Alloy catalyst, its preparation method and application

Abstract

The application provides an alloy catalyst and a preparation method and application thereof, and relates to the field of catalysis technology.The alloy catalyst provided by the application comprises a nitride base and alloy nanoparticles dispersed on the nitride base; the alloy nanoparticles are formed by an active component and an active assistant component; the active component comprises one or more of Pd, Pt, Ni, Rh, Ru and In; and the active assistant component comprises one or more of Ti, Fe, Co, Cu, Zn, Bi, Ga, Mo and Sn. The application utilizes the nitride as the base to inhibit overflow diffusion of active hydrogen on the surface of the alloy nanoparticles, to improve the local hydrogen species density of the active component, so that the catalyst has excellent selectivity and activity in the acetylene hydrogenation reaction, and is beneficial to the purification of ethylene gas prepared by cracking of pure oil.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and in particular to an alloy catalyst, its preparation method, and its application. Background Technology

[0002] Ethylene is an important basic chemical raw material, and its production is a key indicator of a country's petrochemical development level. Ethylene produced through petroleum cracking often contains a small amount of acetylene (0.5-2%). This small amount of acetylene can poison the Ziegler-Natta catalyst used in downstream polyethylene production, therefore the acetylene content needs to be reduced to below 5 ppm.

[0003] Selective hydrogenation can hydrogenate impurity acetylene to the target product ethylene, exhibiting extremely high atom utilization and is therefore widely used in industrial production processes. However, since ethylene in the reactants can also be hydrogenated, and the concentration of ethylene is much higher than that of acetylene, to prevent the hydrogenation of ethylene from leading to feedstock waste, the catalyst for the selective hydrogenation of acetylene is required to have high acetylene hydrogenation activity and selectivity.

[0004] Currently, supported palladium-based catalysts are used in industrial production. By diluting the palladium sites with silver as a promoter, the adsorption energy of palladium for ethylene is weakened to improve selectivity. However, this also reduces the activation ability of palladium for acetylene and hydrogen, thus severely reducing catalytic activity. Therefore, developing an acetylene selective hydrogenation catalyst that combines high ethylene selectivity with high hydrogenation activity presents a significant challenge. Summary of the Invention

[0005] The purpose of this invention is to provide an alloy catalyst, its preparation method, and its application. The catalyst provided by this invention has both high ethylene selectivity and high hydrogenation activity.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides an alloy catalyst comprising a nitride substrate and alloy nanoparticles dispersed on the nitride substrate;

[0008] The alloy nanoparticles are formed from an active component and a co-active component; the active component includes one or more of Pd, Pt, Ni, Rh, Ru, and In; the co-active component includes one or more of Ti, Fe, Co, Cu, Zn, Bi, Ga, Mo, and Sn.

[0009] The content of the active component in the alloy catalyst is 0.01-10 wt%; the content of the co-active component is 0.01-10 wt%.

[0010] Preferably, the nitride in the nitride substrate is composed of one or more elements selected from B, C, Al, Si, Ti, Fe, Zr, Nb, Ba and La, along with N.

[0011] Preferably, the nitride substrate includes a carbon nitride substrate, a titanium nitride substrate, or a lanthanum nitride substrate.

[0012] Preferably, the active component includes Pd or Ni; the co-active component includes Bi or Cu.

[0013] This invention provides a method for preparing the alloy catalyst described above, comprising the following steps:

[0014] The active component precursor, the co-active component precursor, the reducing agent and the capping agent are dissolved in a solvent and a reduction reaction is carried out to obtain alloy nanoparticles.

[0015] The alloy nanoparticles were impregnated into a dispersion of a nitride substrate, and the solid and liquid were separated. The resulting solid was then dried and calcined to obtain an alloy catalyst precursor.

[0016] The alloy catalyst precursor was reduced in a hydrogen atmosphere to obtain the alloy catalyst.

[0017] The amounts of the active component precursor, the co-active component precursor, and the nitride substrate correspond to the contents of the active component, the co-active component, and the nitride substrate in the target alloy catalyst, respectively.

[0018] Preferably, the reducing agent is one or more of hydrazine hydrate, sodium borohydride, polyvinylpyrrolidone, ascorbic acid, and sodium citrate; the mass ratio of the reducing agent to the total mass of the active component precursor and the co-active component precursor is (1-20):1.

[0019] Preferably, the capping agent is one or more of ammonium bromide, hexadecyltrimethylammonium bromide, oleylamine, and hexadecylamine, and the mass ratio of the capping agent to the total mass of the active component precursor and the co-active component precursor is (2-10):1.

[0020] Preferably, the calcination temperature is 100–500°C and the holding time is 12–48 h; the reduction temperature is 100–300°C and the time is 0.5–2 h.

[0021] This invention provides the application of the alloy catalyst described above in the selective hydrogenation of acetylene to ethylene.

[0022] Preferably, the reaction conditions for the selective hydrogenation of acetylene to ethylene include: a reaction pressure of 0.1–0.3 MPa, a reaction temperature of 50–120 °C, a molar ratio of H2 to C2H2 of (5–20):1, and a volume hourly space velocity of 20,000–40,000 h⁻¹. -1 .

[0023] This invention provides an alloy catalyst comprising a nitride substrate and alloy nanoparticles dispersed on the nitride substrate; the alloy nanoparticles are formed of an active component and a co-active component; the active component includes one or more of Pd, Pt, Ni, Rh, Ru, and In; the co-active component includes one or more of Ti, Fe, Co, Cu, Zn, Bi, Ga, Mo, and Sn; the content of the active component in the alloy catalyst is 0.01–10 wt%; the content of the co-active component is 0.01–10 wt%. This invention utilizes a nitride substrate to suppress the overflow diffusion of active hydrogen on the surface of the alloy nanoparticles, increasing the local hydrogen species density of the active component, thus giving the catalyst excellent selectivity and activity in the acetylene hydrogenation reaction, which is beneficial for purifying ethylene gas produced from petroleum cracking.

[0024] This invention provides a method for preparing the alloy catalyst described above. The invention utilizes a method of first preparing alloy nanoparticles and then supporting them to prepare the alloy catalyst. The alloy nanoparticles have a narrow size distribution and are uniformly dispersed on the support. The prepared alloy nanoparticles exhibit high component uniformity, possess the intrinsic characteristic of being ethylene-inactive, can maintain ethylene selectivity under conditions of complete acetylene conversion, and have a wide operating temperature window. Attached Figure Description

[0025] Figure 1 This is a transmission electron microscope image of the catalyst in Example 1 of the present invention. Detailed Implementation

[0026] This invention provides an alloy catalyst comprising a nitride substrate and alloy nanoparticles dispersed on the nitride substrate;

[0027] The alloy nanoparticles are formed from an active component and a co-active component; the active component includes one or more of Pd, Pt, Ni, Rh, Ru, and In; the co-active component includes one or more of Ti, Fe, Co, Cu, Zn, Bi, Ga, Mo, and Sn.

[0028] The content of the active component in the alloy catalyst is 0.01-10 wt%; the content of the co-active component is 0.01-10 wt%.

[0029] The alloy catalyst provided by this invention comprises a nitride substrate, wherein the nitride in the nitride substrate is preferably composed of one or more elements selected from B, C, Al, Si, Ti, Fe, Zr, Nb, Ba, and La, and N; more preferably, the nitride substrate comprises a carbon nitride (C3N4) substrate, a titanium nitride (TiN) substrate, or a lanthanum nitride (LaN) substrate. This invention utilizes nitrides as a substrate to suppress the overflow diffusion of active hydrogen on the surface of alloy nanoparticles, thereby increasing the local hydrogen species density of the active component, resulting in excellent selectivity and activity of the alloy catalyst in the acetylene hydrogenation reaction.

[0030] The alloy catalyst provided by the present invention comprises alloy nanoparticles dispersed on the nitride substrate; the alloy nanoparticles are formed of an active component and a co-active component; the active component comprises one or more of Pd, Pt, Ni, Rh, Ru and In, more preferably Pd or Ni; the co-active component comprises one or more of Ti, Fe, Co, Cu, Zn, Bi, Ga, Mo and Sn, more preferably Bi or Cu.

[0031] In this invention, the content of the active component in the alloy catalyst is 0.01-10 wt%, preferably 1-9 wt%, more preferably 3-7 wt%; the content of the co-active component is 0.01-10 wt%, preferably 1-9 wt%, more preferably 3-7 wt%.

[0032] In this invention, the average particle size of the alloy nanoparticles is preferably 3-6 nm, more preferably 4-5 nm.

[0033] In this invention, the alloy nanoparticles have a narrow size distribution and are uniformly dispersed on a nitride substrate; the alloy nanoparticles have high compositional uniformity, possess the intrinsic characteristic of ethylene inactivation, can maintain ethylene selectivity under acetylene full conversion conditions, and have a wide operating temperature window.

[0034] This invention provides a method for preparing the alloy catalyst described above, comprising the following steps:

[0035] The active component precursor, the co-active component precursor, the reducing agent and the capping agent are dissolved in a solvent and a reduction reaction is carried out to obtain alloy nanoparticles.

[0036] The alloy nanoparticles were impregnated into a dispersion of a nitride substrate, and the solid and liquid were separated. The resulting solid was then dried and calcined to obtain an alloy catalyst precursor.

[0037] The alloy catalyst precursor was reduced in a hydrogen atmosphere to obtain the alloy catalyst.

[0038] The amounts of the active component precursor, the co-active component precursor, and the nitride substrate correspond to the contents of the active component, the co-active component, and the nitride substrate in the target alloy catalyst, respectively.

[0039] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0040] This invention involves dissolving an active component precursor, a co-active component precursor, a reducing agent, and a capping agent in a solvent to carry out a reduction reaction, thereby obtaining alloy nanoparticles.

[0041] This invention does not impose special requirements on the specific type of the active component precursor, as long as it can dissolve in the solvent. Specifically, it can be a metal salt and / or hydroxide of the active component. The metal salt of the active component can be one or more of the following: nitrate, sulfate, carbonate, chloride, acetate, acetylacetonate, and n-propoxide. In an embodiment of this invention, when the active component is Pd, the precursor of the active component is palladium acetylacetonate.

[0042] This invention does not impose special requirements on the specific type of the precursor of the co-active component, as long as it can dissolve in the solvent. Specifically, it can be a metal salt and / or hydroxide of the co-active component. The metal salt of the co-active component can be one or more of the following: nitrate, sulfate, carbonate, chloride, acetate, acetylacetonate, and n-propoxide. In an embodiment of this invention, when the co-active component is Bi, the precursor of the co-active component is bismuth nitrate pentahydrate.

[0043] In this invention, the reducing agent is preferably one or more of hydrazine hydrate, sodium borohydride, polyvinylpyrrolidone, ascorbic acid, and sodium citrate; the mass ratio of the reducing agent to the total mass of the active component precursor and the co-active component precursor is preferably (1-20):1, more preferably (5-15):1.

[0044] In this invention, the capping agent is preferably one or more of ammonium bromide, hexadecyltrimethylammonium bromide, oleylamine, and hexadecylamine. The mass ratio of the capping agent to the total mass of the active component precursor and the co-active component precursor is preferably (2-10):1, more preferably (4-8):1. In this invention, the function of the capping agent is to control the uniform size distribution (3-6 nm) of the formed alloy nanoparticles.

[0045] In this invention, the solvent is preferably one or more of deionized water, methanol, glacial acetic acid, anhydrous ethanol, ethylene glycol, acetone and n-hexane. In this invention, it is preferred to select a suitable solvent according to the type of active component precursor and co-active component precursor to ensure that the active component and co-active component precursor can be dissolved.

[0046] The present invention does not have special requirements on the amount of solvent used, as long as it can completely dissolve all components.

[0047] In this invention, the dissolution preferably includes: first ultrasonic treatment for 20-60 minutes, then stirring on a magnetic stirrer at room temperature for 20-60 minutes.

[0048] In this invention, the temperature of the reduction reaction is preferably 100–240°C, more preferably 140–200°C; the time of the reduction reaction is preferably 1–12 h, more preferably 4–8 h. In this invention, the reduction reaction is preferably carried out in a constant temperature bath. During the reduction reaction, the reducing agent reduces the active component precursor and the co-active component precursor to form alloy nanoparticles of the active component and the co-active component.

[0049] After the reduction reaction is completed, the present invention preferably further includes naturally cooling the reaction system to room temperature, collecting the product by centrifugation, and washing it multiple times with an ethanol-acetone mixed solution. The resulting solid is the alloy nanoparticle. In the present invention, the volume ratio of ethanol to acetone in the ethanol-acetone mixed solution is preferably 1:(1-10).

[0050] After obtaining the alloy nanoparticles, the present invention impregnates the alloy nanoparticles into a dispersion of nitride substrate, performs solid-liquid separation, and sequentially dries and calcines the resulting solid to obtain an alloy catalyst precursor.

[0051] In this invention, the dispersion of the nitride substrate is preferably obtained by dispersing the nitride substrate in a solvent, and the type of solvent is the same as described above, so it will not be repeated here. This invention does not have special requirements on the amount of solvent used, as long as it is sufficient to disperse the nitride substrate uniformly. In this invention, the dispersion is preferably carried out under ultrasonic conditions, and the dispersion time is preferably 20–60 minutes.

[0052] In this invention, the impregnation is preferably carried out under ultrasonic conditions; the impregnation time is preferably 30 to 90 minutes, more preferably 40 to 60 minutes.

[0053] In this invention, the solid-liquid separation method is preferably centrifugation. After solid-liquid separation, the invention preferably further includes washing the obtained solid three times with anhydrous ethanol, followed by drying and calcination.

[0054] In this invention, the drying temperature is preferably 60-120°C, and the drying time is preferably 6-24 h; the calcination temperature is preferably 100-500°C, more preferably 200-400°C; the calcination time is preferably 12-48 h, more preferably 20-40 h; and the calcination is preferably carried out in an air atmosphere.

[0055] In the calcination process described in this invention, residual reducing agents and anions (such as nitrate ions) in the precursors are removed from the surface of the alloy nanoparticles.

[0056] After obtaining the alloy catalyst precursor, the present invention reduces the alloy catalyst precursor in a hydrogen atmosphere to obtain the alloy catalyst.

[0057] In this invention, the reduction temperature is preferably 100-300°C, more preferably 150-250°C; the reduction time is preferably 0.5-2 hours, more preferably 1-1.5 hours.

[0058] Since calcination in air causes oxidation on the surface of alloy nanoparticles, this invention utilizes hydrogen reduction to remove oxygen from the catalyst.

[0059] This invention utilizes a method of first preparing alloy nanoparticles and then loading them to prepare alloy catalysts. The alloy nanoparticles have a narrow size distribution and are uniformly dispersed on the support. The prepared alloy nanoparticles have high component uniformity, possess the intrinsic characteristic of ethylene inactivation, can maintain ethylene selectivity under acetylene full conversion conditions, and have a wide operating temperature window.

[0060] This invention provides the application of the alloy catalyst described above in the selective hydrogenation of acetylene to ethylene.

[0061] The reaction conditions for the selective hydrogenation of acetylene to ethylene include: a reaction pressure preferably of 0.1–0.3 MPa, more preferably 0.15–0.25 MPa; a reaction temperature preferably of 50–120 °C, more preferably 70–100 °C; a molar ratio of H2 to C2H2 preferably of (5–20):1, more preferably (10–15):1; and a volume hourly space velocity preferably of 20,000–40,000 h⁻¹. -1 More preferably 25,000 to 35,000 hours -1 .

[0062] In this invention, the selective hydrogenation of acetylene to ethylene is preferably carried out in a fixed-bed reactor.

[0063] In this invention, the acetylene is preferably acetylene present in ethylene produced by petroleum cracking, wherein the molar ratio of C2H4 to C2H2 is preferably (20-40):1. The alloy catalyst provided by this invention, under conditions where the feed gas contains ethylene, can achieve complete conversion of acetylene impurities, meeting the requirement of acetylene impurity content below 5 ppm, and achieving ethylene selectivity of over 85%.

[0064] The following detailed description of the alloy catalyst, its preparation method, and its application provided by the present invention, with reference to specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0065] Comparative Example 1

[0066] The catalyst was Pd nanoparticles supported on an Al2O3 substrate, prepared as follows: 0.1 g palladium acetylacetonate, 0.5 g polyvinylpyrrolidone, and 0.4 g ammonium bromide were added to 100 mL ethylene glycol, sonicated for 30 min, and stirred at room temperature for 30 min. The mixture was then transferred to a constant-temperature oil bath at 160 °C for reduction for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain nanoparticles. 2 g of Al2O3 substrate was dispersed in 50 mL anhydrous ethanol and sonicated for 30 min to disperse the support. Then, 0.02 g of nanoparticles were added, and sonication was continued for 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in an oven at 60°C for 12 hours, then calcined in air at 200°C for 6 hours, and reduced with hydrogen at 200°C for 1 hour to obtain the comparative catalyst, in which the Pd content was 1.0 wt% (measured by inductively coupled plasma optical emission spectrometry (ICP-OES)).

[0067] Comparative Example 2

[0068] The catalyst was PdBi nanoparticles supported on an Al₂O₃ substrate, prepared as follows: 0.1 g palladium acetylacetonate, 0.08 g bismuth nitrate pentahydrate, 0.5 g polyvinylpyrrolidone, and 0.4 g ammonium bromide were dispersed in 100 mL ethylene glycol. After sonication for 30 min, the mixture was stirred at room temperature for 30 min, then transferred to a constant temperature oil bath at 160 °C for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain alloy nanoparticles. 2 g of Al₂O₃ substrate was dispersed in 50 mL anhydrous ethanol and sonicated for 30 min to disperse the carrier. Then, 0.035 g of alloy particles were added, and sonication was continued for 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in an oven at 60°C for 12 hours, then calcined in air at 200°C for 6 hours, and reduced with hydrogen at 200°C for 1 hour to obtain the comparative catalyst. The content of Pd was 1.0 wt% and the content of Bi was 0.7 wt% as determined by ICP-OES.

[0069] Comparative Example 3

[0070] The catalyst was Pd nanoparticles supported on a C3N4 substrate, prepared as follows: 0.1 g palladium acetylacetonate, 0.5 g polyvinylpyrrolidone, and 0.4 g ammonium bromide were dispersed in 100 mL ethylene glycol, sonicated for 30 min, and stirred at room temperature for 30 min. The mixture was then transferred to a constant-temperature oil bath at 160 °C for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain nanoparticles. 2 g of the C3N4 substrate was dispersed in 50 mL anhydrous ethanol and sonicated for 30 min to disperse the support. Then, 0.02 g of nanoparticles were added, and sonication was continued for 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in a 60 °C oven for 12 h, then calcined in a muffle furnace at 200 °C under air for 6 h, and reduced with hydrogen at 200 °C for 1 h to obtain the control catalyst. The Pd content was determined to be 1.0 wt% by ICP-OES.

[0071] Comparative Example 4

[0072] The catalyst was Pd nanoparticles supported on a TiN substrate, prepared as follows: 0.1 g palladium acetylacetonate, 0.5 g polyvinylpyrrolidone, and 0.4 g ammonium bromide were dispersed in 100 mL ethylene glycol, sonicated for 30 min, and stirred at room temperature for 30 min. The mixture was then transferred to a constant-temperature oil bath at 160 °C for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain nanoparticles. 2 g of TiN substrate was dispersed in 50 mL anhydrous ethanol, sonicated for 30 min for carrier dispersion, and then 0.02 g of nanoparticles were added and sonicated for another 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in a 60 °C oven for 12 h, then calcined in a muffle furnace at 200 °C under air for 6 h, and reduced with hydrogen at 200 °C for 1 h to obtain the comparative catalyst. The Pd content was determined to be 1.0 wt% by ICP-OES.

[0073] Comparative Example 5

[0074] The catalyst is a commercial palladium-on-carbon catalyst.

[0075] Example 1

[0076] The catalyst was PdBi nanoparticles supported on a C3N4 substrate, prepared as follows: 0.1 g palladium acetylacetonate, 0.08 g bismuth nitrate pentahydrate, 0.5 g polyvinylpyrrolidone, and 0.4 g ammonium bromide were dispersed in 100 mL ethylene glycol. After sonication for 30 min, the mixture was stirred at room temperature for 30 min, then transferred to a constant temperature oil bath at 160 °C for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain alloy nanoparticles. 2 g of the C3N4 substrate was dispersed in 50 mL anhydrous ethanol and sonicated for 30 min to disperse the carrier. Then, 0.035 g of alloy particles were added, and sonication was continued for 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in an oven at 60°C for 12 hours, then calcined in air at 200°C for 6 hours, and reduced with hydrogen at 200°C for 1 hour to obtain the alloy catalyst. The content of Pd was 1.0 wt% and the content of Bi was 0.7 wt% as determined by ICP-OES.

[0077] The alloy catalyst prepared in Example 1 was observed by transmission electron microscopy, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the alloy nanoparticles are uniformly dispersed on the substrate, and the size distribution of the alloy nanoparticles is narrow, about 4.5 nm.

[0078] Example 2

[0079] The catalyst was PdBi nanoparticles supported on a TiN substrate, prepared as follows: 0.1 g palladium acetylacetonate, 0.08 g bismuth nitrate pentahydrate, 0.5 g polyvinylpyrrolidone, and 0.4 g ammonium bromide were dispersed in 100 mL ethylene glycol. After sonication for 30 min, the mixture was stirred at room temperature for 30 min, then transferred to a constant temperature oil bath at 160 °C for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain alloy nanoparticles. 2 g of TiN substrate was dispersed in 50 mL anhydrous ethanol and sonicated for 30 min to disperse the support. Then, 0.035 g of alloy particles were added, and sonication was continued for 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in an oven at 60°C for 12 hours, then calcined in air at 200°C for 6 hours, and reduced with hydrogen at 200°C for 1 hour to obtain the alloy catalyst. The content of Pd was 1.0 wt% and the content of Bi was 0.7 wt% as determined by ICP-OES.

[0080] Example 3

[0081] The catalyst was NiCu nanoparticles supported on a C3N4 substrate, prepared as follows: 0.1 g of nickel nitrate hexahydrate, 0.04 g of copper nitrate trihydrate, 0.8 g of polyvinylpyrrolidone, and 0.5 g of ammonium bromide were dispersed in 100 mL of ethylene glycol. After sonication for 30 min, the mixture was stirred at room temperature for 30 min, then transferred to a constant temperature oil bath at 180 °C for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain alloy nanoparticles. 2 g of the C3N4 substrate was dispersed in 50 mL of anhydrous ethanol and sonicated for 30 min to disperse the carrier. Then, 0.028 g of alloy particles were added, and sonication was continued for 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in an oven at 60°C for 12 hours, then calcined in air at 300°C for 6 hours, and reduced with hydrogen at 300°C for 1 hour to obtain the alloy catalyst. The content of Ni was 1.0 wt% and the content of Cu was 0.4 wt% as determined by ICP-OES.

[0082] Example 4

[0083] The catalyst was PdBi nanoparticles supported on a LaN substrate, prepared as follows: 0.1 g palladium acetylacetonate, 0.08 g bismuth nitrate pentahydrate, 0.5 g polyvinylpyrrolidone, and 0.4 g ammonium bromide were dispersed in 100 mL ethylene glycol. After sonication for 30 min, the mixture was stirred at room temperature for 30 min, then transferred to a constant temperature oil bath at 160 °C for 3 h. After cooling, the solid product was collected by centrifugation and washed three times with a 1:4 ethanol-acetone mixture to obtain alloy nanoparticles. 2 g of LaN substrate was dispersed in 50 mL anhydrous ethanol and sonicated for 30 min to disperse the support. Then, 0.035 g of alloy particles were added, and sonication was continued for 1 h. The solid was collected by centrifugation and washed three times with anhydrous ethanol. The obtained solid was vacuum dried in an oven at 60°C for 12 hours, then calcined in air at 200°C for 6 hours, and reduced with hydrogen at 200°C for 1 hour to obtain the alloy catalyst. The content of Pd was 1.0 wt% and the content of Bi was 0.7 wt% as determined by ICP-OES.

[0084] Performance testing:

[0085] Acetylene hydrogenation was carried out using the catalysts from Comparative Examples 1-5 and Examples 1-4. The specific activity evaluation experimental procedure is as follows: The catalyst activity was tested using a fixed-bed reactor. 20 mg of catalyst was weighed and placed in the isothermal section of the reactor. Both ends of the catalyst were fixed with quartz wool. The composition of the reaction gas was 1% C2H2, 10% C2H4, 20% H2 and Ar (by volume). The total gas flow rate was 40 mL / min and the volume hourly space velocity was 38000 h⁻¹. -1The reaction temperature is 100℃ and the reaction pressure is 110kPa.

[0086] The results of selective hydrogenation of acetylene using the catalysts of Comparative Examples 1-5 and Examples 1-4 are shown in Table 1:

[0087] Table 1 Results of selective hydrogenation of acetylene using various catalysts

[0088]

[0089]

[0090] As can be seen from Table 1, compared with the comparative catalyst, the alloy catalyst in this embodiment of the invention has significantly improved selectivity. Under the condition that the feed gas contains ethylene, it can achieve the complete conversion of acetylene impurities, meet the requirement that the acetylene impurity content is less than 5 ppm, and achieve ethylene selectivity of more than 85%.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An alloy catalyst for the selective hydrogenation of acetylene to ethylene, characterized in that, It includes a nitride substrate and alloy nanoparticles dispersed on the nitride substrate; The alloy nanoparticles are formed from an active component and a co-active component; the active component is Pd or Ni; the co-active component is Bi or Cu. The alloy catalyst contains 0.01-10 wt% of the active component and 0.01-10 wt% of the co-active component. The nitride substrate is a carbon nitride substrate, a titanium nitride substrate, or a lanthanum nitride substrate; The preparation method of the alloy catalyst includes the following steps: The active component precursor, the co-active component precursor, the reducing agent and the capping agent are dissolved in a solvent and a reduction reaction is carried out to obtain alloy nanoparticles. The alloy nanoparticles were impregnated into a dispersion of a nitride substrate, and the solid and liquid were separated. The resulting solid was then dried and calcined to obtain an alloy catalyst precursor. The alloy catalyst precursor was reduced in a hydrogen atmosphere to obtain the alloy catalyst. The amounts of the active component precursor, the co-active component precursor, and the nitride substrate correspond to the contents of the active component, the co-active component, and the nitride substrate in the target alloy catalyst, respectively.

2. The method for preparing the alloy catalyst according to claim 1, characterized in that, Includes the following steps: The active component precursor, the co-active component precursor, the reducing agent and the capping agent are dissolved in a solvent and a reduction reaction is carried out to obtain alloy nanoparticles. The alloy nanoparticles were impregnated into a dispersion of a nitride substrate, and the solid and liquid were separated. The resulting solid was then dried and calcined to obtain an alloy catalyst precursor. The alloy catalyst precursor was reduced in a hydrogen atmosphere to obtain the alloy catalyst. The amounts of the active component precursor, the co-active component precursor, and the nitride substrate correspond to the contents of the active component, the co-active component, and the nitride substrate in the target alloy catalyst, respectively.

3. The preparation method according to claim 2, characterized in that, The reducing agent is one or more of hydrazine hydrate, sodium borohydride, polyvinylpyrrolidone, ascorbic acid, and sodium citrate; the mass ratio of the reducing agent to the total mass of the active component precursor and the co-active component precursor is (1~20):

1.

4. The preparation method according to claim 2 or 3, characterized in that, The capping agent is one or more of ammonium bromide, hexadecyltrimethylammonium bromide, oleylamine and hexadecylamine, and the mass ratio of the capping agent to the total mass of the active component precursor and the co-active component precursor is (2~10):

1.

5. The preparation method according to claim 2, characterized in that, The calcination temperature is 100~500℃, and the holding time is 12~48 h; the reduction temperature is 100~300℃, and the time is 0.5~2 h.

6. The application of the alloy catalyst according to claim 1 or the alloy catalyst prepared by any one of claims 2 to 5 in the selective hydrogenation of acetylene to ethylene.

7. The application according to claim 6, characterized in that, The reaction conditions for the selective hydrogenation of acetylene to ethylene include: a reaction pressure of 0.1–0.3 MPa, a reaction temperature of 50–120 °C, a molar ratio of H2 to C2H2 of (5–20):1, and a volume hourly space velocity of 20,000–40,000 h⁻¹. -1 .

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