An ethylene hydrofining catalyst and a method for its preparation

Abstract

The application provides an ethylene hydrofining catalyst and a preparation method thereof. The catalyst comprises a carrier and an active component, wherein 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 Ga, 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, carrying out a hydrothermal reaction, and then carrying out 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 ethylene hydrofining catalyst. The ethylene hydrofining catalyst provided by the application exhibits excellent hydrogenation activity, selectivity and long-period operation stability.

Description

Technical Field

[0001] This invention relates to an ethylene hydrogenation refining catalyst and its preparation method, belonging to the field of hydrogenation catalyst technology. Background Technology

[0002] Polymer-grade ethylene production is a leading industry in the petrochemical sector, and polymer-grade ethylene and propylene are the most basic raw materials for downstream polymerization units. Selective hydrogenation of acetylene has a crucial impact on ethylene processing. Besides ensuring that the acetylene content at the outlet of the hydrogenation reactor meets standards, excellent catalyst selectivity minimizes the formation of ethane from ethylene, which is significant for improving the overall ethylene yield and enhancing the economic efficiency of the plant.

[0003] Cracked C2 fractions typically contain 0.5%–2.5% acetylene. During polyethylene production, even small amounts of acetylene in ethylene can reduce the activity of the polymerization catalyst and degrade the physical properties of the polymer. Therefore, the acetylene content in ethylene must be reduced to a certain level to be used as a monomer for polymer synthesis. Thus, acetylene separation and conversion is one of the most important processes in ethylene plants.

[0004] Catalytic selective hydrogenation in ethylene plants includes pre-hydrogenation and post-hydrogenation processes. Pre-hydrogenation and post-hydrogenation refer to the position of the acetylene hydrogenation reactor relative to the demethanizer. Pre-hydrogenation involves the hydrogenation reactor being located before the demethanizer, while post-hydrogenation involves the reactor being located after. Currently, pre-hydrogenation of C2 fractions for acetylene removal is increasingly common. This process is characterized by the hydrogenation reactor being located before the demethanizer. Pre-hydrogenation is further divided into pre-propane removal and pre-ethane removal processes. In the pre-ethane removal hydrogenation process, the hydrogenation reactor is located after the deethaneizer and before the demethanizer. In the pre-propane removal hydrogenation process, the hydrogenation reactor is located after the depropaneizer and before the demethanizer. These differences in process flow result in differences in the composition of the hydrogenation feedstock. The pre-deethane hydrogenation feed contains methane, hydrogen, carbon monoxide, and C2 fractions (acetylene, ethylene, ethane); the pre-depropane hydrogenation feed contains methane, hydrogen, carbon monoxide, C2 fractions (acetylene, ethylene, ethane), and C3 fractions (propyne, propadiene, propylene, propane).

[0005] After the material in the ethylene plant passes through the C2 hydrogenation reactor and then undergoes ethylene distillation, it still contains 1-10 ppm of acetylene and trace amounts of CO. As the requirements for raw materials for polymer-grade ethylene products are becoming increasingly stringent, and the presence of these impurities can affect the performance of ethylene polymerization catalysts, it is necessary to selectively hydrogenate the trace amounts of acetylene in the ethylene material before ethylene polymerization to reduce its content to below 1 ppm.

[0006] Selective hydrogenation catalysts for alkynes and dienes are obtained by supporting noble metals such as palladium on porous inorganic material supports (US4762956). To increase catalyst selectivity and reduce catalyst deactivation caused by green oil produced during oligomerization during hydrogenation, existing technologies employ methods such as adding Group IB elements as co-catalytic components: Pd-Au (US4490481), Pd-Ag (US4404124), Pd-Cu (US3912789), or adding alkali metals or alkaline earth metals (US5488024), etc. Supports used include alumina, silica (US5856262), and honeycomb lapis lazuli (CN1176291). US4404124 prepared a selective hydrogenation catalyst with a palladium shell distribution of active component using a stepwise impregnation method, applicable to the selective hydrogenation of C2 and C3 fractions to eliminate acetylene from ethylene and propyne and propadiene from propylene. US5587348 describes a high-performance C2 hydrogenation catalyst prepared by using alumina as a support, adjusting the interaction between the co-catalysts silver and palladium, and adding alkali metals and chemically bonded fluorine. This catalyst exhibits characteristics such as reduced green oil formation, improved ethylene selectivity, and reduced formation of oxygen-containing compounds. US5519566 discloses a wet reduction method for preparing silver and palladium catalysts, which involves adding organic or inorganic reducing agents to the impregnation solution to prepare a silver and palladium bicomponent selective hydrogenation catalyst.

[0007] The above-mentioned traditional C2 hydrogenation catalysts are all prepared by impregnation, and their active phases are mostly Pd and Ag bimetals. This method has the following disadvantages: (1) Due to the influence of the pore structure of the support, the dispersion of the active components cannot be precisely controlled and has strong randomness; (2) Due to the influence of the surface tension and solvation effect of the impregnation liquid, the precursor of the metal active component is deposited on the surface of the support in the form of aggregates and cannot form a uniform distribution; (3) C2 hydrogenation has high requirements for catalyst selectivity. The traditional preparation method promotes the role of Ag promoter by increasing the amount of Ag, which leads to the obstruction of hydrogen transfer, the increased possibility of oligomerization reaction, and the increase of green oil generation, which affects the catalyst lifetime. The occurrence of the above three phenomena easily leads to poor dispersion of metal active components, low reaction selectivity, and high green oil generation, which in turn affects the overall performance of the catalyst.

[0008] CN102205243A involves adsorbing specific polymeric compounds onto a support, forming a polymeric coating of a certain thickness on the support surface. The compound with functional groups reacts with the polymer, imbuing it with functional groups capable of complexing with the active component. Through the complexation reaction of the active component on the functional groups on the support surface, the active component is ensured to be ordered and highly dispersed. Using this method, the support adsorbs specific polymeric compounds, and the polymer undergoes chemisorption through the hydroxyl groups of alumina. However, the amount of polymeric compound adsorbed by the support is limited by the number of hydroxyl groups in the alumina. Furthermore, the complexation between the functionalized polymer and Pd is not strong, sometimes resulting in insufficient loading of the active component, leaving some active component residue in the impregnation solution, thus increasing the catalyst cost.

[0009] To improve the anti-coking performance of catalysts and reduce the degree of surface coking, C2 selective hydrogenation catalysts and their preparation methods using bimodal porous supports and microemulsion methods for loading active components have been disclosed in recent years. CN104098427A discloses a selective hydrogenation catalyst whose support is mainly alumina with a bimodal porous structure, wherein the pore size is less than 50 nm and the macropore size is 60–800 nm. Based on 100% of the total mass of the catalyst, it contains 0.01–0.5% Pd in ​​a shell distribution with a thickness of 1–500 μm; and 0.2–5% Ni. The anti-coking component Ni is controlled by microemulsion method, where the microemulsion particle size is larger than the support pore size, so that Ni is mainly distributed in the macropores of the support. CN104096573A discloses a method for preparing a hydrogenation catalyst, where the catalyst support is mainly alumina with a bimodal porous structure. This catalyst contains two active components, Pd and Ni. During catalyst preparation, the anti-coking component Ni is introduced into the macropores of the support in the form of a microemulsion, while the active component Pd is mainly distributed on the support surface, particularly in the micropores. CN104098426A discloses a selective hydrogenation method for C2 fractions suitable for pre-propane dehydrogenation processes. This method uses a selective hydrogenation catalyst whose support is alumina or mainly alumina, with a bimodal pore distribution structure, containing two active components, Pd and Ni. The anti-coking component Ni is mainly distributed in the macropores. While this method improves the catalyst's anti-coking performance, the single-component Ni in the macropores of the catalyst support reaches reduction temperatures above 500℃. Reduction at this temperature causes the active component Pd to aggregate, significantly reducing catalyst activity. To compensate for the loss of catalyst activity, the amount of active component needs to be increased, leading to a decrease in catalyst selectivity and a reduction in the utilization rate of the active component.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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. 2The 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

[0016] To address the aforementioned technical problems, the present invention aims to provide an ethylene hydrorefining catalyst and its preparation method. The ethylene hydrorefining catalyst provided by the present invention exhibits excellent hydrogenation activity, selectivity, and anti-coking properties.

[0017] To achieve the above objectives, the first aspect of the present invention provides an ethylene hydrorefining 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 Ga, the main active component and the co-active component being atomically dispersed on the support.

[0018] 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 0.025-0.45%, the content of the co-active component is 0.01-1.00%, 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 0.025-0.18%, the content of the co-active component is 0.01-0.20%, and the balance is the support.

[0019] 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 Ga, wherein Pd and Ga are atomically dispersed on the support, and the Pd content is 0.025-0.45% and the Ga content is 0.01-1.00% based on 100% of the total mass of the catalyst, with the remainder being the support; more preferably, the Pd content is 0.025-0.18% and the Ga content is 0.01-0.20% based on 100% of the total mass of the catalyst, with the remainder being the support.

[0020] 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.

[0021] According to a specific embodiment of the present invention, preferably, the ethylene hydrorefining catalyst is prepared by the following steps:

[0022] (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.

[0023] (2) The active component is loaded onto the phosphorus-doped carbon material support to obtain a catalyst semi-finished product;

[0024] (3) The catalyst semi-finished product is reduced to obtain the reduced catalyst, which is the ethylene hydrogenation refining catalyst.

[0025] In the catalyst preparation steps described above, preferably, in step (1), the phosphorus-containing compound includes phosphoric acid and / or phytic acid, etc.

[0026] In the catalyst preparation steps described above, preferably, in step (1), the carbohydrates include glucose and / or sucrose, etc.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In the catalyst preparation steps described above, preferably, step (2) specifically includes:

[0035] (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.

[0036] (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.

[0037] Alternatively, step (2) may specifically include:

[0038] (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.

[0039] (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.

[0040] 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.

[0041] 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.

[0042] In the catalyst preparation steps described above, preferably, in step (2), the precursor of the co-active component includes gallium salt compounds, specifically including one or a combination of gallium nitrate, gallium sulfate, gallium oxalate, and gallium acetate.

[0043] 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.

[0044] 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 Ga / mL Ga precursor aqueous solution.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] A second aspect of the present invention provides a method for preparing the above-mentioned ethylene hydrogenation refining catalyst, comprising the following steps:

[0051] (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.

[0052] (2) The active component is loaded onto the phosphorus-doped carbon material support to obtain a catalyst semi-finished product;

[0053] (3) The catalyst semi-finished product is reduced to obtain the reduced catalyst, which is the ethylene hydrogenation refining catalyst.

[0054] In the above preparation method, preferably, in step (1), the phosphorus-containing compound includes phosphoric acid and / or phytic acid, etc.

[0055] In the above preparation method, preferably, in step (1), the carbohydrate includes glucose and / or sucrose, etc.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] In the above preparation method, preferably, in step (1), the drying temperature is 120-160°C and the time is 4-12 hours.

[0061] 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.

[0062] 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.

[0063] In the above preparation method, preferably, step (2) specifically includes:

[0064] (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.

[0065] (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.

[0066] Alternatively, step (2) may specifically include:

[0067] (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.

[0068] (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.

[0069] 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.

[0070] 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.

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

[0072] 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.

[0073] 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 Ga / mL Ga precursor aqueous solution.

[0074] 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.

[0075] In the above preparation method, preferably, in step (2), the irradiation time under ultraviolet xenon lamp is 0.5 to 5.0 h.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] This invention provides a catalyst for the hydrogenation refining of ethylene, particularly a catalyst for selectively hydrogenating impurities such as acetylene from ethylene to prepare polymer-grade ethylene feedstock. Conventional hydrogenation catalysts often have active components existing in nanoparticle or sub-nano cluster structures, thus affecting catalyst performance. The ethylene hydrogenation refining 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 or gallium) in a single-atom state on the support (surface and within the pores), rather than forming nanoparticle or sub-nano cluster structures. The atomically dispersed Pd and Ga exhibit the following characteristics in the ethylene hydrogenation refining reaction: the atomic dispersion of the active component particles increases the utilization rate of metal atoms, thereby improving the catalyst's hydrogenation activity; the adsorption capacity for olefins, especially ethylene, is reduced, thus improving the catalyst's hydrogenation selectivity; the probability of simultaneous adsorption of alkynes / dienes at adjacent active sites decreases, significantly reducing the probability of polymerization coking, thereby improving the catalyst's anti-coking performance. Therefore, the ethylene hydrorefining catalyst of the present invention exhibits excellent hydrogenation activity, selectivity and long-term operational stability. Attached Figure Description

[0080] Figure 1 Aberration-corrected transmission electron microscope image of the ethylene hydrorefining catalyst provided in Example 1.

[0081] Figure 2 Transmission electron microscopy (TEM) image of the hydrogenation catalyst provided for Comparative Example 5.

[0082] Figure 3This is a flowchart of an ethylene refining process using a post-hydrogenation process, provided as a specific embodiment of the present invention.

[0083] Figure 4 This is a flowchart of an ethylene refining process using a pre-ethane removal process, provided as a specific embodiment of the present invention.

[0084] Figure 5 This is a flowchart of an ethylene refining process using a pre-propane removal process, provided as a specific embodiment of the present invention.

[0085] 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. C2 hydrogenation reactor, 12. Ethylene distillation tower, 13. Ethylene refining reactor, 14. Pre-deethanerizer, 15. Pre-depropanerizer. Detailed Implementation

[0086] 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.

[0087] According to a specific embodiment of the present invention, preferably, the ethylene hydrorefining catalyst of the present invention is prepared by the following steps:

[0088] (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;

[0089] 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;

[0090] (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.

[0091] (2) a2 The palladium-supported support is added to the gallium 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 inert atmosphere to obtain catalyst semi-finished product;

[0092] or,

[0093] (2)-b1 The phosphorus-doped carbon material support is added to the gallium 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 gallium-loaded support.

[0094] (2)-b2 The gallium-supported support is added to the palladium precursor aqueous solution, stirred evenly, and then rapidly frozen in liquid nitrogen. 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;

[0095] 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;

[0096] The gallium precursor includes gallium salt compounds, specifically including one or a combination of gallium nitrate, gallium sulfate, gallium oxalate, and gallium acetate; the concentration of gallium in the aqueous solution of the gallium precursor is 0.1–10 mg Ga / mL Ga precursor aqueous solution;

[0097] (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 ethylene hydrogenation refining catalyst.

[0098] The technical solution of the present invention will be further described below through specific embodiments.

[0099] In the following specific embodiments and comparative examples, the analytical testing methods used include:

[0100] Content of active component in catalyst: atomic absorption spectrometry;

[0101] Single-atom morphology characterization: aberration-corrected transmission electron microscopy;

[0102] Conversion rate and selectivity are calculated using the following formula:

[0103] Acetylene conversion rate (%) = 100 × (inlet acetylene content - outlet acetylene content) / inlet acetylene content,

[0104] Ethylene selectivity (%) = 100 × (exit ethylene content - inlet ethylene content) / (inlet acetylene content - outlet acetylene content).

[0105] Example 1

[0106] This embodiment provides an ethylene hydrorefining catalyst, which is prepared through the following steps:

[0107] (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;

[0108] (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;

[0109] The palladium-supported support was added to an aqueous gallium nitrate solution containing 3.7 mg of gallium nitrate. After stirring 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.

[0110] (3) The catalyst semi-finished product is reduced by 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 ethylene hydrogenation refining catalyst.

[0111] According to atomic absorption spectrometry, the catalyst contains 0.025% Pd and 0.01% Ga by 100% of its total mass, with the remainder being a phosphorus-doped carbon material support.

[0112] 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 Ga are atomically dispersed on the support.

[0113] Example 2

[0114] This embodiment provides an ethylene hydrorefining catalyst, which is prepared through the following steps:

[0115] (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;

[0116] (2) Take 8 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.

[0117] The palladium-supported support was added to an aqueous gallium nitrate solution containing 36.7 mg of gallium 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.

[0118] (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 ethylene hydrogenation refining catalyst.

[0119] According to atomic absorption spectrometry, the catalyst contains 0.08% Pd and 0.1% Ga by 100% of its total mass, with the remainder being a phosphorus-doped carbon material support.

[0120] Example 3

[0121] This embodiment provides an ethylene hydrorefining catalyst, which is prepared through the following steps:

[0122] (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;

[0123] (2) 10g of the phosphorus-doped carbon material support was added to a gallium nitrate aqueous solution containing 73.4mg gallium nitrate. After stirring evenly at room temperature, the material 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 a gallium-loaded support.

[0124] Measure 15 mL of 1 mg Pd / mL palladium sulfate aqueous solution, add it to the gallium-supported support, 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.

[0125] (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 ethylene hydrogenation refining catalyst.

[0126] According to atomic absorption spectrometry, the catalyst contains 0.15% Pd and 0.2% Ga by 100% of its total mass, with the remainder being a phosphorus-doped carbon material support.

[0127] Example 4

[0128] This embodiment provides an ethylene hydrorefining catalyst, which is prepared through the following steps:

[0129] (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.

[0130] (2) 10g of the phosphorus-doped carbon material carrier was added to a gallium nitrate aqueous solution containing 220.1mg gallium 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 a gallium-loaded carrier.

[0131] Measure 25 mL of 1 mg Pd / mL Pd(NO3)2 aqueous solution, add it to the gallium-supported carrier, stir evenly at room temperature, place it in liquid nitrogen for rapid freezing, and then irradiate it under ultraviolet xenon lamp for 3 h; then freeze-dry it under vacuum of 18 Pa for 5 h, and then calcine it at 400 °C for 4 h under an inert atmosphere to obtain the catalyst semi-finished product.

[0132] (3) The catalyst semi-finished product is reduced by 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 ethylene hydrogenation refining catalyst.

[0133] According to atomic absorption spectrometry, the catalyst contains 0.25% Pd and 0.6% Ga by 100% of its total mass, with the remainder being a phosphorus-doped carbon material support.

[0134] Example 5

[0135] This embodiment provides an ethylene hydrorefining catalyst, which is prepared through the following steps:

[0136] (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;

[0137] (2) Take 45 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.

[0138] The palladium-supported support was added to an aqueous gallium nitrate solution containing 366.8 mg of gallium nitrate. After stirring 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.

[0139] (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 ethylene hydrogenation refining catalyst.

[0140] According to atomic absorption spectrometry, the catalyst contains 0.45% Pd and 1% Ga by 100% of its total mass, with the remainder being a phosphorus-doped carbon material support.

[0141] Comparative Example 1

[0142] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0143] (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.

[0144] (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;

[0145] The palladium-supported support was added to an aqueous gallium nitrate solution containing 3.7 mg of gallium nitrate. After stirring 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.

[0146] (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.

[0147] Atomic absorption spectrometry analysis revealed that, based on the total mass of the catalyst (100%), the Pd content was 0.025%, the Ga content was 0.01%, 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.

[0148] Comparative Example 2

[0149] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0150] (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.

[0151] (2) Take 8 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, 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.

[0152] The palladium-supported support was added to an aqueous gallium nitrate solution containing 36.7 mg of gallium 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.

[0153] (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.

[0154] According to atomic absorption spectrometry, the total mass of the catalyst is 100%, the Pd content is 0.08%, the Ga content is 0.1%, and the balance is the catalyst support.

[0155] Comparative Example 3

[0156] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0157] (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);

[0158] (2) 10g of the phosphorus-doped carbon material support was added to a gallium nitrate aqueous solution containing 73.4mg gallium nitrate. After stirring evenly at room temperature, the material 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 a gallium-loaded support.

[0159] Measure 10 mL of 10 mg Pd / mL palladium sulfate aqueous solution, add it to the gallium-supported support, 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.

[0160] (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.

[0161] According to atomic absorption spectrometry, the total mass of the catalyst is 100%, the Pd content is 1.0%, the Ga content is 0.2%, and the balance is a phosphorus-doped carbon material support.

[0162] Comparative Example 4

[0163] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0164] (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);

[0165] (2) 10g of the phosphorus-doped carbon material carrier was added to a gallium nitrate aqueous solution containing 1100.4mg gallium 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 a gallium-loaded carrier.

[0166] Measure 25 mL of 1 mg Pd / mL Pd(NO3)2 aqueous solution, add it to the gallium-supported carrier, stir evenly at room temperature, place it in liquid nitrogen for rapid freezing, and then irradiate it under ultraviolet xenon lamp for 3 h; then freeze-dry it under vacuum of 18 Pa for 5 h, and then calcine it at 400 °C for 4 h under an inert atmosphere to obtain the catalyst semi-finished product.

[0167] (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.

[0168] According to atomic absorption spectrometry, the total mass of the catalyst is 100%, with a Pd content of 0.25%, a Ga content of 3%, and the remainder being a phosphorus-doped carbon material support.

[0169] Comparative Example 5

[0170] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0171] (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);

[0172] (2) Take 45 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.

[0173] The palladium-supported support was added to an aqueous solution of gallium nitrate containing 366.8 mg of gallium 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.

[0174] (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.

[0175] Atomic absorption spectrometry analysis revealed that, based on the total mass of the catalyst (100%), the Pd content was 0.45%, the Ga content was 1%, 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 Ga are almost dispersed at the nanoparticle level.

[0176] Comparative Example 6

[0177] This comparative example provides a hydrogenation catalyst, which is prepared by the following steps:

[0178] (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.

[0179] (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;

[0180] The palladium-supported support was added to an aqueous gallium nitrate solution containing 3.7 mg of gallium nitrate. After stirring 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.

[0181] (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.

[0182] According to atomic absorption spectrometry, the total mass of the catalyst is 100%, the Pd content is 0.025%, the Ga content is 0.01%, and the balance is a nitrogen-phosphorus co-doped carbon support.

[0183] The catalysts provided in the above embodiments and comparative examples were evaluated in a single-stage fixed-bed reactor. The inlet material composition and reaction conditions of the single-stage fixed-bed reactor are shown in Table 1, and the evaluation results are shown in Table 2.

[0184] Table 1. Composition of reactants and reaction conditions

[0185]

[0186] Table 2 Catalyst Evaluation Results

[0187]

[0188]

[0189] The catalyst provided in the embodiments of the present invention can be applied to the ethylene refining reactor in an ethylene plant employing a post-hydrogenation process, or to the ethylene refining reactor in an ethylene plant employing a pre-ethane removal process, or to the ethylene refining reactor in an ethylene plant employing a pre-propane removal process.

[0190] The ethylene refining process using the post-hydrogenation process is shown in the following flowchart. Figure 3 As shown, the process mainly includes: feeding the raw material of the ethylene unit into the cracking furnace 1 for high-temperature cracking; cooling the product through the quench system 2; then processing it sequentially through the oil washing tower 3, water washing tower 4, first compressor 5, alkali washing tower 6, and dryer 7 before entering the demethanizer tower 8; separating methane and hydrogen at the top of the demethanizer tower 8; and compressing the bottom material through the second compressor 9 before entering the deethanerizer tower 10; separating C2 fraction at the top of the deethanerizer tower 10 and C3 fraction at the bottom; the C2 fraction separated at the top of the deethanerizer tower 10 entering the C2 hydrogenation reactor 11 for selective hydrogenation to remove alkyne, and then entering the ethylene distillation tower 12; separating ethane at the bottom of the ethylene distillation tower 12; and entering the top material of the ethylene distillation tower 12 into the ethylene refining reactor 13 for hydrogenation refining to obtain refined ethylene, which can then be sent to the ethylene polymerization system.

[0191] The ethylene refining process using the pre-ethane removal process is shown in the following diagram. Figure 4As shown, the process mainly includes: feeding the raw material of the ethylene unit into the cracking furnace 1 for high-temperature cracking; cooling the product through the quench system 2; then processing it sequentially through the oil washing tower 3, water washing tower 4, first compressor 5, alkali washing tower 6, and dryer 7 before entering the pre-ethane removal tower 14; the top material of the pre-ethane removal tower 14 is compressed by the second compressor 9 and then enters the C2 hydrogenation reactor 11 for selective hydrogenation to remove alkyne; the material after hydrogenation to remove alkyne enters the demethanizer tower 8; methane and hydrogen are separated from the top of the demethanizer tower 8; the bottom material enters the ethylene distillation tower 12; ethane is separated from the bottom of the ethylene distillation tower 12; the top material of the ethylene distillation tower 12 enters the ethylene refining reactor 13 for hydrogenation refining to obtain refined ethylene, which can be sent to the ethylene polymerization system.

[0192] The ethylene refining process using the pre-propane removal process is shown in the following diagram. Figure 5 As shown, the process mainly includes: feeding the raw material of the ethylene unit into the cracking furnace 1 for high-temperature cracking; cooling the product through the quench system 2; then processing it sequentially through the oil washing tower 3, water washing tower 4, first compressor 5, alkali washing tower 6, and dryer 7 before entering the pre-propane stripper 15; the top material of the pre-propane stripper 15 is compressed by the second compressor 9 and then enters the C2 hydrogenation reactor 11 for selective hydrogenation to remove alkyne; the material after hydrogenation to remove alkyne enters the demethanizer 8; methane and hydrogen are separated from the top of the demethanizer 8; the bottom material enters the deethanerizer 10; the top material of the deethanerizer 10 enters the ethylene distillation tower 12; ethane is separated from the bottom of the ethylene distillation tower 12; the top material enters the ethylene refining reactor 13 for hydrogenation refining to obtain refined ethylene, which can be sent to the ethylene polymerization system.

Claims

1. An ethylene hydrorefining 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 Ga. 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 0.025~0.45%, the content of the co-active component is 0.01~1.00%, and the balance is the support. The ethylene hydrorefining catalyst is 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 ethylene hydrogenation refining 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 ethylene hydrorefining catalyst according to claim 1, wherein, Based on the total mass of the catalyst (100%), the content of the main active component is 0.025~0.18%, the content of the co-active component is 0.01~0.20%, and the balance is the support.

3. A method for preparing the ethylene hydrorefining catalyst according to claim 1 or 2, 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 ethylene hydrogenation refining 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.

4. The preparation method according to claim 3, wherein, In step (1), the phosphorus-containing compound includes phosphoric acid and / or phytic acid.

5. The preparation method according to claim 3, wherein, In step (1), the carbohydrates include glucose and / or sucrose.

6. The preparation method according to claim 3, wherein, In step (1), the molar ratio of the phosphorus-containing compound and the carbohydrate is 0.02 to 0.

4.

7. The preparation method according to claim 3, 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.

8. The preparation method according to claim 3, wherein, In step (1), the temperature of the hydrothermal reaction is 160~300℃ and the time is 4~12h.

9. The preparation method according to claim 3, wherein, In step (1), the drying temperature is 120~160℃ and the time is 4~12h.

10. The preparation method according to claim 3, 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.

11. The preparation method according to claim 3, wherein, In step (1), the calcination is carried out under an inert atmosphere at a temperature of 600-1000°C for 1-5 hours.

12. The preparation method according to claim 3, wherein, In step (2), the precursor of the main active component includes a palladium salt compound.

13. The preparation method according to claim 12, wherein, In step (2), the precursor of the main active component includes one or a combination of palladium chloride, palladium nitrate and palladium sulfate.

14. The preparation method according to claim 3, wherein, In step (2), the precursor of the co-active component includes a gallium salt compound.

15. The preparation method according to claim 14, wherein, In step (2), the precursor of the co-active component includes one or a combination of gallium nitrate, gallium sulfate, gallium oxalate and gallium acetate.

16. The preparation method according to claim 3, 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.

17. The preparation method according to claim 3, 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 mgGa / mL Ga precursor aqueous solution.

18. The preparation method according to claim 3, wherein, In step (2), the illumination time under the ultraviolet xenon lamp is 0.5~5.0h.

19. The preparation method according to claim 3, wherein, 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.

20. The preparation method according to claim 3, wherein, 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.

21. The preparation method according to claim 3, 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.

22. The preparation method according to claim 21, 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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