M1-co3sn2 monatomic intermetallic compound catalyst for selective hydrogenation of alkyne to olefin and preparation method thereof

Abstract

This invention belongs to the field of catalyst preparation technology, and provides an M1-Co3Sn2 single-atom intermetallic compound catalyst for the selective hydrogenation of alkynes to olefins and its preparation method. The preparation method employs a one-pot process: first, a Co / Mg / Al ternary layered hydroxide is prepared by co-precipitation; then, a noble metal M precursor solution is added to obtain an M / Co / Mg / Al-LDHs material; subsequently, a Sn precursor solution is added to obtain a Sn / M / Co / Mg / Al-LDHs material; finally, thermal reduction treatment yields the M1-Co3Sn2 single-atom intermetallic compound catalyst. M is selected from any one of Pd, Pt, Ru, Ir, and Rh, and the loading of M is 0.08~0.25%. This catalyst preparation process is simple, requiring no complex operations. Furthermore, when applied to the selective hydrogenation of alkynes to olefins, this catalyst can achieve high alkyne conversion and olefin selectivity under mild reaction conditions with low noble metal loading.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and particularly relates to an M1-Co3Sn2 single-atom intermetallic compound catalyst for an alkyne selective hydrogenation reaction to produce alkenes and a preparation method thereof. BACKGROUND

[0002] In the ethylene industry, the selective hydrogenation of acetylene and propyne is one of the core steps to achieve the purification of polymer-grade ethylene. Crude ethylene obtained by steam cracking of naphtha or ethane contains 0.5-2% (volume fraction) of acetylene and a certain amount of propyne. These highly active alkynes can cause poisoning of the polymerization device or degradation of product quality in the polymerization reaction. Therefore, the acetylene content must be reduced to below 5 ppm, and the propyne content must be reduced to 5-10 ppm to meet the requirements of polymerization grade. In theory, solvent absorption, acetylene copper precipitation, low-temperature rectification extraction, and catalytic hydrogenation can be used to remove alkynes. However, due to the advantages of simple process, low energy consumption, and direct conversion of alkynes to high-value alkenes, the selective hydrogenation process has become the current industrial purification route.

[0003] In the research of selective hydrogenation catalysts, noble metals (such as Pd, Pt, Ru, Rh, and Ir) are widely used for the removal of acetylene and propyne due to their excellent hydrogen activation ability and high hydrogenation activity of alkyne. Traditional noble metal catalysts are usually in the form of nanoparticles supported on porous carriers, and the selectivity is improved by controlling the metal particle size and dispersion. However, the surface of the nanoparticles has multiple adsorption sites (including polydentate adsorption configurations), which can easily lead to the deep hydrogenation of acetylene and propyne to form ethane and propane, reducing the selectivity of alkenes. In addition, noble metals are expensive and scarce in resources, and are prone to sintering, agglomeration, or surface carbon deposition during the reaction, leading to catalyst deactivation. Therefore, how to maximize the utilization efficiency of noble metals and inhibit side reactions has become the core technical demand in this field.

[0004] Due to the easy hydrogenation and aggregation of noble metals, the selectivity of olefins is poor, and the prior art often alloys the active metal with a relatively low active metal or constructs intermetallic compounds to dilute the active site and increase the intermetallic distance. In recent years, the strategy of single-atom intermetallic compounds (SAICs) has emerged: by replacing the parent alloy surface with noble metal atoms in an atomic dispersion manner, a long-range ordered intermetallic structure is constructed, thereby accurately regulating the active center at the geometric and electronic levels. For example, patent CN119114072A constructs "isolated active Pd sites" to improve ethylene selectivity, and reports PdAgNa / SiO2 and PdAgK / SiO2 supported catalysts, which use alkali metals and non-active metals Ag to modify and spatially isolate the active component to improve the performance of acetylene selective hydrogenation. The noble metal Pd loading in such catalysts is 0.01-0.5wt%, and the Ag loading is 0.5-5wt%; under the condition of about 250°C, high conversion and selectivity can be achieved. However, the deficiency is that a second noble metal Ag still needs to be introduced into the system (cost and resource constraints still exist), and a higher operating temperature of more than 200°C is usually required to balance activity and ethylene selectivity, which is not conducive to energy consumption and long-term stability.

[0005] The research team of the applicant has conducted long-term research on the reaction of noble metals in the hydrogenation of alkyne to prepare olefins, and in the latest research results, a Pd-Sb intermetallic catalyst has been successfully constructed (J. Am. Chem. Soc. 2025, 147, 30178-30189). The preparation process of the catalyst is as follows: under the condition of PH=10, Mg / Al-LDHs is first prepared, washed, dried, dispersed in deionized water, and under the condition of PH=10, Pd metal salt solution is added, and then washed, dried, mixed with Sb, and finally obtained after high-temperature induction. The Pd-Sb intermetallic catalyst. In the catalytic reaction of acetylene hydrogenation to prepare ethylene, the catalyst shows excellent catalytic effect, and at a reaction temperature of 70°C, 100% selectivity and >95% ethylene selectivity can be obtained, significantly reducing the temperature of the catalytic reaction. However, in the catalyst, the loading of noble metal Pd is about 5%, and the amount of noble metal Pd is large; and due to the complicated preparation steps, the cost of subsequent industrial production is further increased.

[0006] Therefore, it is still necessary to provide an intermetallic catalyst with simple preparation process, low noble metal content and excellent catalytic effect in the reaction of alkyne hydrogenation to prepare olefins. SUMMARY

[0007] Therefore, the application provides an M1-Co3Sn2 single-atom intermetallic compound catalyst for an alkyne selective hydrogenation reaction for preparing alkenes and a preparation method thereof, realizes high conversion and high alkenes selectivity under mild reaction conditions with low noble metal consumption, and is simple in catalyst preparation process operation and convenient for popularization and application.

[0008] To achieve the above object, the technical scheme of the application is as follows.

[0009] In a first aspect, the application provides a preparation method of an M1-Co3Sn2 single-atom intermetallic compound catalyst for an alkyne selective hydrogenation reaction for preparing alkenes, comprising the following steps:

[0010] (1) Co, Mg and Al metal salts are used as precursors to prepare a Co / Mg / Al metal salt mixed solution, and Co / Mg / Al ternary layered hydroxide is prepared by a coprecipitation method;

[0011] (2) A noble metal M precursor solution is added to the Co / Mg / Al-LDHs solution obtained in step (1), the pH of the reaction system is adjusted to 8.0-9.5, ion exchange is performed, and M / Co / Mg / Al-LDHs material is obtained;

[0012] (3) A Sn precursor solution is further added to the M / Co / Mg / Al-LDHs solution obtained in step (2), the pH of the reaction system is adjusted to 7.0-8.0, in-situ growth is performed, and Sn / M / Co / Mg / Al-LDHs material is obtained;

[0013] (4) The reaction product of step (3) is filtered, washed and dried, and is subjected to a thermal reduction treatment to prepare the M1-Co3Sn2 single-atom intermetallic compound catalyst;

[0014] In the preparation process, the molar ratio of Co, M, Sn, Mg and Al in the precursors added is 1:(0.002-0.025):(0.6-2.1):(2-8):(1-3); and the loading amount of the noble metal M in the prepared M1-Co3Sn2 single-atom intermetallic compound catalyst is 0.08-0.25%.

[0015] The application is further provided that in step (1), the pH of the reaction system is adjusted to 10.0-11.0.

[0016] The application is further provided that in step (1), the precipitant used is selected from a Na2CO3 solution, a NaHCO3 solution or a K2CO3 solution; and the molar concentration is 0.3-0.5 mol / L.

[0017] The present invention is further configured such that, in step (2), the pH of the reaction system is adjusted to 8.5~9.5.

[0018] The present invention is further configured such that the reaction system of steps (1) to (3) is carried out in the same reaction device and the temperature of the reaction system is 55~75°C.

[0019] The present invention is further configured such that, in step (3), after the addition of materials is completed, the reaction is continued to be stirred for 10 to 14 hours.

[0020] The present invention further specifies that, in the reaction system of steps (1) to (3), the pH adjuster used to adjust the pH is a NaOH or KOH solution with a concentration of 2.0 to 3.0 mol·L⁻¹. -1 .

[0021] The present invention is further configured such that, in step (4), the temperature of the thermal reduction treatment is 700~900°C, the reduction time is 3~5h, and the reducing gas is a mixture of H2 / N2.

[0022] Secondly, the present invention provides a single-atom intermetallic compound catalyst of M1-Co3Sn2 prepared according to the above preparation method, the structure of which is as follows: Co3Sn2 is used as the parent alloy, M1Co1Sn2 multidentate rhombic active sites are constructed on the near surface of the catalyst to form a fourfold site cooperative structure of electron-rich M1 single atom-electron-deficient Co1Sn2, and M1 forms a bridge site with Co on the adjacent surface.

[0023] The present invention is further configured such that, in the M1-Co3Sn2 single-atom intermetallic compound catalyst, the content of Co is 10~15wt% and the content of noble metal M is 0.08~0.25wt%.

[0024] The present invention is further configured such that the content of noble metal M in the M1-Co3Sn2 single-atom intermetallic compound catalyst is 0.08~0.20wt%; preferably 0.10~0.15wt%.

[0025] The present invention is further configured such that the content of Co in the M1-Co3Sn2 single-atom intermetallic compound catalyst is 12~14wt%, and the content of Sn is 13~18.5%wt%.

[0026] Thirdly, the present invention provides an application of the above-mentioned M1-Co3Sn2 single-atom intermetallic compound catalyst in the selective hydrogenation of alkynes to olefins, wherein the reaction conditions are: atmospheric pressure and reaction temperature of 40℃~130℃, for example 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃ or 130℃.

[0027] The present invention is further configured such that the reaction temperature is 70~100℃.

[0028] It should be noted that, in industrial applications, this type of catalytic reaction is typically used to remove trace amounts of alkyne impurities from ethylene or propylene gases.

[0029] The present invention is further configured to be applied in the catalytic hydrogenation reaction of selective hydrogenation of acetylene to ethylene, wherein the gas composition is: 0.5~1.0% C2H2, 40~60% C2H4, 5~10% H2, and the remainder is N2.

[0030] The present invention is further configured to be applied in the catalytic hydrogenation reaction of selective hydrogenation of propyne to propylene, wherein the gas composition is: 0.5~1.5% C3H4, 5~15% C3H6, 5~10% H2, and the remainder is N2.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) This invention employs a one-pot method, in which raw materials are added in a specific order and the pH value of the reaction system is controlled, followed by high-temperature reduction to prepare the M1-Co3Sn2 single-atom intermetallic compound catalyst. When this catalyst is applied to the reaction of alkyne hydrogenation to olefins, under relatively mild reaction conditions (70~100℃), with a lower noble metal loading, high conversion and high olefin selectivity are obtained, and perhydrogenation and by-product C are effectively suppressed. x The generation of .

[0033] (2) The M1-Co3Sn2 single-atom intermetallic compound catalyst provided by the present invention has a simple preparation process and can be carried out in the same device. There is no need to process the product of each step before proceeding to the next step. This one-pot preparation method is conducive to industrial promotion.

[0034] (3) Compared with traditional single-atom catalysts, the M1-Co3Sn2 single-atom intermetallic compound formed after reduction in this invention further strengthens the coupling between particles and substrate and further inhibits high-temperature agglomeration. This invention provides a replicable and scalable general strategy for single-atom construction, which has broad significance for the fine control and industrial application of noble metals such as Pd, Pt, Ru, Ir, and Rh in Co-Sn-based or other intermetallic environments. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the synthesis of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst according to the present invention.

[0036] Figure 2These are high-angle annular dark-field scanning transmission electron microscope images and corresponding elemental analysis diagrams of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Example 1.

[0037] Figure 3 Figure (a) is an aberration-corrected high-angle annular dark-field scanning transmission electron microscope image and corresponding fast Fourier transform diagram of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Example 1; Figure (b) is an enlarged view of the orange rectangular marked area in Figure (a); Figure (c) is the three-dimensional simulation diagram corresponding to Figure (b); Figure (d) is the line intensity profile of the red area in Figure (b) along the XY direction; Figure (e) is a schematic diagram of the structure of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst.

[0038] Figure 4 The hydrogen dissociation energy barrier curve is shown on the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Example 1.

[0039] Figure 5 The H2–D2 exchange experiment of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Example 1 and the Co3Sn2 intermetallic compound catalyst prepared in Comparative Example 1 is shown in Figure (a), which shows the evolution of the HD signal after switching the inlet, and Figure (b) shows the quantitative analysis results.

[0040] Figure 6 This is a Bader charge analysis of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Example 1.

[0041] Figure 7 The adsorption configuration and adsorption energy of acetylene and ethylene on the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Example 1 are shown.

[0042] Figure 8 This is a high-angle annular dark-field scanning transmission electron microscope image and elemental analysis diagram of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Comparative Example 3.

[0043] Figure 9 Figure (a) shows the Pd prepared in Example 6. n -Aberration-corrected high-angle annular dark-field scanning transmission electron microscope image and corresponding fast Fourier transform plot of Co3Sn2 alloy catalyst; Figure (b) is the three-dimensional simulation plot corresponding to Figure (a); Figure (c) is the particle size distribution plot corresponding to Figure (a); Figure (d) is the Pd n -Schematic diagram of the structure of the Co3Sn2 alloy catalyst.

[0044] Figure 10This is the XRD pattern of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared in Example 1.

[0045] Figure 11 These are the XRD patterns of the prepared Pd1-CoSn2 and Pd1-Co2Sn single-atom intermetallic compound catalysts. Detailed Implementation

[0046] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. It should be understood that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of the present invention.

[0047] Example 1

[0048] This embodiment provides a method for preparing a Pd1-Co3Sn2 intermetallic compound catalyst, which specifically includes the following steps:

[0049] (1) Dissolve 2.92g Co(NO3)2·6H2O, 12.83g Mg(NO3)2·6H2O and 7.50g Al(NO3)3·9H2O in 60mL of ultrapure water and disperse by ultrasonication to obtain a mixed nitrate solution; weigh 0.00727g PdCl2 and 0.083mL concentrated hydrochloric acid, prepare and disperse by ultrasonication in 40mL of ultrapure water to obtain chloropalladium acid (H2PdCl4) solution; weigh 2.34g SnCl4·5H2O, dissolve in 30mL of ultrapure water and disperse by ultrasonication to obtain tin chloride solution; separately, dissolve 4.24g Na2CO3 in 100mL of ultrapure water to obtain the required precipitant, and dissolve 20.00g NaOH in 200mL of ultrapure water to obtain the required pH adjuster.

[0050] The Na₂CO₃ precipitant solution was transferred to a 500 mL three-necked flask and kept at a constant temperature of 65°C in an oil bath for 1 hour; the temperature was then adjusted at 200 rpm. -1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1A mixed nitrate solution was added dropwise, simultaneously titrated with NaOH solution to maintain a constant pH of 10.5 ± 0.1, completing the co-precipitation of Co / Mg / Al and the formation of layered hydroxide (LDH). Subsequently, H₂PdCl₄ solution was slowly added dropwise, utilizing its acidity and the synergistic effect of NaOH to stabilize the pH at 9.0 ± 0.1, promoting atomic-level dispersion of Pd at the lamellar sites via ion exchange. Then, SnCl₄ solution was added dropwise, with NaOH used to adjust the pH to 7.5 ± 0.1, facilitating the in-situ uniform formation and film formation of Sn(OH)₄ on the lamellar / particle surface, achieving nanoscale coating and confinement of the anchored Pd single atoms. After all materials were added, the mixture was stirred and aged at 65°C for 12 hours, followed by filtration and washing with water to obtain a brown wet solid.

[0051] (2) The brown blocky solid obtained in step (1) is dried at 110°C for 12 hours to obtain Sn / Pd / Co / Mg / Al pentagonal LDH material.

[0052] (3) The pentagonal LDH material from step (2) was placed in an atmosphere of H2 / Ar=1 / 4 (volume fraction 20% H2) and reduced at 800°C for 3 h to obtain a Pd1-Co3Sn2 intermetallic compound catalyst, denoted as X1. The catalyst was characterized and the contents of Pd, Co and Sn in the catalyst were determined by ICP. The contents of Pd were 0.11 wt%, Co were 13.33 wt%, and Sn were 17.92 wt%.

[0053] The preparation process of the Pd1-Co3Sn2 single-atom intermetallic compound catalyst described in this embodiment is as follows: Figure 1 As shown, this invention employs a one-pot method, first introducing Co, then introducing Pd and Sn according to a programmed sequence of "Pd first, then Sn," and controlling the pH value during the corresponding reaction processes to prepare the Pd1-Co3Sn2 single-atom intermetallic compound catalyst. In this preparation process, a Pd precursor is first added dropwise to form an atomic-level dispersion via ion exchange; subsequently, a Sn precursor is introduced, and Sn(OH)4 is generated in situ, uniformly coating and confining the anchored Pd single atoms. This provides spatial isolation and site fixation during drying and high-temperature reduction, effectively preventing Pd-Pd proximity and aggregation, and ensuring the formation and stability of characteristic sites of the single-atom intermetallic compound (e.g., ...). Figure 2 and Figure 3 (As shown).

[0054] according to Figures 4-7It can be seen that the electron-rich single-atom Pd sites and adjacent near-surface Co sites in the prepared single-atom intermetallic compound catalyst synergistically promote the spontaneous dissociation of hydrogen. Simultaneously, Pd redistributes electrons to the neighboring Co1Sn2 triatomic sites, placing them in an electron-deficient state, thereby enhancing the adsorption of alkyne molecules and jointly promoting the acetylene hydrogenation reaction. Furthermore, thanks to the regulation of the electronic properties of the surface Co sites by the Pd sites, and the geometrical isolation and localization of Pd and Co by Sn, the two synergistically reduce the adsorption of olefins, thereby promoting the desorption of olefin products and effectively preventing excessive hydrogenation of olefins to alkanes. Finally, the Pd1-Co3Sn2 catalyst achieves a coupled pathway of "fast hydrogen supply-strong selective adsorption-easy desorption" through the ternary geometric-electronic synergistic effect of M1 single atom-electron-deficient Co1Sn2-surface Co atoms, thus achieving high conversion and high olefin selectivity in the low-temperature range of 70-100°C (see Tables 1-3), and effectively suppressing over-hydrogenation and byproduct C. x The generation of .

[0055] Example 2

[0056] Compared with Example 1, the only difference is the amount of Sn raw material added in step (1). In this example, the amount of SnCl4·5H2O added was increased to 7.04g. The final Pd1-CoSn2 catalyst (Sn enriched, Co / Sn=1:2) was obtained and denoted as X2. The contents of Pd, Co and Sn in the catalyst were measured, where the Pd content was 0.10wt%, the Co content was 13.37wt%, and the Sn content was 17.94wt%. According to the measurement results of the contents of each metal element in this example, the catalyst prepared by the preparation steps of the present invention has a fixed configuration. Therefore, when more Sn raw material is added, the Sn content in the final Pd1-CoSn2 catalyst product is basically the same as that in the Pd1-Co3Sn2 catalyst in Example 1.

[0057] Example 3

[0058] Compared with Example 1, the only difference is that the pH conditions after adding Pd raw material in step (1) are different.

[0059] In this embodiment, the preparation step (1) is as follows: the precipitant is placed in a 500mL three-necked flask and kept at a constant temperature of 65°C in an oil bath for 1 hour; at 200r·min -1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1A mixed nitrate solution was added dropwise, with NaOH solution added simultaneously to adjust the pH of the system to 10.5 ± 0.1, completing the co-precipitation of Co / Mg / Al and the construction of layered hydroxide (LDH). Subsequently, H₂PdCl₄ solution was added dropwise, with a small amount of NaOH / dilute acid used to adjust the pH to stabilize it at 8.0 ± 0.1, allowing Pd to be anchored in situ at the lamellar sites via ion exchange / coordination and achieving atomic-level dispersion. Then, SnCl₄ solution was added dropwise, with NaOH used to adjust the pH to 7.5 ± 0.1. After all materials were added, the mixture was continuously stirred vigorously at 65°C for 12 hours for aging. After filtration and washing with water, a brown wet solid was obtained.

[0060] The brown wet solid obtained in step (1) was treated with the same steps (2) and (3) as in Example 1 to obtain a Pd1-Co3Sn2 intermetallic compound catalyst, denoted as X3. The contents of Pd, Co and Sn in the catalyst were determined, wherein the Pd content was 0.08 wt%, the Co content was 13.34 wt%, and the Sn content was 17.76 wt%.

[0061] Example 4

[0062] Compared with Example 1, the only difference is the amount of Pd raw material added in step (1). In this example, the amount of PdCl2 added was increased to 0.01436 g. The final Pd1-Co3Sn2 catalyst was denoted as X4. The contents of Pd, Co and Sn in the catalyst were determined, wherein the Pd content was 0.21 wt%, the Co content was 13.37 wt%, and the Sn content was 17.94 wt%.

[0063] Example 5

[0064] Compared with Example 1, the only difference is the amount of Pd raw material added in step (1). In this example, the amount of PdCl2 added was increased to 0.01077 g. The final Pd1-Co3Sn2 catalyst was designated as X5. The contents of Pd, Co, and Sn in the catalyst were determined, with Pd content of 0.15 wt%, Co content of 13.39 wt%, and Sn content of 17.87 wt%.

[0065] Example 6

[0066] Compared with Example 1, the only difference is that the precious metal Pd raw material is replaced with Ru raw material, and all other aspects are the same.

[0067] In this embodiment, the Ru precursor was prepared according to the same molar amount of metal as Pd in ​​Example 1: 0.0085 g of anhydrous RuCl3 was weighed, 0.083 mL of concentrated hydrochloric acid was added, and then 40 mL of ultrapure water was added and sonicated to obtain a ruthenium chloride complex solution (RuCl3 / HCl).

[0068] The Ru1-Co3Sn2 intermetallic compound catalyst was finally prepared and designated as X6. The contents of Ru, Co and Sn in the catalyst were determined, and the contents of Ru were 0.11 wt%, Co were 13.35 wt%, and Sn were 17.79 wt%.

[0069] Example 7

[0070] Compared with Example 1, the only difference is that the precious metal Pd raw material is replaced with Rh raw material, and all other aspects are the same.

[0071] In this embodiment, the Rh precursor was prepared using the same molar amount of metal as Pd in ​​Example 1: 0.0086 g of RhCl3 was weighed, added to 0.083 mL of concentrated hydrochloric acid, and then diluted with 40 mL of ultrapure water and sonicated to obtain a rhodium chloride complex solution (RhCl3 / HCl). The final Rh1-Co3Sn2 intermetallic compound catalyst was obtained, denoted as X7. The contents of Rh, Co, and Sn in the catalyst were determined, with Rh content of 0.10 wt%, Co content of 13.41 wt%, and Sn content of 17.86 wt%.

[0072] Example 8

[0073] Compared with Example 1, the only difference is that the precious metal Pd raw material is replaced with Ir raw material, and all other aspects are the same.

[0074] In this embodiment, the Ir precursor was prepared with the same molar amount of metal as Pd in ​​Example 1: 0.021 g of H2IrCl6·6H2O was weighed, dissolved in 40 mL of ultrapure water, and ultrasonically dispersed (a small amount of dilute hydrochloric acid was used to aid dissolution / water hydrolysis if necessary) to obtain an H2IrCl6 solution.

[0075] The final Ir1-Co3Sn2 intermetallic compound catalyst was prepared and designated as X8. The contents of Ir, Co and Sn in the catalyst were determined, and the contents of Ir, Co and Sn were 0.11 wt%, Co, and Sn were 13.43 wt% and 17.90 wt%, respectively.

[0076] Example 9

[0077] Compared with Example 1, the only difference is that the precious metal Pd raw material is replaced with Pt raw material, and all other aspects are the same.

[0078] In this embodiment, the Pt precursor was prepared with the same molar amount of metal as Pd in ​​Example 1: 0.0213g of H2PtCl6·6H2O was weighed, dissolved in 40mL of ultrapure water, and ultrasonically dispersed (a small amount of dilute hydrochloric acid was used to aid dissolution / water hydrolysis if necessary) to obtain an H2PtCl6 solution.

[0079] The final Pt1-Co3Sn2 intermetallic compound catalyst was prepared and designated as X9. The contents of Pt, Co and Sn in the catalyst were determined and recorded in Table 1, where the Pt content was 0.10 wt%, the Co content was 13.56 wt%, and the Sn content was 17.68 wt%.

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing a Co3Sn2 intermetallic compound catalyst. The difference from Example 1 is that, while keeping other conditions unchanged, Pd is not introduced in step (1). The specific process is as follows:

[0082] (1) Dissolve 2.92g Co(NO3)2·6H2O, 12.83g Mg(NO3)2·6H2O and 7.50g Al(NO3)3·9H2O in 60mL of ultrapure water and disperse by ultrasonication to obtain a mixed nitrate solution; weigh 2.34g SnCl4·5H2O, dissolve in 30mL of ultrapure water and disperse by ultrasonication to obtain a tin chloride solution; separately, dissolve 4.24g Na2CO3 in 100mL of ultrapure water to obtain the required precipitant, and dissolve 20.00g NaOH in 200mL of ultrapure water to obtain the required pH adjuster.

[0083] The precipitant was transferred to a 500 mL three-necked flask and kept at a constant temperature of 65°C in an oil bath for 1 hour; then heated at 200 rpm. -1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1 The mixed nitrate solution was added dropwise, while simultaneously adjusting the pH with NaOH solution to maintain a constant pH of 10.5 ± 0.1, completing the formation of Co / Mg / Al coprecipitation and LDH. Subsequently, without the Pd introduction step, tin chloride solution was added dropwise, again adjusted with NaOH to maintain the pH at 7.5 ± 0.1, promoting the in-situ formation and uniform film formation of Sn(OH)4 on the surface of the sheets / particles. After the addition was complete, the mixture was vigorously stirred and aged at 65°C for 12 hours, followed by filtration and washing with water to obtain a pink wet solid.

[0084] (2) The solid obtained in step (1) is dried at 110°C for 12 hours to obtain Sn / Pd / Co / Mg / Al pentagonal LDH material.

[0085] (3) The sample obtained in step (2) was placed in an atmosphere of H2 / Ar=1 / 4 (volume fraction 20% H2) and reduced at 800°C for 3h to obtain the Co3Sn2 intermetallic compound catalyst, denoted as X10.

[0086] Comparative Example 2

[0087] Compared with Example 1, the only difference is that in step (1), the pH of the reaction system in different stages remains consistent at 10.5 ± 0.1. The preparation steps of step (1) are as follows: the precipitant is placed in a 500 mL three-necked flask, kept at a constant temperature of 65°C in an oil bath for 1 h, and then heated at 200 r·min. -1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1 A mixed nitrate solution was added dropwise, and NaOH solution was used to maintain the pH of the system at 10.5 ± 0.1 to complete the co-precipitation of Co / Mg / Al and the construction of LDH. Then, H₂PdCl₄ solution was added dropwise, and NaOH was used to adjust the pH of the system to stabilize at 10.5 ± 0.1. Next, SnCl₄ solution was added dropwise, and NaOH was used to further adjust the pH to maintain it at 10.5 ± 0.1. After all the materials were added, the system was continuously stirred vigorously at 65°C for 12 hours to age the solid. After filtration and washing with water, a brown wet solid was obtained.

[0088] The brown wet solid obtained in step (1) was processed in the same steps (2) and (3) as in Example 1 to obtain Pd. x The Co3Sn2 intermetallic compound catalyst, denoted as X11, had its Pd, Co, and Sn contents determined. The Pd content was 0.11 wt%, the Co content was 13.24 wt%, and the Sn content was 17.73%.

[0089] Comparative Example 3

[0090] Compared with Example 1, the only difference is that the pH conditions after adding Pd raw material in step (1) are different.

[0091] In this embodiment, the preparation step (1) is as follows: the precipitant is placed in a 500mL three-necked flask and kept at a constant temperature of 65°C in an oil bath for 1 hour; at 200r·min -1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1 A mixed nitrate solution was added dropwise, with NaOH solution added simultaneously to adjust the system pH to 10.5 ± 0.1, completing the co-precipitation of Co / Mg / Al and the construction of layered hydroxide (LDH). Subsequently, H₂PdCl₄ solution was added dropwise to adjust the pH, stabilizing it at 10 ± 0.1, allowing Pd to be anchored in situ at the lamellar sites via ion exchange / coordination and achieving atomic-level dispersion. Then, SnCl₄ solution was added dropwise, with NaOH used to adjust the pH to 7.5 ± 0.1. After all materials were added, the mixture was continuously stirred vigorously at 65°C for 12 hours for aging. After filtration and washing with water, a brown wet solid was obtained.

[0092] The brown wet solid obtained in step (1) was treated with the same steps (2) and (3) as in Example 1 to obtain a Pd1-Co3Sn2 intermetallic compound catalyst, denoted as X12. The contents of Pd, Co and Sn in the catalyst were determined, with Pd content of 0.11 wt%, Co content of 13.32 wt%, and Sn content of 17.92 wt%.

[0093] The prepared Pd1-Co3Sn2 single-atom intermetallic compound catalyst was characterized, and the results are as follows: Figure 8 As shown: pH=10±0.1 causes strong hydrolysis of the Pd precursor, triggering rapid, multi-point heterogeneous nucleation and local aggregation on the surface, resulting in a morphology in which single atomic sites and small clusters coexist and are spatially unevenly distributed.

[0094] Comparative Example 4

[0095] Compared with Example 1, the only difference is that the pH conditions after adding Sn raw material in step (1) are different.

[0096] In this embodiment, the preparation step (1) is as follows: the precipitant is placed in a 500mL three-necked flask and kept at a constant temperature of 65°C in an oil bath for 1 hour; at 200r·min -1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1 A mixed nitrate solution was added dropwise, and the pH was adjusted to 10.5 ± 0.1 using NaOH solution, completing the co-precipitation of Co / Mg / Al and the construction of layered hydroxide (LDH). Subsequently, H₂PdCl₄ solution was added dropwise, and the pH was adjusted using NaOH to stabilize the system at 9.0 ± 0.1, promoting Pd to be anchored in situ at the lamellar sites via ion exchange / coordination and achieving atomic-level dispersion. Then, SnCl₄ solution was added dropwise, and the pH was adjusted to 6.5 ± 0.1 using NaOH / dilute acid. After all materials were added, the mixture was continuously and vigorously stirred at 65°C for 12 hours for aging. After filtration and washing with water, a brown wet solid was obtained.

[0097] The brown wet solid obtained in step (1) was treated with the same steps (2) and (3) as in Example 1 to obtain a Pd1-Co3Sn2 intermetallic compound catalyst, denoted as X13. The contents of Pd, Co and Sn in the catalyst were determined, wherein the Pd content was 0.07 wt%, the Co content was 13.06 wt%, and the Sn content was 17.07%.

[0098] Based on the determination results of the content of each metal element in this embodiment, it can be seen that after the Pd step, the system was further adjusted to pH=6.5±0.2 and SnCl4 was introduced. The H in the system + / Cl -As the concentration increases, the adsorbed Pd(II) is more easily re-coordinated by Pd(OH)2 (by Pd(OH)2). x Internal ligands revert to [PdCl4] 2- The Pd molecules are desorbed into the supernatant and then washed away, resulting in a decrease in the actual load.

[0099] Comparative Example 5

[0100] Compared with Example 1, the only difference is that the pH conditions after adding Sn raw material in step (1) are different.

[0101] In this embodiment, the preparation step (1) is as follows: the precipitant is placed in a 500mL three-necked flask and kept at a constant temperature of 65°C in an oil bath for 1 hour; at 200r·min -1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1 A mixed nitrate solution was added dropwise, and the system pH was adjusted to 10.5 ± 0.1 by titration with NaOH solution, completing the co-precipitation of Co / Mg / Al and the construction of layered hydroxide (LDH). Subsequently, H₂PdCl₄ solution was added dropwise to adjust the pH to 9.0 ± 0.1, promoting Pd to be anchored in situ at the lamellar sites and achieve atomic-level dispersion via ion exchange / coordination. Then, SnCl₄ solution was added dropwise, and the pH was adjusted to 8.5 ± 0.1 by NaOH. After all materials were added, the mixture was continuously and vigorously stirred at 65°C for 12 hours for aging. After filtration and washing with water, a brown wet solid was obtained.

[0102] The brown wet solid obtained in step (1) was treated with the same steps (2) and (3) as in Example 1 to obtain the Pd1-Co3Sn2 intermetallic compound catalyst, denoted as X14. The contents of Pd, Co and Sn in the catalyst were determined, wherein the Pd content was 0.11 wt%, the Co content was 13.42 wt%, and the Sn content was 16.05 wt%.

[0103] According to the measurement results of the content of each metal element in this embodiment, adding SnCl4 under the condition of pH=8.5±0.1 will lead to "rapid hydrolysis, more resolubility, and weak binding". Combined with the volatilization / migration during the high-temperature reduction process, the final measured Sn content is lower than the actual value.

[0104] Comparative Example 6

[0105] Compared with Example 1, the only difference is that the order of feeding precious metals Pd and Sn in step (1) is different.

[0106] In this comparative example, the preparation steps of step (1) are as follows: the precipitant is transferred to a 500 mL three-necked flask and kept at a constant temperature of 65°C in an oil bath for 1 h; at 200 r·min-1 With stirring, use a constant flow pump at a rate of 1.0 ± 0.1 mL / min. -1 A mixed nitrate solution was added dropwise, and NaOH solution was used to maintain the pH of the system at 10.5 ± 0.1 to complete the co-precipitation of Co / Mg / Al and the construction of LDH. Then, SnCl4 solution was added dropwise first, and the pH of the system was adjusted to 7.5 ± 0.1. After the Sn addition was complete, H2PdCl4 solution was added dropwise, and NaOH solution was used to stabilize the pH at 9.0 ± 0.1. After all the materials were added, the system was continuously stirred vigorously at 65°C for 12 hours for aging. After filtration and washing with water, a brown wet solid was obtained.

[0107] The brown wet solid obtained in step (1) was processed in the same steps (2) and (3) as in Example 1 to obtain Pd. n The -Co3Sn2 intermetallic compound catalyst, denoted as X15, was determined to contain Pd, Co, and Sn. The Pd content was 0.10 wt%, the Co content was 13.30 wt%, and the Sn content was 17.87%.

[0108] For the obtained Pd n The -Co3Sn2 single-atom intermetallic compound catalyst was characterized, and the results are as follows: Figure 9 As shown, in this catalyst, Pd appears on the surface of the support as multiple sub-nanometer Pd clusters, rather than as uniformly dispersed single atoms.

[0109] Comparative Example 7

[0110] Compared with Example 1, the only difference is the amount of Sn raw material added in step (1). In this example, the amount of SnCl4·5H2O added was reduced to 1.76g. The final Pd1-Co2Sn intermetallic compound catalyst (Sn-depleted ratio, Co / Sn=2:1) ​​was denoted as X16. The contents of Pd, Co and Sn in the catalyst were determined, where the Pd content was 0.11wt%, the Co content was 13.34wt%, and the Sn content was 13.30wt%.

[0111] The Pd1-Co3Sn2 intermetallic compound catalyst prepared in Example 1, the Pd1-CoSn2 catalyst prepared in Example 2, and the Pd1-Co2Sn catalyst prepared in Comparative Example 7 were characterized by XRD and compared. The results are as follows: Figure 10 and Figure 11As shown. The results indicate that, using the preparation method of this invention, regardless of the different Co:Sn precursor ratios, the main phase of the samples after high-temperature hydrogen reduction is consistently Co3Sn2. In Example 2, with the addition of excess Sn, due to Sn's low melting point, certain vapor pressure under high-temperature reduction conditions, and ease of migration / volatilization, the resulting catalyst ultimately exhibits the Co3Sn2 main phase. However, for the catalyst prepared in Comparative Example 7, with excess Co content ("Co2Sn type" ratio), in addition to the Co3Sn2 main phase, XRD shows characteristic peaks of metallic Co, indicating that the excess Co precipitates in a metallic state.

[0112] Comparative Example 8

[0113] Compared with Example 1, the only difference is the amount of Pd raw material added in step (1). In this example, the amount of PdCl2 added was reduced to 0.00372g. The final Pd1-Co3Sn2 catalyst was designated as X17. The contents of Pd, Co, and Sn in the catalyst were determined, with Pd content of 0.05wt%, Co content of 13.48wt%, and Sn content of 17.65wt%.

[0114] Test Example 1

[0115] Performance evaluation of acetylene catalytic hydrogenation

[0116] The catalysts prepared in Examples 1-9 and Comparative Examples 1-8 were used to evaluate the selective hydrogenation activity of acetylene. The performance evaluation of the acetylene hydrogenation reaction was carried out on the ZKJC-RJ-X system of Beijing Wanlonghe Technology Co., Ltd., wherein the components in the reactants and products were analyzed online using a 4-channel microchromatograph microGC3000 (INFICON, USA).

[0117] Hydrogen and nitrogen were analyzed using molecular sieve columns, acetylene using Plot-U columns, and ethylene and ethane using alumina columns. Very low levels of C4 components in the feed gas were analyzed using OV-1 capillary columns. The detector was a thermal conductivity detector (TCD), and the carrier gases were Ar and He.

[0118] Evaluation conditions: Total inlet gas flow rate was 100 mL / min; the feed gas consisted of 0.5% C2H2, 50.0% C2H4, and 5.0% H2, with the remainder being N2; the reaction temperature was 40–130°C at atmospheric pressure; and the catalyst loading was 100 mg. 100 mg of catalyst sample was weighed and mixed thoroughly with 10 times its weight of quartz sand, then loaded into the isothermal zone of a stainless steel reaction tube. After catalyst loading, the reaction system was leak-tested by introducing N2 at a certain pressure (e.g., 10 bar). If the pressure remained constant, it indicated good sealing of the reaction system, allowing for further evaluation.

[0119] Set the nitrogen flow rate to 20 sccm (Standard Cubic Centimeter Per Minute) and heat to the reduction temperature. Then, turn off the nitrogen flow and set the hydrogen flow rate to 20 sccm. After a certain reduction time, turn off the hydrogen flow. Set the nitrogen flow rate to 20 sccm and cool to the reaction temperature, and set the required reaction pressure. Once the reaction conditions are stable, set the flow rates of each reaction component and switch the Furnace six-way valve to bypass, allowing the mixed gas to directly enter the chromatograph to detect the concentration of each component before the reaction. After stabilization, switch the Furnace six-way valve back to the inlet of the reaction tube to start the reaction. The gas exiting the reaction tube is then detected by an online chromatograph.

[0120] The acetylene conversion rate of the catalysts prepared by the test examples and comparative examples was determined. ethylene selectivity With ethylene yield To evaluate the catalytic performance of the catalyst for the selective hydrogenation of acetylene to ethylene, wherein:

[0121]

[0122]

[0123]

[0124] After reacting for 1 hour, the catalytic performance evaluation results of the catalysts prepared in each embodiment and comparative example are shown in Tables 1-3 below:

[0125] Table 1. Acetylene conversion rate (%) at different temperatures

[0126]

[0127] Table 2. Ethylene selectivity (%) at different temperatures

[0128]

[0129] Table 3. Ethylene yield (%) at different temperatures

[0130]

[0131] As shown in Tables 1 to 3, under normal reaction pressure and with ethylene-rich feedstock, the M1-Co3Sn2 single-atom intermetallic compound catalyst of this invention significantly improves acetylene conversion and yield compared to the parent alloy Co3Sn2 intermetallic compound catalyst. Within the temperature range of 40–130°C, the Pd1-Co3Sn2 single-atom intermetallic compound catalysts prepared in the examples all exhibit extremely high ethylene selectivity. This demonstrates that the Pd1-Co3Sn2 single-atom intermetallic compound catalyst prepared using the technical solution of this invention can significantly improve acetylene conversion, ethylene selectivity, and yield compared to the Co3Sn2 intermetallic compound catalyst.

[0132] This patent achieves the production of Pd1-Co3Sn2 single-atom intermetallic compound (IMC) through a programmed feeding method of "introducing Pd first and then Sn" combined with staged pH control: first, Co / Mg / Al-LDH is formed through co-precipitation, then Pd is atomically anchored at pH=8.0~9.5 via ion exchange / internal coordination, and then Sn(OH)4 is generated in situ at pH=7.0~8.0 to thin-layer coating and confine the Pd sites; after high-temperature hydrogen reduction, Pd1-Co3Sn2 single-atom intermetallic compound is obtained. Thanks to the structural characteristics of the catalyst, the electron-rich single-atom Pd efficiently cracks H2 and modulates the electronic structure of the neighboring Co1Sn2 sites. Sn geometric isolation reduces ethylene re-adsorption. The catalyst achieves a coupled pathway of "rapid hydrogen donation-selective adsorption-easy desorption" at 70-100°C, exhibiting high activity and high ethylene selectivity at low temperatures with relatively low noble metal loading. Replacing Pd with Ru / Rh / Ir / Pt also demonstrates superior catalytic performance. Furthermore, the preparation method provided by this invention is simple and easy for industrial application.

[0133] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of this patent.

Claims

1. A method for preparing a M1-Co3Sn2 monatomic intermetallic compound catalyst for the selective hydrogenation of alkyne to alkene reaction, characterized in that, The method comprises the following steps: (1) preparing Co / Mg / Al ternary layered hydroxide by co-precipitation method using metal salts of Co, Mg and Al as precursors, and preparing a Co / Mg / Al metal salt mixed solution; (2) adding a noble metal M precursor solution to the Co / Mg / Al-LDHs solution obtained in step (1), adjusting the pH of the reaction system to 8.0-9.5, and performing ion exchange to obtain a M / Co / Mg / Al-LDHs material; (3) continuously adding a Sn precursor solution to the M / Co / Mg / Al-LDHs solution obtained in step (2), adjusting the pH of the reaction system to 7.0-8.0, and performing in-situ growth to obtain a Sn / M / Co / Mg / Al-LDHs material; (4) filtering, washing and drying the reaction product of step (3), and performing a thermal reduction treatment to obtain the M1-Co3Sn2 monatomic intermetallic compound catalyst; wherein the noble metal M is selected from any one of Pd, Pt, Ru, Ir and Rh; in the precursors added during the preparation, the molar ratio of Co, M, Sn, Mg and Al is 1:(0.002-0.025):(0.6-2.1):(2-8):(1-3); and the loading amount of the noble metal M in the obtained M1-Co3Sn2 monatomic intermetallic compound catalyst is 0.08-0.25wt%.

2. The production method according to claim 1, characterized by, In step (2), the pH of the reaction system is adjusted to 8.5-9.

5.

3. The preparation method according to claim 1, characterized in that, The reaction systems of steps (1)-(3) are performed in the same reaction device, and the temperature of the reaction system is 55-75℃.

4. The production method according to claim 1, characterized by, In step (3), after the feeding is completed, the stirring is continued for 10-14 h.

5. The production method according to claim 1, characterized by, In step (4), the temperature of the thermal reduction treatment is 700-900℃, the reduction time is 3-5 h, and the reduction gas is H2 / N2 mixed gas.

6. A single-atom intermetallic compound catalyst of M1-Co3Sn2 prepared by the preparation method according to any one of claims 1 to 5, characterized in that, The structure is that Co3Sn2 is used as a parent alloy, M1Co1Sn2 multi-tooth rhombic active sites are constructed near the surface of the catalyst, a four-site synergistic structure of electron-rich M1 monatomic-electron-deficient Co1Sn2 is formed, and a bridge site formed by M1 and adjacent surface Co.

7. The M1-Co3Sn2 single-atom intermetallic compound catalyst of claim 6, wherein, In the catalyst, the content of Co is 10-15wt%, and the content of the noble metal M is 0.08-0.25wt%.

8. The M1-Co3Sn2 single-atom intermetallic compound catalyst of claim 7, wherein, In the catalyst, the content of the noble metal M is 0.08-0.20wt%.

9. The M1-Co3Sn2 single-atom intermetallic compound catalyst of claim 8, wherein, In the catalyst, the content of the noble metal M is 0.10-0.15wt%.

10. Use of a M1-Co3Sn2 monatomic intermetallic compound catalyst according to any one of claims 6 to 9, characterized in that, The catalyst is used for the reaction of selective hydrogenation of alkyne to olefin, and the reaction conditions are as follows: the reaction temperature is 40-130℃, and the reaction is carried out under normal pressure.

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