Preparation method of CuZn-based catalyst and application thereof

Abstract

This application discloses a method for preparing a CuZn-based catalyst and its application. The method for preparing the CuZn-based catalyst includes the following steps: (S1) obtaining a CuZn-based catalyst precursor; (S2) mixing the CuZn-based catalyst precursor and an additive, and dry granulating; (S3) placing the granulated sample obtained after dry granulation in a dielectric barrier plasma discharge region, and passing a dielectric gas through it for discharge treatment to obtain the CuZn-based catalyst. During the preparation process, plasma treatment is used to regulate the electron distribution of Cu species on the catalyst surface, enhancing the interaction between the active component nanoparticles, significantly improving the catalytic activity and stability of the catalyst in the hydrogenation of methyl acetate to ethanol, exhibiting excellent catalytic performance.

Description

Technical Field

[0001] This application relates to a method for preparing a CuZn-based catalyst and its application, belonging to the field of catalysts. Background Technology

[0002] Ethanol is an important chemical intermediate and organic solvent, and it is widely used in the production of bulk chemicals such as pharmaceuticals, paints, and cleaning agents. At the same time, as a fuel additive, ethanol gasoline has a high octane number and good anti-knock properties, which can significantly reduce the emission of hydrocarbons and nitrogen oxides.

[0003] Ethanol catalysis often uses Cu-based catalysts. Cu has a significant activating effect on the selective hydrogenation of carbonyl groups and, as an inexpensive transition metal, is suitable for industrial application. CN 112691674 B discloses a ZrO2 and CeO2-doped CuZnAl catalyst. First, Zr and Ce species are used to modify the Al2O3 support using a deposition precipitation method, and then the CuZn catalyst is loaded. The catalyst is tested at 230℃, 5.0 MPa, n(H2) / n(dimethyl 1,4-cyclohexanedicarboxylate) = 140, and WHSV = 0.3 h⁻¹. 1 Under the given reaction conditions, the hydrogenation conversion rate of dimethyl 1,4-cyclohexanedicarboxylate reached 99.5%, demonstrating that Cu-based catalysts have high activity for ester hydrogenation, and the interaction between Cu and Zn improves the dispersibility of Cu particles to some extent.

[0004] Cu-based catalysts often exhibit Cu-like properties in catalytic reactions such as hydrogenation. 0 and Cu + Coexisting chemical states, with Cu 0 and Cu + The increase in species and the enhanced interaction between Cu and ZnO are also considered important factors in improving the catalytic active sites. Therefore, it is crucial to enhance the synergistic effect at the copper-zinc interface, strengthen the active sites of the catalyst, and improve its activity and stability. Summary of the Invention

[0005] This invention provides a method for preparing a CuZn-based catalyst and its application. The method involves thoroughly mixing a CuZn-based catalyst precursor with graphite as an additive, followed by dry granulation to form particles of a certain strength. After plasma discharge treatment, the excellent charge conductivity of graphite allows the chemical environment altered by the plasma on the surface of the particles to migrate to the interior, activating the CuZn catalyst. 0 and Cu + The synergistic active centers work together at the interface of the CuZn-based catalyst, thereby improving the catalytic activity and stability of the catalyst in the hydrogenation of methyl acetate to ethanol.

[0006] According to the first aspect of this application, a method for preparing a CuZn-based catalyst is provided. When a sample is treated with plasma discharge, the input electrical energy couples to charged particles, which collide with the medium gas, causing ionization and dissociation, generating electrons, ions, free radicals, and excited-state atoms. This promotes the electron configuration on the surface of the Cu-based catalyst. Because graphite has good charge conductivity, it will migrate from the chemical environment altered by plasma on the particle sample surface to the interior, where Zn... 2+ Ions are Cu + Substitution generates oxygen vacancies and free ions, which excite Cu + It provides electrophilic sites, further providing catalytic active centers, making C=O readily polarizable to stabilize methyl and acetyl groups, and promoting the role of Cu. 0 The ability of Cu to dissociate and adsorb H2 enhances its ability to adsorb H2. 0 and Cu + The synergistic effect between them enhances the catalytic activity and stability of the hydrogenation reaction of methyl acetate to ethanol.

[0007] A method for preparing a CuZn-based catalyst includes the following steps:

[0008] (S1) Obtain CuZn-based catalyst precursor;

[0009] (S2) The CuZn-based catalyst precursor and the additive are mixed and then dry-granulated.

[0010] (S3) The particle sample obtained after dry granulation is placed in the dielectric barrier plasma discharge region and a dielectric gas is introduced for discharge treatment to obtain the CuZn-based catalyst.

[0011] Optionally, in step (S3), the operating power of the plasma used is 5 to 500 W;

[0012] The discharge treatment can be performed continuously or intermittently. The duration of continuous treatment is 0.1 to 5 hours, and the duration of intermittent treatment is 0.1 to 20 hours.

[0013] Optionally, in step (S3), the operating power of the plasma used is 100-200W;

[0014] The discharge treatment can be performed continuously or intermittently. The duration of continuous treatment is 0.2 to 2 hours, and the duration of intermittent treatment is 0.5 to 5 hours.

[0015] Optionally, the operating power of the plasma used is independently selected from any value of 5W, 10W, 50W, 80W, 100W, 120W, 140W, 150W, 170W, 180W, 200W, 250W, 300W, 350W, 400W, 450W, or 500W, or any value between the two.

[0016] Optionally, the duration of continuous processing is independently selected from any value among 0.2h, 0.4h, 0.5h, 0.7h, 0.8h, 1h, 1.2h, 1.5h, 1.7h, and 2h, or any intermediate value between the two.

[0017] Optionally, the duration of the intermittent treatment is independently selected from any value of 0.5h, 0.7h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or any intermediate value between the two.

[0018] Intermittent treatment refers to processing for a period of time, followed by stirring, and then continuing the processing.

[0019] Optionally, in step (S3), the medium gas includes a reducing gas, which is selected from at least one of H2, CO, and CH4.

[0020] Optionally, the medium gas further includes an inactive gas, which is selected from at least one of N2 and Ar;

[0021] The volume ratio of the inactive gas to the reducing gas is 10 to 30:1.

[0022] Optionally, the volume ratio of the inactive gas to the reducing gas is 10 to 25:1.

[0023] Optionally, the volume ratio of the inactive gas to the reducing gas is independently selected from any value of 10:1, 12:1, 15:1, 17:1, 20:1, 22:1, 25:1, 27:1, 30:1 or any intermediate value between the two.

[0024] Optionally, the flow rate of the medium gas is 30 to 500 ml / min.

[0025] Optionally, the flow rate of the medium gas is 100-200 ml / min.

[0026] Optionally, the flow rate of the medium gas is independently selected from any value of 30 ml / min, 50 ml / min, 70 ml / min, 100 ml / min, 120 ml / min, 150 ml / min, 170 ml / min, 200 ml / min, 220 ml / min, 250 ml / min, 270 ml / min, 300 ml / min, or any intermediate value between two of them.

[0027] Optionally, a non-reactive gas may be used for purging before plasma discharge treatment.

[0028] The inactive gas is selected from at least one of N2 and Ar.

[0029] Optionally, in step (S1), the method for obtaining the CuZn-based catalyst precursor includes:

[0030] Prepare mixed metal salt solutions of copper and zinc, and prepare alkaline solutions;

[0031] The two were mixed and subjected to a co-precipitation reaction, followed by aging, washing, drying and calcination to obtain the CuZn-based catalyst precursor.

[0032] Optionally, the mixed metal salt solution of copper and zinc is a mixed solution of copper nitrate and zinc nitrate;

[0033] The alkaline solution contains at least one of hydroxides, carbonates, bicarbonates, ammonia, and urea.

[0034] Optionally, the carbonate is sodium carbonate.

[0035] Optionally, the aging temperature is 30–90°C, and the aging time is 0.5–24 hours;

[0036] Optionally, the calcination conditions include: being carried out in an oxygen-containing atmosphere, a calcination temperature of 300–600°C, and a calcination time of 1–10 h.

[0037] Optionally, when preparing a mixed metal salt solution of copper and zinc, a synergistic metal salt may be added;

[0038] The synergistic metal is selected from at least one of Al, Mg, Mn, Ni, Co, Cr, Ce, and Ti.

[0039] Optionally, in step (S2), the particle size of the particle sample obtained after dry granulation is 0.1 to 5 mm.

[0040] Optionally, the particle size of the particle sample obtained after dry granulation is 1 to 2 mm.

[0041] Optionally, in step (S2), the additive is graphite.

[0042] Optionally, the amount of the additive is 3 wt% to 20 wt% of the mass of the CuZn-based catalyst precursor.

[0043] Optionally, the amount of the additive is 5 wt% to 15 wt% of the mass of the CuZn-based catalyst precursor.

[0044] Optionally, the amount of the additive added as a percentage of the mass of the CuZn-based catalyst precursor is independently selected from any value of 3wt%, 5wt%, 7wt%, 10wt%, 12wt%, 15wt%, 17wt%, 20wt%, or any intermediate value between the two.

[0045] According to a second aspect of this application, a CuZn-based catalyst is provided.

[0046] The CuZn-based catalyst prepared by the above-described method has a CuO to ZnO mass ratio of 1:0.01 to 5.

[0047] Optionally, the mass ratio of CuO to ZnO is 1:0.5 to 2.

[0048] Optionally, the mass ratio of CuO to ZnO is independently selected from any value among 1:0.01, 1:0.02, 1:0.05, 1:0.07, 1:0.1, 1:0.5, 1:0.7, 1:1, 1:1.2, 1:1.5, 1:1.7, 1:2, 1:3, 1:4, 1:5 or any intermediate value between the two.

[0049] Optionally, the CuZn-based catalyst is reduced and activated to obtain an active Cu species, wherein the active Cu species includes Cu. 2 + Cu 0 and Cu + .

[0050] Optionally, in the active Cu species, Cu 0 and Cu + The proportion of a species to the total number of species is denoted as a;

[0051] a=(Cu 0 +Cu + ) / (Cu 2+ +Cu 0 +Cu + );

[0052] 0.75≥a≥0.60.

[0053] Optionally, 0.70 ≥ a ≥ 0.65.

[0054] Optionally, 'a' is independently selected from any value among 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, and 0.75, or an intermediate value between any two.

[0055] According to a third aspect of this application, the application of the CuZn-based catalyst described above in the hydrogenation of methyl acetate to ethanol is provided.

[0056] The CuZn-based catalyst prepared by the above-described method is used in the hydrogenation of methyl acetate to ethanol.

[0057] Optionally, the CuZn-based catalyst is used after being compressed, crushed, and screened to obtain catalyst particles of 20-40 mesh.

[0058] This invention prepares an ethanol catalyst using a dielectric barrier plasma treatment method. Dielectric barrier plasma discharge is characterized by high electron energy, high electric field strength, and easy formation of free radicals and excimers. This method alters the peripheral electronic structure of the copper-based catalyst, allowing it to maintain the Cu content during the catalytic reaction. 0 and Cu + The aim is to increase the catalytic active centers by combining various states, thereby improving the conversion rate of methyl acetate and the selectivity of ethanol in the hydrogenation of methyl acetate to ethanol.

[0059] The beneficial effects that this application can produce include:

[0060] The method for preparing CuZn-based catalysts provided in this application effectively modulates the electron distribution of Cu species on the catalyst surface using dielectric barrier discharge (DBD) plasma technology, enhances the synergistic effect at the CuZn interface, and promotes the reduction of Cu species. 0 and Cu + The formation of [a specific catalyst] enhances the catalyst's activation of H2 and carbonyl groups. It also strengthens the interaction between Cu species and the support surface, improving the dispersibility and stability of Cu nanoparticles and extending the catalyst's lifespan. The CuZn-based catalyst exhibits excellent catalytic performance in the hydrogenation of methyl acetate to ethanol. Attached Figure Description

[0061] Figure 1 This is a comparison chart of temperature programmed reduction (TPR) of catalysts in Comparative Example 1 and Example 1.

[0062] Figure 2 shows a comparison of XPS graphs of the catalysts in Comparative Example 1 and Example 1. Figure 2A To make Cu 2p 3 / 2 Deconvolution of the spectrum. Figure 2B The deconvolution plot of the Auger electron spectrum of Cu(LMM) is shown. Figure 2C For reference Zn 2p 3 / 2 Spectrum. Detailed Implementation

[0063] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0064] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0065] The analysis method in the embodiments of this application is as follows:

[0066] The catalyst activity evaluation calculations are as follows:

[0067]

[0068]

[0069] x represents different products. The target product of MAc hydrogenation is ethanol (EtOH), and the main byproducts are methanol (MeOH) and ethyl acetate (EA).

[0070] The evaluation process of the catalyst in the reaction of methyl acetate to ethanol is as follows:

[0071] 3.0 g of the prepared catalyst was loaded into the isothermal section of the reaction tube. A thermocouple was placed in the center of the catalyst bed, and the airtightness was checked at 5.0 MPa. The hydrogenation reaction was then carried out. Under normal pressure, the hydrogen flow rate was adjusted to 10 ml / min and the nitrogen flow rate to 90 ml / min. At room temperature, the temperature was first increased to 250 °C at a rate of 5 °C / min to reduce the catalyst. After holding at this temperature for 2 hours, the temperature was lowered to 210 °C (or 190 °C) to prepare for the reaction. A constant flow pump was used at a liquid hourly space velocity (LHSV) of 2 h⁻¹. -1 Methyl acetate is pumped in and vaporized through a thermostatic pipeline, then mixed with hydrogen at a hydrogen-to-ester ratio of 15:1. The mixture then enters the reactor through a heat-insulated line. The resulting reaction gas is then analyzed online by a gas chromatograph via a thermostatic pipeline.

[0072] The test method for temperature-programmed reduction (TPR) of catalysts is as follows: A US AMI-300 chemisorption analyzer was used for the temperature-programmed reduction reaction. Approximately 0.1 g of sample was weighed and purged at room temperature (30℃) for half an hour under argon (50 mL / min). Then, reduction was carried out by heating from 30℃ to 600℃ under a 10% H2 / Ar (50 mL / min) atmosphere at a heating rate of 10℃ / min. The curve was recorded and the H2 consumption was calculated.

[0073] The catalyst was measured using a Thermo Fisher Scientific 250xi X-ray instrument, with a monochromatic AlKα (1486.6 eV) X-ray source as the incident source. The C1s peak position at 284.8 eV was used as the reference for calibrating the binding energy. Prior to testing, 1 g of the sample was reduced at 350 °C for 2 h in an atmosphere of hydrogen at a flow rate of 2 ml / min and argon at a flow rate of 32 ml / min.

[0074] Comparative Example 1

[0075] 90.6 g of copper nitrate trihydrate and 111.55 g of zinc nitrate hexahydrate were dissolved in 500 ml of deionized water to prepare a 1.5 mol / L mixed metal salt solution, which served as the salt solution. 79.5 g of anhydrous sodium carbonate was dissolved in 500 ml of deionized water to prepare a 1.5 mol / L solution, which served as the alkali solution. The sodium carbonate solution and the metal nitrate solution were mixed together using a micro-mixer at a flow rate of 50 ml / min using a horizontal pump for a total of 5 min. The pH of the mixed solution was maintained between 7 and 9, and the temperature was approximately 70°C. The mixed solution was then rapidly transferred to a water bath for aging. During aging, the stirring speed was 500 rpm, the temperature was approximately 75°C, and the aging time was 200 min. After aging, the mixture was filtered, and the filter cake was washed until no Na was detectable in the filtrate. + The filter cake was dried in a 110℃ oven for 12 hours to obtain the precursor, which was then calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. These particles were then pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst D1, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 210℃.

[0076] Comparative Example 2

[0077] The preparation and treatment of the catalyst precursor were the same as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed evenly with graphite powder (10 wt.%) and dry-granulated to obtain 1-2 mm particles. The particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20-40 mesh catalyst particles, i.e., CuZn-based catalyst D2, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 190℃.

[0078] Comparative Example 3

[0079] The preparation and processing of the catalyst precursor were the same as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was dry-granulated to obtain 1-2 mm particles. The particles were then pressed into sheets at 40 MPa, crushed, and sieved to obtain 20-40 mesh catalyst particles, i.e., CuZn-based catalyst D3, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 210℃.

[0080] Comparative Example 4

[0081] 86.5 g of copper nitrate trihydrate, 104 g of zinc nitrate hexahydrate, and 16 g of aluminum nitrate nonahydrate were dissolved in 500 ml of deionized water to prepare a 1.5 mol / L mixed metal salt solution, which served as the salt solution. 79.5 g of sodium carbonate was dissolved in 500 ml of deionized water to prepare a 1.5 mol / L solution, which served as the alkali solution. The sodium carbonate solution and the metal nitrate solution were mixed together using a micro-mixer at a flow rate of 50 ml / min for 5 minutes, maintaining the pH of the mixed solution between 7 and 9 and the temperature at approximately 70°C. The mixed solution was then rapidly transferred to a water bath for aging at a stirring speed of 500 rpm and a temperature of approximately 75°C for a total of 200 minutes. After aging, the mixture was filtered, and the filter cake was washed until no Na+ was detected in the filtrate. The filter cake was then placed in a 110°C oven for 12 hours to obtain the precursor, which was then calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and then dry-granulated to obtain 1-2 mm particles. These particles were then pressed into sheets at 40 MPa, crushed, and sieved to obtain 20-40 mesh catalyst particles, i.e., CuZnAl-based catalyst D4, with a CuO:ZnO:Al2O3 ratio of 13:13:1 (mass ratio). The evaluation temperature was 210℃.

[0082] Example 1

[0083] 90.6 g of copper nitrate trihydrate and 111.55 g of zinc nitrate hexahydrate were dissolved in 500 ml of deionized water to prepare a 1.5 mol / L mixed metal salt solution, which served as the salt solution. 79.5 g of anhydrous sodium carbonate was dissolved in 500 ml of deionized water to prepare a 1.5 mol / L solution, which served as the alkali solution. The sodium carbonate solution and the metal nitrate solution were mixed together using a micro-mixer at a flow rate of 50 ml / min using a horizontal pump for a total of 5 min. The pH of the mixed solution was maintained between 7 and 9, and the temperature was approximately 70°C. The mixed solution was then rapidly transferred to a water bath for aging. During aging, the stirring speed was 500 rpm, the temperature was approximately 75°C, and the aging time was 200 min. After aging, the mixture was filtered, and the filter cake was washed until no Na was detectable in the filtrate. +The filter cake was placed in a 110℃ oven for 12 hours, and then the sample was calcined in a 350℃ muffle furnace for 4 hours. The calcined sample was then mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region, purged with nitrogen at 80 ml / min for 20 min. A 120 W plasma source was used, with a nitrogen and hydrogen mixture as the discharge medium, a total gas flow rate of 120 ml / min, and a nitrogen-to-hydrogen volume ratio of 23:1. The discharge treatment lasted 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst C1, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 210℃.

[0084] Example 2

[0085] The preparation and treatment of the catalyst precursor were the same as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region, and purged with nitrogen at 80 ml / min for 20 min. A 150 W plasma emission source was used, with a nitrogen and hydrogen mixture as the discharge medium, a total gas flow rate of 150 ml / min, and a nitrogen-to-hydrogen volume ratio of 14:1. The discharge treatment lasted for 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst C2, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 210℃.

[0086] Example 3

[0087] The preparation and treatment of the catalyst precursor were the same as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region. Nitrogen gas was purged at 80 ml / min for 20 min. A 150 W plasma source was used, with a nitrogen and hydrogen mixture as the discharge medium. The total gas flow rate was 120 ml / min, and the nitrogen-hydrogen volume ratio was 23:1. The discharge was performed for 30 min, paused for 5 min, and the sample was stirred appropriately before continuing the discharge for another 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst C3, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 210℃.

[0088] Example 4

[0089] The catalyst precursor was prepared and processed in the same manner as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed uniformly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region, purged with nitrogen at 80 ml / min for 20 min. A 120 W plasma source was used, with a nitrogen and methane mixture as the discharge medium, a total gas flow rate of 150 ml / min, and a nitrogen-to-methane volume ratio of 14:1. The discharge treatment lasted for 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst C4, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 210℃.

[0090] Example 5

[0091] The catalyst precursor was prepared and processed in the same manner as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed uniformly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region. Nitrogen gas was purged at 80 ml / min for 20 min. A 120 W plasma source was used, with a nitrogen and carbon monoxide mixture as the discharge medium. The total gas flow rate was 120 ml / min, and the nitrogen-to-carbon monoxide volume ratio was 23:1. The discharge was performed for 30 min, paused for 5 min, and the sample was stirred appropriately before continuing the discharge for another 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst C5, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 210℃.

[0092] Example 6

[0093] The catalyst precursor was prepared and processed in the same manner as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed uniformly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region, purged with nitrogen at 80 ml / min for 20 min. A 150 W plasma source was used, with a nitrogen-hydrogen mixture as the discharge medium, a total gas flow rate of 120 ml / min, and a nitrogen-hydrogen volume ratio of 23:1. The discharge treatment lasted 60 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst C6, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 190℃.

[0094] Example 7

[0095] The preparation and treatment of the catalyst precursor were the same as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed evenly with graphite powder (10 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region. Nitrogen gas was purged at 80 ml / min for 20 min. A 150 W plasma source was used, with a nitrogen and hydrogen mixture as the discharge medium. The total gas flow rate was 120 ml / min, and the nitrogen-hydrogen volume ratio was 23:1. The discharge was performed for 30 min, paused for 5 min, and the sample was stirred appropriately before continuing the discharge for another 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, i.e., CuZn-based catalyst C7, CuO:ZnO = 1:1 (mass ratio). The evaluation temperature was 190℃.

[0096] Example 8

[0097] The preparation and treatment of the catalyst precursor were the same as in Comparative Example 4. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1–2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region, and purged with nitrogen at 80 ml / min for 20 min. A 120 W plasma emission source was used, with a mixture of nitrogen and hydrogen as the discharge medium, a total gas flow rate of 120 ml / min, and a nitrogen-to-hydrogen volume ratio of 23:1. The discharge treatment lasted for 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20–40 mesh catalyst particles, namely CuZnAl-based catalyst C8, CuO:ZnO:Al2O3 = 13:13:1 (mass ratio). The evaluation temperature was 210℃.

[0098] Example 9

[0099] The preparation and treatment of the catalyst precursor were the same as in Comparative Example 4. The precursor was calcined in a muffle furnace at 350℃ for 4 hours. The calcined sample was then mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1-2 mm particles. The particles were spread evenly in a quartz dish and placed in a dielectric barrier plasma discharge region. Nitrogen gas was purged at 80 ml / min for 20 min. A 120 W plasma source was used, with a mixture of nitrogen and methane as the discharge medium. The total gas flow rate was 120 ml / min, and the nitrogen-methane volume ratio was 23:1. The discharge was carried out for 30 min, paused for 5 min, and the sample was stirred appropriately before continuing the discharge for another 30 min. After the sample cooled to room temperature, the particles were pressed into sheets at 40 MPa, crushed, and sieved to obtain 20-40 mesh catalyst particles, namely CuZnAl-based catalyst C9, CuO:ZnO:Al2O3 = 13:13:1 (mass ratio). The evaluation temperature was 210℃.

[0100] Taking the catalyst prepared in Example 1 as an example, Figure 1 This is a comparison graph of the temperature-programmed reduction (TPR) of the catalysts prepared in Comparative Example 1 and Example 1. The C1 catalyst has a lower reduction temperature and consumes more hydrogen, indicating that under the same activation conditions, the C1 catalyst is more completely activated at a lower temperature, and the reduced species Cu in the catalyst... 0 and Cu + An increased species ratio enhances synergistic effects, thereby improving the catalytic activity and lifespan of the catalyst.

[0101] Figure 2A , Figure 2B and Figure 2C This is a comparison of the XPS images of the catalysts prepared in Comparative Example 1 and Example 1, showing Cu2p... 3 / 2Deconvolution of the spectrum yields Figure 2A The peaks at 934.5 eV and 932.6 eV are attributed to Cu, respectively. 2+ and reduced Cu species (Cu + +Cu 0 Comparative Example 1 and Comparative Example 1 Cu 2p 3 / 2 The spectrum revealed Cu 2p in the example. 3 / 2 Spectrum main peak, Cu 2+ Both the peaks of the reduced Cu species spectrum and the peaks of the reference Zn 2p spectrum shifted significantly toward higher binding energies; meanwhile, the peaks of the reference Zn 2p spectrum also shifted significantly toward higher binding energies. 3 / 2 Spectrum Figure 2C In the example, Zn 2p was found 3 / 2 The spectral peaks shifted significantly towards lower binding energies. This is because oxygen escapes from the ZnO crystals under plasma conditions, generating oxygen vacancies and free ions. This fully demonstrates the strong interactions between CuZn nanoparticles, effectively regulating the electron distribution of CuZn species on the ethanol catalyst surface. Deconvolution results show that the proportion of reduced Cu in Example 1 (0.66) is much higher than in Comparative Example 1 (0.45). This is due to the enhanced synergistic effect at the CuZn interface, leading to an increased proportion of reduced Cu species, which is the direct reason for the higher catalytic activity of Example 1 compared to Comparative Example 1. The Cu Auger electron spectroscopy (LMM) spectrum... Figure 2B The deconvolution results show that Cu in Example 1 0 The proportion (0.43) was significantly higher than that of Comparative Example 1 (0.38), indicating that plasma treatment has a significant promoting effect on the formation of electron-rich states of Cu, thereby improving the dissociation and adsorption capacity of the catalyst in the examples for H2.

[0102] The corresponding process conditions for preparing the catalysts in the comparative examples and embodiments above are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] The data in Table 1 show that the catalyst (Cu) after plasma treatment... 0 +Cu + ) / (Cu 2+ +Cu 0 +Cu + There has been a significant improvement.

[0107] The performance evaluation results of the catalysts prepared in the comparative examples and embodiments above are shown in Table 2.

[0108] Table 2

[0109]

[0110] As can be seen from the data in Table 2, the plasma-treated catalyst significantly improved the conversion rate of methyl acetate and the selectivity of ethanol in the hydrogenation of methyl acetate to ethanol. After a period of reaction time, the catalytic activity remained almost unchanged, demonstrating excellent stability.

[0111] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a CuZn-based catalyst, characterized in that, Includes the following steps: (S1) Obtain CuZn-based catalyst precursor; (S2) The CuZn-based catalyst precursor and the additive are mixed and then dry-granulated. (S3) The particle sample obtained after dry granulation is placed in the dielectric barrier plasma discharge region and a dielectric gas is introduced for discharge treatment to obtain the CuZn-based catalyst. In step (S1), the method for obtaining the CuZn-based catalyst precursor includes: Prepare mixed metal salt solutions of copper and zinc, and prepare alkaline solutions; The two were mixed and subjected to a co-precipitation reaction, followed by aging, washing, drying and calcination to obtain the CuZn-based catalyst precursor; In step (S2), the additive is graphite; In step (S3), the operating power of the plasma used is 5~500W; The discharge treatment can be performed continuously or intermittently. The duration of continuous treatment is 0.1 to 5 hours, and the duration of intermittent treatment is 0.1 to 20 hours. The medium gas includes a reducing gas, which is selected from at least one of H2, CO, and CH4.

2. The preparation method according to claim 1, characterized in that, In step (S3), The medium gas also includes an inactive gas, which is selected from at least one of N2 and Ar. The volume ratio of the inactive gas to the reducing gas is 10~30:

1.

3. The preparation method according to claim 1, characterized in that, In step (S3), the flow rate of the medium gas is 30~500 ml / min.

4. The preparation method according to claim 1, characterized in that, In step (S1), the mixed metal salt solution of copper and zinc is a mixed solution of copper nitrate and zinc nitrate; The alkaline solution contains at least one of hydroxides, carbonates, bicarbonates, ammonia, and urea.

5. The preparation method according to claim 1, characterized in that, In step (S1), the aging temperature is 30~90°C. o C, the aging time is 0.5~24 h.

6. The preparation method according to claim 1, characterized in that, In step (S1), the calcination conditions include: being carried out in an oxygen-containing atmosphere, a calcination temperature of 300~600℃, and a calcination time of 1~10 h.

7. The preparation method according to claim 1, characterized in that, In step (S1), when preparing the mixed metal salt solution of copper and zinc, a synergistic metal salt is added; The synergistic metal is selected from at least one of Al, Mg, Mn, Ni, Co, Cr, Ce, and Ti.

8. The preparation method according to claim 1, characterized in that, In step (S2), the particle size of the particle sample obtained after dry granulation is 0.1~5 mm.

9. The preparation method according to claim 1, characterized in that, In step (S2), the amount of the additive added is 3wt% to 20wt% of the mass of the CuZn-based catalyst precursor.

10. The CuZn-based catalyst prepared by the method according to any one of claims 1 to 9, characterized in that, In the CuZn-based catalyst, the mass ratio of CuO to ZnO is 1:0.01~5.

11. The CuZn-based catalyst according to claim 10, characterized in that, The CuZn-based catalyst was reduced and activated to obtain active Cu species, which include Cu... 2+ Cu 0 and Cu + Cu 0 and Cu + The proportion of a species to the total number of species is denoted as a; a= (With 0 +With + ) / (With 2+ +With 0 +With + ); 0.75≥a≥0.60。 12. The application of the CuZn-based catalyst prepared by the method of any one of claims 1 to 9 in the hydrogenation of methyl acetate to ethanol.

13. The application according to claim 12, characterized in that, The CuZn-based catalyst is used after being compressed, crushed, and screened to obtain catalyst particles of 20-40 mesh.

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