A copper-gallium bimetallic silicon-based carrier catalyst, a preparation method and application thereof

Abstract

This invention relates to the field of catalysis technology, and discloses a copper-gallium bimetallic silicon-based supported catalyst, its preparation method, and its applications. The copper-gallium bimetallic silicon-based supported catalyst of this invention comprises a silicon-based support, copper species nanoparticles attached to the surface of the silicon-based support, and gallium species coated on the surface of the copper species nanoparticles; in the copper-gallium bimetallic silicon-based supported catalyst, the copper loading is 20-40 wt%, and the gallium loading is 3-7 wt%. This invention uses an ammonia stripping method to load copper species onto a silicon-based support and introduces gallium species to partially cover the surface of the copper species, thereby obtaining a catalyst with copper-gallium dual active metals. This catalyst has the advantages of simple preparation method and low cost (no precious metals); furthermore, when this catalyst is used in the hydrogenation of dimethyl oxalate to ethylene glycol, it exhibits high catalytic activity, high selectivity, and high stability.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and in particular to a copper-gallium bimetallic silicon-based supported catalyst, its preparation method, and its application. Background Technology

[0002] Ethylene glycol (EG) is an important basic chemical raw material, widely used in industries such as antifreeze, coolant, polyester fiber, and plastics. Currently, EG synthesis routes mainly include the traditional petroleum route and the coal chemical route. The traditional chemical route (oxyethane hydration method) is a mature technology and the dominant technology globally; however, its production raw materials are highly dependent on petroleum, and it has high water and energy consumption. The coal chemical route is an important supplement to EG production, mainly consisting of three steps: coal reacts with steam and oxygen to generate syngas; the hydrogen content in CO is further reduced, and then it is coupled to synthesize dimethyl oxalate (DMO); dimethyl oxalate reacts with hydrogen in the presence of a catalyst to produce EG. This route has attracted widespread attention due to its advantages such as wide availability of raw materials, high atom economy, and mild conditions.

[0003] However, a drawback of the dimethyl oxalate hydrogenation to ethylene glycol route is the limitation of the copper-silicon catalyst's lifetime. Under polar solvent reaction atmospheres, the active copper nanoparticles in the catalyst are prone to sintering and deactivation; and the sintering of active copper nanoparticles is even more severe under atmospheric pressure. In existing technologies, although the addition of fullerenes can improve the stability of the copper-silicon catalyst and the ethylene glycol yield under atmospheric pressure to some extent, the cost of this catalyst is high.

[0004] Therefore, designing and developing a copper-silicon catalyst that is inexpensive, highly active, selective, and stable is of great significance for achieving high-performance and long-lasting catalytic hydrogenation of dimethyl oxalate to ethylene glycol. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a copper-gallium bimetallic silicon-based catalyst, its preparation method, and its applications. This invention uses an ammonia stripping method to load copper species onto a silicon-based support and introduces gallium species to partially cover the surface of the copper species, thereby obtaining a catalyst with both copper and gallium active metals. This catalyst features a simple preparation method and low cost (no precious metals). Furthermore, when used in the hydrogenation of dimethyl oxalate to ethylene glycol, this catalyst exhibits high catalytic activity, high selectivity, and high stability.

[0006] The specific technical solution of this application includes:

[0007] First, a copper-gallium bimetallic silicon-based catalyst includes a silicon-based support, copper species nanoparticles attached to the surface of the silicon-based support, and gallium species coated on the surface of the copper species nanoparticles.

[0008] The catalyst of this invention uses silicon-based materials as a support and copper and gallium species as the main active components. It contains no precious metals, thus offering the advantage of low cost. This invention reveals that when applied to the hydrogenation of dimethyl oxalate to ethylene glycol, this catalyst exhibits high catalytic activity, high selectivity, and high stability. The reasons for this are as follows: First, gallium modification of the copper species nanoparticles alters the electronic properties and geometry of the catalyst's active components, thereby enhancing the dissociation ability of hydrogen. The synergistic effect between the copper and gallium species improves reaction activity and product selectivity, achieving highly efficient catalysis of the hydrogenation of dimethyl oxalate to ethylene glycol. Second, the gallium species clusters in the catalyst coat the surface of the copper species nanoparticles, inhibiting their migration and aggregation, thus significantly improving the catalyst's stability.

[0009] In the copper-gallium bimetallic silicon-based supported catalyst, the copper loading is 20-40 wt% (the numerator is the copper element content, and the denominator is the total catalyst content), more preferably 25-35 wt%, and the gallium loading is 3-7 wt% (the numerator is the gallium element content, and the denominator is the total catalyst content).

[0010] The reason why the loading of copper and gallium in this invention is within the above range is that: (1) if the gallium content is too high, the outer layer of copper species nanoparticles will be over-covered, the exposed active sites will be reduced, and the catalytic activity will decrease; at the same time, excessive gallium species will also make gallium species clusters unevenly distributed, forming flocculent matter that leads to particle agglomeration, resulting in decreased activity and selectivity; (2) if the copper content is too high, larger copper species nanoparticles will be formed, which will also cause a decrease in activity.

[0011] Preferably, the copper species nanoparticles have a particle size of 2-12 nm; more preferably, they have a particle size of 3-6 nm.

[0012] If the copper species nanoparticles are too small, they will have a higher number of unsaturated coordination sites. These sites are more prone to hydrogenolysis of the CO bond, leading to decarbonylation / dealkoxylation side reactions in MG, generating large amounts of unwanted methyl glycolate and glycolic acid, causing a sharp decrease in EG selectivity. Simultaneously, small-diameter copper species nanoparticles have high surface energy, making them more likely to migrate and aggregate during the exothermic hydrogenation reaction, resulting in a gradual decrease in activity and selectivity. Conversely, if the copper species nanoparticles are too large, the total number of active sites will decrease, reducing the activity of the second step of MG hydrogenation to form EG, leading to incomplete reaction.

[0013] Preferably, the silicon-based support comprises one or more of silicon-based molecular sieves, amorphous silica, diatomaceous earth, and silicon-based porous glass.

[0014] Preferably, the copper species nanoparticles are elemental copper nanoparticles and / or copper oxide nanoparticles.

[0015] Preferably, the gallium species are gallium elemental nanoparticles and / or gallium oxide nanoparticles.

[0016] Secondly, a method for preparing the above-mentioned copper-gallium bimetallic silicon-based supported catalyst includes the following steps: dispersing copper salt in deionized water, adding ammonia water and stirring evenly, adding silicon-based support, heating and steaming ammonia, filtering and washing, drying the obtained product, calcining, and then physically mixing gallium source and reducing to obtain copper-gallium bimetallic silicon-based supported catalyst.

[0017] The preparation principle described above is as follows: by adding ammonia to a copper salt solution, a soluble copper-ammonia complex is formed. Then, by heating to drive out the ammonia gas, the pH value of the solution slowly and uniformly decreases, and copper ions are simultaneously and uniformly co-precipitated in a specific form. During the high-temperature hydrogen reduction process, metallic gallium exists in liquid form and has a certain dispersion and migration ability. After interacting with copper nanoparticles, it coats their surface.

[0018] This invention employs an ammonia stripping process, which, compared to the conventional impregnation method (using gallium nitrate, gallium chloride, and gallium acetate as precursors), results in stronger interaction between copper and gallium species after reduction, better ethylene glycol yield, and better catalytic performance.

[0019] Preferably, the copper salt is copper nitrate; and the gallium source is liquid metallic gallium.

[0020] This invention reveals that the choice of gallium source has a significant impact on the preparation process. Metallic gallium is more likely to synergize with copper species, resulting in a better bond between the two metals and higher activity.

[0021] Preferably, the mass ratio of ammonia to copper salt is 1.2-2:1.

[0022] During the ammonia stripping process, the amount of ammonia added has a significant impact on the catalyst structure and catalytic performance. Excessive ammonia will cause copper species to agglomerate into larger particles, reducing active sites and decreasing catalytic activity and selectivity. Insufficient ammonia will prevent the formation of a sufficient amount of stable copper-ammonia complex, and copper species will not be uniformly released and loaded onto the support, resulting in poor dispersion, reduced active sites, and decreased catalytic performance.

[0023] Preferably, the temperature for heating and steaming ammonia is 75-90°C.

[0024] Preferably, the roasting temperature is 200-600℃.

[0025] Preferably, the temperature of the reduction treatment is 200-500℃ (more preferably 250-350℃).

[0026] Finally, a method for preparing ethylene glycol by catalyzing the hydrogenation of dimethyl oxalate using the above-mentioned copper-gallium bimetallic silicon-based supported catalyst includes the following steps:

[0027] S1: The copper-gallium bimetallic silicon-based supported catalyst is granulated and mixed evenly with quartz sand, then fixedly packed into a fixed-bed reactor for reduction treatment.

[0028] S2: Using hydrogen as the carrier gas, the reaction liquid containing dimethyl oxalate is vaporized and then passed into a fixed-bed reactor. During the transport process, dimethyl oxalate undergoes a hydrogenation reaction to obtain ethylene glycol.

[0029] Preferably, in S1, the loading amount of the copper-gallium bimetallic silicon-based support catalyst is 0.1-2g.

[0030] Preferably, in S1, the reduction process involves passing hydrogen gas into a fixed-bed reactor, and the reduction temperature is 200-600℃ (more preferably 250-350℃).

[0031] Preferably, in S2, the concentration of dimethyl oxalate in the reaction solution is 5-20 wt%.

[0032] Preferably, in S2, the solvent of the reaction solution includes one or more of methanol, ethanol, butanol, dimethyl carbonate, tetrahydrofuran, and water.

[0033] Preferably, in S2, the volume ratio of hydrogen to dimethyl oxalate is 50-250:1.

[0034] Preferably, in S2, the conditions for the hydrogenation reaction are: LHSV of 0.1-5 h. -1 The reaction pressure is 0.1-3 MPa and the reaction temperature is 150-300℃.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] (1) The catalyst of this invention uses silicon-based materials as a support, with copper and gallium species as the main active components, and gallium species clusters are coated on the surface of copper species nanoparticles. When this catalyst is applied to the hydrogenation of dimethyl oxalate to ethylene glycol, it has the characteristics of high catalytic activity, high selectivity and high stability.

[0037] (2) In this invention, copper species are loaded onto a silicon-based support by ammonia stripping, and gallium species are introduced to partially cover the surface of the copper species, thereby obtaining a catalyst with copper-gallium dual-active metals. The metals used in this preparation method are all non-precious metals, which are widely available and low in cost, and the preparation process is simple, which is conducive to large-scale production.

[0038] (3) This invention provides a method for the hydrogenation of dimethyl oxalate to ethylene glycol. The method has mild reaction conditions (carried out at low temperature), high atom economy, and no toxic or harmful substances are generated in the entire synthesis process, making it green and environmentally friendly. Attached Figure Description

[0039] Figure 1 The image shows a scanning electron microscope (SEM) image of the catalyst (pure silicon ZSM-5 supported with 30 wt% Cu + 1% Ga / SiO2) prepared in Example 2.

[0040] Figure 2 Transmission electron microscopy (TEM) image of the catalyst prepared in Example 2 after hydrogenation reaction;

[0041] Figure 3 The particle size distribution diagram is shown for the catalyst prepared in Example 2.

[0042] Figure 4 The image shows the XRD pattern of the catalyst prepared in Example 2 after the reaction.

[0043] Figure 5 The image shows the EELS diagram of the catalyst prepared in Example 2 after the reaction. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to specific embodiments. The reactions in the following examples and comparative examples were all carried out in a fixed-bed reactor. These examples are intended to enable those skilled in the art to gain a more comprehensive understanding of the invention, but do not limit the invention in any way.

[0045] First, a copper-gallium bimetallic silicon-based catalyst includes a silicon-based support, copper species nanoparticles attached to the surface of the silicon-based support, and gallium species coated on the surface of the copper species nanoparticles.

[0046] In the copper-gallium bimetallic silicon-based supported catalyst, the copper loading is 20-40 wt%, more preferably 25-35 wt%, and the gallium loading is 3-7 wt%.

[0047] In some embodiments, the particle size of the copper species nanoparticles is 2-12 nm; more preferably 3-6 nm.

[0048] In some embodiments, the silicon-based support includes one or more of silicon-based molecular sieves, amorphous silica, diatomaceous earth, and silicon-based porous glass.

[0049] In some embodiments, the copper species nanoparticles are elemental copper nanoparticles and / or copper oxide nanoparticles.

[0050] In some embodiments, the gallium species are gallium elemental nanoparticles and / or gallium oxide nanoparticles.

[0051] Secondly, a method for preparing the above-mentioned copper-gallium bimetallic silicon-based supported catalyst includes the following steps: dispersing copper salt in deionized water, adding ammonia water and stirring evenly, adding silicon-based support, heating and steaming ammonia, filtering and washing, drying the obtained product, calcining, and then physically mixing gallium source and reducing to obtain copper-gallium bimetallic silicon-based supported catalyst.

[0052] In some embodiments, the copper salt is copper nitrate.

[0053] In some implementations, the gallium source is metallic gallium.

[0054] In some embodiments, the mass ratio of the ammonia water (ammonia water concentration of 25-28%) to the copper salt is 1.2-2:1.

[0055] In some implementations, the temperature for heating and vaporizing ammonia is 75-90°C.

[0056] In some embodiments, the calcination temperature is 200-600°C.

[0057] In some embodiments, the reduction treatment temperature is 200-500°C (more preferably 250-350°C).

[0058] Finally, a method for preparing ethylene glycol by catalyzing the hydrogenation of dimethyl oxalate using the above-mentioned copper-gallium bimetallic silicon-based supported catalyst includes the following steps:

[0059] S1: The copper-gallium bimetallic silicon-based supported catalyst is granulated and mixed evenly with quartz sand, then fixedly packed into a fixed-bed reactor for reduction treatment.

[0060] In some embodiments, in S1, the loading amount of the copper-gallium bimetallic silicon-based supported catalyst is 0.1-2g.

[0061] In some embodiments, in S1, the reduction process involves passing hydrogen gas into a fixed-bed reactor, and the reduction temperature is 200-600°C (more preferably 250-350°C).

[0062] S2: Using hydrogen as the carrier gas, the reaction liquid containing dimethyl oxalate is vaporized and then passed into a fixed-bed reactor. During the transport process, dimethyl oxalate undergoes a hydrogenation reaction to obtain ethylene glycol.

[0063] In some embodiments, in S2, the concentration of dimethyl oxalate in the reaction solution is 5-20 wt%.

[0064] In some embodiments, in S2, the solvent of the reaction solution includes one or more of methanol, ethanol, butanol, dimethyl carbonate, tetrahydrofuran, and water.

[0065] In some embodiments, in S2, the volume ratio of hydrogen to dimethyl oxalate is 50-250:1.

[0066] In some embodiments, in S2, the conditions for the hydrogenation reaction are: LHSV of 0.1-5 h. -1 The reaction pressure is 0.1-3 MPa and the reaction temperature is 150-300℃.

[0067] Catalyst reduction methods and catalyst evaluation conditions

[0068] The methods for online reduction and catalytic performance evaluation of the catalysts in Examples 1-6 and Comparative Examples 1-6 of this application are as follows: 0.5g of catalyst was mixed with 2g of quartz sand and placed in the middle of a fixed-bed reactor. Hydrogen reduction was performed at 200-300°C for 3 hours. After reduction, the reaction temperature was adjusted to 180°C. Using hydrogen as the carrier gas, a 10wt% DMO / MeOH solution was vaporized and introduced into the fixed-bed reactor. The hydrogen-to-ester ratio (volume ratio of hydrogen to dimethyl oxalate) was 100:1, and the LHSV was 0.6-5 hours. -1 The reaction pressure was 0.1 MPa. After condensation and gas-liquid separation, the reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol were calculated.

[0069] Example 1

[0070] Preparation of copper-gallium bimetallic silicon-based supported catalyst (metallic gallium, physically mixed gallium, copper-gallium mass ratio 30:1):

[0071] Preparation of copper-based catalyst by ammonia stripping method: 5.7 g of copper nitrate trihydrate was weighed and added to 150 mL of deionized water, followed by 8 mL of ammonia solution (28% concentration). The mixture was stirred for 10 min until the copper nitrate was completely dissolved. Then, 3.5 g of pure silicon ZSM-5 was added, and the mixture was stirred at 80°C for 6 h to strip ammonia. The mixed solution was then filtered and washed with deionized water. The resulting sample was dried overnight in a 100°C oven and finally calcined in a muffle furnace at 400°C for 4 h to obtain a copper-based catalyst with a Cu loading of approximately 30 wt%.

[0072] Preparation of copper-gallium bimetallic silicon-based supported catalyst: 3g of the copper-based catalyst obtained above was placed in a round-bottom flask and vacuum-dried in a sand bath at 160°C for 2h to remove moisture. After cooling to room temperature, 30.3mg of metallic gallium was added, and vacuum treatment in a sand bath at 160°C continued for 2h. After cooling to room temperature, it was ground for 20min, and then reduced at 300°C with hydrogen permeation at 30mL / min for 3h to obtain the copper-gallium bimetallic silicon-based supported catalyst with a Ga loading of approximately 1wt%.

[0073] In this embodiment, the catalyst was reduced at 300°C for 3 hours under the aforementioned reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 hours. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 68.2%, while the EG selectivity was 78.3%.

[0074] Example 2

[0075] Preparation of copper-gallium bimetallic silicon-based supported catalyst (metallic gallium, physically mixed gallium, copper-gallium mass ratio 30:5):

[0076] The copper-gallium mass ratio of 30:1 in Example 1 is replaced with 30:5, and the other conditions are the same as in Example 1, as follows:

[0077] 3g of the copper-based catalyst prepared by the ammonia distillation method was placed in a round-bottom flask and vacuum-dried in a sand bath at 160°C for 2 hours to remove moisture. After cooling to room temperature, the corresponding mass of metallic gallium (mass ratio Cu:Ga = 30:5) was added, and vacuum treatment in a sand bath at 160°C continued for 2 hours. After cooling to room temperature, it was ground for 20 minutes, and then reduced at 300°C with hydrogen permeation at 30 mL / min for 3 hours to obtain the catalyst with a Ga loading of approximately 5 wt%.

[0078] In this embodiment, the catalyst was reduced at 300°C for 3 hours under the aforementioned reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 hours. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 100%, while the EG selectivity was 91.1%.

[0079] Example 3

[0080] Preparation of copper-gallium bimetallic silicon-based supported catalyst (metallic gallium, physically mixed gallium, copper-gallium mass ratio 30:10):

[0081] The copper-gallium mass ratio of 30:1 in Example 1 is replaced with 30:10, and the other conditions are the same as in Example 1, as follows:

[0082] 3g of the copper-based catalyst prepared by the ammonia distillation method was placed in a round-bottom flask and vacuum-dried in a sand bath at 160°C for 2 hours to remove moisture. After cooling to room temperature, the corresponding mass of metallic gallium (mass ratio Cu:Ga = 30:10) was added, and vacuum treatment in a sand bath at 160°C continued for 2 hours. After cooling to room temperature, it was ground for 20 minutes, and then reduced at 300°C with hydrogen permeation at 30 mL / min for 3 hours to obtain the catalyst with a Ga loading of approximately 10 wt%.

[0083] In this embodiment, the catalyst was reduced at 300°C for 3 hours under the aforementioned reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 hours. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 42.3%, while the EG selectivity was 50.6%.

[0084] Example 4

[0085] The reduction temperature of 300°C in the preparation process and before catalytic use of the catalyst in Example 3 was replaced with 200°C, and the other conditions were the same as in Example 3.

[0086] In this embodiment, the catalyst was reduced at 200°C for 3 hours under the aforementioned reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 hours. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 20.3%, while the EG selectivity was 32.8%.

[0087] Example 5

[0088] Preparation of copper-gallium bimetallic silicon-based supported catalyst (metallic gallium, physically mixed gallium, copper-gallium mass ratio 20:5):

[0089] The Cu loading in Example 2 was replaced with 20 wt%, the copper-gallium mass ratio of 30:5 was replaced with 20:5, and the other conditions were the same as in Example 2, as follows:

[0090] 3.8 g of copper nitrate trihydrate was weighed and added to 150 mL of deionized water, followed by 8 mL of ammonia (28% concentration). The mixture was stirred for 10 min until the copper nitrate was completely dissolved. Then, 4 g of pure silicon ZSM-5 was added, and the mixture was stirred at 80°C for 6 h to remove ammonia. The mixture was then filtered and washed with deionized water. The resulting sample was dried overnight in a 100°C oven and finally calcined in a muffle furnace at 400°C for 4 h to obtain a copper-based catalyst with a Cu loading of approximately 20 wt%.

[0091] 3g of the copper-based catalyst prepared by the ammonia distillation method was placed in a round-bottom flask and vacuum-dried in a sand bath at 160°C for 2 hours to remove moisture. After cooling to room temperature, the corresponding mass of metallic gallium (mass ratio Cu:Ga = 20:5) was added, and vacuum treatment in a sand bath at 160°C continued for 2 hours. After cooling to room temperature, it was ground for 20 minutes, and then reduced at 300°C with hydrogen permeation at 30 mL / min for 3 hours to obtain the catalyst with a Ga loading of approximately 5 wt%.

[0092] In this embodiment, the catalyst was reduced at 300°C for 3 hours under the aforementioned reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 h. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 56.4%, while the EG selectivity was 21.4%.

[0093] Example 6

[0094] Preparation of copper-gallium bimetallic silicon-based supported catalyst (metallic gallium, physically mixed gallium, copper-gallium mass ratio 20:10):

[0095] The copper-gallium mass ratio of 20:5 in Example 4 is replaced with 20:10, and the other conditions are the same as in Example 4, as follows:

[0096] 3g of the copper-based catalyst prepared by the ammonia distillation method was placed in a round-bottom flask and vacuum-dried in a sand bath at 160°C for 2 hours to remove moisture. After cooling to room temperature, the corresponding mass of metallic gallium (mass ratio Cu:Ga = 20:10) was added, and vacuum treatment in a sand bath at 160°C continued for 2 hours. After cooling to room temperature, it was ground for 20 minutes, and then reduced at 300°C with hydrogen permeation at 30 mL / min for 3 hours to obtain the catalyst with a Ga loading of approximately 10 wt%.

[0097] In this embodiment, the catalyst was reduced at 300°C for 3 hours under the aforementioned reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 h. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 25.6%, while the EG selectivity was 22.8%.

[0098] Comparative Example 1

[0099] Preparation of copper-gallium bimetallic silicon-based supported catalyst (gallium nitrate, impregnation method, copper-gallium mass ratio 30:1):

[0100] This comparative example describes the preparation of a copper-gallium bimetallic silicon-based supported catalyst by introducing gallium species through an impregnation method, as detailed below:

[0101] Preparation of copper-based catalyst by ammonia stripping method: 5.7 g of copper nitrate trihydrate was weighed and added to 150 mL of deionized water, followed by 8 mL of ammonia solution (28% concentration). The mixture was stirred for 10 min until the copper nitrate was completely dissolved. Then, 3.5 g of pure silicon ZSM-5 was added, and the mixture was stirred at 80°C for 6 h to strip ammonia. The mixed solution was then filtered and washed with deionized water. The resulting sample was dried overnight in a 100°C oven and finally calcined in a muffle furnace at 400°C for 4 h to obtain a copper-based catalyst with a Cu loading of approximately 30 wt%.

[0102] Preparation of gallium-modified copper-based catalyst: 3g of the copper-based catalyst obtained above was mixed with 5 mL of deionized water, and the corresponding amount of gallium nitrate (mass ratio Cu:Ga=30:1) was added. After sonication at room temperature for 2h, the catalyst was dried in an oven at 60°C overnight, then calcined in a muffle furnace at 400°C for 3h, and then reduced at 300°C and 30mL / min under hydrogen gas conditions for 3h to obtain the catalyst with a Ga loading of about 1wt%.

[0103] The comparative catalyst was reduced at 300°C for 3 h under the above reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 h. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 33.4%, while the EG selectivity was 26.4%.

[0104] Comparative Example 2

[0105] Preparation of copper-gallium bimetallic silicon-based supported catalyst (gallium nitrate, impregnation method, copper-gallium mass ratio 30:5):

[0106] Replace the copper-gallium mass ratio of 30:1 in Comparative Example 1 with 30:5, and keep all other conditions the same as in Comparative Example 1, as follows:

[0107] 3 g of copper-based catalyst obtained by ammonia distillation was mixed with 5 mL of deionized water and the corresponding amount of gallium nitrate (mass ratio Cu:Ga=30:5) was added. After sonication at room temperature for 2 h, the catalyst was dried in an oven at 60°C overnight. Then, it was calcined in a muffle furnace at 400°C for 3 h and then reduced at 300°C and 30 mL / min of hydrogen gas for 3 h to obtain the catalyst with a Ga loading of about 5 wt%.

[0108] The comparative catalyst was reduced at 300°C for 3 h under the above reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 h. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 30.8%, while the EG selectivity was 25.1%.

[0109] Comparative Example 3

[0110] Preparation of copper-gallium bimetallic silicon-based supported catalyst (gallium chloride, impregnation method, copper-gallium mass ratio 30:5):

[0111] In Comparative Example 2, gallium nitrate, the gallium precursor, was replaced with gallium chloride, and all other conditions remained the same as in Comparative Example 2, as follows:

[0112] 3 g of copper-based catalyst obtained by ammonia distillation was mixed with 5 mL of deionized water and the corresponding amount of gallium chloride (mass ratio Cu:Ga=30:5) was added. After sonication at room temperature for 2 h, the catalyst was dried in an oven at 60°C overnight. Then, it was calcined in a muffle furnace at 400°C for 3 h and then reduced at 300°C and 30 mL / min of hydrogen gas for 3 h to obtain the catalyst with a Ga loading of about 5 wt%.

[0113] The comparative catalyst was reduced at 300°C for 3 h under the above reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 h. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 25.3%, while the EG selectivity was 28.9%.

[0114] Comparative Example 4

[0115] Preparation of copper-gallium bimetallic silicon-based supported catalyst (gallium acetate, impregnation method, copper-gallium mass ratio 30:5):

[0116] In Comparative Example 2, gallium nitrate, the gallium precursor, was replaced with gallium acetate, and all other conditions remained the same as in Comparative Example 2, as follows:

[0117] 3 g of copper-based catalyst obtained by ammonia distillation was mixed with 5 mL of deionized water and the corresponding amount of gallium acetate (mass ratio Cu:Ga=30:5) was added. After sonication at room temperature for 2 h, the catalyst was dried in an oven at 60°C overnight. Then, it was calcined in a muffle furnace at 400°C for 3 h and then reduced at 300°C and 30 mL / min of hydrogen gas for 3 h to obtain the catalyst with a Ga loading of about 5 wt%.

[0118] The comparative catalyst was reduced at 300°C for 3 h under the above reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 h. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 31.8%, while the EG selectivity was 26.7%.

[0119] Comparative Example 5

[0120] Preparation of copper-gallium bimetallic silicon-based supported catalyst (ammonia to copper nitrate mass ratio 3:1, metallic gallium, copper-gallium mass ratio 30:5):

[0121] The amount of ammonia water added in the preparation of copper-based catalysts by the ammonia stripping method in Example 2 was changed from 8 mL to 17.1 mL, and the other conditions were the same as in Example 2, as follows:

[0122] Preparation of copper-based catalyst by ammonia stripping method: 5.7 g of copper nitrate trihydrate was weighed and added to 150 mL of deionized water, followed by 17.1 mL of ammonia solution (28% ammonia concentration). The mixture was stirred for 10 min until the copper nitrate was completely dissolved. Then, 3.5 g of pure silicon ZSM-5 was added, and the mixture was stirred at 80°C for 6 h to strip ammonia. The mixed solution was then filtered and washed with deionized water. The resulting sample was dried overnight in a 100°C oven and finally calcined in a muffle furnace at 400°C for 4 h to obtain a copper-based catalyst with a Cu loading of approximately 30 wt%.

[0123] 3g of the copper-based catalyst prepared by the ammonia distillation method was placed in a round-bottom flask and vacuum-dried in a sand bath at 160°C for 2 hours to remove moisture. After cooling to room temperature, the corresponding mass of metallic gallium (mass ratio Cu:Ga = 30:5) was added, and vacuum treatment in a sand bath at 160°C continued for 2 hours. After cooling to room temperature, it was ground for 20 minutes, and then reduced at 300°C with hydrogen permeation at 30 mL / min for 3 hours to obtain the catalyst with a Ga loading of approximately 5 wt%.

[0124] The comparative catalyst was reduced at 300°C for 3 hours under the above reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 hours. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 55.4%, while the EG selectivity was 65.3%.

[0125] Comparative Example 6

[0126] Preparation of copper-gallium bimetallic silicon-based supported catalyst (ammonia to copper nitrate mass ratio 1:1, metallic gallium, copper-gallium mass ratio 30:5):

[0127] The amount of ammonia water added in the preparation of copper-based catalysts by the ammonia stripping method in Example 2 was changed from 8 mL to 5.7 mL, and the other conditions were the same as in Example 2, as follows:

[0128] Preparation of copper-based catalyst by ammonia stripping method: 5.7 g of copper nitrate trihydrate was weighed and added to 150 mL of deionized water, followed by 5.7 mL of ammonia solution (28% ammonia concentration). The mixture was stirred for 10 min until the copper nitrate was completely dissolved. Then, 3.5 g of pure silicon ZSM-5 was added, and the mixture was stirred at 80°C for 6 h to strip ammonia. The mixed solution was then filtered and washed with deionized water. The resulting sample was dried overnight in a 100°C oven and finally calcined in a muffle furnace at 400°C for 4 h to obtain a copper-based catalyst with a Cu loading of approximately 30 wt%.

[0129] 3g of the copper-based catalyst prepared by the ammonia distillation method was placed in a round-bottom flask and vacuum-dried in a sand bath at 160°C for 2 hours to remove moisture. After cooling to room temperature, the corresponding mass of metallic gallium (mass ratio Cu:Ga = 30:5) was added, and vacuum treatment in a sand bath at 160°C continued for 2 hours. After cooling to room temperature, it was ground for 20 minutes, and then reduced at 300°C with hydrogen permeation at 30 mL / min for 3 hours to obtain the catalyst with a Ga loading of approximately 5 wt%.

[0130] In this embodiment, the catalyst was reduced at 300°C for 3 hours under the aforementioned reduction method and catalyst evaluation conditions, with a normal pressure of H2 of 0.1 MPa and an LHSV of 1.2 hours. -1 The product was evaluated by gas chromatography, and the DMO conversion rate was 40.8%, while the EG selectivity was 36.7%.

[0131] Performance Comparison

[0132] Table 1: Catalytic performance data of various catalysts for the hydrogenation of dimethyl oxalate to ethylene glycol

[0133]

[0134] A comparison of the data in Table 1 shows that:

[0135] As can be seen from Examples 1-3, the catalyst activity tends to increase first and then decrease as the Ga loading increases. The performance is best when Cu:Ga = 30:5. The conversion rate of dimethyl oxalate in Example 2 is the highest, reaching 100%. The conversion rate of Example 1 is 68.2%, indicating that the increase in active sites generated by the synergistic effect of copper and gallium in Example 2 leads to the increase in activity. However, the conversion rate of Example 3 is only 42.3%, indicating that the excessive gallium species cover the copper active sites, resulting in a decrease in activity.

[0136] As can be seen from Examples 3 and 4, Example 4 reduced the reduction temperature and the yield was only 6.6%, while Example 3 had a yield of 21.4%. The reduction conditions have a significant impact on the preparation process. The lower reduction temperature cannot enable strong interactions between copper and gallium species to improve catalytic activity.

[0137] The comparison between Examples 2 and 5, and Examples 3 and 6, shows that changing the mass ratio and loading of copper and gallium during catalyst preparation alters both the activity and selectivity of the catalyst. Higher loading results in more active sites and higher catalytic activity.

[0138] Examples 1, 2, 1, 2, 3, and 4 show that the gallium precursor has a significant impact on the preparation process. Metallic gallium is more likely to synergize with copper species, resulting in better bonding between the two metals and higher activity. However, the copper-gallium bimetallic silicon-based catalysts synthesized using the impregnation method with gallium nitrate, gallium chloride, and gallium acetate as precursors and supporting Ga exhibit weaker interaction between copper and gallium species after reduction, with EG yields all below 10% and poorer catalytic performance.

[0139] As can be seen from Examples 2 and Comparative Examples 5 and 6, the amount of ammonia added during the preparation of copper-based catalysts by the ammonia stripping method has a significant impact on the catalyst structure and catalytic performance. Excessive ammonia will cause copper species to agglomerate into larger particles, reducing the number of active sites and decreasing catalytic activity and selectivity. Insufficient ammonia will prevent the formation of a sufficient amount of stable copper-ammonia complex, and the copper species will not be uniformly released and loaded onto the support, resulting in poor dispersion, reduced active sites, and decreased catalytic performance.

[0140] As can be seen from the above, the catalyst prepared in Example 2 (pure silicon ZSM-5 supported with 30wt% Cu + 1% Ga / SiO2) exhibits the best catalytic effect. Therefore, further tests were conducted on it, as follows:

[0141] Figure 1 The image shows a scanning electron microscope (SEM) image of the catalyst prepared in Example 2; it can be observed that the copper species nanoparticles are uniformly distributed on the support and maintain a good molecular sieve structure of pure silicon ZSM-5.

[0142] Figure 2 The image shows a transmission electron microscope (TEM) image of the catalyst prepared in Example 2 after hydrogenation. Observation reveals that the copper nanoparticles were not sintered into clusters after the reaction, but maintained a small particle size and were uniformly dispersed on the support surface.

[0143] Figure 3 The particle size distribution diagram of copper species nanoparticles in the catalyst prepared in Example 2 is shown.

[0144] Figure 4 The image shows the XRD pattern of the catalyst prepared in Example 2 after reaction. In the image, 38.7º and 43.2º are the characteristic peaks of Cu2O and Cu, respectively.

[0145] Figure 5 The image shown is an EELS image of the catalyst prepared in Example 2 after the reaction, which shows that copper species nanoparticles are dispersed on the surface of the support, while gallium species are coated on the surface of copper species nanoparticles, and the two interact with each other.

[0146] Example 7

[0147] Take 0.5 g of the copper-gallium bimetallic silicon-based supported catalyst (metallic gallium, physically mixed gallium, copper-gallium mass ratio 30:5) prepared in Example 2, and reduce it at 300°C for 3 h. After reduction, adjust the reaction temperature to 180°C, use hydrogen as the carrier gas, vaporize a 10 wt% DMO / MeOH solution and pass it into a fixed-bed reactor, with a hydrogen-to-ester ratio (volume ratio of hydrogen to dimethyl oxalate) of 100:1 and an LHSV of 3 h. -1 The reaction pressure was 3 MPa. After condensation and gas-liquid separation, the reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate was calculated to be 100%, and the selectivity of ethylene glycol was 98.1%.

[0148] Example 8

[0149] 0.5 g of the copper-gallium bimetallic silicon-based supported catalyst (metallic gallium, physically mixed gallium, copper-gallium mass ratio 20:5) prepared in Example 5 was taken and reduced at 300°C for 3 h. After reduction, the reaction temperature was adjusted to 180°C, and a 10 wt% DMO / MeOH solution was vaporized and introduced into a fixed-bed reactor using hydrogen as the carrier gas. The hydrogen-to-ester ratio (volume ratio of hydrogen to dimethyl oxalate) was 100:1, and the LHSV was 3 h. -1 The reaction pressure was 3 MPa. After condensation and gas-liquid separation, the reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate was calculated to be 78.4%, and the selectivity of ethylene glycol was 88.3%.

[0150] Example 9

[0151] 0.5 g of the copper-gallium bimetallic silicon-based supported catalyst (gallium nitrate, impregnation method, copper-gallium mass ratio 30:5) prepared in Comparative Example 2 was taken and reduced at 300°C for 3 h. After reduction, the reaction temperature was adjusted to 180°C, and a 10 wt% DMO / MeOH solution was vaporized and introduced into a fixed-bed reactor using hydrogen as the carrier gas. The hydrogen-to-ester ratio (volume ratio of hydrogen to dimethyl oxalate) was 100:1, and the LHSV was 3 h. -1 The reaction pressure was 3 MPa. After condensation and gas-liquid separation, the reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate was calculated to be 36.8%, and the selectivity of ethylene glycol was 54.3%.

[0152] As can be seen from Examples 7, 8 and 9, the catalyst prepared under high pressure (3MPa) using metallic gallium as a gallium precursor also has high selectivity, while the catalyst prepared by impregnation method with gallium species has low activity and selectivity. This indicates that metallic gallium can generate strong interaction with copper species, and the performance of the catalyst is improved by the synergistic effect of the two metals.

[0153] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A copper gallium bimetallic silicon-based support catalyst characterized by: It includes a silicon-based carrier, copper species nanoparticles attached to the surface of the silicon-based carrier, and gallium species coated on the surface of the copper species nanoparticles. In the copper-gallium bimetallic silicon-based supported catalyst, the copper loading is 25-35 wt%, and the gallium loading is 3-5 wt%. The preparation method of the copper-gallium bimetallic silicon-based supported catalyst includes: dispersing copper salt in water, adding ammonia water and stirring evenly, adding silicon-based support, heating and steaming ammonia, filtering and washing, drying the obtained product, calcining to obtain copper-based catalyst; then physically mixing liquid metallic gallium and reducing it to obtain copper-gallium bimetallic silicon-based supported catalyst. The physical mixing process involves vacuum drying the copper-based catalyst in a sand bath at 160°C for 2 hours to remove moisture, then adding gallium metal after cooling to room temperature, continuing the vacuum treatment in a sand bath at 160°C for 2 hours, and then grinding for 20 minutes after cooling to room temperature. The reduction treatment temperature is 250-350℃; The ratio of ammonia to copper salt is 8 mL: 5.7 g or 8 mL: 3.8 g.

2. The copper-gallium bimetallic silicon-based supported catalyst as described in claim 1, characterized in that: The copper species nanoparticles have a particle size of 2-12 nm.

3. The copper-gallium bimetallic silicon-based supported catalyst as described in claim 1 or 2, characterized in that: The silicon-based support includes one or more of silicon-based molecular sieves, amorphous silica, diatomaceous earth, and silicon-based porous glass. The copper species nanoparticles are elemental copper nanoparticles and / or copper oxide nanoparticles. The gallium species are gallium elemental nanoparticles and / or gallium oxide nanoparticles.

4. The copper gallium bimetallic silicon-based support catalyst of claim 1, wherein: The copper salt is copper nitrate.

5. The copper-gallium bimetallic silicon-based supported catalyst as described in claim 4, characterized in that: The temperature for ammonia vaporization is 75-90℃; The roasting temperature is 200-600℃.

6. The application of the copper-gallium bimetallic silicon-based supported catalyst as described in any one of claims 1-5 in the catalytic hydrogenation of dimethyl oxalate to ethylene glycol.

7. Use according to claim 6, wherein: Includes the following steps: S1: The copper-gallium bimetallic silicon-based supported catalyst is granulated and mixed evenly with quartz sand, then fixedly packed into a fixed-bed reactor for reduction treatment; S2: Using hydrogen as the carrier gas, the reaction liquid containing dimethyl oxalate is vaporized and then passed into a fixed-bed reactor. During the transport process, dimethyl oxalate undergoes a hydrogenation reaction to obtain ethylene glycol.

8. Use according to claim 7, wherein: In S1, The loading amount of the copper-gallium bimetallic silicon-based supported catalyst is 0.1-2g; The reduction process involves introducing hydrogen gas into a fixed-bed reactor at a reduction temperature of 200-600℃.

9. Use according to claim 8, wherein: In S2, The concentration of dimethyl oxalate in the reaction solution is 5-20 wt%. The solvent of the reaction solution includes one or more of methanol, ethanol, butanol, dimethyl carbonate, tetrahydrofuran, and water. The volume ratio of hydrogen to dimethyl oxalate is 50-250:1; The hydrogenation reaction is carried out under the conditions of LHSV of 0.1-5 h -1 , reaction pressure of 0.1-3 MPa, and reaction temperature of 150-300℃.

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