Pd single-atom catalyst resistant to CO poisoning, preparation method and application thereof

Abstract

The present invention relates to a Pd single-atom catalyst resistant to CO poisoning, wherein the main active component is palladium, the auxiliary active component is molybdenum carbide, and the molybdenum carbide is a nanoparticle of size 2-3nm, the nanoparticles are embedded in a two-dimensional nitrogen-doped carbon support, and palladium is dispersed at the atomic level on the molybdenum carbide; in the catalyst, the Pd content is 0.05wt% to 1wt%, the Mo content is 1wt% to 15wt%, and the molar ratio of Mo to Pd is 50:1 to 3:1. The present invention also relates to a method for preparing the above-mentioned Pd single-atom catalyst resistant to CO poisoning, and the application of the above-mentioned Pd single-atom catalyst resistant to CO poisoning in acetylene selective hydrogenation. In the catalyst, the active component palladium is uniformly dispersed at the atomic level on the MoC-NC support, and the catalyst has high activity and selectivity for acetylene selective hydrogenation reaction, showing high resistance to CO poisoning.

Description

Technical Field

[0001] The present invention relates to the field of acetylene selective hydrogenation catalysis, and in particular to a Pd single-atom catalyst resistant to CO poisoning, a preparation method thereof, and application of the catalyst in acetylene selective hydrogenation. Background Art

[0002] The selective hydrogenation reaction of acetylene is an essential step in the petrochemical production process. In industry, catalytic hydrogenation is used to remove a small amount of acetylene (0.5%-2%) remaining in the ethylene feed gas to avoid poisoning and deactivation of the catalyst in the subsequent polymerization reaction. The supported Pd catalyst has a high activity in the acetylene hydrogenation reaction, but the ethylene selectivity is low. The hydrogenation catalysts currently widely used in industry are appropriately modified Pd-based catalysts, but there are still problems such as low Pd atom utilization. Single-atom catalysts can reduce the cost of catalysts while greatly improving the utilization of precious metals, achieving high selectivity and conversion rate. For example, the catalyst prepared by Academician Li Yadong of Tsinghua University with 0.04wt% Pd single atoms stabilized on nitrogen-doped graphene has a conversion rate of 85% at 110°C and an ethylene selectivity of nearly 90%. (Adv. Mater., 2019, 1901024) Zhang Tierui et al. prepared a single-atom Pd-supported N-doped graphene catalyst. In an ethylene-excess gas atmosphere, under Xe lamp irradiation, at 125°C, the acetylene conversion reached 99% and the ethylene selectivity reached 93.5%. (Adv. Mater., 2019, 31, 1900509) Professor Martin of Peking University supported single Pd atoms on defective nanodiamond-graphene, achieving a conversion of nearly 100% and a selectivity of over 90% at 180°C. (J. Am. Chem. Soc., 2018, 140, 41, 13142-13146)

[0003] Despite numerous advances in the research of Pd-based single-atom catalysts, the industrial application of catalytic hydrogenation often involves small amounts of CO in H₂. Trace CO interacts strongly with precious metal catalysts, quickly occupying active sites during the reaction. This prevents reactant molecules from adsorbing on the catalyst surface, leading to catalyst poisoning and deactivation. Therefore, while developing new, efficient precious metal catalysts, improving their tolerance to CO is also crucial.

[0004] Molybdenum carbide has unique structural and electronic properties, and usually exhibits strong interactions with loaded metals, which can significantly increase the dispersion of loaded metals and the synergistic effect between metals and MoC. For example, thanks to the inherent driving force of high-site-density Pd single atoms, Pd1 / α-MoC reported by Academician Zhang Tao and others showed excellent activity and selectivity in the selective hydrogenation of aromatic nitro compounds. (Angew.Chem.Int.Ed.10.1002 / anie.202007707) However, molybdenum carbide is prone to sintering and agglomeration during the high-temperature preparation process, has a small specific surface area, and has less active surface exposure. Although hard template methods such as NaCl and silica sol can achieve the preparation of nano-scale molybdenum carbide, the particle size is often uneven, and the template agent needs to be removed by acid or alkali etching. The steps are lengthy and not environmentally friendly. For example, in Chinese patent document CN109433242A, although nitrogen-doped carbon materials are also used as carriers to load transition metals and molybdenum carbide, the preparation method uses silica sol as a template, and subsequent steps require silicon removal treatment, and the prepared transition metal particles are nanoparticles rather than metal single atoms.

[0005] In summary, it is of great significance to develop a new type of efficient precious metal catalyst with high CO tolerance. Summary of the Invention

[0006] Based on the above, the main purpose of the present invention is to provide an environmentally friendly Pd single-atom catalyst with strong resistance to CO poisoning and a preparation method thereof. The active component palladium in the catalyst is uniformly dispersed at the atomic level on the MoC-NC support. The catalyst has high activity and selectivity for the selective hydrogenation of acetylene and shows high resistance to CO poisoning.

[0007] To achieve the above objectives, the present invention provides a Pd single-atom catalyst that is resistant to CO poisoning. The main active component is palladium, and the auxiliary active component is molybdenum carbide. The molybdenum carbide is in the form of nanoparticles with a size of 2-3 nm. The nanoparticles are embedded in a two-dimensional nitrogen-doped carbon support, and the palladium is dispersed at the atomic level on the molybdenum carbide.

[0008] In the catalyst, the Pd content is 0.05 wt% to 1 wt%, the Mo content is 1 wt% to 15 wt%, and the molar ratio of Mo to Pd is 50:1 to 3:1.

[0009] Specifically, the present invention uses nitrogen-doped carbon as a carrier, and Pd single atoms are loaded on MoC nanoparticles with a size of 2-3 nanometers as an active component. The nano-confinement effect of the nitrogen-doped carbon carrier during high-temperature heat treatment ensures the uniform distribution of molybdenum carbide nanoparticles with a size of about 2-3 nm. The small-sized molybdenum carbide rich in anchoring sites promotes the formation of highly dispersed and highly stable Pd single atoms. The d-vacant orbital density of Mo atoms on the surface of molybdenum carbide is high, and it has a strong ability to adsorb and dissociate hydrogen. The electronic interaction between small-sized molybdenum carbide and Pd single atoms puts Pd in ​​an electron-deficient state, which is greatly beneficial to the adsorption and dissociation of hydrogen, and is conducive to further improving the activity of acetylene hydrogenation. The stable structure of Pd-MoC-NC can effectively prevent excessive hydrogenation caused by single-atom aggregation during the acetylene hydrogenation reaction. At the same time, by precisely controlling the electronic properties of the Pd-MoC-NC catalyst, CO adsorption can be successfully weakened, effectively avoiding CO poisoning.

[0010] Optionally, the morphology of the two-dimensional nitrogen-doped carbon support is a two-dimensional sheet, and the specific surface area is greater than 420m 2 / g.

[0011] Optionally, the preparation process of the two-dimensional nitrogen-doped carbon carrier is: the nitrogen source and the carbon source are fully stirred in water to obtain a mixed solution, and then placed in liquid nitrogen for rapid freezing, and the mixed solution is freeze-dried, and then calcined under an inert atmosphere to obtain a carrier; preferably, the nitrogen source is selected from at least one of glutamic acid, lysine, urea, and melamine; the carbon source is selected from at least one of sucrose, fructose, and chitosan; more preferably, the molar ratio of the nitrogen source to the carbon source is 100:1 to 1:1, preferably 50:1 to 10:1.

[0012] Optionally, during the preparation of the two-dimensional nitrogen-doped carbon support, the stirring conditions are: temperature 10-30° C., time 30 to 120 minutes.

[0013] Optionally, during the preparation of the two-dimensional nitrogen-doped carbon support, the freeze-drying time is 2 to 7 hours.

[0014] Optionally, during the preparation of the two-dimensional nitrogen-doped carbon support, the calcination conditions are: temperature 700-1000° C., time 2-6 h.

[0015] The present invention also provides a method for preparing the above-mentioned CO-poisoning-resistant Pd single-atom catalyst, comprising the following steps: adding a Pd precursor and a Mo precursor to an aqueous solution containing a two-dimensional nitrogen-doped carbon support, then removing the two-dimensional nitrogen-doped carbon support and drying it until the water is completely volatilized, and calcining it under an inert atmosphere to obtain a Pd-MoC-NC catalyst; wherein the volume of the aqueous solution is 20 to 100 mL, preferably 30 to 60 mL; preferably, the Mo precursor is selected from at least one of ammonium molybdate tetrahydrate, ammonium molybdate, molybdic acid, and molybdenum pentachloride; more preferably, the mass ratio of the Pd precursor to the nitrogen-doped carbon is 0.001:1 to 0.01:1, preferably 0.002:1 to 0.008:1; the molar ratio of the Mo precursor to the Pd precursor is 50:1 to 3:1, preferably 30:1 to 5:1.

[0016] Optionally, in the preparation method of the Pd single-atom catalyst resistant to CO poisoning, the drying conditions are: temperature 60-80°C, time 6-12 hours, and the calcination conditions are: temperature 700-900°C, time 1-6 hours.

[0017] Optionally, in the preparation method of the Pd single-atom catalyst resistant to CO poisoning, the Pd precursor is selected from at least one of palladium chloride and palladium nitrate; the molybdenum precursor is selected from at least one of ammonium molybdate, ammonium molybdate tetrahydrate, molybdic acid, and molybdenum pentachloride.

[0018] The present invention also provides a method for preparing ethylene by selective hydrogenation of acetylene, wherein the CO-poisoning-resistant Pd single-atom catalyst is used to reduce the acetylene with a reducing gas before catalyzing the selective hydrogenation reaction. Preferably, the reducing gas is a mixture of H2 and an inert gas, wherein the H2 content is 1% to 99% by volume. The reduction conditions are: temperature 50 to 300°C, more preferably 100 to 250°C; pressure 0.1 MPa to 1.0 MPa, more preferably 0.5 MPa to 1.0 MPa; and time 0.5 to 8 hours, more preferably 2 to 6 hours. The reaction atmosphere is ethylene and hydrogen, with a volume fraction of 0.5 to 3% for C2H2, 50 to 90% for C2H4, 5 to 20% for H2, and the remainder being inert gas. The dosage of Pd-MoC-NC single-atom catalyst is 10 to 200 mg, preferably 100 to 150 mg. The reaction temperature for selective hydrogenation of acetylene is 60 to 200° C., preferably 80 to 150° C. The reaction gas flow rate is 0.1 to 100 ml / min, preferably 60 to 80 ml / min, and the space velocity is preferably 10,000 to 30,000 ml / g·h.

[0019] To achieve the above objectives, the specific preparation process of the Pd single-atom catalyst described in the present invention is as follows: the main active component of the catalyst is palladium, the carrier is molybdenum carbide nanoparticles embedded in a two-dimensional nitrogen-doped carbon material, the palladium is dispersed on the carrier at the atomic level, and the mass percentage of Pd is 0.05 to 1wt%;

[0020] 1) Preparation of nitrogen-doped carbon support: The nitrogen source and the carbon source are fully stirred in an aqueous solution for 30 to 120 minutes, and then placed in liquid nitrogen for rapid freezing. The solution is freeze-dried for 2 to 7 hours, and then calcined at 700 to 1000°C under an inert atmosphere for 2 to 6 hours to obtain a support with a two-dimensional sheet morphology and a specific surface area of ​​>420 m 2 / g;

[0021] 2) Preparation of Pd single-atom catalyst: Pd and molybdenum precursors are added to a nitrogen-doped carbon aqueous solution, dried in an oven at 60-80°C for 6-12 hours until the water evaporates completely, and then calcined at 700-900°C for 1-6 hours under an inert atmosphere.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. Pd is in a single atomic state and is evenly dispersed on the MoC nanoparticles rather than forming nanoparticles or sub-nano cluster structures;

[0024] 2. In the selective hydrogenation reaction of acetylene, when the conversion rate is 100%, the ethylene selectivity can reach 90%, taking into account both high conversion rate and high selectivity;

[0025] 3. The catalyst has excellent resistance to CO poisoning. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a transmission electron microscopy image of the nitrogen-doped carbon support prepared in Example 1.

[0027] Figure 2 This is a diagram of the specific surface area of ​​the nitrogen-doped carbon support prepared in Example 1.

[0028] Figure 3a This is a spherical aberration electron microscope scanning image of the catalyst prepared in Example 1.

[0029] Figure 3b This is the distribution diagram of Pd element in the catalyst prepared in Example 1.

[0030] Figure 3c This is the distribution diagram of Mo element in the catalyst prepared in Example 1.

[0031] Figure 4 This is the X-ray diffraction pattern of the catalyst prepared in Example 1.

[0032] Figure 5 This is a transmission electron microscope image of the catalyst prepared in Comparative Example 2.

[0033] Figure 6 This is a transmission electron microscope image of the catalyst prepared in Comparative Example 3. DETAILED DESCRIPTION

[0034] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and processes. However, the protection scope of the present invention is not limited to the following embodiments. The experimental methods in the following embodiments where specific conditions are not specified are generally based on conventional conditions.

[0035] The activity test method of the catalyst of the present invention is as follows:

[0036] The selective hydrogenation of acetylene to ethylene in the presence of large amounts of ethylene and hydrogen uses a fixed-bed reactor. Prior to the reaction, the catalyst is reduced with an H2 / He mixture containing 1% to 100% H2 by volume. The reduction temperature is set at 50-300°C, preferably 100-250°C, and the pressure is 0.1 MPa to 1.0 MPa, preferably 0.5 MPa to 1.0 MPa. The reduction time is 0.5 to 8 hours, preferably 2-6 hours. The reaction atmosphere is ethylene and hydrogen, with a C2H2 volume fraction of 0.5-3%, a C2H4 volume fraction of 50-90%, and a H2 volume fraction of 5-20%, with the remainder being inert gases. The Pd-MoC-NC single-atom catalyst is used in an amount of 10 to 200 mg, preferably 100 to 150 mg. The acetylene selective hydrogenation reaction temperature is 60 to 200°C, preferably 80 to 150°C. The reaction gas flow rate is 0.1 to 100 ml / min, preferably 60 to 80 ml / min, and the space velocity is preferably 10,000 to 30,000 ml / g·h. 0.5% to 1% CO is introduced during the reaction to test its toxicity resistance.

[0037] The chemical reagents used in the examples of the present invention are all chemically pure and can be purchased freely from the market. The conversion rate and selectivity in the examples are calculated according to the following formula:

[0038] Acetylene conversion rate (%) = 100 × △ acetylene / inlet acetylene content

[0039] Ethylene selectivity (%) = 100 × Δethylene / Δacetylene

[0040] Examples 1-5

[0041] Preparation method of Pd single-atom catalyst using melamine as nitrogen source and sucrose as carbon source

[0042] 1) Preparation of nitrogen-doped carbon support: 10 g of melamine and 2 g of sucrose were thoroughly stirred in 30 mL of water. The mixture was stirred at 25°C for 120 minutes and then rapidly frozen in liquid nitrogen. The solution was freeze-dried for 7 hours and then calcined at 800°C for 3 hours under an argon atmosphere.

[0043] 2) Preparation of Pd single atom catalyst: PdCl2 and ammonium molybdate tetrahydrate were added to an aqueous solution containing 2 g of the above nitrogen-doped carbon. The PdCl2 concentration was 0.0002 g mL -1 , placed in an oven at 65°C for 12 hours until the water is completely evaporated, and then calcined at 800°C for 3 hours in an argon atmosphere.

[0044] The difference between Examples 1-5 lies in the amount of PdCl2 and ammonium molybdate tetrahydrate used; the loading amounts of Pd and Mo in the Pd single atom catalyst in each example are shown in Table 1.

[0045] Table 1

[0046] Example Pd loading amount / wt% Mo loading / wt% 01 0.05 1.44 02 0.2 4.46 03 0.9 8.61 04 0.2 3.5 05 0.2 5.5

[0047] Examples 6-12

[0048] Preparation method of Pd single-atom catalyst using palladium nitrate as precursor

[0049] 1) Preparation of nitrogen-doped carbon support: 20 g of glutamic acid and 1 g of fructose were fully stirred in 50 mL of aqueous solution for 120 minutes and then rapidly frozen in liquid nitrogen. The solution was freeze-dried for 7 hours and then calcined at 900 °C under nitrogen for 3 hours. The specific surface area of ​​the nitrogen-doped carbon was 400 m 2 g -1 .

[0050] 2) Preparation of Pd single-atom catalyst: Palladium nitrate and ammonium molybdate tetrahydrate were added to an aqueous solution containing 3 g of nitrogen-doped carbon. The concentration of palladium nitrate was 0.0003 g mL -1 , dried in an oven at 75°C for 12 h until the water evaporates completely, and then calcined at 600°C-1000°C for 3 h in a N2 atmosphere.

[0051] The differences between Examples 6-10 are: the amounts of palladium nitrate and ammonium molybdate tetrahydrate used and the calcination temperature; the loading amounts of Pd and Mo in the Pd single atom catalyst and the calcination temperature in each example are shown in Table 2.

[0052] Table 2

[0053]

[0054] Examples 11-13

[0055] Preparation method of Pd single-atom catalyst using melamine as nitrogen source and sucrose as carbon source

[0056] 1) Preparation of nitrogen-doped carbon support: Melamine and sucrose were thoroughly stirred in 30 mL of aqueous solution at 25°C for 120 minutes, then rapidly frozen in liquid nitrogen. The solution was freeze-dried for 7 hours and then calcined at 800°C for 3 hours under a nitrogen atmosphere.

[0057] 2) Preparation of Pd single atom catalyst: PdCl2 and ammonium molybdate tetrahydrate were added to an aqueous solution containing 2 g of the above nitrogen-doped carbon. The PdCl2 concentration was 0.0002 g mL -1 , placed in an oven for 12 hours until the moisture evaporates completely, and then calcined at 800℃ for 3 hours under an inert atmosphere.

[0058] The differences between Examples 11-13 are: the amounts of melamine and sucrose used; the Pd loading amount in the Pd single-atom catalyst in each example is 0.05%, and the Mo loading amount is 1.5%.

[0059] Table 3

[0060]

[0061]

[0062] Comparative Example 1

[0063] The preparation method of the nitrogen-doped carbon support was the same as that of Example 2, except that only PdCl2 was added during the catalyst preparation without adding ammonium molybdate tetrahydrate to obtain a Pd-NC comparative sample.

[0064] Comparative Example 2

[0065] 10 g of fructose was dispersed in 30 mL of water in a water bath and stirred for 12 h until evaporated to dryness. The carbon support was then calcined at 800 ° C for 3 h under a nitrogen atmosphere. The preparation of the Pd single atom catalyst was the same as in Example 2 to obtain a Pd-MoC-C comparative sample. The electron microscope scanning image of the Pd-MoC-C comparative sample is shown in FIG. Figure 5 As shown, the size of MoC is around 15 nm.

[0066] Comparative Example 3

[0067] The preparation method of nitrogen-doped carbon support is the same as that of Example 2. Only ammonium molybdate tetrahydrate is added during the catalyst preparation, and no PdCl2 is added to obtain a MoC-NC comparative sample. The electron microscope scanning image of the comparative sample is shown in FIG. Figure 6 As shown, the size of MoC is around 4 nm.

[0068] Activity Evaluation of Examples 1-13 and Comparative Examples 1-3

[0069] 100 mg of sample was pre-reduced with 10 v% H2 / He mixed gas at 150 °C for 2 h at a space velocity of 40000 mL·h -1 ·g -1 The reaction was carried out in a fixed bed microreactor with the raw gas volumes of 2.18% C2H2, 80.53% C2H4, and 8.73% H2, He as the balance gas, and a gas flow rate of 20 ml min -1 , space velocity 24000 mL·h -1 ·g -1 , the reaction temperature is 100℃.

[0070] Table 3. Catalyst activity evaluation

[0071]

[0072]

[0073] Catalyst anti-toxicity evaluation

[0074] 100 mg of the catalyst samples prepared in Example 2, Comparative Example 1 and Comparative Example 2, i.e., 0.2 wt% Pd-MoC-NC, 0.2 wt% Pd-NC and 0.2 wt% Pd-MoC-C containing large-sized molybdenum carbide, were pre-reduced at 150° C. with a 10% H 2 / He mixed gas for 2 h at a space velocity of 40,000 mL·h. -1 ·g -1 The reaction was carried out in a fixed bed microreactor with the raw gas volumes of 2.18% C2H2, 80.53% C2H4, and 8.73% H2, He as the balance gas, and a gas flow rate of 20 ml min -1 , space velocity 24000 mL·h -1 ·g -1 The reaction temperature range is 50°C to 150°C. To investigate the CO resistance of the catalyst, 0.5% to 1% CO was introduced during the reaction, and the changes in catalyst conversion and selectivity before and after the introduction of CO were measured.

[0075] Table 4. Anti-toxicity evaluation

[0076]

[0077]

[0078] According to the results in Tables 3 and 4, it can be concluded that the catalyst activity and CO poisoning resistance designed in the present invention are better than those of Pd-NC without MoC and Pd-MoC-C containing large-sized molybdenum carbide, indicating that the introduction of small-sized molybdenum carbide and homemade nitrogen-doped carbon material support with large specific surface area can significantly improve the selectivity and conversion rate of acetylene to the target product ethylene in the hydrogenation reaction of single-atom Pd, and the electronic interaction between molybdenum carbide and single-atom Pd can significantly enhance the CO poisoning resistance of Pd.

[0079] Figure 1 This is a transmission electron microscope image of the nitrogen-doped carbon support prepared in Example 1, which shows that it is a two-dimensional nanosheet structure with few layers. Figure 2 The specific surface area of ​​the nitrogen-doped carbon support prepared in Example 1 was tested by nitrogen adsorption and desorption experiments. The results showed that the specific surface area of ​​the nitrogen-doped carbon support was 424 m 2 g -1 The large specific surface area facilitates the uniform distribution of molybdenum carbide nanoparticles, preventing aggregation during the reaction. Figure 3 shows a dark-field spherical aberration electron microscopy image of the catalyst prepared in Example 1, along with a distribution diagram of Pd and Mo elements. The results show that Pd is uniformly distributed on the MoC nanoparticles, the molybdenum carbide nanoparticles are 2-3 nm in size, and there are no aggregated Pd nanoclusters. It can be inferred that catalysts below this loading are all single-atom catalysts. Figure 4 This is the X-ray diffraction pattern of the catalyst prepared in Example 1. The results show that, except for the characteristic diffraction peak of MoC, there are no peaks related to metal Pd and its oxides, which is consistent with the electron microscopy results.

[0080] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the present invention.

Claims

1. A Pd single-atom catalyst resistant to CO poisoning, characterized in that: The main active component is palladium, and the auxiliary active component is molybdenum carbide, and the molybdenum carbide is a nanoparticle with a size of 2-3 nm. The nanoparticles are embedded in a two-dimensional nitrogen-doped carbon support, and the palladium is dispersed at the atomic level on the molybdenum carbide; In the catalyst, the Pd content is 0.05 wt% to 1 wt%, the Mo content is 1 wt% to 15 wt%, and the molar ratio of Mo to Pd is 50:1 to 3:

1.

2. The catalyst according to claim 1, characterized in that The morphology of the two-dimensional nitrogen-doped carbon carrier is a two-dimensional sheet, and the specific surface area is greater than 420m 2 / g.

3. The catalyst according to claim 2, characterized in that The preparation process of the two-dimensional nitrogen-doped carbon carrier is as follows: a nitrogen source and a carbon source are fully stirred in water to obtain a mixed solution, which is then placed in liquid nitrogen for rapid freezing, and the mixed solution is freeze-dried and then calcined under an inert atmosphere to obtain the carrier.

4. The catalyst according to claim 3, characterized in that The stirring conditions are: temperature 10-30° C., time 30 to 120 minutes.

5. The catalyst according to claim 3, characterized in that The freeze-drying time is 2 to 7 hours.

6. The catalyst according to claim 3, characterized in that The calcination conditions are: temperature 700-1000° C., time 2-6 hours.

7. The catalyst according to claim 3, characterized in that The nitrogen source is selected from at least one of glutamic acid, lysine, urea, and melamine; and the carbon source is selected from at least one of sucrose, fructose, and chitosan.

8. The catalyst according to claim 3, characterized in that The molar ratio of the nitrogen source to the carbon source is 100:1 to 1:

1.

9. The catalyst according to claim 8, characterized in that The molar ratio of the nitrogen source to the carbon source is 50:1 to 10:

1.

10. A method for preparing the Pd single-atom catalyst resistant to CO poisoning according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding a Pd precursor and a Mo precursor to an aqueous solution containing a two-dimensional nitrogen-doped carbon support, then removing the two-dimensional nitrogen-doped carbon support and drying it until the water is completely volatilized, and then calcining it under an inert atmosphere to obtain a Pd-MoC-NC catalyst; wherein the volume of the aqueous solution is 20 to 100 mL.

11. The method for preparing a catalyst according to claim 10, characterized in that: The drying conditions are: temperature 60-80° C., time 6-12 hours, and the calcination conditions are: temperature 700-900° C., time 1-6 hours.

12. The method for preparing the catalyst according to claim 10, characterized in that: The Pd precursor is selected from at least one of palladium chloride and palladium nitrate; the molybdenum precursor is selected from at least one of ammonium molybdate tetrahydrate, ammonium molybdate, molybdic acid, and molybdenum pentachloride.

13. The method for preparing the catalyst according to claim 10, characterized in that: The volume of the aqueous solution is 30 to 60 mL.

14. The method for preparing a catalyst according to claim 10, characterized in that: The Mo precursor is selected from at least one of ammonium molybdate tetrahydrate, ammonium molybdate, molybdic acid, and molybdenum pentachloride.

15. The method for preparing a catalyst according to claim 10, characterized in that: The mass ratio of the Pd precursor to the nitrogen-doped carbon is 0.001:1 to 0.01:

1.

16. The method for preparing a catalyst according to claim 15, characterized in that: The mass ratio of the Pd precursor to the nitrogen-doped carbon is 0.002:1 to 0.008:

1.

17. The method for preparing a catalyst according to claim 10, characterized in that: The molar ratio of the Mo precursor to the Pd precursor is 50:1 to 3:

1.

18. The method for preparing a catalyst according to claim 17, characterized in that: The molar ratio of the Mo precursor to the Pd precursor is 30:1 to 5:

1.

19. A method for preparing ethylene by selective hydrogenation of acetylene, characterized in that: The Pd single-atom catalyst resistant to CO poisoning according to any one of claims 1 to 9 is used.

20. The method for preparing ethylene by selective hydrogenation of acetylene according to claim 19, characterized in that: Before catalyzing the selective hydrogenation reaction of acetylene, reduction is first performed with a reducing gas; the reduction conditions are: temperature 50-300° C., pressure 0.1 MPa-1.0 MPa, and time 0.5-8 hours.

21. The method for preparing ethylene by selective hydrogenation of acetylene according to claim 20, characterized in that: The reducing gas is a mixture of H2 and inert gas, wherein the content of H2 is 1v% to 99v%.

22. The method for preparing ethylene by selective hydrogenation of acetylene according to claim 20, characterized in that: The temperature in the reducing condition is 100 to 250°C.

23. The method for preparing ethylene by selective hydrogenation of acetylene according to claim 20, characterized in that: The pressure in the reducing condition is 0.5 MPa to 1.0 MPa.

24. The method for preparing ethylene by selective hydrogenation of acetylene according to claim 20, characterized in that: The time under the reducing conditions is 2 to 6 hours.

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