable Cu⁺ / Cu ratio throughout long-term operation through strong Nb-O-Cu electronic interactions. 2 The redox balance effectively inhibited the valence state changes, migration, aggregation, and sintering of copper species during the reaction process. In a 240-hour continuous fixed-bed operation test, the furfural conversion rate remained at 100%, and the 2-MF yield only slightly decreased from the initial 92.41% to 91.00% (a decrease of only 1.41 percentage points), demonstrating extremely high potential for continuous industrial production.

[0018] 4. The catalyst preparation of this invention abandons the use of expensive precious metals (such as Re) and adopts conventional equal-volume impregnation and air calcination processes. The reaction process uses isopropanol as a solvent, which can also provide auxiliary hydrogen supply during the reaction. At the same time, hydrogen is introduced as a reducing and activating atmosphere and a supplementary hydrogen source during the reaction start-up and continuous operation, thereby achieving efficient and continuous conversion of furfural to 2-MF under normal pressure and low temperature conditions. This not only greatly reduces the raw material cost and preparation difficulty of the catalyst, but also significantly reduces the energy consumption and equipment pressure resistance requirements of subsequent reaction processes (normal pressure is sufficient). The process is green and efficient, meeting the actual needs of industrialization, economic efficiency, and continuous production of bio-based fuels. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The image shows the XRD pattern of the 5Cu-3Nb / MCM-41 catalyst in Example 1 of this invention. Figure 2 These are SEM and TEM images of the 5Cu-3Nb / MCM-41 catalyst in Example 1 of this invention; Figure 3 This is the BET plot of the 5Cu-3Nb / MCM-41 catalyst in Example 1 of the present invention; Figure 4 The image shows the NH3-TPD of the 5Cu-3Nb / MCM-41 catalyst in Example 1 of this invention. Figure 5 This is a comparison chart of furfural conversion rates after cyclic reaction using the 5Cu-3Nb / MCM-41 catalyst in Example 1 of this invention. Figure 6 The diagram shows the 2-MF yield of this invention and a comparison of XPS values ​​before and after the reaction. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] A method for preparing 2-methylfuran (2-MF) from biomass-derived furfural, the core step of which is: under the catalysis of a bifunctional catalyst, a mixed raw material prepared by furfural and an alcohol hydrogen donor undergoes a gas-phase hydrogenation and deoxygenation reaction to generate the target product 2-MF. Specifically, a fixed-bed continuous flow reactor is used, in which the mixed feedstock is continuously fed in gaseous form into a reaction bed pre-loaded with a bifunctional catalyst. Hydrodeoxygenation conversion is carried out at a reaction temperature of 120℃~180℃ and a pressure of atmospheric pressure to 3MPa to obtain 2-MF. Wherein: The furfural is derived from the pyrolysis products of biomass hemicellulose or pentose platform compounds and is soluble in alcohol solvents such as methanol, ethanol, and isopropanol. In this invention, isopropanol is selected as the solvent, which can participate in hydrogen donation in the reaction, while external hydrogen gas is added to provide a reducing atmosphere and supplement the hydrogen source.

[0023] The reaction was carried out in a fixed-bed continuous flow reactor, with the reaction temperature maintained at 120℃–180℃ and the system hydrogen pressure at atmospheric pressure to 3 MPa. The liquid hourly space velocity (LHSV) of the feedstock was controlled at 0.2 h⁻ 1 Up to 1.0 h⁻ 1 The hydrogen flow rate is set between 5 and 50 mL / min.

[0024] In the mixed raw materials, the mass concentration of furfural is preferably 5 wt%, and the alcohol hydrogen donor used is isopropanol.

[0025] The bifunctional catalyst used in the method has the following structural features and composition; Active component A: The active metal component consists of copper (Cu) and niobium (Nb); Carrier B: Selected with a specific surface area between 600 m² 2 / g to 1200 m 2 MCM-41 mesoporous molecular sieve material with a pore size distribution ranging from 2 nm to 4 nm and a density between / g.

[0026] Loading amounts: In this catalyst, the loading amount of the active component Cu is 3 wt% to 10 wt%; the loading amount of the co-catalyst metal is 3 wt%; One preparation process for this bifunctional catalyst is as follows: S1, carrier pretreatment: The MCM-41 molecular sieve was dried at 120℃ for 6 hours to remove the water physically adsorbed on its surface. The resulting dried solid was used as carrier B for later use. S2. Preparation of precursor solution: The copper compound and the niobium compound are dissolved separately in an alcohol solvent or a mixed solvent containing alcohol to form a precursor solution. The niobium compound is preferably niobium pentachloride. To inhibit its rapid hydrolysis, it is preferable to first dissolve it in anhydrous ethanol solvent and then mix it with the copper precursor solution to obtain a clear or uniformly dispersed mixed metal precursor solution. S3, Loading and Post-treatment: Using an equal-volume impregnation method, the support B obtained in step S1 is impregnated in the metal mixed precursor solution prepared in step S2. Subsequently, it undergoes aging, drying, and calcination at a set temperature to finally obtain the bifunctional catalyst.

[0027] The technical solution of the present invention will be described below through the following embodiments; in the embodiments, the sources of the relevant raw materials are as follows: Furfural (FAL, 99% purity), niobium pentachloride (NbCl5, 99% purity), aluminum trichloride (AlCl3, 99% purity), copper nitrate trihydrate (Cu(NO3)2·3H2O, 99% purity), γ-valerolactone (98%), ammonium perrhenate (NH4ReO4, 98%), cyclopentanone (98%), sodium tungstate (Na2O4W·2H2O, 98%), and magnesium nitrate (Mg(NO3)2, 99%) were all purchased from Aladdin Biochemical Technology Co., Ltd. The all-silica MCM-41 and HZSM-5 mesoporous molecular sieve supports were provided by Nankai University Catalyst Co., Ltd.

[0028] In this embodiment, the furfural conversion rate and product yield were measured as follows: the collected liquid samples were diluted tenfold and identified using gas chromatography-mass spectrometry (GC-MS, Agilent 8860-5977C), and quantitatively analyzed using a gas chromatograph (GC-FID, Shimadzu GC-2014C) equipped with an HP-5 capillary column (30 m × 0.32 mm × 0.25 μm). Gaseous products were analyzed using an Agilent 8890 gas chromatograph with a thermal conductivity detector (TCD) and three packed columns (3 ft HayeSep Q, 6 ft HayeSep Q, and 6 ft MolSieve 5A).

[0029] Example 1 This embodiment describes the preparation and application of the Cu-Nb / MCM-41 catalyst; Weigh an appropriate amount of MCM-41 molecular sieve and dry it at 120℃ for 6 h to remove the physically adsorbed water on the surface.

[0030] 0.42 g of niobium pentachloride was slowly added to anhydrous ethanol and stirred at room temperature until a clear, pale yellow solution was formed. Meanwhile, different amounts of copper nitrate trihydrate were dissolved in a small amount of deionized water. The two solutions were then mixed under stirring, with the water content and addition order controlled as needed to suppress rapid hydrolysis of niobium pentachloride, yielding a mixed precursor solution for impregnation. By adjusting the amount of copper nitrate trihydrate added, three Cu-Nb / MCM-41 catalysts with Cu loadings of 3 wt%, 5 wt%, and 10 wt% were prepared while maintaining a constant Nb loading of 3 wt%, and were designated as 3Cu-3Nb / MCM-41, 5Cu-3Nb / MCM-41, and 10Cu-3Nb / MCM-41, respectively.

[0031] Weigh 5.0 g of the pretreated MCM-41 support and place it in a 250 mL round-bottom flask. While stirring vigorously, add the metal precursor solution dropwise to the support, performing equal-volume impregnation. After the addition is complete, continue stirring for 30 min to ensure uniform dispersion of the metal precursor. Then, allow to age at room temperature for 12 h to allow the metal precursor to fully diffuse into the support pores.

[0032] The aged samples were transferred to an oven and dried at 100 °C for 12 h to remove the solvent. Then, the dried samples were placed in a muffle furnace and heated to 500 °C at a heating rate of 2 °C / min, and calcined in air for 4 h. After naturally cooling to room temperature, the three Cu-Nb / MCM-41 catalysts with different Cu loadings were obtained.

[0033] To further analyze the structural characteristics of representative samples among catalysts with different Cu loadings, the 5Cu-3Nb / MCM-41 catalyst with the best catalytic performance was selected for XRD, TEM, BET, and NH3-TPD characterization. The results are as follows: Figures 1 to 4 As shown in the figure. The XRD and TEM results of the 5Cu-3Nb / MCM-41 catalyst are shown in the figure. Figure 1 and Figure 2The image shows the morphology, elemental distribution, and structural stability of the 5Cu-3Nb / MCM-41 catalyst. The sample still exhibits a broad diffraction pattern of amorphous silica support within the 2θ = 15–32° range, indicating that the mesoporous structure remains intact. The most crucial difference lies in the significantly enhanced intensity and sharper peak shapes of the characteristic diffraction peaks corresponding to the CuO crystal plane at 35.5°, 38.6°, and 48.7°. This clearly confirms that the introduction of Nb species effectively promotes the crystallization and structural ordering of CuO species. Combined with the fact that no crystalline Nb₂O₅ diffraction peaks were detected in the 22–28° range, it can be inferred that the highly dispersed amorphous niobium species form strong Nb–O–Cu interfacial bonds with the silicon framework and copper species. This anchoring effect not only stabilizes the highly dispersed copper species but also optimizes its local coordination environment, thereby inducing an increase in CuO crystallinity.

[0034] TEM analysis revealed that the catalyst particles exhibited a locally enriched structure of active components, forming high-density active microregions. This structure promoted close synergy between the hydrogenation and dehydration active sites, thereby effectively improving catalytic efficiency and product selectivity. Simultaneously, this stable aggregated state helped suppress the migration and sintering of active components during the reaction process, providing a structural basis for the long-term operational stability of the catalyst. This is consistent with the high activity, high selectivity, and excellent stability exhibited by the catalyst in macroscopic performance tests.

[0035] XRD and TEM images together show that the 5Cu-3Nb / MCM-41 catalyst has excellent mesoporous structure integrity and high-density active regions. Nb doping is a key optimization factor, providing a structural basis for low-temperature and high-efficiency conversion.

[0036] like Figure 3 The figure shows the nitrogen adsorption-desorption isotherm and pore size distribution of the catalyst (5Cu-3Nb / MCM-41) of this invention. Figure 3 b. The catalyst exhibits a typical type IV isotherm and a type H1 hysteresis loop, indicating that the mesoporous structure is perfectly preserved, combined with the pore size distribution ( Figure 3 The narrow peaks concentrated at 2–3 nm in (a) confirm that the material possesses regular, uniform cylindrical mesoporous channels, a classic characteristic of capillary condensation. This phenomenon indicates that the introduction of Nb species not only does not disrupt the mesoscopically ordered structure, but also further stabilizes and optimizes the mesoporous pore walls through strong interactions (Nb–O–Si or Nb–O–Cu bonds) with silanol and copper species, thereby forming a more unobstructed and developed pore system. The increased adsorption capacity is directly related to a higher specific surface area and a larger pore volume, which provides reactant molecules with more accessible active sites and more efficient mass transfer pathways.

[0037] The NH3-TPD characterization results of the MCM-41 series catalysts (e.g.) Figure 4 Analysis of the catalyst (as shown) clearly reveals the crucial regulatory role of Nb introduction on surface acidity and its distribution. The unsupported pure MCM-41 support exhibits only a weak acid signal, indicating its inherently weak acidity. Further introduction of Nb promoters (5Cu-3Nb / MCM-41) significantly increases the overall acidity of both catalysts, but the acid intensity distribution shows decisive differences. The spectrum of 5Cu-3Nb / MCM-41 shows a significantly enhanced and concentrated desorption peak in the medium-high temperature region (typically 300-450℃), clearly indicating that the introduction of Nb promoters selectively and efficiently creates a large number of medium-strong acid sites on the catalyst surface.

[0038] The subsequent process involves the hydrogenation and deoxygenation of furfural to produce 2-MF, specifically including: The prepared catalyst particles were controlled to be 20-30 mesh and loaded into a stainless steel fixed-bed reactor (1.0 g loading). Hydrogen gas was introduced at a rate of 10 mL / min, and the reactor was pretreated at 300 °C for 3 h before being cooled to the target reaction temperature.

[0039] Using a 5wt% furfural-isopropanol solution as raw material, the solution was metered at a rate of 0.5 h / min. -1 The liquid hourly space velocity (LHSV) was continuously fed into the reactor at atmospheric pressure, with a hydrogen flow rate of 10 mL / min.

[0040] The reaction data for Cu-Nb / MCM-41 are shown in Table 1 below: Table 1 Reaction data for Cu-Nb / MCM-41 Table 1 shows the results of the catalytic hydrogenation deoxygenation of furfural to 2-MF using Cu-Nb / MCM-41 catalysts with different Cu loadings at different reaction temperatures. As shown in Table 1, with the Nb loading remaining constant at 3 wt%, the Cu loading has a significant impact on the furfural conversion, 2-MF yield, and byproduct distribution of the catalyst.

[0041] Specifically, when the Cu loading is low, the furfural conversion rate of the 3Cu-3Nb / MCM-41 catalyst is generally low in the temperature range of 120–200 °C, and the 2-MF yield remains consistently low, indicating insufficient hydrogenation activity of the catalyst, making it difficult to effectively promote the deep conversion of furfural to the target product 2-MF. Meanwhile, the proportion of other byproducts in this catalyst system is relatively high, suggesting that in the absence of sufficient active metal sites, the reaction is more likely to proceed along non-target pathways.

[0042] The catalytic performance was significantly improved when the Cu loading increased to 5 wt%. The 5Cu-3Nb / MCM-41 achieved 100% furfural conversion at temperatures of 140℃ and above, and the 2-MF yield exhibited a distinct volcanic-like trend with increasing temperature: at 120℃, the 2-MF yield was only 13.02%, with furfuryl alcohol and γ-valerol being the main products, indicating that the reaction at low temperatures mainly remained in the intermediate hydrogenation stage; as the temperature increased to 150℃, the 2-MF yield rapidly increased to 89.78%; it reached a maximum of 92.41% at 160℃, at which point furfural was completely converted, and the contents of byproducts such as furfuryl alcohol, cyclopentanone, and γ-valerol were all low, indicating that the hydrogenation and deoxygenation steps achieved optimal synergy at this temperature; when the temperature continued to rise above 170℃, the 2-MF yield decreased significantly, and other byproducts increased, indicating that excessively high temperatures promote side reactions, thereby reducing the selectivity of the target product.

[0043] When the Cu loading was further increased to 10 wt%, the furfural conversion rate of the 10Cu-3Nb / MCM-41 catalyst increased significantly with increasing temperature, reaching near-complete conversion at high temperatures. However, its 2-MF yield was still significantly lower than that of 5Cu-3Nb / MCM-41, especially at 160℃ where it was only 15.00%. Meanwhile, the yields of γ-valerol and other byproducts were higher. This indicates that excessively high Cu loading did not further improve the selectivity of the target product. Instead, due to the relative enrichment of metal sites, the synergistic matching between Cu hydrogenation sites and Nb acidic sites was disrupted, leading to enhanced side reactions.

[0044] In summary, it can be seen that under the condition of a fixed Nb loading of 3 wt%, there is a clear optimal range for Cu loading. When the Cu loading is too low, the hydrogenation activity is insufficient; when the Cu loading is too high, the selectivity of the target product decreases and side reactions increase; while a Cu loading of 5 wt% achieves the best balance between hydrogenation activity and deoxygenation capacity. Therefore, 5Cu-3Nb / MCM-41 is the preferred catalyst composition of this invention, with an optimal reaction temperature of 160℃, under which 100% furfural conversion and a high yield of 92.41% 2-MF can be achieved.

[0045] Example 2 This embodiment describes the preparation and application of the Cu-Re / MCM-41 catalyst; A certain amount of MCM-41 (used in Example 1) was weighed and dispersed in anhydrous ethanol. Copper nitrate and ammonium perrhenate were dissolved separately in deionized water and mixed in a ratio of 5 wt% Cu and 3 wt% Re to prepare a metal precursor solution. This mixed solution was impregnated into the support under stirring and aged at room temperature for 12 h. Subsequently, it was dried at 100 °C for 12 h and then calcined at 500 °C for 4 h to obtain the Cu-Re / MCM-41 catalyst.

[0046] 1 g of catalyst was loaded into a fixed-bed reactor and reduced at 300 °C for 2 h with hydrogen at a flow rate of 50 mL / min. A 5 wt% furfural-isopropanol solution was prepared as the feedstock. The solution was then reduced at 0.5 h. -1 The liquid hourly gas (LIB) is pumped into the fixed-bed reactor at a reaction temperature of 120–160 °C, a hydrogen flow rate of 10 mL / min, and a pressure of atmospheric pressure.

[0047] The reaction data for Cu-Re / MCM-41 are shown in Table 2 below: Table 2 Reaction data for Cu-Re / MCM-41 As shown in Table 2, both furfural conversion and 2-MF yield increased with increasing temperature. When the temperature reached 160℃, furfural was almost completely converted, and the 2-MF yield reached 82.65%.

[0048] Example 3 This embodiment describes the preparation and application of the Cu–W / MCM-41 catalyst; MCM-41 (used in Example 1) was dispersed in anhydrous ethanol. Copper nitrate and sodium tungstate were weighed and dissolved in water, and a mixed solution was prepared according to a loading ratio of 5 wt% Cu and 3 wt% W. The solution was added dropwise to the support using an equal-volume impregnation method, aged for 10 h, dried overnight at 100 °C, and then calcined at 500 °C for 2 h to obtain the Cu–W / MCM-41 catalyst.

[0049] 1 g of catalyst was loaded, and reduction was carried out at 350 °C for 1 h with hydrogen gas at a flow rate of 50 mL / min. A 5 wt% furfural-isopropanol solution was then used at atmospheric pressure with an LHSV of 0.5 h. -1 The hydrogen flow rate is 10 mL / min, and the reaction temperature is 140–180 °C.

[0050] The reaction data for Cu-W / MCM-41 are shown in Table 3 below: Table 3 Reaction data for Cu-W / MCM-41 As shown in Table 3, as the reaction temperature increases from 140℃ to 180℃, the furfural conversion rate of the Cu-W / MCM-41 catalyst gradually increases from 92.20% to 99.66%, while the 2-MF yield shows a trend of first increasing and then decreasing, reaching a peak of 60.98% at 160℃. At this point, the furfuryl alcohol yield drops to 9.89%, indicating that this temperature is the optimal reaction temperature. If the temperature is too low, incomplete deoxygenation will lead to furfuryl alcohol accumulation, while if the temperature is too high, the side reactions will increase significantly.

[0051] Example 4 This embodiment describes the preparation and application of the Cu–Mg / MCM-41 catalyst; A mixed solution of copper nitrate and magnesium nitrate in a 5:3 mass ratio was prepared by impregnation, and MCM-41 (used in Example 1) was impregnated with the solution. After drying, the solution was calcined at 500°C for 2 hours to obtain the Cu–Mg / MCM-41 catalyst. In this catalyst, the loading of Cu was 5 wt% and the loading of Mg was 3 wt%.

[0052] Reduction was carried out at 300℃ and 50 mL / min for 2 h. A 5 wt% furfural-isopropanol solution was used at atmospheric pressure with an LHSV of 0.5 h. -1 The hydrogen flow rate was 10 mL / min, and the reaction temperature was 140–170 °C.

[0053] The reaction data for Cu–Mg / MCM-41 are shown in Table 4 below: Table 4 Reaction data for Cu–Mg / MCM-41 As shown in Table 4, as the reaction temperature increased from 140℃ to 170℃, the furfural conversion rate of the Cu-Mg / MCM-41 catalyst gradually increased from 45.85% to 90.01%. The 2-MF yield reached a peak of 49.66% at 160℃, but at 170℃, the yield decreased to 41.05% due to a significant increase in side reactions (other byproducts reached 45.59%). This indicates that the optimal reaction temperature for this catalyst is 160℃.

[0054] Example 5 This embodiment describes the preparation and application of the Cu–Nb / HZSM-5 catalyst; HZSM-5 mesoporous molecular sieve was weighed and pre-dried at 120°C for 6 hours to remove moisture before use. Copper nitrate and niobium pentachloride were dissolved in deionized water to prepare a mixed precursor solution with a Cu:Nb loading ratio of 5:3. HZSM-5 was added to the above solution under an equal volume impregnation condition, mixed thoroughly, and aged for 12 hours. The impregnated solid was dried at 100°C for 10 hours, and then calcined at 500°C for 2 hours in air to obtain the Cu–Nb / HZSM-5 catalyst. After calcination, the catalyst was pale blue, and the metal species were uniformly dispersed.

[0055] 1.0 g of catalyst was loaded into a fixed-bed reactor and reduced for 1 h at a hydrogen flow rate of 50 mL / min and a temperature of 300°C. The catalyst was then cooled to the reaction temperature for later use.

[0056] A 5 wt% furfural-isopropanol solution was introduced into the reactor at an LHSV of 0.5 h⁻¹, with a hydrogen flow rate of 10 mL / min. The reaction temperature was controlled within the range of 140–180°C, and the operation was carried out at atmospheric pressure.

[0057] The reaction data for Cu-Nb / HZSM-5 are shown in Table 5: Table 5 Reaction data for Cu-Nb / HZSM-5 As shown in Table 5, as the reaction temperature increases from 140℃ to 180℃, the furfural conversion rate of the Cu-Nb / HZSM-5 catalyst increases from 81.02% to 99.00%, and the 2-MF yield reaches a peak of 61.44% at 160℃. At this temperature, the furfural residue is low and the side reactions are relatively controllable, which is the optimal reaction temperature for this catalyst.

[0058] Example 6 The 5Cu-3Nb / MCM-41 catalyst prepared in Example 1 was selected as the subject of investigation. The catalyst was pressed into tablets, sieved to obtain 20-30 mesh particles, and then packed into a stainless steel fixed-bed microreactor with a loading of 1.0 g, secured at both ends with quartz wool. After loading, the catalyst underwent reduction pretreatment under a hydrogen atmosphere: hydrogen gas was introduced (10 mL / min), the temperature was raised to 300 °C, held for 2 h, and then cooled to the reaction temperature of 160 °C.

[0059] The reaction feedstock was a 5 wt% furfural-isopropanol solution, where isopropanol served as the solvent and also acted as an auxiliary hydrogen donor in the reaction. Hydrogen gas was continuously introduced at a rate of 10 mL / min during the reaction to maintain the stability of the active species on the catalyst surface and facilitate their participation in the hydrodeoxygenation reaction. The reaction temperature was fixed at 160℃, and the reaction was continuously run for 240 h under these conditions. Liquid phase samples of the reaction products were collected online or offline after condensation, and the furfural conversion rate and the selectivity of each product were analyzed periodically using gas chromatography-FID (GC-FID), with samples taken every 24 h.

[0060] The test results are shown in Table 6: Table 6. Stability test results of 5Cu-3Nb / MCM-41 after continuous operation at 160℃ for 240 hours. As shown in Table 6, the stability test results of the 5Cu-3Nb / MCM-41 catalyst after 240 hours of continuous operation at 160℃ and atmospheric pressure show that the furfural conversion rate remained at 100%, and the 2-MF yield remained stable at 92.41% in the first 72 hours, then slowly decreased, reaching 91.00% after 240 hours, a decrease of only about 1.41 percentage points. Simultaneously, the furfuryl alcohol yield gradually decreased from 6.90% to 3.00%, while the yields of other byproducts slowly increased from 0.69% to 6.00%. These data indicate that the catalyst can maintain a target product yield of over 91% after 240 hours of continuous operation, demonstrating good catalytic stability and resistance to deactivation, and possessing the potential for long-term industrial operation.

[0061] To investigate the changes in the surface chemical state of the 5Cu-3Nb / MCM-41 catalyst after long-term operation, Cu 2p XPS characterization analysis was performed on both fresh catalyst and catalyst after 240 hours of continuous reaction. The results are as follows: Figure 4 As shown in the figure, a comparison of the Cu2p XPS spectra reveals a high degree of similarity between the fresh and used catalysts: both exhibit distinct characteristic peaks near ~933 eV (Cu 2p3 / 2) and ~953 eV (Cu 2p1 / 2), accompanied by typical Cu... 2 ⁺ Satellite peak structure. Through meticulous peak shape fitting and quantitative analysis, it was found that the Cu⁺ / Cu ratio of the catalyst after use... 2 The Cu⁺ ratio showed only a slight change compared to the fresh catalyst, maintaining a high relative proportion of Cu⁺ species. This result indicates that after 240 hours of continuous reaction, the chemical state and valence distribution of copper species on the catalyst surface were well maintained, and the stabilizing effect of the Nb promoter on Cu⁺ species through strong Nb–O–Cu electronic interactions remained effective during long-term operation.

[0062] Combined with reaction performance data (the yield of 2-MF decreased by only about 2.0% within 240 hours), XPS analysis confirmed from the electronic state level that the 5Cu-3Nb / MCM-41 catalyst maintained a stable Cu⁺ / Cu²⁺ redox equilibrium throughout long-term operation. The Nb promoter effectively suppressed the valence state changes and migration and aggregation of copper species, indicating that the excellent stability of the catalyst is closely related to the valence state of Cu species.

[0063] This invention discloses a method for preparing 2-MF from biomass-derived furfural as a raw material, the core of which lies in constructing a Cu-Nb bifunctional catalyst system. The catalyst uses MCM-41 mesoporous molecular sieve as a support, and the active metal Cu and the auxiliary agent Nb are loaded onto the surface of the support by an equal-volume impregnation method, followed by aging, drying, and calcination.

[0064] The results show that Nb plays multiple key regulatory roles as a promoter in copper-based catalysts: XRD analysis confirms that Nb species effectively promote the crystallization and structural ordering of CuO by forming strong Nb–O–Cu interfacial bonds with the silicon framework and copper species; BET analysis shows that the introduction of Nb further stabilizes and optimizes the mesoporous channel structure, increasing the specific surface area and pore volume; NH3-TPD characterization reveals that the Nb promoter selectively creates a large number of medium-strong acid sites on the catalyst surface, providing the optimal acid strength for furfuryl alcohol dehydration to 2-MF; XPS analysis shows that Nb stabilizes a high proportion of Cu⁺ active centers through strong electronic interactions, which is the electronic reason for achieving excellent hydrodeoxygenation performance.

[0065] To further clarify the influence of auxiliary elements and support structure on catalytic performance, a comparative analysis was conducted on the results of different catalysts in Examples 1-5 under similar reaction conditions. Using 160°C as a representative temperature, the furfural conversion rate and 2-MF yield of each catalyst showed significant differences.

[0066] Among them, the 5Cu-3Nb / MCM-41 catalyst achieved 100% furfural conversion and 92.41% 2-MF yield at 160℃, which was significantly better than Cu-Re / MCM-41 (82.65%), Cu-W / MCM-41 (60.98%), Cu-Mg / MCM-41 (49.66%) and Cu-Nb / HZSM-5 (61.44%).

[0067] The above results indicate that the type of promoter has a decisive influence on the catalyst's hydrogenation activity, deoxygenation capacity, and side reaction suppression ability. Specifically: The role of Nb as a promoter is the most prominent. Compared with Re, W, and Mg, the introduction of Nb not only maintains the excellent carbonyl hydrogenation ability of Cu species, but also enhances the interaction between Cu species and the support by constructing an Nb-O-Cu interface, which is beneficial to stabilizing Cu⁺ active centers. At the same time, Nb can also introduce more suitable medium-strong acid sites on the surface, promoting the dehydration and deoxygenation steps of furfuryl alcohol to 2-MF, thus exhibiting the best synergistic effect in the tandem reaction.

[0068] Although Re can improve the yield of 2-MF, its overall performance is still inferior to that of Nb. This indicates that Re also promotes hydrodeoxygenation, but its effects on acid regulation and side reaction suppression are not as balanced as those of the Nb system.

[0069] The effects of W and Mg additives are relatively limited. Although the W system can achieve a high conversion rate at 160℃, the 2-MF yield is significantly low and there are many byproducts, indicating that its selective control over the target pathway is insufficient. The overall conversion rate and target yield of the Mg system are both low, indicating that it is difficult to simultaneously meet the synergistic requirements of hydrogenation activity and deoxygenation acidity.

[0070] The support effect is also crucial. Under the same Nb promoter conditions, the 2-MF yield of 5Cu-3Nb / MCM-41 supported at 160℃ reached 92.41%, while that of HZSM-5 supported was only 61.44%. This indicates that the regular mesoporous structure, higher specific surface area, and more suitable pore environment of MCM-41 are more conducive to the high dispersion loading of Cu and Nb species, reactant mass transfer, and spatial synergy between hydrogenation sites and acid sites. In contrast, the stronger acidity and pore structure confinement of HZSM-5 make it more likely to induce side reactions, thereby reducing the selectivity of the target product.

[0071] In summary, the data from the examples fully demonstrate that Nb is a superior promoter compared to Re, W, and Mg, while MCM-41 is a superior support compared to HZSM-5; the Cu-Nb / MCM-41 catalyst synergistically constructed by the two can achieve efficient and directional conversion of furfural to 2-MF at lower temperatures.

[0072] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A Cu-Nb bifunctional catalyst, characterized in that, It includes a support and an active metal component loaded on the support; the active metal component includes Cu and Nb; the support is a mesoporous molecular sieve MCM-41.

2. The Cu-Nb bifunctional catalyst according to claim 1, characterized in that, Based on the total mass of the catalyst, the loading of Cu is 3wt% to 10wt%, and the loading of Nb is 3wt%.

3. The Cu-Nb bifunctional catalyst according to claim 1, characterized in that, The specific surface area of ​​the mesoporous molecular sieve MCM-41 is 600 m². 2 / g~1200m 2 / g, with a pore size distribution range of 2nm~4nm.

4. The method for preparing the Cu-Nb bifunctional catalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: The mesoporous molecular sieve MCM-41 was dried to obtain a pre-dried carrier. Copper and niobium compounds are dissolved separately in alcohol solvents or mixed alcohol solvents to form precursor solutions. The niobium compound is preferably niobium pentachloride; to suppress its rapid hydrolysis, it is preferably first dissolved in anhydrous ethanol solvent before being mixed with the copper precursor solution to obtain a uniformly dispersed mixed metal precursor solution. The mixed metal precursor solution is loaded onto the pre-dried support using an equal-volume impregnation method to obtain the impregnated mesoporous molecular sieve MCM-41. The impregnated mesoporous molecular sieve MCM-41 was subjected to aging, drying and calcination in sequence to obtain the Cu-Nb bifunctional catalyst.

5. The method for preparing the Cu-Nb bifunctional catalyst according to claim 4, characterized in that, The calcination is carried out in an air atmosphere at a temperature of 500°C.

6. The use of the Cu-Nb bifunctional catalyst according to any one of claims 1-3 in the preparation of 2-methylfuran using furfural.

7. A method for preparing 2-methylfuran from biomass-derived furfural, characterized in that, Includes the following steps: The Cu-Nb bifunctional catalyst according to any one of claims 1-3 is subjected to reduction and activation treatment under a hydrogen atmosphere to obtain the activated catalyst; A mixed feedstock containing furfural and alcohol hydrogen donors is mixed with the activated catalyst and subjected to a gas-phase hydrodeoxygenation reaction to obtain 2-methylfuran.

8. The method for preparing 2-methylfuran from biomass-derived furfural according to claim 7, characterized in that, The hydrogen donor for the alcohol is isopropanol.

9. A method for preparing 2-methylfuran from biomass-derived furfural according to claim 7, characterized in that, The temperature of the gas-phase hydrogenation deoxygenation reaction is 150℃~170℃.

10. A method for preparing 2-methylfuran from biomass-derived furfural according to claim 7, characterized in that, The temperature of the gas-phase hydrogenation deoxygenation reaction is 160°C.

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