Preparation method for and use of cuzn-based catalyst

Abstract

A preparation method for a CuZn-based catalyst. The preparation method comprises the following steps: (S1) acquiring a CuZn-based catalyst precursor; (S2) mixing the CuZn-based catalyst precursor with an auxiliary agent, and subjecting same to dry granulation; and (S3) placing a particle sample obtained after dry granulation into a dielectric barrier plasma discharge area, and introducing a dielectric gas for a discharge treatment, so as to obtain the CuZn-based catalyst. In the process of preparation, the electron distribution of Cu species on the surface of the catalyst is regulated and controlled by means of a plasma treatment, and therefore interaction between active component nanoparticles is enhanced, and the catalyst has significantly improved catalytic activity and stability when being used in a reaction for preparing ethyl alcohol from methyl acetate by means of hydrogenation, and shows good catalytic performance.

Description

Preparation method and application of CuZn-based catalyst Technical Field

[0001] The present application relates to a preparation method of a CuZn-based catalyst and its application, belonging to the field of catalysts. Background Art

[0002] As an important chemical intermediate and organic solvent, ethanol is widely used in the production of bulk chemicals, including pharmaceuticals, paints, and detergents. Furthermore, as a fuel additive, ethanol gasoline boasts a high octane rating and excellent anti-knock properties, significantly reducing hydrocarbon and nitrogen oxide emissions. The promotion of ethanol gasoline is strongly supported by national policies. The National Energy Administration's "2023 Key Points for Energy Supervision Work" incorporates ethanol gasoline usage into the routine oversight of dispatched agencies, ensuring that refined oil distributors sell ethanol gasoline in compliance with regulations.

[0003] Cu-based catalysts are often used in ethanol catalysis technology. Cu has a significant activation effect on the selective hydrogenation of carbonyl groups and, as a low-cost transition metal, is suitable for industrial promotion and use. CN 112691674B discloses a ZrO2- and CeO2-doped CuZnAl catalyst. First, Zr and Ce species are modified on an Al2O3 support by a deposition precipitation method, and then the CuZn catalyst is loaded. The catalyst is heated at 230°C, 5.0 MPa, n(H2) / n(1,4-cyclohexanedicarboxylic acid dimethyl ester) = 140, and WHSV = 0.3h. ‐1 Under the reaction conditions, the hydrogenation conversion rate of dimethyl 1,4-cyclohexanedicarboxylate reached 99.5%, which proved that the Cu-based catalyst has high activity for ester hydrogenation, and the interaction between Cu and Zn improves the dispersion of Cu particles to a certain extent.

[0004] Cu-based catalysts often exhibit Cu 0 and Cu + Coexisting chemical states, as Cu 0 and Cu + The increase in species and the enhanced interaction between Cu and ZnO are also considered to be important factors in improving the catalytic active centers. It is crucial to improve the synergistic effect of the copper-zinc interface, enhance the active centers of the catalyst, and improve the catalyst activity and stability.

[0005] Summary of the Invention

[0006] The present invention provides a preparation method and application of a CuZn-based catalyst. The CuZn-based catalyst precursor is fully mixed with the auxiliary agent graphite, and a particle sample with a certain strength is formed after dry granulation. The particle sample is treated with plasma discharge. Combined with the good charge conductivity of graphite, the chemical environment changed by the plasma on the surface of the particle sample is transferred to the interior to activate the CuZn catalyst.0 and Cu + The synergistic active centers act together on the interface of the CuZn-based catalyst, thereby improving the catalytic activity and stability of the catalyst for the hydrogenation of methyl acetate to ethanol reaction.

[0007] According to the first aspect of the present application, a method for preparing a CuZn-based catalyst is provided. When a sample is treated with plasma discharge, the input electrical energy is coupled to the charged particles, which collide through the medium gas to cause ionization and dissociation, generating electrons, ions, free radicals, and excited atoms, which promote the electronic arrangement on the surface of the Cu-based catalyst. Because graphite has good charge conductivity, the chemical environment on the surface of the particle sample, which is changed by the plasma, is transferred to the interior, and Zn 2+ Cu + After substitution, oxygen vacancies and free ions will be generated, which will stimulate Cu + Provides electrophilic sites and further provides catalytic active centers, making C=O easy to polarize and stabilize the role of methyl and acetyl groups, and promoting Cu 0 The dissociative adsorption capacity of H2 enhances the Cu 0 and Cu + The synergistic effect between the two improves the catalytic activity and stability of the hydrogenation of methyl acetate to ethanol.

[0008] A method for preparing a CuZn-based catalyst comprises the following steps:

[0009] (S1) obtaining a CuZn-based catalyst precursor;

[0010] (S2) mixing the CuZn-based catalyst precursor and the auxiliary agent, and dry granulating the mixture;

[0011] (S3) placing the particle sample obtained after dry granulation in a dielectric barrier plasma discharge region, introducing a dielectric gas for discharge treatment, and obtaining the CuZn-based catalyst.

[0012] Optionally, in step (S3), the operating power of the plasma used is 5 to 500 W;

[0013] The discharge treatment is carried out in a continuous treatment or intermittent treatment manner. The duration of the continuous treatment is 0.1 to 5 hours, and the duration of the intermittent treatment is 0.1 to 20 hours.

[0014] Optionally, in step (S3), the operating power of the plasma used is 100 to 200 W;

[0015] The discharge treatment is carried out in a continuous or intermittent manner. The duration of the continuous treatment is 0.2 to 2 hours, and the duration of the intermittent treatment is 0.5 to 5 hours.

[0016] 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, 500W, or any intermediate value therebetween.

[0017] Optionally, the duration of continuous treatment is independently selected from any value among 0.2h, 0.4h, 0.5h, 0.7h, 0.8h, 1h, 1.2h, 1.5h, 1.7h, 2h or any intermediate value therebetween.

[0018] Optionally, the duration of the intermittent treatment is independently selected from any value among 0.5h, 0.7h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or any intermediate value therebetween.

[0019] Intermittent treatment refers to stirring after treating for a period of time and then continuing the treatment.

[0020] Optionally, in step (S3), the medium gas includes a reducing gas, and the reducing gas is selected from at least one of H2, CO, and CH4.

[0021] Optionally, the medium gas further includes an inert gas, and the inert gas is selected from at least one of N2 and Ar;

[0022] The volume ratio of the inert gas to the reducing gas is 10 to 30:1.

[0023] Optionally, the volume ratio of the inert gas to the reducing gas is 10 to 25:1.

[0024] Optionally, the volume ratio of the inert gas to the reducing gas is independently selected from any value among 10:1, 12:1, 15:1, 17:1, 20:1, 22:1, 25:1, 27:1, 30:1 or any intermediate value therebetween.

[0025] Optionally, the flow rate of the medium gas is 30 to 500 ml / min.

[0026] Optionally, the flow rate of the medium gas is 100-200 ml / min.

[0027] Optionally, the flow rate of the medium gas is independently selected from any value among 30ml / min, 50ml / min, 70ml / min, 100ml / min, 120ml / min, 150ml / min, 170ml / min, 200ml / min, 220ml / min, 250ml / min, 270ml / min, 300ml / min or any intermediate value between any two of them.

[0028] Optionally, before the plasma discharge treatment, a purge is performed using an inert gas.

[0029] The inert gas is selected from at least one of N2 and Ar.

[0030] Optionally, in step (S1), the method for obtaining the CuZn-based catalyst precursor includes:

[0031] Prepare a mixed metal salt solution of copper and zinc and prepare an alkaline solution;

[0032] The two are mixed to carry out a co-precipitation reaction, and then aged, washed, dried and calcined to obtain the CuZn-based catalyst precursor.

[0033] Optionally, the mixed metal salt solution of copper and zinc is a mixed solution of copper nitrate and zinc nitrate;

[0034] The alkali in the alkaline solution includes at least one of hydroxide, carbonate, bicarbonate, ammonia water and urea.

[0035] Optionally, the carbonate is sodium carbonate.

[0036] Optionally, the aging temperature is 30-90° C., and the aging time is 0.5-24 h;

[0037] Optionally, the calcination conditions include: carrying out in an oxygen-containing atmosphere, a calcination temperature of 300-600° C., and a calcination time of 1-10 h.

[0038] Optionally, when preparing the mixed metal salt solution of copper and zinc, a synergistic metal salt is added;

[0039] The synergistic metal is selected from at least one of Al, Mg, Mn, Ni, Co, Cr, Ce, and Ti.

[0040] Optionally, in step (S2), the particle size of the granule sample obtained after dry granulation is 0.1 to 5 mm.

[0041] Optionally, the particle size of the granule sample obtained after dry granulation is 1 to 2 mm.

[0042] Optionally, in step (S2), the auxiliary agent is graphite.

[0043] Optionally, the additive is added in an amount of 3 wt% to 20 wt% of the mass of the CuZn-based catalyst precursor.

[0044] Optionally, the additive is added in an amount of 5 wt% to 15 wt% of the mass of the CuZn-based catalyst precursor.

[0045] Optionally, the amount of the additive added is a proportion of the mass of the CuZn-based catalyst precursor independently selected from any value among 3wt%, 5wt%, 7wt%, 10wt%, 12wt%, 15wt%, 17wt%, 20wt% or any intermediate value therebetween.

[0046] According to a second aspect of the present application, a CuZn-based catalyst is provided.

[0047] The CuZn-based catalyst prepared by the above-mentioned method for preparing the CuZn-based catalyst has a mass ratio of CuO to ZnO of 1:0.01-5.

[0048] Optionally, the mass ratio of CuO to ZnO is 1:0.5-2.

[0049] Optionally, the mass ratio of CuO to ZnO is independently selected from any value of 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 therebetween.

[0050] Optionally, the CuZn-based catalyst is reduced and activated to obtain active Cu species, and the active Cu species include Cu 2+ 、Cu 0 and Cu + 。

[0051] Alternatively, among the active Cu species, Cu 0 and Cu + The proportion of species to the total species is recorded as a; a=(Cu 0 +Cu + ) / (Cu 2+ +Cu 0 +Cu + ); 0.75≥a≥0.60.

[0052] Optionally, 0.70≥a≥0.65.

[0053] 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, 0.75 or any intermediate value therebetween.

[0054] According to a third aspect of the present application, there is provided a use of the above-mentioned CuZn-based catalyst in the hydrogenation of methyl acetate to produce ethanol.

[0055] Application of the CuZn-based catalyst prepared by the above-mentioned preparation method of the CuZn-based catalyst in the hydrogenation of methyl acetate to produce ethanol.

[0056] Optionally, the CuZn-based catalyst is tableted, crushed, and screened to obtain catalyst particles of 20 to 40 mesh before use.

[0057] The present invention prepares ethanol catalyst by dielectric barrier plasma treatment. Dielectric barrier plasma discharge has the characteristics of high electron energy, high electric field strength, easy formation of free radicals and excimers, etc., which changes the peripheral electronic structure of the copper-based catalyst, so that the copper-based catalyst maintains Cu in the catalytic reaction. 0 and Cu + The purpose of the present invention is to increase the catalytic active centers together with the state, thereby improving the conversion rate of methyl acetate and the selectivity of ethanol in the reaction of hydrogenation of methyl acetate to ethanol.

[0058] The beneficial effects of this application include:

[0059] The preparation method of the CuZn-based catalyst provided in this application utilizes dielectric barrier discharge (DBD) plasma technology to effectively regulate the electron distribution of Cu species on the catalyst surface, enhance the synergistic effect of the CuZn interface, and promote the reduction of the reduced Cu species Cu 0 and Cu + The formation of CuZn-based catalysts enhances the activation of the catalyst for H2 and carbonyl groups. This enhances the interaction between the Cu species and the support surface, improves the dispersibility and stability of the Cu nanoparticles, and increases the service life of the catalyst. The CuZn-based catalyst exhibits excellent catalytic performance when used in the hydrogenation of methyl acetate to ethanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIG1 is a comparison chart of temperature-programmed reduction (TPR) of the catalysts of Comparative Example 1 and Example 1.

[0061] FIG2 is a XPS comparison chart of the catalysts of Comparative Example 1 and Example 1, wherein FIG2A is a ... 3 / 2 The spectra were deconvoluted. Figure 2B is the deconvoluted Auger electron spectrum of Cu(LMM), and Figure 2C is the deconvoluted spectrum of the reference Zn 2p3 / 2 Spectrum. DETAILED DESCRIPTION

[0062] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0063] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0064] The analysis method in the examples of this application is as follows:

[0065] The catalyst activity evaluation calculation is as follows:

[0066] x represents different products. The target product of MAc hydrogenation is ethanol (EtOH), and the by-products are mainly methanol (MeOH) and ethyl acetate (EA).

[0067] The evaluation process of the catalyst in the reaction of methyl acetate to ethanol is as follows:

[0068] Take 3.0g of the prepared catalyst and load it into the constant temperature section of the reaction tube. Place the thermocouple in the center of the catalyst bed. Check the air tightness at 5.0MPa and carry out the hydrogenation reaction. Under normal pressure, adjust the hydrogen flow rate to 10ml / min and the nitrogen flow rate to 90ml / min. At room temperature, first increase the temperature to 250℃ at 5℃ / min to reduce the catalyst. After keeping the temperature for 2h, cool it down to 210℃ (or 190℃) to prepare for the reaction. Use a constant flow pump to press the liquid mass space velocity for 2h. -1 Methyl acetate is pumped in and vaporized through a constant-temperature pipeline. It is then mixed with hydrogen at a hydrogen-to-ester ratio of 15:1 and then enters the reactor through an insulated line. The mixed reaction gas then passes through a constant-temperature pipeline and enters a gas chromatograph for online analysis.

[0069] The catalyst temperature-programmed reduction (TPR) test method is as follows: A US AMI-300 chemical adsorption instrument was used for the temperature-programmed reduction reaction. Approximately 0.1 g of sample was purged under argon (50 mL / min) at room temperature (30°C) for half an hour. The sample was then reduced by heating from 30°C to 600°C in a 10% H2 / Ar atmosphere (50 mL / min) at a rate of 10°C / min. The curve was recorded and H2 consumption was calculated.

[0070] The catalyst was measured using a Thermo Fisher 250xi instrument, using a monochromatic AlKα (1486.6 eV) X-ray source as the incident light source. Binding energies were calibrated based on the C1s peak position at 284.8 eV. Prior to testing, 1 g of sample was reduced at 350°C for 2 h in an atmosphere of 2 ml / min hydrogen and 32 ml / min argon.

[0071] Comparative Example 1

[0072] Dissolve 90.6g of copper nitrate trihydrate and 111.55g of zinc nitrate hexahydrate in 500ml of deionized water to prepare a 1.5mol / L mixed metal salt solution as a salt solution; dissolve 79.5g of anhydrous sodium carbonate in 500ml of deionized water to prepare a 1.5mol / L solution as an alkaline solution. Use a horizontal flow pump to mix the sodium carbonate solution and the metal nitrate solution through a micro mixer at a speed of 50ml / min, and feed them for a total of 5 minutes. Maintain the pH of the mixed solution between 7 and 9 and the temperature at about 70°C. Quickly transfer the mixed solution into a water bath for aging. During aging, the stirring speed is 500rpm, the temperature is about 75°C, and the duration is 200 minutes. After aging, filter and wash the filter cake until no Na can be detected in the filtrate. + The filter cake was placed in a 110°C oven for 12 hours to obtain a precursor, which was then calcined in a 350°C muffle furnace for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1-2 mm particles. The particles were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles with a mesh size of 20-40, namely CuZn-based catalyst D1, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 210°C.

[0073] Comparative Example 2

[0074] The catalyst precursor was prepared and processed as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed with graphite powder (10 wt.%) and dry-granulated to obtain 1-2 mm particle samples. The granular samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles with a mesh size of 20-40 mesh, i.e., CuZn-based catalyst D2, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 190°C.

[0075] Comparative Example 3

[0076] The catalyst precursor was prepared and treated as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was dry-granulated to obtain 1-2 mm particles. The particles were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles with a mesh size of 20-40. This is the CuZn-based catalyst D3, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 210°C.

[0077] Comparative Example 4

[0078] 86.5g of copper nitrate trihydrate, 104g of zinc nitrate hexahydrate, and 16g of aluminum nitrate nonahydrate were dissolved in 500ml of deionized water to prepare a 1.5mol / L mixed metal salt solution as the salt solution. 79.5g of sodium carbonate was dissolved in 500ml of deionized water to prepare a 1.5mol / L solution as the base solution. The sodium carbonate solution and the metal nitrate solution were mixed using a micromixer at a rate of 50ml / min using a horizontal flow pump for 5 minutes, maintaining the pH of the mixed solution between 7 and 9 at a temperature of approximately 70°C. The mixed solution was then quickly transferred to a waterbath for aging at a stirring rate of 500rpm and a temperature of approximately 75°C for 200 minutes. After aging, the filter cake was filtered and 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 uniformly mixed with graphite powder (5 wt.%) and dry-granulated to obtain 1-2 mm particle samples. The granular samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles with a mesh size of 20-40, namely, CuZnAl-based catalyst D4, with a mass ratio of CuO:ZnO:Al2O3 = 13:13:1. The evaluation temperature was 210°C.

[0079] Example 1

[0080] Dissolve 90.6g of copper nitrate trihydrate and 111.55g of zinc nitrate hexahydrate in 500ml of deionized water to prepare a 1.5mol / L mixed metal salt solution as a salt solution; dissolve 79.5g of anhydrous sodium carbonate in 500ml of deionized water to prepare a 1.5mol / L solution as an alkaline solution. Use a horizontal flow pump to mix the sodium carbonate solution and the metal nitrate solution through a micro mixer at a speed of 50ml / min, and feed them for a total of 5 minutes. Maintain the pH of the mixed solution between 7 and 9 and the temperature at about 70°C. Quickly transfer the mixed solution into a water bath for aging. During aging, the stirring speed is 500rpm, the temperature is about 75°C, and the duration is 200 minutes. After aging, filter and wash the filter cake until no Na can be detected in the filtrate. +After the filter cake was placed in a 110°C oven for 12 hours, the sample was calcined in a 350°C muffle furnace for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 120 W plasma emission source was used, with a mixture of nitrogen and hydrogen as the discharge medium. The total gas flow rate was 120 ml / min, and the nitrogen to hydrogen volume ratio was 23:1. The discharge treatment lasted for 30 minutes. After the sample cooled to room temperature, the particle sample was pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely the CuZn-based catalyst C1, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 210°C.

[0081] Example 2

[0082] The catalyst precursor was prepared and treated as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 150 W plasma emission source was used, with a nitrogen and hydrogen mixture as the discharge medium at 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 minutes. After the sample cooled to room temperature, the particle sample was pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely, the CuZn-based catalyst C2, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 210°C.

[0083] Example 3

[0084] The catalyst precursor was prepared and treated as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and dry-granulated to produce 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 150 W plasma source was used, with a nitrogen and hydrogen mixture as the discharge medium at a total gas flow rate of 120 ml / min and a nitrogen:hydrogen volume ratio of 23:1. The discharge process was continued for 30 minutes, followed by a 5-minute pause, followed by appropriate stirring of the sample, and a further 30 minutes of discharge. After the sample cooled to room temperature, the particle samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely, the CuZn-based catalyst C3, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 210°C.

[0085] Example 4

[0086] The catalyst precursor was prepared and treated as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and dry-granulated to obtain 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 120 W plasma emission source was used, with a nitrogen and methane mixture as the discharge medium at 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 minutes. After the sample cooled to room temperature, the particle samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely, the CuZn-based catalyst C4, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 210°C.

[0087] Example 5

[0088] The catalyst precursor was prepared and treated as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed with graphite powder (5 wt.%) and dry-granulated to produce 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 120 W plasma source was used, with a nitrogen and carbon monoxide mixture as the discharge medium at a total gas flow rate of 120 ml / min and a nitrogen to carbon monoxide volume ratio of 23:1. The discharge process was continued for 30 minutes, followed by a 5-minute pause, followed by appropriate stirring of the sample, and a further 30 minutes of discharge. After the sample cooled to room temperature, the particle samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely, the CuZn-based catalyst C5, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 210°C.

[0089] Example 6

[0090] The catalyst precursor was prepared and treated as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed with graphite powder (5 wt.%) and dry-granulated to produce 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 150 W plasma source was used, with a nitrogen and hydrogen mixture as the discharge medium at a total gas flow rate of 120 ml / min and a nitrogen to hydrogen volume ratio of 23:1. The discharge treatment lasted for 60 minutes. After the sample cooled to room temperature, the particle samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles with a mesh size of 20-40, namely, the CuZn-based catalyst C6, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 190°C.

[0091] Example 7

[0092] The catalyst precursor was prepared and treated as in Comparative Example 1. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed with graphite powder (10 wt.%) and dry-granulated to produce 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 150 W plasma source was used, with a nitrogen and hydrogen mixture as the discharge medium at a total gas flow rate of 120 ml / min and a nitrogen to hydrogen volume ratio of 23:1. The discharge process was continued for 30 minutes, followed by a 5-minute pause, followed by appropriate stirring of the sample, and a further 30 minutes of discharge. After the sample cooled to room temperature, the particle samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely, the CuZn-based catalyst C7, with a CuO:ZnO ratio of 1:1 (mass ratio). The evaluation temperature was 190°C.

[0093] Example 8

[0094] The catalyst precursor was prepared and treated as in Comparative Example 4. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed evenly with graphite powder (5 wt.%) and dry-granulated to produce 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. A 120 W plasma emission source was used, with a nitrogen and hydrogen mixture as the discharge medium at 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 minutes. After the sample cooled to room temperature, the particle samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely, the CuZnAl-based catalyst C8, with a mass ratio of CuO:ZnO:Al2O3 of 13:13:1. The evaluation temperature was 210°C.

[0095] Example 9

[0096] The catalyst precursor was prepared and treated as in Comparative Example 4. The precursor was calcined in a muffle furnace at 350°C for 4 hours. The calcined sample was mixed with graphite powder (5 wt.%) and dry-granulated to produce 1-2 mm particle samples. The particle samples were spread flat in a quartz dish and placed in a dielectric barrier plasma discharge area. 80 ml / min of nitrogen was introduced for 20 minutes. Using a 120 W plasma source, a nitrogen and methane mixture was used as the discharge medium at a total gas flow rate of 120 ml / min, with a nitrogen:methane volume ratio of 23:1. The discharge process lasted for 30 minutes, followed by a 5-minute pause, appropriate stirring, and a further 30 minutes of discharge. After the sample cooled to room temperature, the particle samples were pressed into tablets at 40 MPa, crushed, and sieved to obtain catalyst particles of 20-40 mesh, namely, the CuZnAl-based catalyst C9, with a mass ratio of CuO:ZnO:Al2O3 of 13:13:1. The evaluation temperature was 210°C.

[0097] Taking the catalyst prepared in Example 1 as an example, Figure 1 is a comparison of the temperature programmed reduction (TPR) of the catalysts prepared in Comparative Example 1 and Example 1. The reduction temperature of the C1 catalyst is lower and the hydrogen consumption is higher, 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 is 0 and Cu + The proportion of species increases, the synergistic effect is enhanced, and the catalytic activity and service life of the catalyst are improved.

[0098] Figures 2A, 2B and 2C are XPS comparisons of the catalysts prepared in Comparative Example 1 and Example 1. 3 / 2 The spectrum was deconvoluted to obtain Figure 2A. The peaks at 934.5eV and 932.6eV were attributed to Cu2+ and reduced Cu species (Cu + +Cu 0 ). Comparative Example 1 and Comparative Example 1 Cu 2p 3 / 2 Spectrum, found that the Cu 2p 3 / 2 Main peak of the spectrum, Cu 2+ and reduced Cu species peaks are significantly shifted toward the direction of high binding energy; at the same time, the reference Zn 2p 3 / 2 Spectrum, Figure 2C, found that Zn 2p 3 / 2 The spectral peak shifts significantly toward the low binding energy direction. This is because oxygen escapes from the ZnO crystal under the action of plasma, generating oxygen vacancies and free ions. This fully demonstrates that strong interactions occur between CuZn nanoparticles, effectively regulating the electronic distribution of CuZn species on the surface of the ethanol catalyst. From the deconvolution results, it can be concluded that the proportion of reduced Cu in Example 1 (0.66) is much higher than that in Comparative Example 1 (0.45). This is due to the enhanced synergistic effect of the CuZn interface, which increases the proportion of reduced Cu species and is the direct reason why the catalytic activity of Example 1 is higher than that of Comparative Example 1. From the Cu Auger electron spectroscopy (LMM) spectrum, the deconvolution results of Figure 2B show that the Cu in Example 1 0 The ratio (0.43) is significantly improved compared with 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 dissociative adsorption capacity of the example catalyst for H2.

[0099] The corresponding process conditions for preparing the catalysts in the above comparative examples and examples are shown in Table 1.

[0100] Table 1

[0101] From the data in Table 1, it can be seen that the catalyst (Cu 0 +Cu + ) / (Cu 2+ +Cu 0 +Cu + ) has been significantly improved.

[0102] The corresponding performance evaluation results of the catalysts prepared in the above comparative examples and examples are shown in Table 2.

[0103] Table 2

[0104] The data in Table 2 show that the plasma-treated catalyst significantly improves both the methyl acetate conversion rate and the ethanol selectivity in the methyl acetate hydrogenation to ethanol reaction. After a period of reaction time, the catalytic activity remains almost unchanged, demonstrating excellent stability.

[0105] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A preparation method of a CuZn-based catalyst, characterized in that, It includes the following steps: (S1) Obtain a CuZn-based catalyst precursor; (S2) Mix the CuZn-based catalyst precursor and an auxiliary agent, and perform dry granulation; (S3) Place the particle sample obtained after dry granulation in a dielectric barrier plasma discharge region, introduce a dielectric gas for discharge treatment to obtain the CuZn-based catalyst.

2. The preparation method according to claim 1, characterized in that, In step (S3), the operating power of the plasma used is 5 - 500 W; The discharge treatment method is continuous treatment or intermittent treatment. The duration of continuous treatment is 0.1 - 5 h, and the duration of intermittent treatment is 0.1 - 20 h.

3. The preparation method according to claim 1 or 2, characterized in that, In step (S3), the dielectric gas includes a reducing gas, and the reducing gas is selected from at least one of H2, CO, and CH4.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The dielectric gas further includes an inert gas, and the inert gas is selected from at least one of N2 and Ar; The volume ratio of the inert gas to the reducing gas is 10 - 30:

1.

5. The preparation method according to any one of claims 1-4, characterized in that, The flow rate of the dielectric gas is 30 - 500 ml / min.

6. The preparation method according to any one of claims 1-5, characterized in that, In step (S1), the method for obtaining the CuZn-based catalyst precursor includes: Prepare a mixed metal salt solution of copper and zinc, and prepare an alkaline solution; Mix the two for coprecipitation reaction, and after aging, washing, drying, and calcination, obtain The CuZn-based catalyst precursor.

7. The preparation method according to claim 6, characterized in that, The mixed metal salt solution of copper and zinc is a mixed solution of copper nitrate and zinc nitrate; The alkali in the alkaline solution includes at least one of hydroxides, carbonates, bicarbonates, ammonia water, and urea.

8. The preparation method according to claim 6 or 7, characterized in that, The temperature of the aging is 30 - 90 °C, and the duration of the aging is 0.5 - 24 h.

9. The preparation method according to any one of claims 6 - 8, characterized in that, Preferably, the calcination conditions include: carried out in an oxygen-containing atmosphere, the calcination temperature is 300 - 600 °C, and the calcination time is 1 - 10 h.

10. The preparation method according to any one of claims 6-9, characterized in that, When preparing the mixed metal salt solution of copper and zinc, add a synergistic metal salt; The synergistic metal is selected from at least one of Al, Mg, Mn, Ni, Co, Cr, Ce, and Ti.

11. The preparation method according to any one of claims 1-10, characterized in that, In step (S2), the particle size of the particle sample obtained after dry granulation is 0.1 - 5 mm.

12. The preparation method according to any one of claims 1-11, characterized in that, In step (S2), the auxiliary agent is graphite.

13. The preparation method according to any one of claims 1-12, characterized in that, The addition amount of the auxiliary agent is 3 wt% - 20 wt% of the mass of the CuZn-based catalyst precursor.

14. The CuZn-based catalyst prepared by the preparation method of the CuZn-based catalyst according to any one of claims 1 to 13, characterized in that, In the CuZn-based catalyst, the mass ratio of CuO to ZnO is 1:0.01 - 5.

15. The CuZn-based catalyst according to claim 14, wherein The CuZn-based catalyst is reduced and activated to obtain active Cu species, and the active Cu species include Cu 2+ , Cu 0 and Cu + . The proportion of Cu 0 and Cu + species in the total species is denoted as a; a = (Cu 0 + Cu + ) / (Cu 2+ + Cu 0 + Cu + ); 0.75 ≥ a ≥ 0.

60.

16. Application of the CuZn-based catalyst prepared by the preparation method of the CuZn-based catalyst according to any one of claims 1 - 13 in the hydrogenation of methyl acetate to prepare ethanol.

17. The application according to claim 16, wherein The CuZn-based catalyst is used after being tableted, crushed, and screening out catalyst particles with a mesh size of 20 - 40.

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