La-doped ZnFe-LDHs stabilized Cu nanoparticles catalyst, preparation method thereof and application of the catalyst in preparation of furfuryl alcohol from furfural by hydrogenation

Abstract

This invention discloses a La-doped ZnFe-LDHs catalyst for stabilizing Cu nanoparticles, its preparation method, and its application in the hydrogenation of furfural to furfuryl alcohol. It belongs to the technical field of catalytic material preparation and high-value utilization of biomass resources. The catalyst uses ZnFe-LDHs as a support, Cu as the active component, and La as a modifier to prepare a catalyst with the composition La-Cu / ZnFe-LDHs. The La modifier is partially doped into the ZnFe-LDHs layers and partially distributed on the support surface as La2O2(CO3) nanoparticles. This invention achieves multi-scale stabilization of Cu nanoparticles through La doping in the ZnFe-LDHs layers and the formation of the surface La2O2(CO3) nanophase. La regulates the electronic structure of the layers, keeping Cu in a low valence state through charge redistribution, while simultaneously improving the catalyst's resistance to sintering; the surface La2O2(CO3) inhibits Cu migration through structural anchoring. The catalyst maintained a high conversion rate of 93.5% after seven cycles in the hydrogenation of furfural to furfuryl alcohol, with a Cu loading as low as 4.74 wt%, significantly improving the stability of the Cu-based catalyst.

Description

Technical Field

[0001] This invention belongs to the technical field of catalytic material preparation and high-value utilization of biomass resources, specifically involving a La-doped ZnFe-LDHs stabilized Cu nanoparticle catalyst, its preparation method, and its application in furfural hydrogenation to furfuryl alcohol. Background Technology

[0002] Selective hydrogenation of furfural to furfuryl alcohol (FOL) is a key pathway for the high-value utilization of biomass resources. However, traditional copper-based catalysts are prone to sintering and deactivation due to the low Schütty temperature of Cu nanoparticles, and the high loading requirement (10-30%) limits their atom economy. To address this challenge, the applicant previously constructed a low-loading bulk-doped S-Cu / ZnFe catalyst using a layered metal replacement strategy. However, the gradual sintering of Cu species still occurred during long-term cycling. Experiments showed that after four reaction cycles, the selectivity of furfuryl alcohol decreased from 98.5% to 89.3%, with a significant reduction in low-valence Cu active species. This phenomenon indicates that the anchoring effect of heteronuclear metals in the hydrotalcite layers is insufficient to completely suppress the dynamic migration of Cu active sites in a high-temperature hydrogen atmosphere. Therefore, how to further improve the stability of copper species through a synergistic strategy of electronic structure modulation and geometric confinement has become a key challenge in optimizing this system.

[0003] In recent years, the role of rare earth metals as electronic catalysts in catalytic materials has attracted much attention. Among them, rare earth metal La has been used to stabilize active sites of transition metals (such as improving the anti-sintering ability of Pt / Al2O3 through SMSI), but the synergistic effect of La and Zn / Fe heteronuclear metals on the regulation of the Cu electronic microenvironment in two-dimensional layered ZnFe-LDHs is still unclear, and there is a lack of systematic research on multi-scale stabilization of Cu nanoparticles.

[0004] Therefore, inventing a La-doped ZnFe-LDHs-stabilized Cu nanoparticle catalyst is of great significance for improving the cycle stability of furfural hydrogenation reaction. Summary of the Invention

[0005] The first objective of this invention is to provide a La-doped ZnFe-LDHs catalyst for stabilizing Cu nanoparticles; the second objective is to provide a method for preparing the La-Cu / ZnFe-LDHs catalyst; and the third objective is to provide applications of the La-Cu / ZnFe-LDHs catalyst. The catalyst, through multi-scale modulation of La (structural anchoring, electronic modulation, and mass transfer optimization), significantly enhances the anti-sintering ability of Cu nanoparticles and extends the catalyst lifetime.

[0006] The first objective of this invention is achieved by preparing a catalyst with the composition La-Cu / ZnFe-LDHs using ZnFe-LDHs as a support, Cu as the active component, and La as a modifier.

[0007] Preferably, the molar ratio of Cu, La, Zn and Fe in the catalyst is 1:(0.5-2):(10-15):(4-6).

[0008] Furthermore, the molar ratio of Cu, La, Zn, and Fe in the catalyst is 1:1:13:5.

[0009] Preferably, the La is partially doped in the ZnFe-LDHs layer and partially distributed on the carrier surface in the form of La2O2(CO3) nanoparticles.

[0010] Furthermore, the La2O2(CO3) nanoparticles are dispersed on the surface of the carrier, accounting for 50-70% of the total La content.

[0011] Furthermore, the ZnFe-LDHs support exhibits a two-phase La distribution (37% on the layers + 63% on the surface), with La2O2(CO3) nanoparticles acting as a physical diffusion barrier.

[0012] Preferably, the Cu nanoparticles in the catalyst are loaded on the surface of the support, with a loading of 4-5 wt%.

[0013] The second objective of this invention is achieved by the following method for preparing the La-doped ZnFe-LDHs-stabilized Cu nanoparticle catalyst, comprising the following steps:

[0014] (1) Preparation of precursor: Copper nitrate, lanthanum nitrate, zinc nitrate and ferric nitrate were dissolved in deionized water in proportion to obtain solution A; sodium hydroxide and anhydrous sodium carbonate were dissolved in deionized water in proportion to obtain solution B; under vigorous stirring, solution A and solution B were slowly added dropwise to deionized water, and after ultrasonic oscillation, the solution was transferred to a reaction vessel, aged, cooled and separated to obtain a reddish-brown solid product; finally, the product was dried and ground to obtain a bulk doped catalyst precursor material.

[0015] (2) Catalyst preparation: The obtained precursor material was heated to 450°C at a rate of 5°C / min in N2 atmosphere and kept at that temperature for 2 hours. Then, the atmosphere was switched to H2 atmosphere and the reduction was continued at 400°C for 2 hours to obtain the target catalyst.

[0016] Preferably, the molar ratio of copper nitrate, lanthanum nitrate, zinc nitrate and ferric nitrate in step (1) is Cu:La:Zn:Fe=1:(0.5-2):(10-15):(4-6); further, the molar ratio of copper nitrate, lanthanum nitrate, zinc nitrate and ferric nitrate is Cu:La:Zn:Fe=1:1:13:5.

[0017] Preferably, the mass ratio of sodium hydroxide to anhydrous sodium carbonate in step (1) is 2:1.77.

[0018] Preferably, the ultrasonic oscillation in step (1) is to continue oscillating for 10 minutes under ultrasonic conditions of 300 W.

[0019] Preferably, the aging in step (1) is carried out at 100-120°C for 18-24 hours, and the drying is carried out in an oven at 60°C for 12 hours.

[0020] The third objective of this invention is achieved by the application of the La-doped ZnFe-LDHs stabilized Cu nanoparticle catalyst in the hydrogenation of furfural to furfuryl alcohol.

[0021] Preferably, the La-doped ZnFe-LDHs stabilized Cu nanoparticle catalyst is used in furfural hydrogenation for anti-sintering applications, wherein the Cu loading of the catalyst is ≤5wt%.

[0022] Preferably, the reaction conditions for the application of the catalyst in the hydrogenation of furfural to furfuryl alcohol are 150°C, 50 mg catalyst, 1 mmol furfural, 10 mL isopropanol, 2 Mpa H2, and a reaction time of 0-120 min.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This invention constructs a synergistic protective network at the atomic, nanoscale, and mesoscale while maintaining the main structure of layered double hydroxides (LDHs). At the atomic scale, La... 3+ The layer doping balances Cu through charge compensation effect. 2+ / Cu + with Fe 3+ / Fe 2+ The redox oscillations suppressed excessive reduction and deactivation of active components during hydrogen overflow. The in-situ formed La2O2(CO3) nanophase bonded to the Cu-O interface provided both steric hindrance and chemical anchoring, effectively limiting the thermal migration and sintering tendency of Cu particles. At the mesoscale, La-induced mesoporous structure optimization (pore size reduced from 0.21 nm to 0.18 nm) and surface area (from 107 m²) were improved. 2 / g increased to 115 m2 / g) and elemental distribution uniformity (EDS correlation coefficient R) 2 >0.92) Synergistically enhanced reactant mass transfer and accessibility of active sites. These mechanisms together increased the catalyst cycle life from 4 to 7 times, and increased cycle stability by 75%, significantly improving the stability of Cu-based catalysts.

[0025] 2. This invention uses La doping to regulate the electronic structure of the laminations, ensuring the long-term stability of the catalyst through a multi-scale structural regulation mechanism. The structural anchoring effect, through the synergistic effect of lamination doping and the surface-supported phase, anchors Cu to the laminations, increasing the Cu loading from 4.53% to 4.74%. The electronic regulation effect, through charge redistribution, keeps Cu in a low valence state while improving the catalyst's resistance to poisoning. The mass transfer optimization effect, through increasing the proportion of mesopores, facilitates reactant diffusion. The coupling effect of these effects ultimately achieves multi-objective optimization of activity, stability, and selectivity in catalyst design, providing a new theoretical basis for the application of LDHs-based catalysts in biomass conversion. Attached Figure Description

[0026] Figure 1 The XRD patterns of S-Cu / ZnFe-LDHs and La-Cu / ZnFe-LDHs in the embodiments of the present invention are shown below.

[0027] Figure 2 The image shows the XPS plots of La-Cu / ZnFe-LDHs in Example 1; where (a) C 1s, (b) Cu 2p, (c) CuLM2, (d) Fe 2p, (e) La 3d, and (f) O1s.

[0028] Figure 3 SEM images of S-Cu / ZnFe-LDHs in Example 1: (a) 500 nm; SEM images of La-Cu / ZnFe-LDHs: (b) 500 nm, (c) 100 nm; (di) EDS image;

[0029] Figure 4 TEM image of La-Cu / ZnFe-LDHs in Example 1;

[0030] Figure 5 The N2-BET information for La-Cu / ZnFe-LDHs in Example 1;

[0031] Figure 6 For La-Cu / ZnFe-LDHs in Example 1: (a) Comparison of catalytic performance at 150℃; (b) Cyclic performance;

[0032] Figure 7The images show SEM images of La-Cu / ZnFe-LDHs after cycling in Example 1, where (a) is 500 nm, (b) is 300 nm, (c) is 100 nm; and (di) is an EDS image of La-Cu / ZnFe-LDHs.

[0033] Figure 8 The image shows XPS images of La-Cu / ZnFe-LDHs before and after cycling in Example 1. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0035] Example 1

[0036] (1) The chemical reagents used in this embodiment, including furfural, isopropanol, lanthanum nitrate, copper nitrate, zinc nitrate, ferric nitrate, sodium hydroxide (NaOH), and anhydrous sodium carbonate (Na2CO3), are all of analytical grade and can be used directly without purification. The experimental water is deionized water with a conductivity of less than 1 μS / cm.

[0037] (2) Catalyst preparation:

[0038] First, 0.345 g of copper nitrate, 0.619 g of lanthanum nitrate, 5.525 g of zinc nitrate, and 2.886 g of ferric nitrate were weighed and dissolved in 40 mL of deionized water (Cu:La:Zn:Fe = 1:1:13:5 mol / mol) to obtain solution A. Then, 2 g of NaOH and 1.77 g of Na₂CO₃ were dissolved in 40 mL of deionized water to obtain solution B. Under vigorous stirring, 40 mL each of solution A and solution B were slowly added dropwise to a beaker (100 mL) containing 10 mL of deionized water. The mixture was then sonicated at 300 W for 10 min and placed in a 100 mL stainless steel reactor with a polytetrafluoroethylene liner. After aging in an oven at 110 °C for 24 hours, the product was cooled and separated to obtain a reddish-brown solid product. Finally, the product was dried in an oven at 60 °C for 12 hours and then ground to obtain a bulk-doped catalyst precursor material. The obtained precursor material was placed in a tube furnace and heated to 450°C at a rate of 5°C / min under a N2 atmosphere, and then held for 2 h to perform a topological transformation of the plate metal. Then, the gas was changed to hydrogen and the reduction was continued at 400°C for 2 h to obtain a bulk-supported La-Cu / ZnFe-LDHs material.

[0039] Example 2 – Comparative Example

[0040] A low-loading (4.53 wt%) bulk-doped S-Cu / ZnFe-LDHs catalyst was constructed using a co-precipitation method with ZnFe-LDHs as the support. Experiments showed that after four reaction cycles, the furfuryl alcohol selectivity decreased from 98.5% to 89.3%, indicating a significant reduction in low-valent Cu active species.

[0041] Example 3 – Results and Analysis

[0042] 3.1 Characterization Tests of La-Cu / ZnFe-LDHs

[0043] The effects of the dispersion state and electronic environment of La and Cu on the La-Cu-ZnFe-LDHs support, as well as the interaction between La and the support metal, on catalytic performance were analyzed in detail using characterization techniques such as XRD, TEM, BET, and XPS.

[0044] The crystal structure characterization and analysis of S-Cu / ZnFe-LDHs and La-Cu / ZnFe-LDHs catalysts were performed, and their XRD patterns were analyzed. Figure 1 The study clearly revealed the modifying effect of La doping on the layered double hydroxide (LDH) framework. The undoped S-Cu / ZnFe-LDHs sample exhibited sharp diffraction peaks at 2θ = 11.5°, 23.2°, and 34.8°, corresponding to the (003), (006), and (012) crystal planes of the LDH structure, respectively. These peaks correspond to the standard ZnFe-LDHs (JCPDS38-0487), confirming that the material possesses a highly ordered layered stacking structure. The introduction of La... 3+ Subsequently, the position of the (003) peak in La-Cu / ZnFe-LDHs remained essentially unchanged (2θ = 11.5°), but its full width at half maximum (FWHM) increased from 0.45° to 0.58°, indicating a decrease in the long-range order of the laminations. This structural change originates from La 3+ with Fe 3+ The radius mismatch effect. When part of La 3+ Fe replacement 3+ When entering the LDHs layer, the generated lattice stress causes the octahedral units to twist, and the cation arrangement in local areas of the layer deviates from the ideal periodic order.

[0045] Combining the high-resolution C 1s orbital spectrum, it can be seen that ( Figure 2 a) Excessive La 3+La species failed to completely dissolve in the LDHs layers, instead existing as surface-loaded nanoparticles or composite oxides. Combined with the refinement results, the mass percentage of La species in the material was 3.95%, with approximately 63% existing as a surface phase and 37% entering the layer lattice. This dual-phase distribution characteristic was further verified by TEM high-resolution imaging. In the selected area electron diffraction (SAED) pattern, in addition to the characteristic diffraction rings of LDHs, La-Cu / ZnFe-LDHs also showed (104) and (110) crystal plane diffraction spots belonging to La2O2(CO3), further confirming the formation of the surface heterophase.

[0046] The formation of this composite structure exhibits a dual stabilizing effect: firstly, the surface La2O2(CO3) nanoparticles inhibit lattice migration of LDHs during cycling through a pinning effect; secondly, the preferential segregation of La species at the interface between Cu nanoparticles and the support forms a physical diffusion barrier, reducing the Oswald ripening rate constant of Cu particles and ensuring uniform dispersion of Cu nanoparticles after cycling. Related analyses indicate that the formation of La-OM interfacial bonds enhances the bonding between the active component and the support, thereby effectively inhibiting the migration and aggregation of metal particles. This multi-scale structural regulation mechanism provides an important guarantee for the long-term stability of the catalyst.

[0047] High-resolution Cu 2p orbital spectrum ( Figure 2 bc) confirms La 3+ Doping induced a significant interfacial charge redistribution effect. Due to La 3+ It has a higher charge density than Fe³⁺ (ionic potential Z / r = 3.04 vs. 2.76), and its interaction with interlayer CO₃²⁻ 2- The electrostatic interaction energy will be increased, forcing the Cu inside the layer to... 2+ Migrating to the surface. During the migration process, the surface Cu... 2+ Increased local concentration can trigger a self-reduction reaction (Cu) 2+ +e - =Cu + ), forming electron-rich Cu⁺ active sites (Cu + / Cu 0 The ratio increased from 1.015 to 1.029), while the Cu inside the layer... 2+ The lattice charge imbalance caused by loss can be alleviated through a dynamic charge compensation mechanism mediated by the Fe-O-Cu bridging structure: the large amount of Fe present in the catalyst 2+ This allows electrons to transfer to Cu sites, maintaining charge conservation in the crystal structure. Fine spectral analysis of Fe 2p and La 3d orbitals (…) Figure 2 This is also confirmed in (de), where Fe in undoped S-Cu / ZnFe-LDHs 2+It accounts for 62.7% (binding energy 710.5 eV), while the Fe 2p of La-Cu / ZnFe-LDHs... 3 / 2 The peak shifts 0.5 eV towards lower binding energy, Fe 2+ The proportion increased to 83.6%. Due to La 3+ The hybridization of the 4f empty orbital with the 3d orbital of Fe causes the hybridization energy level in the La-O-Fe bonding region to shift upwards compared to the pure Fe-O system, forming a deep local density of states peak. This promotes the formation of more Fe through electron transfer. 2+ This multi-scale electronic reconstruction behavior can also enhance the metal-support strong interaction (SMSI), providing an electronic theoretical basis for improving the cycle stability of catalysts.

[0048] O 1s ( Figure 2 f) This further verifies the structural stability enhancement mechanism: lattice oxygen (O) in La-Cu / ZnFe-LDHs I The proportion of 530.1 eV increased from 68.7% to 70.2%, and the surface hydroxyl oxygen (O) II The percentage of oxygen deficiency (531.5 eV) decreased from 29.4% to 28.5%, while the percentage of defective oxygen (O2) increased. III The lattice oxygen content (533.2 eV) decreased from 1.9% to 1.3%. The increase in the lattice oxygen content (1.5%) is directly related to the increase in oxygen vacancy formation energy. 3+ The strong electrostatic potential effectively suppresses the tendency of oxygen atoms to desorb. In addition, La doping reduces the interplanar spacing of Cu2O(111), and the enhanced anti-collapse ability of the laminate structure is due to the synergistic effect of the strong covalentity of Fe-O-La bonds and the dynamic charge compensation effect.

[0049] The elemental composition results in the catalyst (Table 1) show that in the La-doped Cu / ZnFe-LDHs layered bimetallic hydroxide, the mass fraction of La is 3.95%, and the spatial distribution of La is similar to that of Zn. 2+ Fe 3+ A significant correlation is observed, specifically manifested in the formation of elemental co-distribution characteristics in the LDHs layer region. Figure 3 di). This spatial cooperative distribution phenomenon is La 3+ The isomorphic substitution mechanism provides direct evidence that it may be involved with Zn in the LDH lamellar structure. 2+ Fe 3+ It forms a solid solution.

[0050] Table 1. Elemental content percentage in catalysts

[0051]

[0052] Scanning electron microscopy (SEM) characterization revealed that the surface of the undoped S-Cu / ZnFe-LDHs sample exhibited a typical LDHs layered stacking structure, with orderly arrangement between the layers. Figure 3 a). The La-doped sample surface exhibited a significant morphological evolution, with granular protrusions observed in the 20-50 nm particle size range (a). Figure 3 bc). Combined with high-resolution imaging results from transmission electron microscopy (TEM) ( Figure 4 These surface protrusions were identified as La2O2(CO3) nanoparticles, and their morphology matched that of the standard card (PDF#75-0268). The formation of these nanoparticles is likely attributed to La2O2. 3+ It did not fully participate in the construction of the laminations during the synthesis process, and thus interacted with CO3 in the system. 2- They combine to form independent crystalline phases.

[0053] Table 2 shows the results of specific surface area and porosity analysis. La doping leads to an increase in the BET specific surface area of ​​the catalyst from 10⁷ m² / m³. 2 / g increased to 115m 2 / g, this increase in specific surface area can be attributed to the presence of La species on the LDH surface and their dispersing effect on nanoparticles. However, the pore size distribution curve shows ( Figure 5 The proportion of mesoporous (2-50 nm) pores increased from 65% to 72%, indicating that the introduction of La may have optimized the pore structure of the material through a selective pore modification mechanism. This increase in the proportion of mesoporous pores may have a positive impact on the mass transfer process, facilitating the diffusion of reactant molecules to active sites, thereby exhibiting a synergistic effect in specific catalytic reactions.

[0054] Table 2 Pore structure information of La-Cu / ZnFe-LDHs and S-Cu / ZnFe-LDHs

[0055]

[0056] The unique electronic structure of La-based elements exhibits a significant electronic modulation effect in La-doped Cu / ZnFe-LDHs catalysts. Based on the above characterization results, at the electron transfer level, La… 3+ The unique metallic properties of La₂O₂ (CO₃) nanoparticles can form localized electron centers in the layered structure, inducing a rearrangement of charge density among neighboring metal atoms through an inductive effect. At the nanoscale, the surface modification of La₂O₂ (CO₃) nanoparticles has multiple effects on catalyst performance. By forming La-OM interfacial bonds and anchoring them to the surface of the hydrotalcite support, this strong covalent interaction effectively inhibits the leaching of active Cu species. Simultaneously, the physical isolation effect of the nanoparticles improves the dispersion of Cu nanoparticles, significantly enhancing their thermal stability.

[0057] The revelation of these structure-property relationships provides new theoretical basis for the design of efficient and stable LDH-based catalysts, and has important reference value, especially in the field of biomass conversion involving heterogeneous catalysis.

[0058] 3.2 Catalytic Performance Study

[0059] La was introduced into the Cu / ZnFe-LDHs system to construct a La-Cu / ZnFe-LDHs ternary catalyst. In this study, the catalytic effects of La-Cu / ZnFe-LDHs on S-Cu / ZnFe-LDHs were compared under the reaction conditions (150℃, 50 mg catalyst, 1 mmol FF, 10 mL isopropanol, 2 Mpa H2) at different time points of 0, 10, 20, 40, 50, 60, 90, and 120 min.

[0060] In the catalytic system for selective hydrogenation of molecular furfural to furfuryl alcohol on a biomass platform, a performance comparison between La-doped Cu / ZnFe-LDHs layered bimetallic hydroxides and the benchmark catalyst S-Cu / ZnFe-LDHs reveals the key role of rare earth element La in regulating the activity-stability balance. Figure 6 Kinetic data show that at 150℃, a furfural conversion rate of 99% and a furfuryl alcohol yield of 93% can be achieved in 50 minutes. Compared with S-Cu / ZnFe-LDHs, the furfuryl alcohol yield is slightly lower, possibly due to Cu... 0 / + The decrease in oxygen vacancy content is due to the lack of catalytic activity, but the catalyst still exhibits good catalytic performance, indicating that the introduction of metallic La does not significantly affect the original catalytic activity. Cyclic stability tests were then conducted on La-Cu / ZnFe-LDHs at 150℃ and 2 MPa H2. After the 7th cycle, the initial conversion decreased from 99% to 93.5%, and the furfuryl alcohol selectivity decreased from 93% to 83.1%, but the number of cycles increased from 4 to 7, and the cyclic stability increased by 75%, significantly improving the stability of the Cu-based catalyst. This performance evolution indicates that the introduction of La achieves a dynamic balance between intrinsic activity and durability in catalyst design, and its mechanism can be systematically analyzed from multiple dimensions, including structure, electronics, and mass transfer.

[0061] Crystal structure analysis shows that ( Figure 1 ), La 3+ For Fe 3+The isomorphous substitution induced lattice distortion in the LDHs layers. X-ray diffraction (XRD) patterns showed a 0.3° shift in the diffraction peaks of the ZnO(003) plane to a lower angle, confirming the increase in charge density of the layers. This structural perturbation affects catalytic performance through two pathways: firstly, lattice stress leads to a decrease in the dispersion of the active metal Cu, thereby reducing initial activity; secondly, the mechanical strength of the layers is enhanced, effectively suppressing the aggregation and shedding of active components during cycling. Furthermore, EDS surface scanning revealed that La species not incorporated into the layers are distributed on the catalyst surface as La2O2(CO3) nanoparticles, reducing the sintering rate of Cu nanoparticles through physical isolation.

[0062] Cyclic kinetic studies showed that the main causes of the sharp decrease in activity of S-Cu / ZnFe-LDHs after the fourth cycle included: (1) chemisorption of carbon deposit precursors at Cu active sites; and (2) surface hydroxylation induced by isopropanol solvent under high-pressure H2 conditions (the proportion of hydroxyl oxygen in the XPS O1s peak increased from 28.5% to 37.4%). La doping delayed the deactivation process through a dual mechanism: firstly, the oxyphilic properties of surface La species preferentially captured hydroxyl radicals in the reaction medium, inhibiting the oxidation of Cu sites; secondly, the improvement of surface hydrophilicity promoted the desorption of carbon deposit precursors.

[0063] Comprehensive characterization results indicate that the synergistic mechanism of La involves three dimensions:

[0064] (1) The structural anchoring effect can anchor Cu on the layer through the synergistic effect of layer doping and surface loaded phase, and the Cu loading can be increased from 4.53% to 4.74%;

[0065] (2) The electronic regulation effect keeps Cu in a low valence state through charge redistribution, which can maintain catalytic activity and enhance resistance to poisoning.

[0066] (3) The mass transfer optimization effect is achieved by increasing the proportion of mesoporous materials, which makes the diffusion of reactants smoother.

[0067] The coupling of these effects ultimately enabled multi-objective optimization of activity, stability, and selectivity in catalyst design, providing a new theoretical basis for the application of LDHs-based catalysts in the field of biomass conversion.

[0068] 3.3 Recyclability Research

[0069] In the characterization of the La-Cu / ZnFe-LDHs catalyst after seven cycles of furfural hydrogenation, combined scanning electron microscopy (SEM) analysis revealed its unique structural stabilization mechanism. This was achieved by characterizing the dual stabilizing effect of the La species: on the one hand, EDS surface scanning revealed the unique structural stabilization mechanism of La. 3+The elemental content in the layer reached 3.95%; on the other hand, surface La2O2(CO3) nanoparticles observed by SEM (TEM confirmed to have 0.17 nm lattice fringes) formed a physical protective layer. Figure 4 This reduces the corrosion rate of the reaction medium on the plates. This synergistic stabilization mechanism of structure and morphology increases the stability of the crystal phase during long-term catalyst operation, thereby ensuring the continued availability of active sites.

[0070] In the characterization of the La-Cu / ZnFe-LDHs catalyst after seven cycles, the combined analysis of SEM and XPS revealed its unique structure-electron synergistic stabilization mechanism. Figure 7 , Figure 8 Morphological evolution analysis revealed that the fresh catalyst surface exhibited a layered structure at the 500 nm scale, accompanied by a uniform distribution of 20-50 nm La2O2(CO3) nanoparticles. After seven cycles, 200 nm resolution SEM images showed only slight curling at the edges of the layers (radius of curvature increased from 5.2 μm to 7.8 μm), with no large-area peeling or porous structures observed, and the La particle size maintained a narrow distribution characteristic of 18-55 nm. In contrast, undoped S-Cu / ZnFe-LDHs showed significant interlayer exfoliation after only four cycles, with the average Cu nanoparticle size increasing from 5.2 nm to 12.7 nm. This improved morphological stability is attributed to the dual pinning effect of the La species: firstly, the La 3d binding energy shift (Δ=+0.2eV) detected by XPS confirms the formation of La-O-Zn interfacial bonds, and this strong covalent interaction enhances the migration activation energy of Cu nanoparticles; secondly, the physical isolation effect of La2O2(CO3) nanoparticles keeps the average spacing between Cu particles above 3.5nm, effectively suppressing the Ostwald ripening process under high temperature and high pressure.

[0071] Electronic state stability analysis shows that the valence state distribution of Cu after cycling exhibits dynamic equilibrium characteristics. XPS peak fitting results indicate that ( Figure 8 Cu in the Cu 2p region 2+ The proportion changed from 51.1% to 61.7%, Cu 0 / + The percentage changed from 48.9% to 38.3%, with an overall change range of only about 10%. This phenomenon is related to Cu. 2+ / Cu 0 It is related to the buffering mechanism of redox oscillations. La 3+The strong electron-trapping ability of Cu maintains the stability of Cu active sites in the long term through two pathways: First, charge transfer occurs through the La-OM interface, causing the d-band center of Cu to shift downward, which reduces the excessive adsorption of reaction intermediates; second, the hydroxyl groups of La2O2(CO3) on the surface preferentially consume reactive oxygen species through the proton-coupled electron transfer (PCET) mechanism. This synergistic effect of the two means that the average valence state of Cu nanoparticles after cycling is still close to the initial level.

[0072] The valence state evolution of Fe species further reveals the structure-electron synergy effect. Analysis shows that after cycling, Fe... 2+ The proportion rebounded from an initial 13.4% to 29.4%, indicating that Fe... 3+ / Fe 2+ Redox pairs act as electron buffers in the reaction. According to relevant literature, La doping induces the formation of Fe-O-La charge transport channels, which promote rapid electron transfer by reducing electron migration resistance. The lattice oxygen (O) in the O 1s spectrum... Ⅰ The stability of the oxygen vacancy percentage (70.2% after cycling vs. 61.8% initially) further corroborates the integrity of the oxygen lattice, indicating that oxygen vacancies did not accumulate significantly during long-term reactions.

[0073] Mesoscale elemental distribution analysis showed that the spatial distribution of La, Cu, Zn, and Fe after cycling was highly consistent with the initial state, with no elemental segregation. The percentage of La content decreased slightly from 3.95% to 3.64%, indicating that the strong chemical bond between La and the support effectively suppressed the leaching effect.

[0074] 4. Conclusion

[0075] This study systematically reveals the multi-scale stabilization mechanism of rare earth element La in Cu / ZnFe-LDHs layered double hydroxide catalysts and its optimizing effect on the hydrogenation of furfural to furfuryl alcohol. While maintaining the bulk structure of layered double hydroxides (LDHs), a synergistic protective network at the atomic, nanoscale, and mesoscale was constructed. At the atomic scale, La... 3+ The layer doping balances Cu through charge compensation effect. 2+ / Cu + with Fe 3+ / Fe 2+ The redox oscillations suppressed excessive reduction and deactivation of active components during hydrogen overflow. The in-situ formed La2O2(CO3) nanophase bonded to the Cu-O interface provided both steric hindrance and chemical anchoring, effectively limiting the thermal migration and sintering tendency of Cu particles. On a macroscopic scale, La-induced mesoporous structure optimization (pore size reduced from 0.21 nm to 0.18 nm) and surface area (from 107 m²) were observed. 2 / g increased to 115 m2 The uniformity of elemental distribution ( / g) and other factors synergistically enhance reactant mass transfer and accessibility of active sites. These mechanisms together increase the catalyst's cycle life from 4 to 7 times, and increase cycle stability by 75%, significantly improving the stability of Cu-based catalysts.

Claims

1. The application of a La-doped ZnFe-LDHs-stabilized Cu nanoparticle catalyst in the hydrogenation of furfural to furfuryl alcohol, characterized in that, The La-doped ZnFe-LDHs catalyst for stabilizing Cu nanoparticles uses ZnFe-LDHs as a support, Cu as the active component, and La as a modifier to prepare a catalyst with the composition La-Cu / ZnFe-LDHs. The molar ratio of Cu, La, Zn, and Fe in the catalyst is 1:(0.5-2):(10-15):(4-6). La is partially doped into the ZnFe-LDHs layers and partially distributed on the surface of the support as La2O2(CO3) nanoparticles. The preparation method of the La-doped ZnFe-LDHs stabilized Cu nanoparticle catalyst includes the following steps: (1) Preparation of precursor: Copper nitrate, lanthanum nitrate, zinc nitrate and ferric nitrate were dissolved in deionized water in proportion to obtain solution A; sodium hydroxide and anhydrous sodium carbonate were dissolved in deionized water in proportion to obtain solution B; under vigorous stirring, solution A and solution B were slowly added dropwise to deionized water, and after ultrasonic oscillation, the mixture was transferred to a reaction vessel, aged, cooled, and separated to obtain a reddish-brown solid product; finally, the product was dried and ground to obtain a bulk-doped catalyst precursor material. (2) Catalyst preparation: The obtained precursor material was heated to 450°C at a rate of 5°C / min in a N2 atmosphere and held for 2 hours. Then, the atmosphere was switched to H2 and the reduction was continued at 400°C for 2 hours to obtain the catalyst.

2. The application according to claim 1, characterized in that, The catalyst contains Cu, La, Zn, and Fe in a molar ratio of 1:1:13:5; the Cu nanoparticles are loaded onto the surface of the support with a loading of 4-5 wt%.

3. The application according to claim 1, characterized in that, The molar ratio of copper nitrate, lanthanum nitrate, zinc nitrate, and iron nitrate in step (1) is Cu:La:Zn:Fe = 1:1:13:

5.

4. The application according to claim 1, characterized in that, The mass ratio of sodium hydroxide to anhydrous sodium carbonate in step (1) is 2:1.

77.

5. The application according to claim 1, characterized in that, The ultrasonic oscillation in step (1) is to continue oscillating for 10 minutes under ultrasonic conditions of 300W.

6. The application according to claim 1, characterized in that, The aging process in step (1) involves aging at 100-120℃ for 18-24 hours, and the drying process involves drying the product in an oven at 60℃ for 12 hours.

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