Cu@metal oxide composite interface catalyst with wide hydrogen-acetylene ratio window, preparation method and application thereof

Abstract

The application discloses a Cu@ metal oxide composite interface catalyst with a wide hydrogen acetylene ratio window, a preparation method and application thereof. A Cu@ metal oxide binary synergistic composite interface system is constructed, a high-dispersion nano Cu is used as an active core, a metal oxide is used as a continuous coating shell layer, through a core-shell interface strong electronic interaction, precise regulation of valence state distribution of Cu active sites and controllable construction of shell layer oxygen vacancy concentration are realized, a selective mass transfer channel of acetylene preferential adsorption and ethylene rapid desorption is formed, over-hydrogenation of ethylene and catalyst carbon deposition and sintering deactivation are inhibited from a reaction mechanism level. The preparation method of co-precipitation complexation-high temperature calcination-low temperature reduction is adopted, the core-shell interface structure can be precisely regulated, the process steps are simple and controllable, no noble metal component is added, raw materials are easy to obtain, production cost is low, and the production is easy to be industrialized and scaled up.

Description

Technical Field

[0001] This invention relates to the field of petrochemical ethylene purification and selective hydrogenation catalysis of alkynes, and particularly to a Cu@metal oxide composite interface catalyst with a wide hydrogen-to-alkynyl ratio window, its preparation method, and its application. Background Technology

[0002] Ethylene is a core raw material in modern petrochemicals, and its yield and quality directly determine the quality of downstream key chemical products such as polyolefins and ethylene glycol. Polymerization-grade ethylene has extremely stringent requirements regarding impurity content, especially acetylene, which must be reduced to below 1 ppm by volume. Otherwise, it will severely affect the stability of the polymerization reaction and lead to product performance degradation. Therefore, ethylene purification is a crucial link in the petrochemical industry chain. Among various ethylene purification technologies, selective hydrogenation of acetylene has become the mainstream technology for industrial ethylene purification due to its simplicity, low energy consumption, and wide applicability. Currently, catalysts widely used in industry are mainly divided into two categories: one is noble metal catalysts (such as Pd-based and Pt-based catalysts), and the other is Cu-based catalysts. While precious metal catalysts possess excellent acetylene hydrogenation activity and stability, achieving high acetylene conversion rates under a wide range of reaction conditions, their scarcity and high cost, coupled with the tendency for excessive ethylene hydrogenation under high hydrogen-to-acetylene ratio conditions, leading to decreased product yield, make them difficult to apply on a large scale in continuous industrial production. In contrast, Cu-based catalysts, due to their low cost, good ethylene selectivity, and readily available raw materials, are ideal non-precious metal candidates for acetylene semi-hydrogenation (CN120479425A).

[0003] Although Cu-based catalysts offer significant cost advantages in industrial applications, the continuous development of the modern ethylene industry has led to increased fluctuations in feed gas conditions and more complex impurity compositions. Existing industrial Cu-based catalysts are gradually revealing three major technical bottlenecks, severely restricting the efficiency and quality of ethylene purification and widening the performance gap between them and precious metal catalysts:

[0004] 1) Narrow tolerance window for hydrogen-to-acetylene ratio: The hydrogen-to-acetylene ratio of industrial ethylene cracking gas fluctuates significantly due to factors such as feedstock composition and cracking process. Existing Cu-based catalysts have extremely poor adaptability to hydrogen-to-acetylene ratios and cannot adapt to such volatile operating conditions. Under low hydrogen-to-acetylene ratio conditions, the catalyst activity is insufficient, and the acetylene conversion rate is difficult to meet the purity requirements of polymerization-grade ethylene, requiring additional reaction steps or catalyst dosage. Under high hydrogen-to-acetylene ratio conditions, the catalyst is prone to triggering excessive hydrogenation of ethylene, generating byproducts such as ethane. This not only causes a serious loss in ethylene product yield but also increases the energy consumption of subsequent separation processes. This deficiency is more prominent compared to the wide operating condition adaptability of precious metal catalysts.

[0005] 2) Poor resistance to impurities: In addition to acetylene, ethylene, and hydrogen, industrial ethylene cracking gas also contains trace amounts of impurities such as CO and sulfides (e.g., H2S, organic sulfur). These trace impurities are easily adsorbed onto the active sites of Cu-based catalysts, leading to catalyst poisoning and deactivation, causing a rapid decline in their activity and selectivity. To maintain normal operation of the unit, frequent catalyst switching or catalyst regeneration is required, which not only increases production costs and labor intensity but also affects the continuity of production. In contrast, noble metal catalysts (such as Pd-based catalysts), after modification, typically possess stronger resistance to impurity poisoning, which is one of their core advantages.

[0006] 3) Insufficient stability: The selective hydrogenation of acetylene is accompanied by exothermic reactions. Under prolonged high-temperature conditions, Cu active sites in Cu-based catalysts are prone to migration and aggregation, leading to a reduction in the number of active sites and decreased dispersibility. Simultaneously, carbon deposits generated during the reaction cover the catalyst surface, further clogging active sites, ultimately resulting in rapid catalyst activity decay and a shortened operating cycle. In contrast, noble metal catalysts, due to their higher metal bond energies, exhibit superior high-temperature stability, are less prone to active site aggregation and carbon deposition deactivation, and have a much longer operating cycle than traditional Cu-based catalysts.

[0007] Currently, most of the publicly available research on related technologies at home and abroad focuses on the modification of Cu-based catalysts (such as doping with metal elements and regulating the structure of active sites) (Chemical Engineering Science (2025): 122819.)(CN119186592A) or the optimization of supports (such as selecting novel porous supports and regulating the pore structure of supports) (Nature communications 10.1(2019): 4431), attempting to make up for their performance defects. However, existing modification schemes can often only improve one specific performance, and it is difficult to achieve synergistic improvement of ultra-wide hydrogen-to-acetylene ratio window, high acetylene conversion rate, high ethylene selectivity, long-term resistance to poisoning, and resistance to sintering at the same time. They cannot fully meet the actual needs of industrial ethylene plants with large fluctuations in feed gas, complex impurities, and continuous and stable operation. Furthermore, although precious metal catalysts have advantages in activity, stability, and resistance to impurities, their high cost limits their large-scale industrial application. Therefore, developing Cu-based acetylene semi-hydrogenation catalysts that combine a wide hydrogen-to-acetylene ratio window, high selectivity, strong resistance to poisoning, long lifespan, and controllable cost, and narrowing the performance gap with precious metal catalysts through reasonable modification strategies, is of great industrial value and practical significance for promoting the quality and efficiency improvement, reducing production costs, and enhancing core competitiveness in the ethylene industry. Summary of the Invention

[0008] This invention addresses the technical limitations of existing Cu-based acetylene semi-hydrogenation catalysts by providing a Cu@metal oxide composite interface catalyst with a wide hydrogen-to-acetylene ratio window, its preparation method, and its application. This catalyst achieves efficient acetylene conversion and highly selective ethylene production under ultra-wide hydrogen-to-acetylene ratio conditions, while significantly improving resistance to poisoning, carbon deposition, and sintering, making it suitable for long-term stable industrial operation.

[0009] Unlike existing Cu-based catalysts that use only Cu 0 This invention, based on a Cu / support structure dominated by an active phase or weakly interacting phase, achieves strong electronic coupling between the Cu active component and the metal oxide shell by constructing a Cu@metal oxide core-shell composite interface. This structure can directionally stabilize high Cu content at the interface. + Species, and retain an appropriate amount of Cu 0 This species avoids the Cu content in traditional Cu-based catalysts. 0 Problems such as oligomerization, cracking, and carbon buildup of acetylene caused by excessively high proportions.

[0010] Meanwhile, the metal oxide shell not only acts as a physical protective layer to inhibit the sintering of Cu nanoparticles, but also participates in hydrogen activation and reactant adsorption regulation through oxygen vacancies. This allows the catalyst to maintain high acetylene conversion capacity at low hydrogen-to-acetylene ratios, while inhibiting excessive hydrogenation of ethylene at high hydrogen-to-acetylene ratios. Therefore, this invention is not a traditional supported Cu catalyst, but a Cu-based composite interfacial catalyst that combines electronic regulation, interfacial confinement, and selective mass transfer functions.

[0011] The specific technical solution is as follows:

[0012] One objective of this invention is to provide a Cu@metal oxide composite interfacial catalyst with a wide hydrogen-to-acetylene ratio window, featuring a core-shell coated structure: using highly dispersed nano-Cu... 0 The active core consists of a continuous coating layer of metal oxide, forming a Cu@metal oxide binary synergistic composite interface. The metal oxide is either MgO or a Mg-Co composite oxide, and the nano-Cu... 0 The highly dispersed state of the core allows Cu active sites to exist at the nanoscale, with a molar ratio of Cu to shell metal elements of 1.5-4:1, and the shell thickness can be controlled at the atomic level.

[0013] This invention specifically constructs a Cu@metal oxide binary synergistic composite interface system, with highly dispersed nano-Cu as the active core and metal oxide as the continuous coating shell. Analysis of catalytic performance and characterization results reveals that this structure possesses unique core-shell interface contact and physical coating confinement effects. It not only effectively anchors Cu nanoparticles and inhibits their migration and sintering at high temperatures and during the reaction process, but also synergistically optimizes the adsorption and desorption kinetics of reactants on the catalyst surface. At low temperatures, it exhibits both excellent hydrogen activation capability and ethylene desorption selectivity, thereby significantly inhibiting excessive hydrogenation of ethylene and catalyst deactivation due to carbon deposition at the mechanistic level.

[0014] The second objective of this invention is to provide a method for preparing the above-mentioned catalyst, which adopts a co-precipitation complexation-high temperature calcination-low temperature reduction route. This method can precisely control the core-shell structure, coating thickness and interface electronic state. The process is simple, free of precious metals, has low raw material cost, good reproducibility and is easy to scale up industrially.

[0015] Specifically, it includes the following steps:

[0016] (1) Dissolve soluble copper salt and shell metal nitrate in an organic solvent to obtain solution A, and dissolve oxalic acid in ethanol to obtain solution B;

[0017] (2) After A and B are dissolved by stirring, B is added dropwise to A. Stir at room temperature for 2-4 hours to complete co-precipitation and complexation, then centrifuge and wash.

[0018] (3) The washed precipitate was dried in an oven at 60~80℃ for 8~12h, and then calcined at 300~600℃ for 2~4h in air atmosphere at a heating rate of 5~10℃ / min. After natural cooling to room temperature, the composite oxide precursor was obtained.

[0019] (4) The composite oxide precursor was reduced in H2 / Ar mixed gas at 200-250℃ for 1-3h to obtain Cu@metal oxide composite interface catalyst.

[0020] Furthermore, the copper salt in step (1) is copper nitrate trihydrate, and the organic solvent is anhydrous ethanol; the volume fraction of H2 in step (4) is 5%, and the reduction temperature is 220℃.

[0021] The third objective of this invention is to provide the application of the above-mentioned catalyst in the industrial acetylene semi-hydrogenation to polymer-grade ethylene.

[0022] 1) Applicable operating conditions: atmospheric pressure, 120~180℃, space velocity ≤18000mL / (g·h).

[0023] 2) Hydrogen-to-acetylene ratio window: 0.3~8, preferably 0.3-4.

[0024] 3) Low hydrogen-to-acetylene ratio performance: When the hydrogen-to-acetylene ratio is 0.3, the acetylene conversion rate is ≥90% and the ethylene selectivity is ≥80%.

[0025] 4) Stability: In industrial cracked gas containing trace amounts of CO and sulfides, it can operate stably for ≥48 h with an activity decay rate of <3%.

[0026] The beneficial effects of this invention are as follows:

[0027] The catalyst of this invention breaks through the performance boundaries of traditional Cu-based catalysts, achieving a synergistic effect of wide window, high activity, high selectivity, strong resistance to poisoning, and long lifespan. It can adapt to the needs of industrial ethylene plants with large fluctuations in feed gas, complex impurities, and continuous production, and has significant industrial value. Attached Figure Description

[0028] Figure 1 The conversion and selectivity of Cu@MgO catalysts with different molar ratios in Example 2;

[0029] Figure 2 The optimal molar ratio, conversion rate, and selectivity of the Cu@MgO catalyst at different temperatures were determined in Example 3.

[0030] Figure 3 Stability testing of the Cu@MgO catalyst at the optimal molar ratio and temperature in Example 4;

[0031] Figure 4 HAADF-STEM image analysis of the Cu@metal oxide sample prepared in Example 2;

[0032] Figure 5 The XRD patterns and standard card comparisons of the Cu@MgO composite interface catalyst prepared in Example 2 after calcination, reduction and induced reaction are shown.

[0033] Figure 6 This describes the poisoning effect on the catalyst after introducing a gas containing trace amounts of CO and sulfides in Example 6.

[0034] Figure 7 This section describes the performance of the catalyst under a wide hydrogen-to-acetylene ratio and the catalyst recovery process in Example 7. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. These embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. All reagents used in the present invention are commercially available analytical grade reagents, and the equipment used is conventional laboratory equipment.

[0036] Experimental materials and instruments

[0037] Raw materials: Copper nitrate trihydrate (Cu(NO3)2·3H2O); magnesium nitrate hexahydrate (Mg(NO3)2·6H2O); cobalt nitrate hexahydrate (Co(NO3)2·6H2O); aluminum nitrate hexahydrate (Al(NO3)3·6H2O); zirconium nitrate pentahydrate (Zr(NO3)4·5H2O); cerium nitrate hexahydrate (Ce(NO3)3·6H2O), ferrous nitrate tetrahydrate (Fe(NO3)2·4H2O), chromium nitrate hexahydrate (Cr(NO3)3·6H2O); deionized water (laboratory-made, conductivity ≤18.2MΩ·cm); a mixture of acetylene, oxygen (purity 99.999%), and nitrogen (purity 99.999%), all of which are industrial-grade standard gases.

[0038] Instruments: muffle furnace; electric thermostatic drying oven; electronic analytical balance; ultrasonic cleaner; fixed-bed microreactor; online gas chromatograph (equipped with flame ionization detector (FID) and thermal conductivity detector (TCD)).

[0039] Example 1: Preparation and Performance Testing of Different Cu@Metal Oxide Composite Interface Catalysts

[0040] In this embodiment, Cu@metal oxide composite interface catalysts with different metal oxide shells were prepared by using Cu(NO3)2·3H2O and metal nitrate in a molar ratio of 4:1, to explore the influence of shell type on catalyst structure and performance.

[0041] Copper nitrate trihydrate was used as the Cu active core precursor, and magnesium nitrate hexahydrate and cobalt nitrate hexahydrate were selected as metal oxide shell precursors, denoted as MgO and Co3O4 shell systems, respectively.

[0042] Seven groups of Cu(NO3)2·3H2O were weighed out, 0.04 mol of each group, and mixed with 0.01 mol Al(NO3)3·6H2O, 0.01 mol Zr(NO3)4·6H2O, 0.01 mol Mg(NO3)2·6H2O, 0.01 mol Co(NO3)2·6H2O, 0.01 mol Ce(NO3)3·6H2O, 0.01 mol Fe(NO3)2·6H2O, and 0.01 mol Cr(NO3)3·6H2O, respectively. 25 mL of anhydrous ethanol was added to each mixture, and the mixture was stirred until completely dissolved to obtain seven groups of solutions A (denoted as A1, A2, A3, A4, A5, A6, and A7, respectively).

[0043] Weigh out 7 portions of 0.05 mol oxalic acid, add 15 mL of anhydrous ethanol to each, and stir until completely dissolved to prepare 7 groups of solution B, which correspond one-to-one with solution A above;

[0044] At room temperature, the seven groups of solution B were added dropwise to the corresponding solution A at a rate of 1 mL / min. After the addition was completed, the mixture was stirred at room temperature for 2 h to complete the co-precipitation complexation reaction.

[0045] The above reaction solutions were placed in centrifuges and centrifuged at 8000 rpm for 3 min. They were then washed three times with anhydrous ethanol to remove unreacted precursors and impurities.

[0046] The precipitate after centrifugation was placed in an electric thermostatic drying oven and dried at 80℃ for 12 hours to completely remove moisture.

[0047] The dried samples were placed in alumina crucibles, placed in muffle furnaces, heated at a rate of 5℃ / min, heated to 450℃ in air atmosphere, calcined at constant temperature for 2 h, and then naturally cooled to room temperature.

[0048] The calcined sample was placed in a reduction furnace, and a 5 vol% H2 / Ar mixed gas was introduced. The sample was reduced at 220℃ for 2 h to obtain seven catalysts: Cu@Al2O3, Cu@ZrO2, Cu@MgO, Cu@Co3O4, Cu@CeO2, Cu@Fe2O3, and Cu@Cr2O3.

[0049] The prepared catalyst was ground through a 60-80 mesh sieve. 0.1 g of the catalyst was mixed with 0.2 g of quartz sand and added to a fixed bed. Its conversion rate and selectivity were tested at 120 °C, hydrogen-to-acetylene ratio of 2:1 and space velocity of 18000 mL / (g·h). The results are shown in Table 1 below.

[0050] Table 1. Summary of the effects of different catalysts on acetylene conversion and ethylene selectivity

[0051]

[0052] Table 1 shows that, under the same reaction conditions, different metal oxide supports significantly affect the acetylene hydrogenation performance of Cu-based composite catalysts. Among them, the Cu@Co3O4 catalyst achieved an acetylene conversion of 79.56% and an ethylene selectivity of 91.56%, significantly higher than that of Cu@Al2O3, Cu@ZrO2, Cu@MgO, Cu@CeO2, Cu@Fe2O3, and Cu@Cr2O3 catalysts, while maintaining high ethylene selectivity, demonstrating a superior activity-selectivity match. However, its stability was poor, deactivating after several hours of reaction. The Cu@MgO and Cu@Al2O3 catalysts also exhibited good overall performance, with acetylene conversions of 60.08% and 45.86%, and ethylene selectivities of 93.25% and 94.08%, respectively. The Cu@Fe2O3 and Cu@CeO2 catalysts showed high ethylene selectivity (95.92% and 95.23%, respectively), but relatively low acetylene conversions. In summary, Cu@MgO catalyst exhibits high acetylene conversion capacity, good ethylene selectivity, and stability, making it a preferred Cu@metal oxide composite catalyst for this invention.

[0053] Example 2: Preparation and Performance Testing of Cu@MgO Composite Interface Catalysts with Different Molar Ratios of Cu to Metal Oxides

[0054] In this embodiment, MgO was selected as the optimal metal oxide shell (obtained from Example 1) to prepare Cu@MgO catalysts with different molar ratios of Cu(NO3)2·3H2O to Mg(NO3)2·6H2O. The specific steps are as follows:

[0055] Preparation of Cu to Mg molar ratio: Weigh the corresponding masses of the two nitrates according to the stoichiometric ratios of Cu(NO3)2·3H2O and Mg(NO3)2·6H2O of 1.5:1, 2:1, 2.5:1 and 3:1 respectively, add 25 mL of anhydrous ethanol to each, stir until dissolved, and prepare 4 groups of A solution (referred to as A8~A11 solutions respectively).

[0056] Preparation of solution B: Weigh out oxalic acid equal to the total number of moles of metal ions in each group of solution A, add 15 mL of anhydrous ethanol to each, stir until dissolved, and prepare 4 groups of solutions B, which correspond one-to-one with the above solutions A.

[0057] Co-precipitation complexation: At room temperature, each group of solution B was added dropwise to the corresponding solution A at a rate of 1 mL / min, and stirring was continued at room temperature for 2 hours after the addition was completed;

[0058] Centrifugation and washing: Centrifuge at 8000 rpm for 3 min, wash 3 times with anhydrous ethanol to remove impurities;

[0059] Drying treatment: Place the precipitate in an electric thermostatic drying oven and dry at 80℃ for 12 hours to remove moisture;

[0060] Calcination and curing: Place the dried sample in an alumina crucible, put it in a muffle furnace, and calcine it at 450°C at a rate of 5°C / min under an air atmosphere for 2 hours. Then, let it cool naturally to room temperature.

[0061] Reduction treatment: 5 vol% H2 / Ar mixed gas was introduced and reduced at 220 ℃ for 2 h to obtain Cu@MgO catalysts with different molar ratios, which were named as sample 1 (1.5:1), sample 2 (2:1), sample 3 (2.5:1), and sample 4 (3:1) respectively.

[0062] Post-processing: The above catalyst was ground through a 60-80 mesh sieve. 0.1 g of catalyst was mixed with 0.2 g of quartz sand and placed in a quartz tube for performance testing (same as in Example 1). The results are shown below. Figure 1 As shown.

[0063] Depend on Figure 1 It was found that under the reaction conditions of 120℃ and a hydrogen-to-acetylene ratio of 2:1, Cu@MgO catalysts with different Cu / Mg molar ratios exhibited significant performance differences. As the Cu / Mg molar ratio increased from 1.5:1 (Sample 1) to 3:1 (Sample 4), the acetylene conversion gradually decreased from approximately 62% to approximately 44%, while the ethylene selectivity significantly increased from approximately 92% to approximately 99%. Specifically, when the molar ratio was 2.5:1 (Sample 3), the acetylene conversion was 52%, and the ethylene selectivity reached 98%; when the molar ratio was 3:1 (Sample 4), the ethylene selectivity was as high as 99%, but the conversion was only 44%. Overall, the catalyst with a molar ratio of 2:1 (Sample 2) achieved a better balance between conversion (approximately 64%) and selectivity (approximately 93%). These results indicate that by precisely controlling the Cu / Mg molar ratio, the acetylene hydrogenation activity and ethylene selectivity of the Cu@MgO catalyst can be effectively adjusted, providing a feasible control strategy for achieving high-selectivity ethylene production.

[0064] Example 3 Performance testing of Cu@MgO composite interface catalyst at different temperatures

[0065] This embodiment uses sample 2 (Cu@MgO, Cu to Mg molar ratio 2:1, calcined at 450℃) prepared in Example 2 as the research object to investigate the effect of different reaction temperatures on the acetylene semi-hydrogenation catalytic performance of the Cu@MgO composite interface catalyst, and to determine the optimal reaction temperature range of the catalyst. The specific test steps are as follows:

[0066] Reaction apparatus and conditions: A fixed-bed microreactor was used for testing to simulate industrial ethylene cracking gas conditions. Specific parameters are as follows:

[0067] Catalyst loading: 0.1 g, which is thoroughly mixed with 0.2 g of quartz sand (60-80 mesh) and then loaded into the quartz tube of the reactor (inner diameter 8 mm).

[0068] The reacting gases are a mixture of C2H2-C2H4-H2-N2, wherein the volume fraction of H2 is 0.676%, the volume fraction of C2H2 is 0.329%, the volume fraction of C2H4 is 32.987%, and N2 is the equilibrium gas.

[0069] Reaction pressure: Atmospheric pressure;

[0070] Reaction temperatures were set at 120℃, 140℃, 160℃, and 180℃, respectively.

[0071] Gas hourly space velocity: 18000 mL / (g·h);

[0072] Product detection: The reaction products were detected in real time by an online gas chromatograph. The FID detector detected hydrocarbons such as acetylene, ethylene, and ethane, and the TCD detector detected gases such as hydrogen and nitrogen. The acetylene conversion rate and ethylene selectivity were calculated using the area normalization method. Sampling and detection were started after each temperature point had been running stably for 1 hour. The tests were performed in parallel for 3 times and the average value was taken.

[0073] With increasing reaction temperature, the acetylene conversion rate of the Cu@MgO catalyst gradually increased, while the ethylene selectivity showed a trend of initially stabilizing and then significantly decreasing. At 120℃, the acetylene conversion rate was 64.95%, and the ethylene selectivity was the highest (92.4%). At 140℃, the acetylene conversion rate reached 100%, and the ethylene selectivity remained at 88.4%, indicating the best overall catalytic performance. When the temperature increased to 180℃, although the acetylene conversion rate was 100%, the ethylene selectivity decreased to 80.7%, while the ethane selectivity increased significantly, indicating that high temperatures exacerbate the excessive hydrogenation side reaction of ethylene. In summary, the optimal reaction temperature for this Cu@MgO composite interfacial catalyst is 140℃. (See results below.) Figure 2 As shown, it can maintain excellent catalytic performance in the range of 120~140℃, which is suitable for the temperature fluctuation requirements of industrial production.

[0074] Example 4: Stability Test of Cu@MgO Composite Interface Catalyst

[0075] In this embodiment, the Cu@MgO catalyst (sample 2 prepared in Example 2) was used as the optimal catalyst. A 100-hour long-term stability test was conducted under the optimal reaction conditions of Example 3 (the difference being that the long-term performance of the catalyst was examined; this catalyst was tested in a four-channel fixed-bed reactor at a temperature below 140°C, approximately 130°C). The test results are as follows: Figure 3As shown, during the 100 h reaction process, the acetylene conversion rate of the Cu@MgO composite interface catalyst slowly decreased from 94.8% to 88.5%, a decrease of only 6.3 percentage points, while the ethylene selectivity remained basically between 81.0% and 84.5%, without significant decrease, thus achieving long-term stable operation of the catalyst.

[0076] Example 5: Microstructure and Phase Characterization of Cu@MgO Core-Shell Catalyst

[0077] The microstructure and phase stability of the Cu@MgO catalyst prepared in Example 2 (Sample 2) were analyzed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray diffraction (XRD).

[0078] HAADF-STEM structural analysis: HAADF-STEM images of the catalyst are shown below. Figure 4 As shown in the image, the core-shell coating microstructure of the catalyst is clearly visualized: highly dispersed Cu nanoparticles serve as the active core, completely coated by a continuous and uniform MgO oxide shell. This physically confined structure effectively prevents the migration and aggregation of active Cu nanoparticles at high temperatures and during the reaction process.

[0079] XRD phase evolution and stability analysis: Comparison of XRD spectra and standard cards of the catalyst under different treatment states (after calcination, after reduction, after induced reaction) as follows: Figure 5 As shown.

[0080] Phase transformation: After calcination, the sample exhibited a phase structure of standard CuO (PDF#97-008-7124) and MgO; after reduction at 220℃, the CuO diffraction peaks completely transformed into metallic Cu. 0 The characteristic diffraction peaks of (PDF#00-004-0836) prove that the active phase has been successfully reduced.

[0081] Structural stability verification: Comparison of XRD patterns after reduction and after long-term hydrogenation (induced reaction) revealed that the full width at half maximum (FWHM) of the diffraction peaks of elemental Cu did not narrow significantly after the reaction, and the peak shapes remained highly consistent. This indicates that the coating shell successfully suppressed the sintering and growth of the Cu active phase during the hydrogenation reaction, verifying the high stability of the catalyst's microstructure.

[0082] In summary, HAADF-STEM characterization directly confirms the unique continuous core-shell coating morphology of the catalyst of this invention, while XRD patterns further demonstrate the complete reduction evolution of the precursor and the high stability of Cu grains before and after the reaction at the phase level. The synergistic confirmation of HAADF-STEM and XRD data explains the microscopic reasons for the excellent anti-sintering ability and long-term stability of the catalyst of this invention from both structural and phase perspectives.

[0083] Example 6: Impurity resistance test of Cu@MgO composite interface catalyst

[0084] In this embodiment, the Cu@MgO catalyst (sample 2 prepared in Example 2) was used as the optimal catalyst. The catalyst's resistance to impurities was tested under the optimal reaction conditions of Example 3 to examine its anti-poisoning performance. The test results are as follows: Figure 6 As shown, the Cu@MgO composite interface catalyst did not significantly decrease the acetylene conversion and ethylene selectivity during the reaction process with 5 mL / min of 5 vol% CO.

[0085] Example 7: Performance Testing of Acetylene Semi-Hydroxygenation Catalyst with a Wide Hydrogen-to-Yetyne Ratio Window Cu@Metal Oxide Catalyst

[0086] In this embodiment, Cu@MgO catalyst (sample 2 prepared in Example 2) was used as the optimal catalyst. Under the reaction conditions of Example 3 (reaction temperature 140 °C, atmospheric pressure), a single-channel fixed-bed reactor was used for testing to investigate the effect of different hydrogen-to-acetylene ratios on catalyst performance and the catalyst's resistance to changing operating conditions and its recovery ability. The test results are shown in Figure 7. The performance changes shown by the curves are the steady-state response results of the catalyst after the operating conditions were adjusted.

[0087] When the H2:C2H2 ratio is 2:1, the catalyst exhibits excellent initial activity, with acetylene conversion remaining at 100% and ethylene selectivity at approximately 80%. As the hydrogen-to-acetylene ratio is gradually decreased from 8:1 to 4:1, the acetylene conversion remains constant at 100%. Due to the reduction in excess hydrogen, over-hydrogenation is effectively suppressed, and the ethylene selectivity significantly increases from 35% at 8:1 to 65% at 4:1. As the hydrogen-to-acetylene ratio continues to decrease to 1:1 and 0.3:1, the acetylene conversion slightly decreases (remaining at approximately 95% and 90%, respectively), while the ethylene selectivity further increases to over 80%. These results indicate that the Cu@MgO catalyst of this invention possesses an extremely wide hydrogen-to-acetylene ratio operating window and exhibits excellent reversible recovery capability and structural stability after experiencing fluctuations in high / low hydrogen-to-acetylene ratios.

[0088] Cu / MgO catalysts prepared by different methods

[0089] Comparative Example 1: Traditional Impregnation Method for Supported Cu / MgO Catalysts

[0090] This comparative example illustrates the effect of conventional supported catalysts on the hydrogenation performance of acetylene.

[0091] Raw material preparation: Weigh 0.01 mol of commercial magnesium oxide (MgO) powder and disperse it in 25 mL of anhydrous ethanol; separately weigh 0.02 mol of copper nitrate trihydrate and dissolve it in 25 mL of anhydrous ethanol to prepare copper nitrate impregnation solution (maintaining the Cu to Mg molar ratio of 2:1, consistent with sample 2 in Example 2).

[0092] Impregnation and drying: Copper nitrate solution was added dropwise to MgO suspension using the equal volume impregnation method, and the mixture was ultrasonically impregnated at room temperature for 2 h and allowed to stand for 12 h. Subsequently, it was placed in an electric thermostatic drying oven and dried at 80 ℃ for 12 h.

[0093] Calcination and reduction: The dried sample was placed in a muffle furnace and calcined at 450℃ for 2 h in an air atmosphere at a rate of 5℃ / min. After natural cooling, it was reduced at 220℃ for 2 h in a 5 vol% H2 / Ar mixed gas to obtain a conventional supported Cu / MgO catalyst, which was designated as Comparative Example 1.

[0094] Performance testing: Comparative Example 1 was tested under the test conditions of Example 3 (140 °C, atmospheric pressure, hydrogen-to-acetylene ratio 2:1, space velocity 18000 mL / (g·h)), and the results are shown in Table 2.

[0095] Comparative Example 2: Cu / MgO catalyst prepared by conventional coprecipitation method

[0096] This comparative example illustrates the effect of conventional coprecipitation without complexation precipitation control on catalytic performance. Solution preparation: Weigh 0.02 mol copper nitrate trihydrate and 0.01 mol magnesium nitrate hexahydrate (Cu / Mg molar ratio of 2:1) and dissolve them together in 50 mL of deionized water. Stir well to obtain a mixed metal salt solution.

[0097] Coprecipitation reaction: At room temperature, add 1 mol / L sodium carbonate aqueous solution dropwise to the above solution, adjust the pH of the system to 9.0, and continue stirring for 2 h to complete the coprecipitation; centrifuge and wash 3 times.

[0098] Drying, calcination and reduction: The precipitate was dried at 80 °C for 12 h, calcined at 450 °C for 2 h in an air atmosphere in a muffle furnace, and finally reduced at 220 °C for 2 h in a 5 vol% H2 / Ar mixed gas to obtain a conventional coprecipitated Cu / MgO catalyst, which is referred to as Comparative Example 2.

[0099] Performance testing: Comparative Example 2 was tested according to the test conditions of Example 3, and the results are shown in Table 2.

[0100] Table 2 Summary of performance test results of Cu@MgO obtained by different preparation processes

[0101] .

Claims

1. A Cu@metal oxide composite interfacial catalyst with a wide hydrogen-to-yne ratio window, characterized in that, It is a core-shell coated structure, including highly dispersed nano-Cu 0 The active core is formed by a continuous and uniform coating shell of metal oxide, thus forming a Cu@metal oxide binary synergistic composite interface. By leveraging strong electron interactions at the core-shell interface, precise regulation of the valence state of Cu active sites and controllable construction of shell oxygen vacancy concentration can be achieved.

2. The Cu@metal oxide composite interface catalyst with a wide hydrogen-to-yne ratio window according to claim 1, characterized in that, The metal oxide is MgO or Mg-Co composite oxide.

3. The Cu@metal oxide composite interface catalyst with a wide hydrogen-to-yne ratio window according to claim 1, characterized in that, Nano Cu 0 The highly dispersed state of the core allows Cu active sites to exist at the nanoscale, and the molar ratio of Cu to shell metal elements is 1.5-4:

1.

4. A method for preparing a Cu@metal oxide composite interface catalyst with a wide hydrogen-to-acetylene ratio window as described in any one of claims 1 to 3, characterized in that, The core-shell interface structure and coating thickness are controlled by a co-precipitation complexation-high temperature calcination-low temperature reduction process, specifically including the following steps: (1) Dissolve soluble copper salt and shell metal nitrate in an organic solvent to obtain solution A, and dissolve oxalic acid in ethanol to obtain solution B; (2) After A and B are dissolved by stirring, B is added dropwise to A. Stir at room temperature for 2-4 hours to complete co-precipitation and complexation, then centrifuge and wash. (3) The washed precipitate was dried in an oven at 60~80℃ for 8~12h, and then calcined at 300~600℃ for 2~4h in air atmosphere at a heating rate of 5~10℃ / min. After natural cooling to room temperature, the composite oxide precursor was obtained. (4) The composite oxide precursor was reduced in H2 / Ar mixed gas at 200-250℃ for 1-3h to obtain Cu@metal oxide composite interface catalyst.

5. The preparation method according to claim 4, characterized in that, The copper salt in step (1) is copper nitrate trihydrate, and the organic solvent is anhydrous ethanol; the volume fraction of H2 in step (4) is 5%, and the reduction temperature is 220℃.

6. The application of a Cu@metal oxide composite interfacial catalyst with a wide hydrogen-to-acetylene ratio window as described in any one of claims 1 to 3 in the selective hydrogenation of acetylene to polymer-grade ethylene in industrial applications, characterized in that, The process includes the following steps: a Cu@metal oxide composite interface catalyst is loaded into a fixed-bed reactor, and acetylene-containing ethylene cracking gas is subjected to acetylene semi-hydrogenation under the conditions of atmospheric pressure, reaction temperature of 100~200℃, hydrogen-to-acetylene ratio of 0.3~4, and space velocity ≤18000mL / g·h.

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