A carbon dioxide post-hydrogenation catalyst and a method for preparing the same

Abstract

The application provides a carbon dioxide post-hydrogenation catalyst and a preparation method thereof. The catalyst comprises a carrier and an active component, the carrier is a phosphorus-doped carbon material, the active component comprises a main active component and an auxiliary active component, the main active component comprises Pd, the auxiliary active component comprises Fe, and the main active component and the auxiliary active component are atomically dispersed on the carrier. The preparation method comprises the following steps: mixing a phosphorus-containing compound and a carbohydrate in water, then performing a hydrothermal reaction, and then performing at least drying and calcination to obtain the phosphorus-doped carbon material carrier; loading the active component on the phosphorus-doped carbon material carrier to obtain a catalyst semi-product; and reducing the catalyst semi-product to obtain a reduced catalyst, which is the carbon dioxide post-hydrogenation catalyst. The carbon dioxide post-hydrogenation catalyst provided by the application has excellent hydrogenation activity, selectivity and anti-coking performance.

Description

Technical Field

[0001] This invention relates to a post-hydrogenation catalyst for C2 and its preparation method, belonging to the field of hydrogenation catalyst technology. Background Technology

[0002] Ethylene obtained from petroleum hydrocarbon steam cracking typically contains 0.5%–2.3% acetylene by molar fraction. During polymerization, the acetylene in ethylene reduces the activity of the polymerization catalyst and affects the physical properties of the polymer; therefore, it must be removed. Currently, selective hydrogenation is commonly used industrially to remove acetylene from ethylene, primarily employing noble metal catalysts such as Pd, Pt, and Au. To ensure that the ethylene produced by acetylene hydrogenation and the original ethylene in the feedstock do not undergo further hydrogenation to form ethane, thus preventing ethylene loss, a high hydrogenation selectivity of the catalyst is essential to achieve good economic benefits.

[0003] The terms "post-hydrogenation" and "pre-hydrogenation" refer to the position of the acetylene hydrogenation reactor relative to the demethanizer. Pre-hydrogenation refers to the reactor being located before the demethanizer, while post-hydrogenation refers to the reactor being located after the demethanizer. The advantages of post-hydrogenation are more controllable processes, less prone to temperature runaway, and easier operation. However, it is more complex and requires separate hydrogen preparation. In post-hydrogenation of C2, due to the low hydrogen content in the feedstock, acetylene is prone to hydrogenation dimerization, producing a C4 fraction. This C4 fraction further polymerizes to form oligomers with a wide molecular weight range, commonly known as "green oil." This green oil adsorbs onto the catalyst surface and further forms coke, blocking catalyst pores and preventing reactants from diffusing to the active sites, thus reducing catalyst activity.

[0004] Noble metal catalysts exhibit high activity, but they are prone to generating green oil during use, leading to coking and deactivation, which affects catalyst stability and lifespan. CN101664682A discloses a non-noble metal supported selective hydrogenation catalyst, its preparation method, and its application. The catalyst comprises a support and a main active component and a co-active component supported on that support. The main active component is Ni, and the co-active component is selected from at least one of Mo, La, Ag, Bi, Cu, Nd, Cs, Ce, Zn, and Zr. Both the main active component and the co-active component exist in amorphous form with an average particle size <10 nm. The support is a non-oxidizing porous material. The catalyst is prepared using a microemulsion method.

[0005] US4404124 describes a selective hydrogenation catalyst with a shell distribution of active components prepared via a stepwise impregnation method. This catalyst can be applied to the selective hydrogenation of C2 fractions to eliminate acetylene from ethylene. US5587348 describes a high-performance C2 hydrogenation catalyst prepared using alumina as a support, with the addition of silver and palladium co-catalysts, and the addition of fluorine chemically bonded to alkali metals. This catalyst exhibits characteristics such as reduced green oil formation, improved ethylene selectivity, and reduced formation of oxygen-containing compounds.

[0006] CN1736589A reports a Pd / γ-Al2O3 selective hydrogenation catalyst prepared by a complete adsorption impregnation method, but this catalyst generates a large amount of green oil during use. CN101433845A discloses an unsaturated hydrocarbon selective hydrogenation catalyst and its preparation method. This catalyst uses alumina as a support and palladium as the active component. The catalyst's resistance to impurities and coking is improved by adding rare earth and alkaline earth metals and fluorine, but the selectivity of this catalyst is not ideal.

[0007] The catalysts prepared by the above methods all use catalysts with a single pore size distribution. In fixed-bed reactions, the selectivity of the catalysts is poor due to the influence of internal diffusion. Supports with a bimodal pore distribution can improve catalyst selectivity while ensuring high activity, as the presence of large pores can reduce the influence of internal diffusion. CN104096572A discloses a hydrogenation catalyst with a honeycomb support, a large-pore support, which effectively improves the catalyst's selectivity. CN1129606A discloses a hydrocarbon conversion catalyst with a support including alumina, nickel oxide, and iron oxide. This catalyst includes two types of pores: one to improve the catalytic reaction surface and the other to facilitate diffusion. CN101433842A discloses a hydrogenation catalyst with a bimodal pore distribution. The most probable radius of the small pores is 2–50 nm, and the most probable radius of the large pores is 100–500 nm. Due to the bimodal pore distribution, the catalyst exhibits both good hydrogenation activity and good selectivity, resulting in a large increase in ethylene production.

[0008] In the C2 hydrogenation reaction, the formation of green oil and coking of the catalyst are important factors affecting catalyst lifespan. The catalyst's activity, selectivity, and lifespan constitute its overall performance. While the methods listed above offer good pathways to improve catalyst activity and selectivity, they do not solve the problem of catalyst coking, or they address the issues of green oil formation and coking but not selectivity. Although macroporous supports can improve selectivity, the larger molecules generated by polymerization and chain growth reactions can easily accumulate in the macropores of the support, causing catalyst coking and deactivation, thus affecting catalyst lifespan.

[0009] CN112679301A discloses a hydrogenation catalyst in which the active components include Pd, Ag, and Ni. Pd and Ag are supported using an aqueous solution impregnation method, while Ni is supported using a W / O microemulsion impregnation method. In the catalyst prepared by this method, Pd / Ag and Ni are located in channels of different pore sizes, allowing the generated green oil to undergo saturated hydrogenation in the macropores, thus reducing the amount of coking on the catalyst.

[0010] However, the reduction temperature of Ni often reaches around 500℃. At this temperature, the reduced Pd atoms are very easy to aggregate, which greatly reduces the catalyst activity. It is necessary to increase the amount of active component by a large margin to compensate for the loss of activity, but this will cause a decrease in selectivity.

[0011] CN106654300A discloses a method for preparing monodisperse metal atom / graphene composite materials by electrochemically swelling graphite, providing a novel method for efficiently preparing monodisperse metal atom / graphene composite catalysts with controllable metal atom types and quantities by electrochemically swelling graphite-based raw materials. This method is an electrochemical exfoliation method for preparing monodisperse metal atom / graphene composite materials from graphite in one step under milder conditions, mainly including the following steps: (1) making graphite-based raw materials into electrodes; (2) electrolyzing the electrodes in an electrolytic cell, separating solids and liquids, and recycling the electrolyte; (3) further exfoliating the separated solids to obtain crude monodisperse metal atom / graphene composite materials; (4) separating and purifying the crude monodisperse metal atom / graphene composite materials to obtain monodisperse metal atom / graphene composite materials; (5) heat-treating the composite materials obtained in step (4) and / or the composite materials uniformly mixed with a non-gas-phase nitrogen source under an inert atmosphere and / or an ammonia atmosphere, and cooling to obtain monodisperse metal atom / graphene composite catalysts. In this material, the metal is dispersed in the graphene framework as single atoms. The type and composition of the central metal atoms can be adjusted as needed, and it can be either mononuclear or binuclear. Furthermore, the binuclear metal component can be either a single metal or a bimetallic component. However, this literature does not describe the content and metal state of the active metal component, only prepares a single-atom catalyst, and does not evaluate the catalyst performance for any specific system.

[0012] CN109126857A discloses a metal single-atom catalyst based on a carbon nanocage support and its preparation method. This metal single-atom catalyst based on a carbon nanocage support includes a carbon nanocage support and metal single atoms embedded in the microporous channels of the cage wall of the carbon nanocage support; the metal single atoms are Pt, Pd, Ru, Ir, Ag, or Au; the carbon nanocage support is a doped carbon nanocage, the loading of the metal single atoms is less than 8 wt%, the doped carbon nanocage is a single-element doped carbon nanocage or a co-doped carbon nanocage, the single-element doped carbon nanocage is N-doped, B-doped, S-doped, or P-doped carbon nanocage, the P doping amount in the P-doped carbon nanocage is less than 8 at%, and the pore size of the cage wall micropores of the carbon nanocage support is 0.4–1.5 nm. The preparation method of the metal single-atom catalyst includes: impregnating doped carbon nanocages in a metal precursor solution, followed by separation and heat treatment to obtain a metal single-atom catalyst based on a carbon nanocage support; the metal precursor is a water-soluble metal ion compound corresponding to Pt, Pd, Ru, Ir, Ag or Au; the heat treatment temperature is 40-600℃, the heat treatment time is 0.5-24h, the impregnation temperature is 0-100℃, and the impregnation time is 0.5-50h.

[0013] CN112808288A discloses a catalyst with nitrogen-phosphorus or nitrogen-phosphorus co-doped carbon supporting metal single atoms and its microwave-assisted preparation method. The catalyst includes a support and an active metal component supported on the support; the support is a nitrogen-phosphorus or nitrogen-phosphorus-sulfur co-doped carbon material, and the metal includes any one of palladium, ruthenium, rhodium, iridium, platinum, iron, cobalt, and nickel. By mass percentage, the metal loading in the catalyst is 0.1%-5%. The preparation method of the catalyst includes the following steps: (1) phytic acid and any one or more of nitrogen- and sulfur-containing organic molecules such as thiourea, urea, melamine, dicyandiamide, cyanuric acid, aniline, and pyrrole are mixed at a certain mass ratio and placed in a microwave oven for microwave heating. The obtained black product is a nitrogen-phosphorus or nitrogen-sulfur-phosphorus doped carbon support; (2) a certain amount of metal precursor solution is mixed with the support and reducing agent in step (1), stirred, washed, and dried to obtain the catalyst material with nitrogen-phosphorus or nitrogen-phosphorus-sulfur doped carbon material supporting metal single atoms.

[0014] CN111389437A discloses a molybdenum carbide-supported single-atom hydrogenation catalyst, its preparation method, and its application in the semi-hydrogenation of alkynes. The hydrogenation catalyst comprises: a support comprising MoC; and a metal single atom supported on the support, wherein the metal single atom is chemically bonded to molybdenum atoms in the MoC; wherein the metal single atom comprises at least one selected from single-atom nickel, single-atom cobalt, and single-atom copper.

[0015] CN112844406A discloses a method for preparing a catalyst for selective hydrogenation of C2 fractions from light hydrocarbon cracking. The catalyst uses alumina or primarily alumina as the support, exhibiting a bimodal pore structure. The catalyst contains at least Pd, Ga, Ni, and Cu. The active component Pd is supported using both solution and microemulsion methods. Ga is supported using a solution method, with the solution-supported Pd primarily distributed in the 58–75 nm pores of the support. Ni and Cu are supported using a microemulsion impregnation method, with the emulsion-supported Pd primarily distributed in the 350–700 nm macropores of the support, and are loaded after Ni and Cu. This document discloses a catalyst for selective hydrogenation of C2 fractions to remove alkynes, using solution and emulsion methods for supporting the active components, with a bimodal alumina support, but does not involve single-atom catalyst preparation technology.

[0016] CN106925279A discloses an Fe-based selective hydrogenation catalyst, its preparation method, and its application. The catalyst's active component comprises 2–15 wt% Fe and 0–2 wt% X, where X is selected from one or more of K, La, and Ce, with the remainder being oxygen and a support. The catalyst has a specific surface area of ​​10–300 μm. 2 The catalyst has a pore volume of 0.2–0.65 mL / g and a pore volume of 0.2–0.65 mL / g. This catalyst can be used for the selective hydrogenation of acetylene, propyne, and propadiene (MAPD) ​​in C2–C3 cracked fractions. This literature describes a catalyst for selective hydrogenation of C2 and C3 fractions prepared by impregnation loading of the active component and metal reduction via calcination, without involving single-atom catalyst preparation techniques. Summary of the Invention

[0017] To address the aforementioned technical problems, the present invention aims to provide a C2 post-hydrogenation catalyst and its preparation method. The C2 post-hydrogenation catalyst provided by the present invention exhibits excellent hydrogenation activity, selectivity, and anti-coking properties.

[0018] To achieve the above objectives, the first aspect of the present invention provides a C2 post-hydrogenation catalyst, the catalyst comprising a support and an active component, the support being a phosphorus-doped carbon material, the active component comprising a main active component and a co-active component, the main active component comprising Pd, the co-active component comprising Fe, the main active component and the co-active component being atomically dispersed on the support.

[0019] According to a specific embodiment of the present invention, preferably, based on 100% of the total mass of the catalyst, the content of the main active component is 0.025-0.75%, the content of the co-active component is 0.10-1.60%, and the balance is the support. More preferably, based on 100% of the total mass of the catalyst, the content of the main active component is 0.025-0.21%, the content of the co-active component is 0.10-0.60%, and the balance is the support.

[0020] According to a specific embodiment of the present invention, preferably, the catalyst comprises a support and an active component, wherein the support is a phosphorus-doped carbon material, and the active component comprises Pd and Fe, wherein Pd and Fe are atomically dispersed on the support, and based on 100% of the total mass of the catalyst, the Pd content is 0.025-0.75%, the Fe content is 0.10-1.60%, and the balance is the support; more preferably, based on 100% of the total mass of the catalyst, the Pd content is 0.025-0.21%, the Fe content is 0.10-0.60%, and the balance is the support.

[0021] In the catalyst described above, preferably, the support has a porous structure with a high specific surface area, and the main active component and the co-active component are atomically dispersed on the surface and within the pores of the support. The specific surface area can be tested using methods conventional in the art, such as GB / T-5816.

[0022] According to a specific embodiment of the present invention, preferably, the C2 post-hydrogenation catalyst is prepared by the following steps:

[0023] (1) A phosphorus-containing compound and a carbohydrate are mixed in water, then subjected to a hydrothermal reaction, and then dried and calcined to obtain a phosphorus-doped carbon material carrier.

[0024] (2) The active component is loaded onto the phosphorus-doped carbon material support to obtain a catalyst semi-finished product;

[0025] (3) The catalyst semi-finished product is reduced to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0026] In the catalyst preparation steps described above, preferably, in step (1), the phosphorus-containing compound includes phosphoric acid and / or phytic acid, etc.

[0027] In the catalyst preparation steps described above, preferably, in step (1), the carbohydrates include glucose and / or sucrose, etc.

[0028] In the catalyst preparation steps described above, preferably, in step (1), the molar ratio of the phosphorus-containing compound and the carbohydrate is 0.0001 to 1000, more preferably 0.001 to 10, and even more preferably 0.02 to 0.4.

[0029] In the catalyst preparation step (1) above, the concentrations of the phosphorus-containing compound and the carbohydrate in water can be conventionally adjusted by those skilled in the art, as long as they can be fully dissolved and mixed in water and the reaction can proceed smoothly.

[0030] In the catalyst preparation steps described above, preferably, in step (1), the mixing of the phosphorus-containing compound and the carbohydrate in water is carried out under stirring conditions, and the stirring time is 30 to 120 min.

[0031] In the catalyst preparation steps described above, preferably, in step (1), the hydrothermal reaction is carried out at a temperature of 160–300°C for 4–12 hours. More specifically, the hydrothermal reaction is conducted in a hydrothermal reactor placed in an oven, and the process does not require stirring.

[0032] In the catalyst preparation steps described above, preferably, in step (1), the drying temperature is 120-160°C and the time is 4-12 hours.

[0033] In the catalyst preparation steps described above, preferably, step (1) further includes: ball milling to refine the powder, wherein the ball milling is performed after the drying and before the calcination, and the ball milling time is 3 to 10 minutes.

[0034] In the catalyst preparation steps described above, preferably, in step (1), the calcination is carried out under an inert atmosphere, and the calcination temperature is 600-1000℃ for 1-5 hours.

[0035] In the catalyst preparation steps described above, preferably, step (2) specifically includes:

[0036] (2)-a1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the main active component.

[0037] (2)-a2 The support for the main active component is added to the precursor aqueous solution of the auxiliary active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product.

[0038] Alternatively, step (2) may specifically include:

[0039] (2)-b1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the active component.

[0040] (2)-b2 The carrier loaded with the auxiliary active component is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product.

[0041] In the catalyst preparation step (2) above, the main active component can be loaded onto the support first, and then the auxiliary active component can be loaded; or the auxiliary active component can be loaded onto the support first, and then the main active component can be loaded.

[0042] In the catalyst preparation steps described above, preferably, in step (2), the precursor of the main active component includes a palladium salt compound, specifically including one or a combination of palladium chloride, palladium nitrate, and palladium sulfate.

[0043] In the catalyst preparation steps described above, preferably, in step (2), the precursor of the co-active component includes iron salt compounds, specifically including one or a combination of ferric nitrate, ferric sulfate, ferric chloride, and other soluble iron salts.

[0044] In the catalyst preparation steps described above, preferably, in step (2), the concentration of the main active component in the precursor aqueous solution of the main active component is 0.1 to 5 mg Pd / mL Pd precursor aqueous solution.

[0045] In the catalyst preparation steps described above, preferably, in step (2), the concentration of the co-active component in the precursor aqueous solution of the co-active component is 0.1 to 10 mg Fe / mL Fe precursor aqueous solution.

[0046] In the catalyst preparation step (2) above, the amount of support added to the aqueous solution of the active component precursor can be conventionally adjusted by those skilled in the art, as long as it can be fully mixed and the content of the active component in the prepared catalyst meets the requirements of the present invention.

[0047] In the catalyst preparation steps described above, preferably, in step (2), the irradiation time under an ultraviolet xenon lamp is 0.5 to 5.0 h.

[0048] In the above catalyst preparation steps, preferably, in step (2), the freeze-drying time is 2 to 7 hours and the vacuum degree of the freeze-drying is 15 to 20 Pa.

[0049] In the catalyst preparation steps described above, preferably, in step (2), the calcination is carried out under an inert atmosphere, and the calcination temperature is 300-500°C and the time is 0.5-5h.

[0050] In the above catalyst preparation steps, preferably, in step (3), the catalyst semi-finished product is reduced using a mixture of H2 and He gas with a volume percentage of 10-100% H2 or pure hydrogen gas, at a reduction temperature of 50-300°C, a reduction pressure of 0.1-2.0 MPa, and a reduction time of 0.5-10 h. More preferably, the reduction temperature is 100-200°C, the reduction pressure is 0.5-1.0 MPa, and the reduction time is 2-6 h.

[0051] A second aspect of the present invention provides a method for preparing the above-mentioned C2 post-hydrogenation catalyst, comprising the following steps:

[0052] (1) A phosphorus-containing compound and a carbohydrate are mixed in water, then subjected to a hydrothermal reaction, and then dried and calcined to obtain a phosphorus-doped carbon material carrier.

[0053] (2) The active component is loaded onto the phosphorus-doped carbon material support to obtain a catalyst semi-finished product;

[0054] (3) The catalyst semi-finished product is reduced to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0055] In the above preparation method, preferably, in step (1), the phosphorus-containing compound includes phosphoric acid and / or phytic acid, etc.

[0056] In the above preparation method, preferably, in step (1), the carbohydrate includes glucose and / or sucrose, etc.

[0057] In the above preparation method, preferably, in step (1), the molar ratio of the phosphorus-containing compound and the carbohydrate is 0.0001 to 1000, more preferably 0.001 to 10, and even more preferably 0.02 to 0.4.

[0058] In step (1) of the preparation method described above, the concentrations of the phosphorus-containing compound and the carbohydrate in water can be conventionally adjusted by those skilled in the art, as long as they can be fully dissolved and mixed in water and the reaction can proceed smoothly.

[0059] In the above preparation method, preferably, in step (1), the mixing of phosphorus-containing compound and carbohydrate in water is carried out under stirring conditions, and the stirring time is 30 to 120 min.

[0060] In the above preparation method, preferably, in step (1), the hydrothermal reaction temperature is 160–300°C and the time is 4–12 h. More specifically, the hydrothermal reaction is carried out in a hydrothermal reactor placed in an oven, and the process does not require stirring.

[0061] In the above preparation method, preferably, in step (1), the drying temperature is 120-160°C and the time is 4-12 hours.

[0062] In the above preparation method, preferably, step (1) further includes: ball milling to refine into powder, wherein the ball milling is performed after the drying and before the calcination, and the ball milling time is 3 to 10 minutes.

[0063] In the above preparation method, preferably, in step (1), the calcination is carried out under an inert atmosphere, the calcination temperature is 600-1000℃, and the time is 1-5h.

[0064] In the above preparation method, preferably, step (2) specifically includes:

[0065] (2)-a1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the main active component.

[0066] (2)-a2 The support for the main active component is added to the precursor aqueous solution of the auxiliary active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product.

[0067] Alternatively, step (2) may specifically include:

[0068] (2)-b1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the active component.

[0069] (2)-b2 The carrier loaded with the auxiliary active component is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product.

[0070] In step (2) of the preparation method described above, the main active component can be loaded onto the support first, and then the auxiliary active component can be loaded; or the auxiliary active component can be loaded onto the support first, and then the main active component can be loaded.

[0071] In the above preparation method, preferably, in step (2), the precursor of the main active component includes a palladium salt compound, specifically including one or a combination of palladium chloride, palladium nitrate and palladium sulfate.

[0072] In the above preparation method, preferably, in step (2), the precursor of the auxiliary active component includes iron salt compounds, specifically including one or a combination of ferric nitrate, ferric sulfate, ferric chloride and other soluble iron salts.

[0073] In the above preparation method, preferably, in step (2), the concentration of the main active component in the precursor aqueous solution of the main active component is 0.1 to 5 mg Pd / mL Pd precursor aqueous solution.

[0074] In the above preparation method, preferably, in step (2), the concentration of the co-active component in the precursor aqueous solution of the co-active component is 0.1 to 10 mg Fe / mL Fe precursor aqueous solution.

[0075] In step (2) of the above preparation method, the amount of support added to the aqueous solution of the active component precursor can be conventionally adjusted by those skilled in the art, as long as it can be fully mixed and the content of the active component in the prepared catalyst meets the requirements of the present invention.

[0076] In the above preparation method, preferably, in step (2), the irradiation time under ultraviolet xenon lamp is 0.5 to 5.0 h.

[0077] In the above preparation method, preferably, in step (2), the freeze-drying time is 2 to 7 hours and the vacuum degree of the freeze-drying is 15 to 20 Pa.

[0078] In the above preparation method, preferably, in step (2), the calcination is carried out under an inert atmosphere, the calcination temperature is 300-500℃, and the time is 0.5-5h.

[0079] In the above preparation method, preferably, in step (3), the catalyst semi-finished product is reduced using a mixture of H2 and He gas with a volume percentage of 10-100% H2 or pure hydrogen gas, at a reduction temperature of 50-300°C, a reduction pressure of 0.1-2.0 MPa, and a reduction time of 0.5-10 h. More preferably, the reduction temperature is 100-200°C, the reduction pressure is 0.5-1.0 MPa, and the reduction time is 2-6 h.

[0080] This invention provides a selective hydrogenation catalyst for alkynes in C2 fractions, particularly a post-C2 hydrogenation catalyst for ethylene plants employing a sequential separation process. Conventional hydrogenation catalysts often have active components existing as nanoparticles or sub-nano clusters, which negatively impacts catalyst performance. The hydrogenation catalyst provided by this invention uses phosphorus-doped carbon material as a support. This support has a porous structure and a high specific surface area. A photoreduction method is used to disperse the active components (preferably palladium and iron) in a single-atom state on the support (both on the surface and within the pores), rather than forming nanoparticles or sub-nano clusters. The atomically dispersed Pd and Fe exhibit the following characteristics in the selective hydrogenation of alkynes: increased metal atom utilization due to the atomic dispersion of the active components enhances the catalyst's hydrogenation activity; reduced olefin adsorption capacity improves hydrogenation selectivity; and decreased probability of simultaneous adsorption of alkynes / dienes at adjacent active sites significantly reduces the likelihood of polymerization and coking, thereby improving the catalyst's anti-coking performance. Therefore, the C2 post-hydrogenation catalyst provided by this invention exhibits excellent hydrogenation activity, selectivity, and anti-coking properties. Even when the hydrogenation reactants contain a high amount of heavy fractions and the amount of green oil generated by the catalyst increases significantly, the catalyst activity and selectivity do not show a downward trend when using the C2 post-hydrogenation catalyst provided by this invention. Attached Figure Description

[0081] Figure 1 This is an aberration-corrected transmission electron microscope image of the hydrogenation catalyst provided in Example 1.

[0082] Figure 2 Transmission electron microscopy (TEM) image of the hydrogenation catalyst provided for Comparative Example 5.

[0083] Figure 3 The present invention provides a flow chart of a post-hydrogenation process for C2 using a sequential separation process, which is a specific embodiment of the present invention.

[0084] Explanation of symbols for main components: 1. Cracking furnace, 2. Quenching system, 3. Oil washing tower, 4. Water washing tower, 5. First compressor, 6. Alkali washing tower, 7. Dryer, 8. Demethanizer, 9. Second compressor, 10. Deethanerizer, 11. Post-hydrogenation reactor for C2. Detailed Implementation

[0085] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0086] According to a specific embodiment of the present invention, preferably, the C2 post-hydrogenation catalyst of the present invention is prepared by the following steps:

[0087] (1) A phosphorus-containing compound and a carbohydrate are thoroughly mixed in water for 30-120 min to obtain a mixed solution; the mixed solution is hydrothermally heated in a hydrothermal reactor in an oven at 160-300℃ for 4-12 h, then dried at 120-160℃ for 4-12 h, and then ball-milled for 3-10 min to obtain a powder; the powder is calcined at 600-1000℃ for 1-5 h under an inert atmosphere to obtain a phosphorus-doped carbon material carrier;

[0088] Wherein, the phosphorus-containing compound includes phosphoric acid and / or phytic acid, etc.; the carbohydrate includes glucose and / or sucrose, etc.; the molar ratio of the phosphorus-containing compound and the carbohydrate is 0.0001 to 1000, preferably 0.001 to 10, and more preferably 0.02 to 0.4;

[0089] (2) a1 The phosphorus-doped carbon material support is added to the palladium precursor aqueous solution, stirred evenly, and then placed in liquid nitrogen for rapid freezing. Then it is irradiated under ultraviolet xenon lamp for 0.5 to 5.0 h; then it is freeze-dried under vacuum of 15 to 20 Pa for 2 to 7 h, and then calcined at 300 to 500 °C for 0.5 to 5 h under an inert atmosphere to obtain the palladium-loaded support.

[0090] (2) a2 The palladium-supported support is added to an aqueous solution of iron precursor, stirred evenly, and then rapidly frozen in liquid nitrogen. It is then irradiated under an ultraviolet xenon lamp for 0.5 to 5.0 h. After that, it is freeze-dried under a vacuum of 15 to 20 Pa for 2 to 7 h, and then calcined at 300 to 500 °C for 0.5 to 5 h under an inert atmosphere to obtain a catalyst semi-finished product.

[0091] or,

[0092] (2)-b1 The phosphorus-doped carbon material support is added to the iron precursor aqueous solution, stirred evenly, and then placed in liquid nitrogen for rapid freezing. Then it is irradiated under ultraviolet xenon lamp for 0.5-5.0h; then it is freeze-dried under vacuum of 15-20Pa for 2-7h, and then calcined at 300-500℃ for 0.5-5h under inert atmosphere to obtain the iron-loaded support.

[0093] (2)-b2 The iron-supported carrier is added to the palladium precursor aqueous solution, stirred evenly, and then placed in liquid nitrogen for rapid freezing. Then it is irradiated under ultraviolet xenon lamp for 0.5-5.0h; then it is freeze-dried under vacuum of 15-20Pa for 2-7h, and then calcined at 300-500℃ for 0.5-5h under inert atmosphere to obtain catalyst semi-finished product;

[0094] The palladium precursor includes palladium salt compounds, specifically including one or a combination of palladium chloride, palladium nitrate, and palladium sulfate; the concentration of palladium in the aqueous solution of the palladium precursor is 0.1–5 mg Pd / mL Pd precursor aqueous solution;

[0095] The iron precursor includes one or a combination of several of ferric nitrate, ferric sulfate, ferric chloride, and other soluble iron salts; the concentration of iron in the aqueous solution of the iron precursor is 0.1–10 mg Fe / mL Fe precursor aqueous solution;

[0096] (3) The catalyst semi-finished product is reduced with a mixture of H2 and He or pure hydrogen with a volume percentage of H2 of 10-100%, at a reduction temperature of 50-300℃ (preferably 100-200℃), a reduction pressure of 0.1-2.0MPa (preferably 0.5-1.0MPa), and a reduction time of 0.5-10h (preferably 2-6h) to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0097] The technical solution of the present invention will be further described below through specific embodiments.

[0098] In the following specific embodiments and comparative examples, the analytical testing methods used include:

[0099] Content of active component in catalyst: atomic absorption spectrometry;

[0100] Single-atom morphology characterization: aberration-corrected transmission electron microscopy;

[0101] Conversion rate and selectivity are calculated using the following formula:

[0102] Acetylene conversion rate (%) = 100 × (inlet acetylene content - outlet acetylene content) / inlet acetylene content,

[0103] Ethylene selectivity (%) = 100 × (exit ethylene content - inlet ethylene content) / (inlet acetylene content - outlet acetylene content).

[0104] Example 1

[0105] This embodiment provides a C2 post-hydrogenation catalyst, which is prepared through the following steps:

[0106] (1) 10g of phosphoric acid and 120g of glucose were thoroughly mixed in water for 30 minutes to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 160℃ for 4 hours, then dried at 120℃ for 4 hours, and then ball-milled for 3 minutes to obtain powder; the powder was calcined at 600℃ for 1 hour under an inert atmosphere to obtain a phosphorus-doped carbon material carrier;

[0107] (2) Take 10 mL of 0.25 mg Pd / mL Pd(NO3)2 aqueous solution, add 10 g of the phosphorus-doped carbon material support, stir evenly at room temperature, place in liquid nitrogen for rapid freezing, and then irradiate under ultraviolet xenon lamp for 0.5 h; then freeze dry under 15 Pa vacuum for 2 h, and then calcine at 300 °C for 0.5 h under inert atmosphere to obtain palladium-loaded support;

[0108] The palladium-supported support was added to an aqueous solution of ferric nitrate containing 43.3 mg of ferric nitrate. After stirring evenly at room temperature, the solution was rapidly frozen in liquid nitrogen and then irradiated under a xenon lamp for 0.5 h. After that, it was freeze-dried under a vacuum of 15 Pa for 2 h and then calcined at 300 °C for 0.5 h under an inert atmosphere to obtain a catalyst semi-finished product.

[0109] (3) The catalyst semi-finished product is reduced with a mixture of H2 and He with a volume percentage of 10% H2, at a reduction temperature of 60°C, a reduction pressure of 0.5 MPa, and a reduction time of 1 h to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0110] According to atomic absorption spectrometry, the catalyst contains 0.025% Pd and 0.1% Fe, with the remainder being a phosphorus-doped carbon material carrier, based on a total mass of 100%.

[0111] The aberration-corrected transmission electron microscope image of the catalyst is shown below. Figure 1 As shown, by Figure 1 It can be seen that Pd and Fe are atomically dispersed on the support.

[0112] Example 2

[0113] This embodiment provides a C2 post-hydrogenation catalyst, which is prepared through the following steps:

[0114] (1) 10g of phytic acid and 120g of sucrose were thoroughly mixed in water for 100min to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 200℃ for 6h, then dried at 130℃ for 6h, and then ball-milled for 5min to obtain powder; the powder was calcined at 800℃ for 2h under an inert atmosphere to obtain a phosphorus-doped carbon material carrier;

[0115] (2) Measure 10 mL of 1 mg Pd / mL PdCl2 aqueous solution, add 10 g of the phosphorus-doped carbon material support, stir evenly at room temperature, place in liquid nitrogen for rapid freezing, and then irradiate under ultraviolet xenon lamp for 1 h; then freeze dry under 16 Pa vacuum for 2 h, and then calcine at 300 °C for 2 h under inert atmosphere to obtain palladium-loaded support.

[0116] The palladium-supported support was added to an aqueous solution of ferric nitrate containing 129.9 mg of ferric nitrate. After stirring at room temperature, the solution was rapidly frozen in liquid nitrogen and then irradiated under a xenon lamp for 1 hour. After that, it was freeze-dried under a vacuum of 16 Pa for 2 hours and then calcined at 300 °C for 2 hours under an inert atmosphere to obtain a catalyst semi-finished product.

[0117] (3) The catalyst semi-finished product is reduced by a mixture of H2 and He with a volume percentage of 15% H2, at a reduction temperature of 80°C, a reduction pressure of 1 MPa, and a reduction time of 2 h to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0118] According to atomic absorption spectrometry, the catalyst contains 0.1% Pd and 0.3% Fe, with the remainder being a phosphorus-doped carbon material carrier, based on a total mass of 100%.

[0119] Example 3

[0120] This embodiment provides a C2 post-hydrogenation catalyst, which is prepared through the following steps:

[0121] (1) 10g of phytic acid and 120g of sucrose were thoroughly mixed in water for 120min to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 200℃ for 8h, then dried at 140℃ for 8h, and then ball-milled for 7min to obtain powder; the powder was calcined at 900℃ for 3h under an inert atmosphere to obtain a phosphorus-doped carbon material carrier;

[0122] (2) 10g of the phosphorus-doped carbon material carrier was added to an aqueous solution of ferric nitrate containing 216.5mg of ferric nitrate. After stirring evenly at room temperature, the carrier was placed in liquid nitrogen for rapid freezing and then irradiated under a xenon lamp for 1h. After that, it was freeze-dried under a vacuum of 17Pa for 3h and then calcined at 300℃ for 3h under an inert atmosphere to obtain the iron-loaded carrier.

[0123] Measure 20 mL of 1 mg Pd / mL palladium sulfate aqueous solution, add it to the iron-supported carrier, stir evenly at room temperature, place it in liquid nitrogen for rapid freezing, and then irradiate it under ultraviolet xenon lamp for 1 h; then freeze-dry it under vacuum of 17 Pa for 3 h, and then calcine it at 300 °C for 3 h under an inert atmosphere to obtain the catalyst semi-finished product.

[0124] (3) The catalyst semi-finished product is reduced by a mixture of H2 and He with a volume percentage of 20% H2, at a reduction temperature of 150°C, a reduction pressure of 1 MPa, and a reduction time of 2 h to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0125] According to atomic absorption spectrometry, the catalyst contains 0.2% Pd and 0.5% Fe by mass, with the remainder being a phosphorus-doped carbon material carrier.

[0126] Example 4

[0127] This embodiment provides a C2 post-hydrogenation catalyst, which is prepared through the following steps:

[0128] (1) 10g of phytic acid and 120g of glucose were thoroughly mixed in water for 60 minutes to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 250°C for 10 hours, then dried at 150°C for 10 hours, and then ball-milled for 8 minutes to obtain powder; the powder was calcined at 700°C for 4 hours under an inert atmosphere to obtain a phosphorus-doped carbon material carrier.

[0129] (2) 10g of the phosphorus-doped carbon material carrier was added to an aqueous solution of ferric nitrate containing 433.1mg of ferric nitrate. After stirring evenly at room temperature, the mixture was placed in liquid nitrogen for rapid freezing and then irradiated under a xenon lamp for 3h. After that, it was freeze-dried under a vacuum of 18Pa for 5h and then calcined at 400℃ for 4h under an inert atmosphere to obtain the iron-loaded carrier.

[0130] 50 mL of 1 mg Pd / mL Pd(NO3)2 aqueous solution was measured and added to the iron-supported carrier. After stirring evenly at room temperature, the mixture was rapidly frozen in liquid nitrogen and then irradiated under a UV xenon lamp for 3 h. After that, it was freeze-dried under a vacuum of 18 Pa for 5 h and then calcined at 400 °C for 4 h under an inert atmosphere to obtain a catalyst semi-finished product.

[0131] (3) The catalyst semi-finished product is reduced with a mixture of H2 and He with a volume percentage of 50% H2, at a reduction temperature of 200℃, a reduction pressure of 1.5MPa, and a reduction time of 4h to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0132] According to atomic absorption spectrometry, the catalyst contains 0.5% Pd and 1.0% Fe, with the remainder being a phosphorus-doped carbon material carrier, based on a total mass of 100%.

[0133] Example 5

[0134] This embodiment provides a C2 post-hydrogenation catalyst, which is prepared through the following steps:

[0135] (1) 10g of phosphoric acid and 120g of sucrose were thoroughly mixed in water for 90 minutes to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 300℃ for 12 hours, then dried at 160℃ for 12 hours, and then ball-milled for 10 minutes to obtain powder; the powder was calcined at 1000℃ for 5 hours under an inert atmosphere to obtain a phosphorus-doped carbon material carrier;

[0136] (2) Take 75 mL of 1 mg Pd / mL PdCl2 aqueous solution, add 10 g of the phosphorus-doped carbon material support, stir evenly at room temperature, place in liquid nitrogen for rapid freezing, and then irradiate under ultraviolet xenon lamp for 5 h; then freeze dry under 20 Pa vacuum for 7 h, and then calcine at 500 °C for 5 h under inert atmosphere to obtain palladium-loaded support.

[0137] The palladium-supported support was added to an aqueous solution of ferric nitrate containing 692.9 mg of ferric nitrate. After stirring evenly at room temperature, the solution was rapidly frozen in liquid nitrogen and then irradiated under a xenon lamp for 5 hours. After that, it was freeze-dried under a vacuum of 20 Pa for 7 hours and then calcined at 500 °C for 5 hours under an inert atmosphere to obtain a catalyst semi-finished product.

[0138] (3) The catalyst semi-finished product is reduced with pure hydrogen at a reduction temperature of 250°C, a reduction pressure of 2MPa, and a reduction time of 6h to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst.

[0139] According to atomic absorption spectrometry, the catalyst contains 0.75% Pd and 1.6% Fe by mass, with the remainder being a phosphorus-doped carbon material carrier.

[0140] Comparative Example 1

[0141] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0142] (1) 120g of glucose was thoroughly stirred in water for 30 minutes to obtain a glucose aqueous solution; the glucose aqueous solution was reacted in a hydrothermal reactor in an oven at 160℃ for 4 hours, then dried at 120℃ for 4 hours, and then ball-milled for 3 minutes to obtain powder; the powder was calcined at 600℃ for 1 hour under an inert atmosphere to obtain a carbon material carrier.

[0143] (2) Take 10 mL of 0.25 mg Pd / mL Pd(NO3)2 aqueous solution, add 10 g of the carbon material support, stir evenly at room temperature, place in liquid nitrogen for rapid freezing, and then irradiate under ultraviolet xenon lamp for 0.5 h; then freeze dry under 15 Pa vacuum for 2 h, and then calcine at 300 °C for 0.5 h under inert atmosphere to obtain palladium-loaded support;

[0144] The palladium-supported support was added to an aqueous solution of ferric nitrate containing 43.3 mg of ferric nitrate. After stirring evenly at room temperature, the solution was rapidly frozen in liquid nitrogen and then irradiated under a xenon lamp for 0.5 h. After that, it was freeze-dried under a vacuum of 15 Pa for 2 h and then calcined at 300 °C for 0.5 h under an inert atmosphere to obtain a catalyst semi-finished product.

[0145] (3) The catalyst semi-finished product is reduced with a mixture of H2 and He with a volume percentage of 10% H2, at a reduction temperature of 60°C, a reduction pressure of 0.5 MPa, and a reduction time of 1 h to obtain the reduced catalyst, which is the hydrogenation catalyst.

[0146] Atomic absorption spectrometry analysis revealed that, based on the total mass of the catalyst (100%), the Pd content was 0.025%, the Fe content was 0.1%, and the remainder was a carbon material support. The active components in the catalyst provided in this comparative example are not entirely dispersed as single atoms; nanoparticles are present.

[0147] Comparative Example 2

[0148] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0149] (1) The carrier is a commercially available bimodal spherical alumina carrier with a diameter of 4 mm; the bimodal spherical alumina carrier is calcined at 1250℃ for 4 h to obtain the catalyst carrier.

[0150] (2) Measure 10 mL of 1 mg Pd / mL PdCl2 aqueous solution, add 10 g of the catalyst support, stir evenly at room temperature, place in liquid nitrogen for rapid freezing, and then irradiate under ultraviolet xenon lamp for 1 h; then freeze dry under 16 Pa vacuum for 2 h, and then calcine at 300 °C for 2 h under inert atmosphere to obtain palladium-loaded support.

[0151] The palladium-supported support was added to an aqueous solution of ferric nitrate containing 129.9 mg of ferric nitrate. After stirring at room temperature, the solution was rapidly frozen in liquid nitrogen and then irradiated under a xenon lamp for 1 hour. After that, it was freeze-dried under a vacuum of 16 Pa for 2 hours and then calcined at 300 °C for 2 hours under an inert atmosphere to obtain a catalyst semi-finished product.

[0152] (3) The catalyst semi-finished product is reduced by a mixture of H2 and He with a volume percentage of 15% H2, at a reduction temperature of 80°C, a reduction pressure of 1 MPa, and a reduction time of 2 h to obtain the reduced catalyst, which is the hydrogenation catalyst.

[0153] According to atomic absorption spectrometry, the total mass of the catalyst is 100%, the Pd content is 0.1%, the Fe content is 0.3%, and the balance is the catalyst support.

[0154] Comparative Example 3

[0155] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0156] (1) 10g of phytic acid and 120g of sucrose were thoroughly mixed in water for 120min to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 200℃ for 8h, then dried at 140℃ for 8h, and then ball-milled for 7min to obtain powder; the powder was calcined at 900℃ for 3h under an inert atmosphere to obtain a phosphorus-doped carbon material carrier (same as Example 3);

[0157] (2) 10g of the phosphorus-doped carbon material carrier was added to an aqueous solution of ferric nitrate containing 216.5mg of ferric nitrate. After stirring evenly at room temperature, the carrier was placed in liquid nitrogen for rapid freezing and then irradiated under a xenon lamp for 1h. After that, it was freeze-dried under a vacuum of 17Pa for 3h and then calcined at 300℃ for 3h under an inert atmosphere to obtain the iron-loaded carrier.

[0158] Measure 10 mL of 10 mg Pd / mL palladium sulfate aqueous solution, add it to the iron-supported carrier, stir evenly at room temperature, place it in liquid nitrogen for rapid freezing, and then irradiate it under ultraviolet xenon lamp for 1 h; then freeze-dry it under vacuum of 17 Pa for 3 h, and then calcine it at 300 °C for 3 h under an inert atmosphere to obtain the catalyst semi-finished product.

[0159] (3) The catalyst semi-finished product is reduced by a mixture of H2 and He with a volume percentage of 20% H2, at a reduction temperature of 150°C, a reduction pressure of 1 MPa, and a reduction time of 2 h to obtain the reduced catalyst, which is the hydrogenation catalyst.

[0160] According to atomic absorption spectrometry, the catalyst contains 1.0% Pd and 0.5% Fe by mass, with the remainder being a phosphorus-doped carbon material carrier.

[0161] Comparative Example 4

[0162] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0163] (1) 10g of phytic acid and 120g of glucose were thoroughly mixed in water for 60 minutes to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 250°C for 10 hours, then dried at 150°C for 10 hours, and then ball-milled for 8 minutes to obtain powder; the powder was calcined at 700°C for 4 hours under an inert atmosphere to obtain a phosphorus-doped carbon material carrier (same as Example 4);

[0164] (2) 10g of the phosphorus-doped carbon material carrier was added to an aqueous solution of ferric nitrate containing 2165mg of ferric nitrate. After stirring evenly at room temperature, the carrier was placed in liquid nitrogen for rapid freezing and then irradiated under a xenon lamp for 3h. After that, it was freeze-dried under a vacuum of 18Pa for 5h and then calcined at 400℃ for 4h under an inert atmosphere to obtain an iron-loaded carrier.

[0165] 50 mL of 1 mg Pd / mL Pd(NO3)2 aqueous solution was measured and added to the iron-supported carrier. After stirring evenly at room temperature, the mixture was rapidly frozen in liquid nitrogen and then irradiated under a UV xenon lamp for 3 h. After that, it was freeze-dried under a vacuum of 18 Pa for 5 h and then calcined at 400 °C for 4 h under an inert atmosphere to obtain a catalyst semi-finished product.

[0166] (3) The catalyst semi-finished product is reduced with a mixture of H2 and He with a volume percentage of 50% H2, at a reduction temperature of 200°C, a reduction pressure of 1.5 MPa, and a reduction time of 4 h to obtain the reduced catalyst, which is the hydrogenation catalyst.

[0167] According to atomic absorption spectrometry, the catalyst contains 0.5% Pd and 5.0% Fe, with the remainder being a phosphorus-doped carbon material carrier, based on a total mass of 100%.

[0168] Comparative Example 5

[0169] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0170] (1) 10g of phosphoric acid and 120g of sucrose were thoroughly mixed in water for 90 minutes to obtain a mixed solution; the mixed solution was subjected to hydrothermal reaction in a hydrothermal reactor in an oven at 300°C for 12 hours, then dried at 160°C for 12 hours, and then ball-milled for 10 minutes to obtain powder; the powder was calcined at 1000°C for 5 hours under an inert atmosphere to obtain a phosphorus-doped carbon material carrier (same as Example 5);

[0171] (2) Take 75 mL of 1 mg Pd / mL PdCl2 aqueous solution, adjust the pH of the PdCl2 aqueous solution to 2 with hydrochloric acid, add 10 g of the phosphorus-doped carbon material support, impregnate and adsorb at room temperature for 1 h, dry at 110 °C for 2 h, and then calcine at 480 °C for 6 h to obtain the palladium-loaded support.

[0172] The palladium-supported support was added to an aqueous solution of ferric nitrate containing 692.9 mg of ferric nitrate, and impregnated and adsorbed at room temperature for 1 hour. Then it was dried at 100°C for 3 hours and calcined at 500°C for 4 hours to obtain a catalyst semi-finished product.

[0173] (3) The catalyst semi-finished product is reduced with pure hydrogen at a reduction temperature of 250°C, a reduction pressure of 2MPa, and a reduction time of 6h to obtain the reduced catalyst, which is the hydrogenation catalyst.

[0174] Atomic absorption spectrometry analysis revealed that, based on the total mass of the catalyst (100%), the Pd content was 0.75%, the Fe content was 1.6%, and the remainder was a phosphorus-doped carbon support. A transmission electron microscope (TEM) image of the hydrogenation catalyst in this comparative example is shown below. Figure 2 As shown, by Figure 2 It can be seen that Pd and Fe are almost dispersed at the nanoparticle level.

[0175] Comparative Example 6

[0176] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0177] (1) Weigh 12.5g of melamine into a beaker and add 30mL of water, then add 27.8mL of phytic acid solution (the mass ratio of phytic acid to melamine is 2:1). After sonicating for 30min, put the beaker into a microwave oven and heat it with 1000W power for 120s. After washing and drying, nitrogen and phosphorus co-doped carbon support is obtained.

[0178] (2) Take 10 mL of 0.25 mg Pd / mL Pd(NO3)2 aqueous solution, add 10 g of the nitrogen-phosphorus co-doped carbon support, stir evenly at room temperature, place in liquid nitrogen for rapid freezing, and then irradiate under ultraviolet xenon lamp for 0.5 h; then freeze dry under 15 Pa vacuum for 2 h, and then calcine at 300 °C for 0.5 h under inert atmosphere to obtain palladium-loaded support;

[0179] The palladium-supported support was added to an aqueous solution of ferric nitrate containing 43.3 mg of ferric nitrate. After stirring evenly at room temperature, the solution was rapidly frozen in liquid nitrogen and then irradiated under a xenon lamp for 0.5 h. After that, it was freeze-dried under a vacuum of 15 Pa for 2 h and then calcined at 300 °C for 0.5 h under an inert atmosphere to obtain a catalyst semi-finished product.

[0180] (3) The catalyst semi-finished product is reduced with a mixture of H2 and He with a volume percentage of 10% H2, at a reduction temperature of 60°C, a reduction pressure of 0.5 MPa, and a reduction time of 1 h to obtain the reduced catalyst, which is the hydrogenation catalyst.

[0181] According to atomic absorption spectrometry, the catalyst contains 0.025% Pd and 0.1% Fe by mass, with the remainder being nitrogen-phosphorus co-doped carbon support.

[0182] Performance of catalysts in post-C2 hydrogenation processes

[0183] The catalysts provided in the above examples and comparative examples were evaluated for performance in a single-stage fixed-bed reactor. The inlet material composition of the single-stage fixed-bed reactor is shown in Table 1. The hydrogenation process conditions of the single-stage fixed-bed reactor were: catalyst loading of 50 mL, inert ceramic ball packing of 50 mL, and reactant space velocity of 4000 h⁻¹. -1 The operating pressure was 2.0 MPa, the hydrogen-to-acetylene ratio was 1.3 (molar ratio), and the reactor inlet temperature was 65 °C. The evaluation results of the catalysts provided in the examples and comparative examples are shown in Table 2.

[0184] Table 1 Composition of reactants

[0185] reactants <![CDATA[C2H2]]> <![CDATA[C2H4]]> <![CDATA[C2H6]]> <![CDATA[C3-C4]]> Content (v / v%) 1.8 balance 12 <![CDATA[3×10 -3 ]]>

[0186] Table 2 Catalyst Evaluation Results

[0187]

[0188] Note: Coking amount = (Loss on ignition at 600℃ ÷ Initial catalyst charge) × 100%

[0189] The material used in this performance evaluation experiment can be derived from the ethane removal tower of a C2 post-hydrogenation process employing a sequential separation flow. The process flow diagram of a C2 post-hydrogenation process employing a sequential separation flow is shown below. Figure 3 As shown in the diagram, the process mainly includes: the raw material of the ethylene unit first enters the cracking furnace 1 for high-temperature cracking; the product is first cooled by the quench system 2, and then sequentially passes through the oil washing tower 3, water washing tower 4, first compressor 5, alkali washing tower 6, and dryer 7 for processing, before entering the demethanizer tower 8. Methane and hydrogen are separated at the top of the demethanizer tower 8, and the material at the bottom of the tower is compressed by the second compressor 9 and enters the deethanerizer tower 10. The material separated at the top of the deethanerizer tower 10 enters the C2 post-hydrogenation reactor 11 (i.e., a single-stage fixed-bed reactor) for hydrogenation treatment, and the hydrogenated material goes to the subsequent separation system.

[0190] The above evaluation results show that the C2 post-hydrogenation catalyst provided by this invention uses phosphorus-doped carbon material as a support, and employs photoreduction to disperse palladium and iron in a single-atom state on the support, rather than forming nanoparticles or sub-nano clusters. The atomically dispersed Pd and Fe exhibit the following characteristics in the selective hydrogenation reaction of alkynes: due to the atomic dispersion of the active components, the utilization rate of metal atoms is increased, thereby improving the catalyst's hydrogenation activity; the adsorption capacity for olefins is reduced, thereby improving the catalyst's hydrogenation selectivity; the probability of simultaneous adsorption of alkynes / dienes at adjacent active sites decreases, thus significantly reducing the probability of polymerization and coking, thereby improving the catalyst's anti-coking performance. Therefore, the C2 post-hydrogenation catalyst provided by this invention has excellent hydrogenation activity, selectivity, and anti-coking performance. Even when the hydrogenation reaction feed contains a large amount of heavy distillate and the amount of green oil generated by the catalyst increases significantly, the catalyst activity and selectivity do not show a downward trend when using the C2 post-hydrogenation catalyst provided by this invention.

Claims

1. A C2 post-hydrogenation catalyst, said catalyst comprising a support and an active component, wherein, The support is a phosphorus-doped carbon material. The active component includes a main active component and a co-active component. The main active component includes Pd, and the co-active component includes Fe. The main active component and the co-active component are atomically dispersed on the support. Based on the total mass of the catalyst (100%), the content of the main active component is 0.025~0.75%, the content of the co-active component is 0.10~1.60%, and the balance is the support. The C2 post-hydrogenation catalyst was prepared through the following steps: (1) A phosphorus-containing compound and a carbohydrate are mixed in water, and then subjected to a hydrothermal reaction. After drying and calcination, a phosphorus-doped carbon material carrier is obtained. (2) The active component is loaded onto the phosphorus-doped carbon material support to obtain a catalyst semi-finished product; (3) The catalyst semi-finished product is reduced to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst; Step (2) specifically includes: (2) -a1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the main active component; (2) -a2 The support carrying the main active component is added to the precursor aqueous solution of the auxiliary active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product. Alternatively, step (2) may specifically include: (2) -b1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the active component; (2)-b2 The carrier loaded with the auxiliary active component is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product.

2. The C2 post-hydrogenation catalyst according to claim 1, wherein, Based on the total mass of the catalyst (100%), the content of the main active component is 0.025~0.21%, the content of the co-active component is 0.10~0.60%, and the balance is the support.

3. The C2 post-hydrogenation catalyst according to claim 1, wherein, The catalyst comprises a support and an active component. The support is a phosphorus-doped carbon material, and the active component comprises Pd and Fe, which are atomically dispersed on the support. Based on the total mass of the catalyst (100%), the Pd content is 0.025-0.75%, the Fe content is 0.10-1.60%, and the balance is the support.

4. The C2 post-hydrogenation catalyst according to claim 3, wherein, Based on the total mass of the catalyst (100%), the Pd content is 0.025~0.21%, the Fe content is 0.10~0.60%, and the balance is the support.

5. A method for preparing a C2 post-hydrogenation catalyst according to any one of claims 1-4, comprising the following steps: (1) A phosphorus-containing compound and a carbohydrate are mixed in water, and then subjected to a hydrothermal reaction. After drying and calcination, a phosphorus-doped carbon material carrier is obtained. (2) The active component is loaded onto the phosphorus-doped carbon material support to obtain a catalyst semi-finished product; (3) The catalyst semi-finished product is reduced to obtain the reduced catalyst, which is the C2 post-hydrogenation catalyst; Step (2) specifically includes: (2) -a1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the main active component; (2) -a2 The support carrying the main active component is added to the precursor aqueous solution of the auxiliary active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product. Alternatively, step (2) may specifically include: (2) -b1 The phosphorus-doped carbon material support is added to the precursor aqueous solution of the active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the support loaded with the active component; (2)-b2 The carrier loaded with the auxiliary active component is added to the precursor aqueous solution of the main active component, mixed evenly, frozen in liquid nitrogen, then irradiated under ultraviolet xenon lamp, then freeze-dried, and then calcined to obtain the catalyst semi-finished product.

6. The preparation method according to claim 5, wherein, In step (1), the phosphorus-containing compound includes phosphoric acid and / or phytic acid.

7. The preparation method according to claim 5, wherein, In step (1), the carbohydrates include glucose and / or sucrose.

8. The preparation method according to claim 5, wherein, In step (1), the molar ratio of the phosphorus-containing compound and the carbohydrate is 0.0001 to 1000.

9. The preparation method according to claim 8, wherein, In step (1), the molar ratio of the phosphorus-containing compound and the carbohydrate is 0.001 to 10.

10. The preparation method according to claim 9, wherein, In step (1), the molar ratio of the phosphorus-containing compound and the carbohydrate is 0.02 to 0.

4.

11. The preparation method according to claim 5, wherein, In step (1), the phosphorus-containing compound and carbohydrates are mixed in water under stirring conditions for a duration of 30 to 120 minutes.

12. The preparation method according to claim 5, wherein, In step (1), the temperature of the hydrothermal reaction is 160~300℃ and the time is 4~12h.

13. The preparation method according to claim 5, wherein, In step (1), the drying temperature is 120~160℃ and the time is 4~12h.

14. The preparation method according to claim 5, wherein, Step (1) further includes ball milling, which is performed after drying and before calcination, and the ball milling time is 3 to 10 minutes.

15. The preparation method according to claim 5, wherein, In step (1), the calcination is carried out under an inert atmosphere at a temperature of 600-1000°C for 1-5 hours.

16. The preparation method according to claim 5, wherein, In step (2), the precursor of the main active component includes a palladium salt compound.

17. The preparation method according to claim 16, wherein, In step (2), the precursor of the main active component includes one or a combination of palladium chloride, palladium nitrate and palladium sulfate.

18. The preparation method according to claim 5, wherein, In step (2), the precursor of the co-active component includes an iron salt compound.

19. The preparation method according to claim 18, wherein, In step (2), the precursor of the active component includes one or a combination of ferric nitrate, ferric sulfate and ferric chloride.

20. The preparation method according to claim 5, wherein, In step (2), the concentration of the main active component in the precursor aqueous solution of the main active component is 0.1~5 mgPd / mL Pd precursor aqueous solution.

21. The preparation method according to claim 5, wherein, In step (2), the concentration of the co-active component in the precursor aqueous solution of the co-active component is 0.1~10 mgFe / mL Fe precursor aqueous solution.

22. The preparation method according to claim 5, wherein, In step (2), the illumination time under the ultraviolet xenon lamp is 0.5~5.0h.

23. The preparation method according to claim 5, wherein, In step (2), the freeze-drying time is 2-7 hours and the vacuum degree of the freeze-drying is 15-20 Pa.

24. The preparation method according to claim 5, wherein, In step (2), the calcination is carried out under an inert atmosphere at a temperature of 300-500°C for a time of 0.5-5 hours.

25. The preparation method according to claim 5, wherein, In step (3), the catalyst semi-finished product is reduced by using a mixture of H2 and He gas with a volume percentage of 10-100% or pure hydrogen gas, at a reduction temperature of 50-300℃, a reduction pressure of 0.1-2.0MPa, and a reduction time of 0.5-10h.

26. The preparation method according to claim 25, wherein, In step (3), the reduction temperature is 100~200℃, the reduction pressure is 0.5~1.0MPa, and the reduction time is 2~6h.

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