A method and application of an atomic number accurate mn nanocluster catalyst

Abstract

This invention provides an M with precise atomic number. n Nanocluster catalysts, their preparation methods, and applications. Using Ketjen black as an innovative platform, oxidizing acid treatment was employed to obtain Ketjen black oxide with a surface rich in oxygen-containing functional groups. Utilizing the electrostatic and coordination interactions between its negatively charged surface and the clusters, atomically precise Mo nanocluster catalysts were prepared. n Nanocluster catalysts. The active metal M is highly and stably dispersed on the surface of an oxygen-rich Ketjen black oxide support under electrostatic and coordination interactions. The prepared process is simple and successfully overcomes the problems of easy aggregation and poor stability of nanoclusters during loading. It can be used in selective hydrogenation reactions, exhibiting excellent hydrogenation activity and selectivity, outstanding catalytic performance, easy recovery and reuse, and good stability.

Description

Technical Field

[0001] This invention belongs to the fields of petrochemicals and fine chemicals, specifically relating to a precise atomic number M n Nanocluster catalysts, their preparation methods, and applications are described. These catalysts are mainly used in the selective hydrogenation process of unsaturated carbon-carbon bonds. Background Technology

[0002] Ethylene is a crucial petrochemical product, and its production capacity is often used as a standard to measure a country's petrochemical level. Currently, the main route for ethylene production is through naphtha steam cracking. However, this process generates trace amounts of acetylene impurities, leading to catalyst poisoning during downstream polymerization and causing irreversible deactivation. Therefore, removing trace amounts of acetylene from ethylene is of great significance. In large and medium-sized ethylene plants, selective hydrogenation is typically used for acetylene removal, with supported Pd catalysts. Although Pd catalysts exhibit excellent hydrogenation activity, they are prone to over-hydrogenation and severe polymerization reactions, making it difficult to maintain high ethylene selectivity, and they are also expensive. Non-precious metal Cu single-atom catalysts have good hydrogenation selectivity, but their activity is relatively poor.

[0003] Atomically precise supported nanocluster catalysts, with their adjacent metal active sites, metal-metal bonds, and synergistic effects, can overcome the inherent limitations of single-atom catalysts, opening up new catalytic reaction pathways, lowering reaction energy barriers, and enhancing catalytic activity. Their research provides an important opportunity to reveal synergistic effects in catalytic reactions and elucidate their reaction mechanisms. However, due to their high sensitivity to synthesis conditions and tendency to aggregate, achieving highly uniform dispersion and stable anchoring of metal nanoclusters remains a major challenge in the synthesis of atomically precise supported nanocluster catalysts. Summary of the Invention

[0004] The purpose of this invention is to provide an M with precise atomic number. n Preparation methods of nanocluster catalysts and their application in the selective hydrogenation of unsaturated carbon-carbon bonds.

[0005] The present invention provides a precise M-number of atoms. n Nanocluster catalysts, characterized in that the catalyst is represented as M n / OKB, where M nThe active component is M, which is an active metal, one or two of Cu, Ag, and Au, preferably Cu; n is the atomic number of the active metal M, which is 3-25, preferably 8-25; OKB is a negatively charged support with a large number of oxygen-containing groups; the theoretical loading of M accounts for 0.5-3.0 wt.% of the catalyst content. The structural feature of this catalyst is that the active metal M is highly and stably dispersed on the surface of the oxygen-containing functional group-rich Ketjen black oxide support under electrostatic and coordination effects, forming M atoms with precise atomic numbers under the action of ligands. n Clusters (n is 3-25).

[0006] This invention provides an M with precise atomic number. n The preparation method of the nanocluster catalyst is characterized by the following specific steps: A. Disperse 50-500 mg of carbon black (Ketjen black, KB) thoroughly in an oxidizing acid solution, place it in an oil bath at 50-150 ℃ and stir for 10-50 h, cool it, wash it with deionized water, and dry it in an oven to obtain oxidized Ketjen black (OKB) carrier.

[0007] The oxidizing acid solution is one or two of HNO3, HNO2, H2SO4, HClO4, HClO2, and HClO; the concentration of the oxidizing acid solution is 3-10 mol / L; and the volume used is 10-100 mL.

[0008] B. Dissolve the metal salt M in a mixed solvent, and react in a water bath at 20-50 °C. After stirring, add ligand Y, followed by a reducing agent. After aging for 1-10 h, remove the solvent by rotary evaporation to obtain M. n Y precursor.

[0009] The active metal M salt is one or two of Cu(acac)2, CuCl2, CuSO4, Cu(NO3)2, Cu(OAc)2, CuI, AgNO3, CF3COOAg, HAuCl4·3H2O, and Cu(S2CN(CH3)2)2; the concentration of the salt solution is 5-60 mmol / L.

[0010] The mixed solvent is one of MeOH, EtOH, i-PrOH and one of DCM, THF, CHCl3 mixed in a volume ratio of 0.1-1.0; the amount used is 3-50 mL.

[0011] The ligand Y is one of (p-FPh)3P, PPh3, (p-MePh)3P, and (PPh3)2CuBH4.

[0012] The reducing agent is one of NaBH4, LiBH4, or (PPh3)2CuBH4.

[0013] C. According to the theoretical loading of metal M of 0.5-3.0 wt.%, OKB support and nanocluster precursor M are added. n Y was dispersed in a single organic solvent, stirred until fully loaded, and then dried to obtain M. n Y / OKB.

[0014] The solvent is one of DCM, CHCl3, THF, and EtOAc.

[0015] D. Obtain M from step C n Y / OKB was calcined in an inert atmosphere at 300-800 °C for 5-50 s in a Joule furnace to remove ligands, and then cooled to room temperature to obtain M atoms of Ketjen black oxide supported on it. n / OKB nanoparticle catalyst.

[0016] A precise M with a precise number of atoms n The application of nanocluster catalysts in the selective hydrogenation of unsaturated carbon-carbon bonds is characterized by the following steps: 0.1-1.0 g of the above catalyst and 1-10 g of quartz sand are weighed, mixed, and loaded into a gas-solid phase catalyst evaluation device. A mixture of C2H2, H2, C2H4, and N2 gas is introduced under normal pressure at a space velocity of 2000-20000 h⁻¹. -1 The catalyst performance was evaluated at temperatures ranging from 30 to 300 ℃, and the gaseous products were detected by gas chromatography.

[0017] Figure 1 Cu prepared in Example 1 25 The HRTEM and mapping spectra of / OKB did not reveal any obvious particles, indicating atomically precise Cu. 25 The nanoclusters are atomically distributed on the carrier without agglomeration.

[0018] Figure 2 Cu prepared in Example 1 25 The XRD pattern of / OKB showed no characteristic diffraction peaks of crystalline copper, indicating the absence of large crystalline copper nanoparticles in the sample.

[0019] Figure 3 Cu prepared in Example 1 25 / OKB catalyst conversion and selectivity in the selective hydrogenation of acetylene (line graph). Test results show that Cu 25 The OKB catalyst achieves a high conversion rate of 100% and a high selectivity of 97.2%.

[0020] Figure 4Cu prepared in Example 1 25 Scatter plot of long-term stability of OKB catalyst in selective hydrogenation of acetylene. Test results show that Cu... 25 The conversion and selectivity of the / OKB catalyst remained almost unchanged during a test lasting up to 1000 hours.

[0021] The beneficial effects of this invention are: This invention uses Ketjen black as an innovative platform, employing oxidizing acids to treat it and obtain oxidized Ketjen black with a surface rich in oxygen-containing functional groups. Utilizing the electrostatic and coordination interactions between its negatively charged surface and the clusters, atomically precise M-type carbon black was prepared. n Nanocluster catalysts. The active metal M, under electrostatic and coordination interactions, is highly and stably dispersed on the surface of a Ketjen black oxide support rich in oxygen-containing functional groups, successfully overcoming the challenges of easy aggregation and poor stability of nanoclusters during loading. M has a precisely precise atomic number. n Nanocluster catalysts can be used in selective hydrogenation reactions, exhibiting excellent hydrogenation activity and selectivity, outstanding catalytic performance, easy recovery and reuse, and good stability. Attached Figure Description

[0022] Figure 1 Cu prepared in Example 1 25 HRTEM and mapping spectra of the OKB catalyst.

[0023] Figure 2 Cu prepared in Example 1 25 XRD pattern of OKB catalyst.

[0024] Figure 3 Cu prepared in Example 1 25 / Line graph showing the conversion and selectivity of OKB catalyst in the selective hydrogenation of acetylene.

[0025] Figure 4 Cu prepared in Example 1 25 Scatter plot of long-term stability of OKB catalyst in selective hydrogenation of acetylene. Detailed Implementation Example 1

[0026] A. Disperse 200 mg of carbon black (Ketjenblack, KB) thoroughly in 30 mL of 6 mol / L HNO3 solution, stir in an oil bath at 70 ℃ for 24 h, cool, wash with deionized water, and dry in an oven to obtain oxidized Ketjenblack (OKB) carrier.

[0027] B. 60 mg of Cu(acac)₂ was dissolved in 20 mL of a 1:3 mixture of MeOH and DCM. The reaction was carried out in a 36 °C water bath. After stirring, 101.4 mg of (p-FPh)₃P was added, followed by the addition of NaBH₄ solution (34.68 mg NaBH₄ dissolved in 2 mL of water). After aging for 5 h, the solvent was removed by rotary evaporation after dehydration to obtain Cu. 25 H 22 [(p-FPh)3P] 12 Precursor.

[0028] C. Based on the theoretical Cu loading of 1 wt.%, OKB support and Cu nanoclusters were added. 25 H 22 [(p-FPh)3P] 12 Dispersed in DCM solvent, stirred until fully loaded, and then dried to obtain Cu. 25 H 22 [(p-FPh)3P] 12 / OKB.

[0029] D. The Cu obtained in step C 25 H 22 [(p-FPh)3P] 12 OKB was calcined in a Joule furnace at 550 °C for 10 s under a N2 atmosphere to remove ligands, and then cooled to room temperature to obtain atomically accurate Cu supported on Ketjen black oxide. 25 Nanoparticle catalyst Cu 25 / OKB.

[0030] The catalyst prepared above was used in an experiment on the selective hydrogenation of acetylene: Weigh 0.3 g of the above catalyst and 1.2 g of quartz sand, mix them thoroughly, and load them into a gas-solid phase catalyst evaluation device. The catalyst is introduced under normal pressure with a composition of C2H2 / H2 / C2H4 = 1 / 50 / 99, using N2 as the equilibrium gas, and a space velocity of 8000 h⁻¹. -1 The catalyst performance was evaluated at temperatures ranging from 30 to 300 °C, and the gaseous products were detected by gas chromatography. Results are shown below. Figure 4 This catalyst achieves an ethylene selectivity of 97.2% under conditions of 100% acetylene conversion. Compared with the catalyst obtained in Comparative Example 1 below, the catalytic performance of this catalyst is significantly improved. Example 2

[0031] A. Disperse 200 mg of carbon black (Ketjenblack, KB) thoroughly in 30 mL of 6 mol / L HNO3 solution, stir in an oil bath at 70 ℃ for 24 h, cool, wash with deionized water, and dry in an oven to obtain oxidized Ketjenblack (OKB) carrier.

[0032] B. 31 mg Cu(S2CN(CH3)2)2 and 10 mg BTPH were dispersed in 3 mL of a 1:2 mixture of MeOH and DCM. The reaction was carried out at room temperature, and after stirring, a (PPh3)2CuBH4 solution (80 mg (PPh3)2CuBH4 dissolved in 2 mL of DCM) was added. After aging for 3 h, the supernatant was collected by centrifugation, and the solvent was removed by rotary evaporation and centrifugation with petroleum ether to obtain [Cu8(S2CN(CH3)2)6(PPh3)4]. 2+ Precursor.

[0033] C. Based on the theoretical Cu loading of 1 wt.%, the OKB support was combined with the nanocluster precursor [Cu8(S2CN(CH3)2)6(PPh3)4]. 2+ Dispersed in DCM solvent, stirred until fully loaded, and then dried to obtain [Cu8(S2CN(CH3)2)6(PPh3)4]. 2+ / OKB.

[0034] D. The [Cu8(S2CN(CH3)2)6(PPh3)4] obtained in step C 2+ / OKB was calcined in a Joule furnace at 550 °C for 10 s under N2 atmosphere to remove ligands, and then cooled to room temperature to obtain Cu8 / OKB, an atomically precise Cu8 nanoparticle catalyst supported on Ketjen black oxide.

[0035] The catalyst prepared above was used in an experiment on the selective hydrogenation of acetylene: Weigh 0.3 g of the above catalyst and 1.2 g of quartz sand, mix them thoroughly, and load them into a gas-solid phase catalyst evaluation device. The catalyst is introduced under normal pressure with a composition of C2H2 / H2 / C2H4 = 1 / 50 / 99, using N2 as the equilibrium gas, and a space velocity of 8000 h⁻¹. -1 The catalyst performance was evaluated at temperatures ranging from 30 to 300 °C, and the gaseous products were detected using a gas chromatograph. This catalyst achieved an ethylene selectivity of 96.5% at an acetylene conversion rate of 90.2%. Example 3

[0036] A. Disperse 200 mg of carbon black (Ketjenblack, KB) thoroughly in 30 mL of 6 mol / L HNO3 solution, stir in an oil bath at 70 ℃ for 24 h, cool, wash with deionized water, and dry in an oven to obtain oxidized Ketjenblack (OKB) carrier.

[0037] B. 60 mg Cu(acac)₂ and 4 mg HAuCl₄·3H₂O were dissolved in 20 mL of a 1:3 mixture of MeOH and DCM. The reaction was carried out in a 36 °C water bath. After stirring, 101.4 mg (p-FPh)₃P was added, followed by NaBH₄ solution (34.68 mg NaBH₄ dissolved in 2 mL of water). After aging for 5 h, the solvent was removed by rotary evaporation after dehydration to obtain AuCu. 24 H 22 [(p-FPh)3P] 12 Precursor.

[0038] C. Based on the theoretical metal loading of 1 wt.%, OKB support and AuCu nanoclusters were added. 24 H 22 [(p-FPh)3P] 12 Dispersed in DCM solvent, stirred until fully loaded, and then dried to obtain AuCu. 24 H 22 [(p-FPh)3P] 12 / OKB.

[0039] D. The AuCu obtained in step C 24 H 22 [(p-FPh)3P] 12 OKB was calcined in a Joule furnace at 550 °C for 10 s under a N2 atmosphere to remove ligands, and then cooled to room temperature to obtain atomically precise Au-doped Cu supported on Ketjen black oxide. 24 AuCu nanoparticle catalyst 24 / OKB.

[0040] The catalyst prepared above was used in an experiment on the selective hydrogenation of acetylene: Weigh 0.3 g of the above catalyst and 1.2 g of quartz sand, mix them thoroughly, and load them into a gas-solid phase catalyst evaluation device. The catalyst is introduced under normal pressure with a composition of C2H2 / H2 / C2H4 = 1 / 50 / 99, using N2 as the equilibrium gas, and a space velocity of 8000 h⁻¹. -1 The catalyst performance was evaluated at temperatures ranging from 30 to 300 °C, and the gaseous products were detected using a gas chromatograph. This catalyst achieved an ethylene selectivity of 92.9% at an acetylene conversion rate of 93.8%.

[0041] Comparative Example 1 A. Disperse 200 mg of carbon black (Ketjenblack, KB) thoroughly in 30 mL of 6 mol / L HNO3 solution, stir in an oil bath at 70 ℃ for 24 h, cool, wash with deionized water, and dry in an oven to obtain oxidized Ketjenblack (OKB) carrier.

[0042] B. Based on the theoretical Cu loading of 1 wt.%, 3.4 mg CuCl₂·2H₂O was dissolved in 11 mL EtOH and sonicated for 5 min. 100 mg of the prepared OKB was added to 50 mL EtOH and sonicated for 20 min. Then, 1 mL of the previously prepared mixed solution was added dropwise to the OKB / EtOH solution, stirred until fully loaded, and dried in an oven. This yielded CuCl₂ / OKB.

[0043] C. The CuCl2 / OKB obtained in step B was placed in a tube furnace and calcined at 400 °C for 2 h under an Ar atmosphere at a rate of 5 °C / min and a gas flow rate of 40 mL / min. After cooling to room temperature, Cu nanoparticle catalyst supported on Ketjen black oxide was obtained. NPs / OKB.

[0044] The catalyst prepared above was used in an experiment on the selective hydrogenation of acetylene: Weigh 0.3 g of the above catalyst and 1.2 g of quartz sand, mix them thoroughly, and load them into a gas-solid phase catalyst evaluation device. The catalyst is introduced under normal pressure with a composition of C2H2 / H2 / C2H4 = 1 / 50 / 99, using N2 as the equilibrium gas, and a space velocity of 8000 h⁻¹. -1 The catalyst performance was evaluated at temperatures ranging from 30 to 300 °C, and the gaseous products were detected using a gas chromatograph. Under the same conditions, compared to Example 1, the ethylene selectivity of this catalyst fluctuated within the range of 59-90%.

Claims

1. A precise atomic number M n The preparation method of nanocluster catalysts is characterized by: Prepare according to the following specific steps: A. Disperse carbon black Ketjen black KB in an oxidizing acid solution, place it in an oil bath at 50-150 ℃ and stir for 10-50 h, cool it, wash it with deionized water, and dry it in an oven to obtain oxidized Ketjen black OKB carrier. B. Dissolve the metal salt M in a mixed solvent, and react in a water bath at 20-50 °C. After stirring, add ligand Y, followed by a reducing agent. After aging for 1-10 h, remove the solvent by rotary evaporation to obtain M. n Y precursor; C. According to the theoretical loading of metal M of 0.5-3.0 wt.%, OKB support and nanocluster precursor M were added. n Y was dispersed in a single organic solvent, stirred until fully loaded, and then dried to obtain M. n Y / OKB; D. The M obtained in step C n Y / OKB was calcined in an inert atmosphere at 300-800 °C for 5-50 s in a Joule furnace to remove ligands, and then cooled to room temperature to obtain M atoms of Ketjen black oxide supported on the oxide. n / OKB nanoparticle catalyst.

2. The preparation method according to claim 1, characterized in that the oxidizing acid solution in step A is one or two of HNO3, HNO2, H2SO4, HClO4, HClO2, and HClO; the concentration of the oxidizing acid solution is 3-10 mol / L; and the amount of oxidizing acid solution used in step A corresponding to 50-500 mg of carbon black Ketjen Black KB is 10-100 mL.

3. The preparation method according to claim 1, characterized in that the active metal M salt in step B is one or two of Cu(acac)2, CuCl2, CuSO4, Cu(NO3)2, Cu(OAc)2, CuI, AgNO3, CF3COOAg, HAuCl4·3H2O, Cu(S2CN(CH3)2)2; and the concentration of the salt solution is 5-60 mmol / L.

4. The preparation method according to claim 1, characterized in that the mixed solvent in step B is a mixture of one of MeOH, EtOH, i-PrOH and one of DCM, THF, CHCl3 in a volume ratio of 0.1-1.0; the amount of mixed solvent used in step A corresponding to 50-500 mg of carbon black Ketjen Black KB is 3-50 mL.

5. The preparation method according to claim 1, characterized in that the ligand Y in step B is one of (p-FPh)3P, PPh3, (p-MePh)3P, and (PPh3)2CuBH4.

6. The preparation method according to claim 1, characterized in that the reducing agent in step B is one of NaBH4, LiBH4, and (PPh3)2CuBH4.

7. The preparation method according to claim 1, characterized in that the solvent in step C is one of DCM, CHCl3, THF, and EtOAc.

8. The atomically accurate M prepared by the method of claim 1 n Nanocluster catalysts, characterized by: The catalyst is denoted as M. n / OKB, where M n The active component is one or two of Cu, Ag, and Au; n is the atomic number of the active metal M, ranging from 3 to 25; OKB is a negatively charged support containing oxygen groups; the theoretical loading of M accounts for 0.5-3.0 wt.% of the catalyst content; the structural characteristic of this catalyst is that the active metal M is dispersed on the support surface, forming precisely numbered M atoms under the action of ligands. n Clusters, where n is 3-25.

9. The atomic-number-precise M according to claim 8 n Nanocluster catalysts, characterized by: M is Cu; n is 8-25.

10. The atomic-number-precise M according to claim 8 n The application of nanocluster catalysts in the selective hydrogenation of unsaturated carbon-carbon bonds is characterized by, Weigh 0.1-1.0 g of the above catalyst and 1-10 g of quartz sand, mix them thoroughly, and load them into a gas-solid phase catalyst evaluation device. A mixture of C2H2, H2, C2H4, and N2 gas is introduced under normal pressure at a space velocity of 2000-20000 h⁻¹. -1 The catalyst performance was evaluated at temperatures ranging from 30 to 300 ℃, and the gaseous products were detected by gas chromatography.

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