A magnetic carrier catalyst, its preparation method and application thereof

Abstract

This invention discloses a magnetically supported catalyst, its preparation method, and its applications. The magnetically supported catalyst comprises a magnetic core, a dense coating layer covering the magnetic core, and an active component supported on the dense coating layer. The dense coating layer includes at least one dense polymer layer; or it may also include at least one carbon layer, with the outermost layer being a dense polymer layer. The carbon layer is formed by coating and carbonizing a carbon source or vinylpyrrolidone; the dense polymer layer is formed by coating and densifying polyvinylpyrrolidone. This invention prepares a densely structured coating layer on the surface of the magnetic core. Compared with traditional porous supports, when supporting the active component, it does not trap it inside the pores, but only supports the active component on the surface, reducing the loading of noble metal catalysts by several times or orders of magnitude. Simultaneously, because the active component has a structure at the scale of several to tens of nanometers, it exhibits high hydrogenation activity and can be completely magnetically recovered, resulting in low catalyst usage costs and low impurity content in the hydrogenation product HNBR.

Description

Technical Field

[0001] This invention relates to the field of industrial catalysis technology, specifically to a magnetically supported catalyst, its preparation method, and its application. Background Technology

[0002] Synthetic rubber, plastics, and chemical fibers are the three traditional synthetic materials in the petrochemical industry and are crucial pillar materials in modern industrial production. Nitrile rubber (NBR) is a copolymer of butadiene and acrylonitrile. With its excellent airtightness, water resistance, oil resistance, temperature resistance, and abrasion resistance, it is widely used in the automotive, aerospace, marine, and oil extraction industries. The polymer chain structure of NBR contains C=C and C≡N bonds. The presence of C≡N gives the rubber excellent properties such as oil resistance, high tensile strength, and high modulus, while the presence of C=C double bonds can lead to potential problems in aging resistance and chemical corrosion resistance.

[0003] To improve the performance and application range of nitrile rubber, hydrogenation is often used to eliminate C=C double bonds. However, removing the precious metal catalyst after hydrogenation and purifying the hydrogenated product requires a combination of one or more methods such as centrifugation, filtration, and extraction. The process is quite cumbersome and it is difficult to remove the catalyst completely. How to achieve this goal efficiently has always been one of the hot topics in this technology research.

[0004] CN101703936A discloses a magnetically supported catalyst on which magnetic supports and active components are loaded onto a long-chain organic polymer and its preparation method. From the preparation process, it can be seen that a large amount of active components are encapsulated inside the polymer, resulting in the loss of active components and increasing the cost of the catalyst.

[0005] CN112023939A discloses a magnetic core-shell hydrogenation catalyst and method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanediol, wherein the catalyst is represented as Fe3O4@S / M; wherein Fe3O4 is the core layer, S is the shell support, and M is the main active metal and / or auxiliary metal supported on the shell support; the active metal is one or more of Ru, Ni, Ir, Pd, and Pt, and the loading is 1-50 wt% of the catalyst; the auxiliary metal is one or more of Cu, Fe, Co, Zn, and Sn, and the molar ratio of the auxiliary metal to the main active metal is 0.1-10:1. The catalyst prepared by this method has a porous structure and a large loading of active components. However, in a high-viscosity system like nitrile rubber with a large molecular weight, the active components entering the pores are quickly blocked by the nitrile rubber and cannot function.

[0006] CN104785301A discloses a magnetically supported palladium composite catalyst, its preparation method, and its uses. The magnetic palladium composite catalyst uses superparamagnetic Fe3O4@SiO2 microspheres as a support, and the surface is covalently modified with loaded amino Pd(II) particles. The process involves sequentially preparing Fe3O4 nanoparticles, core-shell structured magnetic nanospheres Fe3O4@SiO2, Fe3O4@SiO2@APTES, and finally loading Pd(II) particles to obtain the Fe3O4@SiO2@APTES@Pd catalyst. The final catalyst has a porous surface structure.

[0007] KR102436881B1 discloses a magnetically supported Fe3O4 / PDA / Pd catalyst for Suzuki-Miyaura coupling, Sonogashira coupling, and Heck coupling reactions, and its preparation method. The preparation method includes the following steps: preparing a hydrophobic compound, polydopamine (PDA), for introducing hydrophobic alkyl groups; preparing a magnetic base support; reacting the hydrophobic compound with the base support; introducing hydrophobic alkyl groups onto the base support; and loading metal nanoparticles onto the base support containing the introduced hydrophobic alkyl groups. Summary of the Invention

[0008] One object of the present invention is to provide a magnetically supported catalyst and a method for preparing the same, specifically a magnetically supported catalyst with a magnetic core@carbon@active hydrogenation component that can be used in the hydrogenation process of unsaturated polymer latex, liquid, or viscous solution.

[0009] Another object of the present invention is to provide the application of the magnetically supported catalyst in the hydrogenation process of polymers containing unsaturated olefin double bonds, especially in the hydrogenation of nitrile rubber.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The present invention provides a magnetically supported catalyst, which includes a magnetic core, a dense coating layer covering the magnetic core, and an active component supported on the dense coating layer;

[0012] The dense coating layer comprises at least one dense polymer layer; or

[0013] The dense coating layer includes at least one carbon layer and at least one dense polymer layer, and the outermost layer of the dense coating layer is the dense polymer layer;

[0014] The carbon layer is formed by coating and carbonizing a carbon source or vinylpyrrolidone; the dense polymer layer is formed by coating and densifying polyvinylpyrrolidone.

[0015] The active component is selected from at least one of Pd, Rh, Ru, Ni, and Mo.

[0016] In some preferred embodiments of the present invention, the carbonization treatment is high-temperature carbonization at 600–800°C under a protective atmosphere; the densification treatment is heat treatment at 180–500°C under a protective atmosphere. The protective gas used in the present invention can be nitrogen or an inert gas, preferably argon. Carbonization after polyvinylpyrrolidone coating also results in the formation of a carbon layer; therefore, the carbon layer in the dense coating layer can also be formed using polyvinylpyrrolidone coating and carbonization.

[0017] This invention prepares a dense coating layer (without through-pores or interconnected channels) on the surface of a magnetic core, and then supports a noble metal active hydrogenation component on this dense coating layer. Compared with traditional porous structures and porous supports, this method avoids trapping the active component inside the channels, supporting it only on the surface. This significantly reduces the loading of the noble metal catalyst. Furthermore, because the active component has a structure at the scale of several to tens of nanometers, it exhibits high hydrogenation activity and can be completely magnetically recovered, resulting in low catalyst usage costs and low impurity content in the hydrogenation product HNBR. Moreover, the magnetic catalyst of this invention can be controlled by adjusting the number of composite coating layers of carbon and dense polymer layers to achieve a final morphology with a dense surface and controllable particle size and specific surface area.

[0018] In some preferred embodiments of the present invention, the magnetically supported catalyst has a particle size of 60 nm to 610 nm and a specific surface area of ​​45 m². 2 / g~95m 2 / g, bulk density is 0.6g / cm³ 3 ~1.25g / cm 3 .

[0019] In some preferred embodiments of the present invention, the particle size of the magnetically supported catalyst is 60 nm to 310 nm, more preferably 150 nm to 310 nm.

[0020] In some preferred embodiments of the present invention, the specific surface area of ​​the magnetically supported catalyst is 50 m². 2 / g~90m 2 / g, more preferably 60m 2 / g~80m 2 / g.

[0021] In some preferred embodiments of the present invention, the packing density of the magnetically supported catalyst is 0.7 g / cm³. 3 ~1.0g / cm 3 .

[0022] In some preferred embodiments of the present invention, the loading of the active component accounts for 0.01 wt% to 6 wt% of the catalyst, preferably 0.2 wt% to 3 wt%, and more preferably 0.5 wt% to 2 wt%.

[0023] The most significant feature of the magnetically supported catalyst of this invention is that the magnetic core is compositely coated with at least one or more layers of carbon and polyvinylpyrrolidone to form a final morphology with a dense surface and controllable catalyst particle size and specific surface area. The final support surface is dense rather than a traditional porous form, with a specific surface area of ​​45 m². 2 / g~95m 2 / g, far lower than the 80m² of conventional porous surfaces. 2 / g~600m 2 / g; bulk density is 0.6g / cm³ 3 ~1.25g / cm 3 It is far higher than the 0.4 g / cm³ of traditional conventional catalysts. 3 ~0.6g / cm 3 The active component loading ranges from 0.01 wt% to 6 wt% of the catalyst, significantly expanding the loading range compared to the 1 wt% to 5 wt% loading of conventional catalysts. This makes it suitable for NBR hydrogenation of different molecular weights. Furthermore, due to the nanoscale particle size, the hydrogenation effect is close to that of homogeneous catalysts, ensuring a consistent hydrogenation performance. Since the active component can be completely recovered, the catalyst cost is significantly reduced while maintaining the same hydrogenation activity.

[0024] In some preferred embodiments of the present invention, the carbon source is selected from at least one of glucose, citric acid, polyacrylic acid, and polyvinyl alcohol.

[0025] In some preferred embodiments of the present invention, the carbon source is preferably glucose and citric acid.

[0026] The catalyst is ultimately formed through composite coating with at least one or more layers, resulting in a final morphology with controllable particle size, bulk density, and specific surface area. Common methods such as hydrolysis and hydrothermal methods can be used for carbon layer coating, with hydrolysis being the preferred method.

[0027] In some preferred embodiments of the present invention, the active component is selected from at least one of Pd, Rh, and Ru.

[0028] In some preferred embodiments of the present invention, the active component is more preferably Pd element.

[0029] In some preferred embodiments of the present invention, the active component is loaded by impregnation or in-situ synthesis. The in-situ synthesis method includes different preparation methods such as titration and in-situ reduction. The present invention does not impose any particular limitation. Any preparation method that can ultimately form active sites of several nanometers to tens of nanometers on the surface of the dense coating layer can be adopted. Titration and in-situ reduction are preferred.

[0030] In some preferred embodiments of the present invention, the magnetic core is selected from at least one of ferromagnetic magnetic nanopowders, such as at least one selected from Fe3O4, Fe3S4, and FeNi. The magnetic core can be commercially available or prepared in a laboratory.

[0031] In some preferred embodiments of the present invention, the particle size of the magnetic core is 50 nm to 500 nm.

[0032] In some preferred embodiments of the present invention, the magnetic core is selected from Fe3O4 magnetic nanopowder with a particle size of 50nm to 300nm.

[0033] In some preferred embodiments of the present invention, the magnetic core is selected from Fe3O4 magnetic nanopowder with a particle size of 50nm to 250nm.

[0034] Another aspect of the present invention provides a method for preparing a magnetically supported catalyst, wherein the preparation method includes the following steps:

[0035] The magnetic core is coated with a carbon source or polyvinylpyrrolidone, and then carbonized at a high temperature of 600-800°C under a protective atmosphere to form the carbon layer; then, polyvinylpyrrolidone is coated and heat-treated at 180-500°C (preferably 200-400°C) under a protective atmosphere to form the dense polymer layer; when the particle size and density of the magnetic catalyst do not meet the hydrogenation requirements, the coating is repeated multiple times to form the carbon layer and / or the dense polymer layer (during the coating process, ensure that the outermost layer is coated with polyvinylpyrrolidone to form a dense surface);

[0036] When the dense coating layer does not include the carbon layer, the step of forming the carbon layer by coating with a carbon source is not included;

[0037] The active component is supported to obtain the magnetically supported catalyst.

[0038] The catalyst preparation method used in this invention is significantly different from the current preparation technology. Its biggest feature is that this multi-layer structure of magnetic core / dense coating layer / active component has a dense surface, requires a small amount of catalyst, and has strong binding force. While ensuring hydrogenation activity, it has low cost and good separation effect.

[0039] The thickness of the dense coating layer outside the magnetic core in this invention can be controlled by adjusting the thickness of the carbon layer and the polyvinylpyrrolidone polymer layer. If the final particle size and packing density are not satisfactory, the carbon layer or polyvinylpyrrolidone coating process can be repeated once or multiple times for adjustment until a satisfactory effect is achieved, ultimately forming a structure with a dense specific surface area and suitable particle size.

[0040] Since the magnetically supported catalyst of this invention targets a high-viscosity rubber system, the purpose of coating the magnetic core is not to prepare a porous system, but to form a dense surface structure by coating carbon materials and densifying them. Ultimately, the particle size, specific surface area, and morphology of the catalyst can be controlled according to different requirements to meet the optimal hydrogenation effect and separation requirements. In addition, by controlling the preparation process, the bonding strength between the active component and the coating layer and the magnetic core can be increased.

[0041] In some preferred embodiments of the present invention, when the carbon source is glucose, the carbon layer coating formation process includes:

[0042] An organic coating layer is formed on the surface of the magnetic core by glucose hydrolysis, and then the carbon layer is formed by high-temperature carbonization at 600-800°C for 2-4 hours under a protective atmosphere.

[0043] As understood by those skilled in the art, different coating thicknesses can be obtained by controlling the concentration of raw materials and the reaction time during the coating process, thereby obtaining the catalyst particle size required for the final practical application.

[0044] In some preferred embodiments of the present invention, the process of forming an organic coating layer on the surface of the magnetic core using a glucose hydrolysis reaction includes:

[0045] The magnetic nucleus was added to deionized water, and then glucose was added for hydrolysis at 18–180°C for 16–24 hours. After the reaction was completed, the precipitate was separated and recovered using a magnet, and then washed and dried.

[0046] In some preferred embodiments of the present invention, the drying can be performed by freeze drying, oven drying, or other methods, wherein the drying temperature does not exceed 60°C. The washing is performed sequentially using water and ethanol.

[0047] In some preferred embodiments of the present invention, the mass ratio of the magnetic nucleus to glucose is 1:(0.5 to 2.0), more preferably 1:(1 to 1.5).

[0048] In some preferred embodiments of the present invention, the process of forming the dense polymer layer includes:

[0049] The magnetic core or the magnetic core coated with a carbon layer is dispersed in deionized water, and polyvinylpyrrolidone is added. The mixture is heated at 25–180°C for 2–4 hours. After cooling to room temperature, the precipitate is separated and recovered using a magnet. The precipitate is washed, dried, and then subjected to heat treatment at 180–500°C for 1–2 hours under a protective atmosphere to form the dense polymer layer.

[0050] In some preferred embodiments of the present invention, the mass ratio of the magnetic core or the carbon-coated magnetic core to polyvinylpyrrolidone is 1:(0.1-2).

[0051] In some preferred embodiments of the present invention, the loading process of the active component includes:

[0052] The magnetic core coated with a carbon layer and a dense polymer layer is dispersed in a solvent, and the precursor of the active component is added to carry out the reaction. After the reaction is completed, the solid is separated and recovered by a magnet, washed and dried, and the resulting solid powder is the magnetically supported catalyst, which can be denoted as Fe3O4@C@M, where M is the active component.

[0053] In the process of adding active components, the precursor of the active components is generally added in excess. In some preferred embodiments of the present invention, the mass ratio of the magnetic core coated with a carbon layer and a dense polymer layer to the precursor of the active components is 1:(0.02 to 3.5).

[0054] In some preferred embodiments of the present invention, the precursor of the active component is selected from at least one of noble metal elements such as Pd, Rh, and Ru, and acetates, halides, and ammonium salts of Ni and Mo. Except for rhodium and ruthenium-based noble metals, the catalysts prepared by the present invention should be activated by hydrogen reduction at 200–400°C before use.

[0055] In some preferred embodiments of the present invention, the solvent for the loading process of the active component is water and / or ethanol.

[0056] The magnetic nuclei of this invention can be commercially available or prepared in a laboratory; the particle size can be between 50 and 500 nm, and the closer the shape is to spherical, the better, which is related to the evaluation device and method used in this invention. In this embodiment, a slurry bed evaluation device is used. The final particle size of the catalyst cannot be too large because the magnetic nucleus density is relatively high, for example, Fe3O4 reaches 5.18 g / cm³. 3 If the particle size is too large, it will settle and cannot be well dispersed in the colloidal solution. Therefore, the sedimentation problem of the catalyst can be solved by controlling the appropriate coating thickness and ultimately by controlling the particle size of the catalyst.

[0057] For example, Fe3O4 magnetic microspheres can be prepared as magnetic cores using a solvothermal method. Specifically, they can be prepared by thermal reaction of iron salts and reducing agents. Organic sodium salts, polyethylene glycol, and caustic sodas can also be added during the preparation process.

[0058] Specifically, the preparation methods of Fe3O4 magnetic microspheres include:

[0059] The reducing agent, iron salt, organic sodium salt, polyethylene glycol, and caustic alkali are added to the reactor in a mass ratio and mixed evenly at 10–45°C to prepare the initial reaction mixture. The mixture is then added to the reaction vessel and heated at 80–220°C for 12–24 hours to obtain a mixture of Fe3O4 magnetic microspheres and reaction solvent. The mixture is cooled to 12–35°C, then separated and recovered using a magnet, washed, freeze-dried, and stored for later use.

[0060] The reducing agent can be an organic alcohol, preferably ethylene glycol and / or propylene glycol. The iron salt can be ferric chloride and / or ferrous chloride. The organic sodium salt can be at least one of sodium acetate, sodium stearate, and sodium benzoate. The polyethylene glycol can be a commercially available product, such as polyethylene glycol 6000; this invention does not specifically limit the type of polyethylene glycol. The caustic alkali can be at least one of sodium hydroxide, potassium hydroxide, and ammonia.

[0061] The preferred mass ratio of the reducing agent, iron salt, organic sodium salt, polyethylene glycol, and caustic alkali is (5-20):1:(1-5):(4-10):(0.1-0.5), more preferably (6-18):1:(2-4):(3-9):(0.15-0.45).

[0062] The particle size of the prepared Fe3O4 magnetic microspheres can be controlled by adjusting the material ratio, reaction time, and reaction temperature.

[0063] In another aspect, the present invention provides the application of any one of the above magnetically supported catalysts in the hydrogenation process of polymers containing unsaturated olefin double bonds, especially the hydrogenation of nitrile rubber.

[0064] The magnetically supported catalyst of this invention can meet the different requirements of different grades of NBR and other latex systems for catalyst systems. By utilizing different formulations and catalyst particle sizes, it can achieve highly selective hydrogenation of unsaturated double bonds while efficiently separating and reusing the catalyst through an external magnetic field. It is a convenient method for using magnetically supported noble metal catalysts to hydrogenate NBR to prepare HNBR and to perform hydrogenation saturation treatment of different latexes.

[0065] In some preferred embodiments of the present invention, the organic solvent in the hydrogenation process is selected from at least one of ethers, chlorinated aromatics and ketones; more preferably, it is one of the ketones, such as acetone or butanone; the weight ratio of nitrile rubber to magnetic catalyst is (1-2):1, and even more preferably (1-1.5):1.

[0066] In some preferred embodiments of the present invention, hydrogenation is carried out in a stirred tank or a slurry tank, preferably in a stirred tank; the hydrogenation temperature is 70–120°C, preferably 70–110°C, more preferably 70–100°C; the hydrogen pressure is 2–16 MPa, preferably 2–10 MPa, more preferably 4–8 MPa; the reaction time is 4–12 hours, preferably 4–10 hours, more preferably 4–8 hours. The reaction is carried out under stirring conditions, with a stirring speed preferably 180–600 rpm, more preferably 200–450 rpm; after the reaction, the original NBR can be converted into HNBR with a hydrogenation degree greater than 95%.

[0067] The magnetically supported catalyst of this invention can be recovered and separated after use by applying an external electromagnetic field or a permanent magnetic field, preferably using a permanent magnet. The catalyst recovery efficiency is not less than 98%, and the recovered catalyst can be reused after solvent washing.

[0068] The magnetically supported catalyst of this invention can achieve highly selective hydrogenation of double bonds in olefins such as nitrile rubber, latex, or emulsion, while having low catalyst cost, low active component content in HNBR, and long service life. It can also efficiently separate the catalyst by an external magnetic field, with high separation efficiency and simple operation. It is a convenient method for preparing HNBR by hydrogenation of NBR using magnetically supported noble metal catalysts.

[0069] The beneficial effects of this invention include:

[0070] 1) In the magnetically supported catalyst of the present invention, the active component loading is low, which can greatly reduce the cost of catalyst use. The catalyst prepared by the present invention has a dense surface structure. Since the catalyst bulk phase is not a conventional porous structure, i.e., the bulk phase has no channels, the catalyst efficiency is high; however, since the catalyst particle size is at the nanoscale, the hydrogenation effect is close to that of homogeneous catalysts, and the hydrogenation effect can be guaranteed.

[0071] 2) Using the magnetically supported catalyst of the present invention in the hydrogenation of NBR to prepare HNBR can improve the separation efficiency of the catalyst, extend the service life of the catalyst, and improve the final performance of HNBR products.

[0072] Compared to existing homogeneous methods, this invention eliminates the need for complex separation processes such as extraction or ion exchange of the catalyst after hydrogenation. Compared to existing heterogeneous methods, this invention eliminates the need for time-consuming catalyst centrifugation and sedimentation processes, enabling magnetic recovery of the catalyst. Furthermore, the recovered catalyst, after washing to remove surface-adhered HNBR gum, can be reused, resulting in a long catalyst lifespan. Therefore, this invention offers advantages in terms of catalyst usage cost, separation efficiency, and significantly reduced final catalyst residue in HNBR processes. Detailed Implementation

[0073] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0074] The key to this invention lies in densifying the magnetic core coating layer, making its surface distinct from conventional porous structures and channels. When the active hydrogenation component is supported on this dense coating layer, it is prevented from being trapped within the pores; instead, the active component is supported only on the surface. This significantly reduces the loading of the noble metal catalyst, by several times or orders of magnitude. Simultaneously, because the active component has a nanostructure, the hydrogenation activity is ensured. Furthermore, the magnetic catalyst of this invention can be controlled by adjusting the number of composite coating layers of carbon and dense polymer layers to achieve a final morphology with a dense surface and controllable catalyst particle size and specific surface area. The magnetically supported catalyst prepared by this invention not only exhibits high hydrogenation activity for nitrile rubber, making it suitable for the harsh hydrogenation environment of nitrile rubber, but also, due to its superparamagnetic nature, allows for efficient recovery and reuse using an external magnetic field, reducing hydrogenation costs.

[0075] The magnetically supported catalyst of the present invention specifically includes a magnetic core, a dense coating layer covering the magnetic core, and an active component supported on the dense coating layer;

[0076] The dense coating layer comprises at least one dense polymer layer; or

[0077] The dense coating layer includes at least one carbon layer and at least one dense polymer layer, and the outermost layer of the dense coating layer is the dense polymer layer;

[0078] The carbon layer is formed by coating and carbonizing a carbon source or polyvinylpyrrolidone; the dense polymer layer is formed by coating and densifying polyvinylpyrrolidone.

[0079] The active component is selected from at least one or more elements among the noble metals Pd, Rh, and Ru, and elements with high hydrogenation activity such as Ni and Mo, preferably at least one of the noble metals palladium and Ni and Mo with high hydrogenation activity.

[0080] The carbonization treatment is a high-temperature carbonization at 600–800°C under a protective gas atmosphere; the densification treatment is a heat treatment at 180–500°C (preferably 200–400°C) under a protective gas atmosphere. The protective gas used in this invention can be argon, nitrogen, or other inert gases, with argon being preferred. Carbonization after polyvinylpyrrolidone coating also results in the formation of a carbon layer; therefore, the carbon layer in the dense coating layer can also be formed using polyvinylpyrrolidone coating and carbonization.

[0081] The magnetically supported catalyst was prepared through the following steps:

[0082] The magnetic core is coated with a carbon source or polyvinylpyrrolidone, and then carbonized at a high temperature of 600-800°C under a protective atmosphere to form the carbon layer; then, polyvinylpyrrolidone is coated and heat-treated at 180-500°C (preferably 200-400°C) under a protective atmosphere to form the dense polymer layer; when the particle size and density of the magnetic catalyst do not meet the hydrogenation requirements, the coating is repeated multiple times to form the carbon layer and / or the dense polymer layer (during the coating process, ensure that the outermost layer is coated with polyvinylpyrrolidone to form a dense surface);

[0083] When the dense coating layer does not include the carbon layer, the step of forming the carbon layer by coating with a carbon source is not included;

[0084] The active component is supported to obtain the magnetically supported catalyst.

[0085] The magnetically supported catalyst prepared by this invention has a particle size of 60 nm to 610 nm, preferably 60 nm to 310 nm, and more preferably 150 nm to 310 nm; its specific surface area is 45 m². 2 / g~95m 2 / g, preferably 50m 2 / g~90m 2 / g, more preferably 60m 2 / g~80m 2 / g; bulk density is 0.6g / cm³ 3 ~1.25g / cm 3 The preferred value is 0.7 g / cm³. 3 ~1.0g / cm 3 The active component is supported on a substrate of 0.01 wt% to 6 wt% of the catalyst, preferably 0.2 wt% to 3 wt%, more preferably 0.5 wt% to 2 wt%. The magnetic core is compositely coated with at least one or more layers of carbon and dense polymer to form a final morphology with a dense surface and controllable catalyst particle size and specific surface area. The final support surface is dense rather than a traditional porous form, with a specific surface area of ​​45 m². 2 / g~95m2 / g, far lower than the 80m² of conventional porous surfaces. 2 / g~600m 2 / g; bulk density is 0.6g / cm³ 3 ~1.25g / cm 3 It is far higher than the 0.4 g / cm³ of traditional conventional catalysts. 3 ~0.6g / cm 3 The active component loading ranges from 0.01 wt% to 6 wt% of the catalyst, which is significantly wider than the 1 wt% to 5 wt% loading of conventional catalysts. This allows for flexible adjustment of the catalyst concentration in different concentrations of colloidal solutions, depending on actual needs. Furthermore, due to the nanoscale particle size, the hydrogenation effect is close to that of homogeneous catalysts. Since the active component can be completely recovered, the catalyst cost is low while maintaining the same hydrogenation activity.

[0086] For the carbon layer coating material, the carbon source is preferably at least one selected from glucose, citric acid, polyacrylic acid, and polyvinyl alcohol. Glucose or citric acid is preferred as the carbon source. The carbon layer coating method can employ common methods such as hydrolysis and hydrothermal methods, with hydrolysis being preferred.

[0087] The active component is loaded using either impregnation or in-situ synthesis. The in-situ synthesis method includes different preparation methods such as titration and in-situ reduction. This invention does not impose any particular limitation on these methods. Any preparation method that can ultimately form active sites of several to tens of nanometers on the surface of the dense coating layer is acceptable. Titration and in-situ reduction are preferred.

[0088] The magnetic core is selected from at least one of ferromagnetic magnetic nanopowders such as Fe3O4, Fe3S4, and FeNi, and can be commercially available or prepared in the laboratory. The particle size of the magnetic core only needs to be between 50 nm and 500 nm. Preferably, the magnetic core is a low-cost, commercially available or laboratory-synthesized Fe3O4 magnetic nanopowder with a particle size of 50 nm to 300 nm, and more preferably, a Fe3O4 magnetic nanopowder with a particle size of 50 nm to 250 nm.

[0089] The magnetic nuclei of this invention can be commercially available or prepared in a laboratory; the particle size can be between 50 and 500 nm, and the closer the shape is to spherical, the better, which is related to the evaluation device and method used in this invention. In this embodiment, a slurry bed evaluation device is used. The final particle size of the catalyst cannot be too large because the magnetic nucleus density is relatively high, for example, Fe3O4 reaches 5.18 g / cm³. 3 If the particle size is too large, it will settle and cannot be well dispersed in the colloidal solution. Therefore, the sedimentation problem of the catalyst can be solved by controlling the appropriate coating thickness and ultimately by controlling the particle size of the catalyst.

[0090] For example, Fe3O4 magnetic microspheres can be prepared as magnetic cores using a solvothermal method. Specifically, they can be prepared by thermal reaction of iron salts and reducing agents. Organic sodium salts, polyethylene glycol, and caustic sodas can also be added during the preparation process.

[0091] Specifically, the preparation methods of Fe3O4 magnetic microspheres include:

[0092] The reducing agent, iron salt, organic sodium salt, polyethylene glycol, and caustic alkali are added to the reactor in a mass ratio and mixed evenly at 10–45°C to prepare the initial reaction mixture. The mixture is then added to the reaction vessel and heated at 80–220°C for 12–24 hours to obtain a mixture of Fe3O4 magnetic microspheres and reaction solvent. The mixture is cooled to 12–35°C, then separated and recovered using a magnet, washed, freeze-dried, and stored for later use.

[0093] The reducing agent can be an organic alcohol, preferably ethylene glycol and / or propylene glycol. The iron salt can be ferric chloride and / or ferrous chloride. The organic sodium salt can be at least one of sodium acetate, sodium stearate, and sodium benzoate. The polyethylene glycol can be a commercially available product, such as polyethylene glycol 6000; this invention does not specifically limit the type of polyethylene glycol. The caustic alkali can be at least one of sodium hydroxide, potassium hydroxide, and ammonia.

[0094] The preferred mass ratio of the reducing agent, iron salt, organic sodium salt, polyethylene glycol, and caustic alkali is (5-20):1:(1-5):(4-10):(0.1-0.5), more preferably (6-18):1:(2-4):(3-9):(0.15-0.45).

[0095] The particle size of the prepared Fe3O4 magnetic microspheres can be controlled by adjusting the material ratio, reaction time, and reaction temperature.

[0096] In some specific embodiments of the present invention, the carbon source is glucose, and the carbon layer coating formation process includes:

[0097] An organic coating layer is formed on the surface of the magnetic core by glucose hydrolysis, and then the carbon layer is formed by high-temperature carbonization at 600-800°C for 2-4 hours under a protective atmosphere.

[0098] As understood by those skilled in the art, different coating thicknesses can be obtained by controlling the concentration of raw materials and the reaction time during the coating process, thereby obtaining the catalyst particle size required for the final practical application.

[0099] More preferably, the process of forming an organic coating layer on the surface of the magnetic nucleus using glucose hydrolysis specifically includes: adding the magnetic nucleus to deionized water, then adding glucose and hydrolyzing at 18–180°C for 16–24 hours; after the reaction, separating and recovering the precipitate using a magnet, washing, and drying. The drying can be performed by freeze-drying, oven drying, etc., wherein the drying temperature does not exceed 60°C. The washing is carried out sequentially using water and ethanol.

[0100] The thickness of the carbon layer formed can be controlled by adjusting the glucose concentration and reaction time. Preferably, the mass ratio of the magnetic core to glucose is 1:(0.5-2.0), more preferably 1:(1-1.5).

[0101] In some specific embodiments of the present invention, the process of forming the dense polymer layer includes:

[0102] The magnetic core or the magnetic core coated with a carbon layer is dispersed in deionized water, and polyvinylpyrrolidone is added. The mixture is heated at 25–180°C for 2–4 hours. After cooling to room temperature, the precipitate is separated and recovered using a magnet. The precipitate is washed, dried, and then subjected to heat treatment at 180–500°C for 1–2 hours under a protective atmosphere to form the dense polymer layer.

[0103] When the dense coating layer does not contain a carbon layer, magnetic cores are used to directly coat polyvinylpyrrolidone.

[0104] During the formation of the dense polymer layer, the thickness of the formed dense polymer layer can be controlled by adjusting the concentration of polyvinylpyrrolidone and the reaction time. Preferably, the mass ratio of the magnetic core or the carbon-coated magnetic core to polyvinylpyrrolidone is 1:(0.1-2).

[0105] In some specific embodiments of the present invention, the loading process of the active component includes:

[0106] A magnetic core coated with a carbon layer and a dense polymer layer is dispersed in a solvent (preferably distilled water or ethanol), and a precursor of the active component is added to initiate a reaction (preferably heated to 30–120°C for 4–10 hours). After the reaction, the solid is separated and recovered using a magnet, washed, and dried. The resulting solid powder is the magnetically supported catalyst, which can be denoted as Fe3O4@C@M, where M is the active component. When the reaction is heated, the temperature is cooled to 12–35°C after the reaction is completed, and then the solid is separated and recovered using a magnet.

[0107] The precursor of the active component is selected from at least one of noble metal elements such as Pd, Rh, and Ru, and acetates, halides, and ammonium salts of Ni and Mo. Except for rhodium and ruthenium-based noble metals, the catalysts prepared in this invention should be activated by hydrogen reduction at 200–400°C before use.

[0108] The precursor of the active component is generally added in excess. Preferably, the mass ratio of the magnetic core coated with a carbon layer and a dense polymer layer to the precursor of the active component is 1:(0.02-3.5).

[0109] The magnetically supported catalyst prepared by this invention can be used in the hydrogenation process of NBR rubber, SBR rubber, latex, and other materials containing unsaturated olefin double bonds. The NBR hydrogenation process is preferred. The organic solvents used in the hydrogenation process include ethers, chlorinated aromatics, and ketones, with chlorinated aromatics and ketones being preferred, and ketones such as acetone and butanone being even more preferred. The weight ratio of the rubber to the catalyst is (1-2):1, and even more preferably (1-1.5):1.

[0110] In some specific embodiments of the present invention, hydrogenation is carried out in a stirred tank or a slurry tank, preferably in a stirred tank; the hydrogenation temperature is 70–120°C, preferably 70–110°C, more preferably 70–100°C; the hydrogen pressure is 2–16 MPa, preferably 2–10 MPa, more preferably 4–8 MPa; the reaction time is 4–12 hours, preferably 4–10 hours, more preferably 4–8 hours. The reaction is carried out under stirring conditions, with a stirring speed preferably 180–600 rpm, more preferably 200–450 rpm; after the reaction, the original NBR can be converted into HNBR with a hydrogenation degree greater than 95%.

[0111] The magnetically supported catalyst of this invention can be recovered and separated after use by applying an external electromagnetic field or a permanent magnetic field, preferably using a permanent magnet. The catalyst recovery efficiency is not less than 98%, and the recovered catalyst can be reused after solvent washing.

[0112] The magnetically supported catalyst of this invention can achieve highly selective hydrogenation of double bonds in olefins such as nitrile rubber, latex, or emulsion, while having low catalyst cost, low active component content in HNBR, and long service life. It can also efficiently separate the catalyst by an external magnetic field, with high separation efficiency and simple operation. It is a convenient method for preparing HNBR by hydrogenation of NBR using magnetically supported noble metal catalysts.

[0113] The following provides some specific embodiments for more detailed illustration, wherein all numerical specifications (e.g., temperature, time, concentration, and weight, including ranges for each) are generally approximate values ​​that may be changed in increments of 0.1 or 1.0 (+) or (-). All numerical specifications are to be understood as being preceded by the term "about".

[0114] Example 1

[0115] This embodiment prepares a magnetically supported catalyst, including the following process:

[0116] 1) Preparation of Fe3O4 nanoparticles:

[0117] Add 500 mL of ethylene glycol to the reaction vessel, then add 32 g of FeCl3·6H2O, 63 g of anhydrous sodium acetate, 138 g of polyethylene glycol-6000, and 6.3 g of sodium hydroxide. Stir the mixture at 25 °C until homogeneous, then transfer it to a reaction vessel and heat it at 200 °C for 15 hours to prepare Fe3O4 nanoparticles. Cool the mixture to 25 °C, and after the reaction is complete, separate and recover the nanoparticles using a magnet, wash them, and freeze-dry them.

[0118] 2) Carbon coating:

[0119] 1.5 g of Fe3O4 nanoparticles with a particle size of 150 nm were redispersed in 500 mL of water, and then 15 mL of 20% glucose aqueous solution was added. The mixture was stirred at 25 °C for 12 hours to prepare Fe3O4@glucose magnetic nanoparticles. After the reaction, the nanoparticles were separated and recovered using a magnet, washed, and freeze-dried. The dried Fe3O4@glucose magnetic nanoparticles were then subjected to carbonization treatment at 800 °C for 3 hours under argon protection to obtain Fe3O4 nanoparticles with a 20 nm C layer coating.

[0120] 3) Coating with a dense polymer layer:

[0121] Weigh 1g of carbonized magnetic nanoparticles and disperse them again in 350mL of distilled water. Add 1.25g of polyvinylpyrrolidone and add the well-mixed reaction mixture to a reaction vessel. Heat the mixture at 180℃ for 4 hours and cool it to 25℃. After the reaction, separate and recover the mixture with a magnet, wash it, freeze dry it, and then heat treat it at 400℃ for 1 hour under nitrogen protection to complete the densification process. The thickness of the dense polymer layer is about 25nm.

[0122] 4) Loaded active components:

[0123] 1 g of densely coated Fe3O4 magnetic spheres were redispersed in 250 mL of 25% ethanol aqueous solution, and 0.021 g of the active component precursor palladium acetate was added. The mixture was stirred evenly, heated to 60 °C and reacted for 4 hours. After cooling to 15 °C, the mixture was separated and recovered using a magnet, washed, and freeze-dried to obtain the magnetically supported catalyst, denoted as Fe3O4@C@PVP@Pd.

[0124] 5) Hydrogenation reduction:

[0125] The obtained Fe3O4@C@PVP@Pd magnetically supported catalyst was reduced with hydrogen at 280℃ for 2 h. Finally, a supported Fe3O4@C@PVP@Pd catalyst with hydrogenation activity was obtained.

[0126] The catalyst was found to have a particle size of 240 nm, contain 0.01 wt% Pd, and have a specific surface area of ​​72 m². 2 / g, with a bulk density of 0.87g / cm³. 3 .

[0127] 6) Evaluation of hydrogenation degree:

[0128] Weigh 1g of NBR (grade 3304) and add it to 200g of acetone solution. Stir thoroughly until completely dissolved, then transfer the solution to a high-pressure reactor. Add 0.98g of Fe3O4@C@PVP@Pd magnetically supported catalyst to the reactor. Purify the reactor three times with 0.4MPa nitrogen and twice with 2MPa H2. React at 100℃, hydrogen pressure of 4MPa, and stirring rate of 401r / min for 6 hours. After the reaction, cool the reactor to room temperature, slowly vent, and after purging the hydrogen gas, open the reactor and take a sample. Separate the solid catalyst from the reaction solution using magnetic separation, with a catalyst recovery rate of 99.2%. Collect the solution in a reagent bottle to obtain a mixture of HNBR and acetone. Infrared analysis determined the degree of hydrogenation of HNBR to be 96.7%. Catalyst recovery rate and degree of hydrogenation are shown in Table 1.

[0129] Example 2

[0130] In this embodiment, the magnetic core used in the catalyst preparation was 1.1g of commercially available Fe3O4 with a particle size of 50nm. The coating process involved carbonizing a 20nm layer of glucose followed by coating with a 30nm layer of polyvinylpyrrolidone. The final densification treatment was a heat treatment at 450℃ for 1.5 hours. The active component was Pd+Mo, and the active precursors were 0.02g of palladium chloride (PdCl2·2H2O) and 0.99g of ammonium molybdate (NH4)2MoO4, ultimately yielding the Fe3O4@C@PVP@Pd+Mo magnetic supported catalyst.

[0131] The specific preparation process includes:

[0132] 1) Carbon coating:

[0133] 1.1 g of commercially available Fe3O4 nanoparticles with a particle size of 50 nm were dispersed in 500 mL of water, and then 10 mL of a 20% glucose aqueous solution was added. The mixture was stirred at 25 °C for 12 hours to prepare Fe3O4@glucose magnetic nanoparticles. After the reaction, the nanoparticles were separated and recovered using a magnet, washed, and freeze-dried. The dried Fe3O4@glucose magnetic nanoparticles were then subjected to carbonization treatment at 800 °C for 3 hours under argon protection to obtain Fe3O4 nanoparticles with a 20 nm C layer coating.

[0134] 2) Coating with a dense polymer layer:

[0135] Weigh 1g of carbonized magnetic nanoparticles and disperse them again in 350mL of distilled water. Add 1.05g of polyvinylpyrrolidone and add the well-mixed reaction mixture to a reaction vessel. Heat the mixture at 180℃ for 4 hours and cool it to 25℃. After the reaction is complete, separate and recover the product using a magnet, wash it, freeze dry it, and then heat treat it at 450℃ for 1.5 hours under nitrogen protection to complete the densification process. The thickness of the dense polymer layer is about 30nm.

[0136] 3) Loaded active components:

[0137] 1 g of densely coated Fe3O4 magnetic spheres were redispersed in 250 mL of 25% ethanol aqueous solution. 0.02 g of the active component precursor palladium acetate and 0.99 g of ammonium molybdate (NH4)2MoO4 were added. The mixture was stirred evenly and heated to 60 °C for 4 hours. After cooling to 15 °C, the mixture was separated and recovered using a magnet. The catalyst was washed and freeze-dried to obtain the magnetically supported catalyst, denoted as Fe3O4@C@PVP@Pd+Mo.

[0138] 4) Hydrogenation reduction:

[0139] The Fe3O4@C@PVP@Pd+Mo magnetically supported catalyst was reduced with hydrogen at 180℃ for 2 h. Finally, a supported Fe3O4@C@PVP@Pd+Mo catalyst with hydrogenation activity was obtained.

[0140] The catalyst has a particle size of 150 nm, contains 0.01 wt% Pd and 0.5 wt% Mo, and has a specific surface area of ​​95 nm. 2 / g; bulk density is 0.61g / cm³ 3 .

[0141] 5) Evaluation of hydrogenation degree:

[0142] Weigh 1g of NBR (grade 3304) and add it to 200g of acetone solution. Stir thoroughly until completely dissolved. Then, transfer the gel solution and 1g of Fe3O4@C@PVP@Pd+Mo to a high-pressure reactor. Purge with 0.4MPa nitrogen three times and 2MPa H2 twice. React at 105℃, hydrogen pressure of 2MPa, and stirring rate of 380r / min for 8 hours. Catalyst recovery and degree of hydrogenation are shown in Table 1.

[0143] Example 3

[0144] In this embodiment, the magnetic core used in the catalyst preparation is commercially available Fe3S4 with a particle size of 150 nm. The coating consists of two layers: a 15 nm layer of polyvinylpyrrolidone coating followed by carbonization at 600 °C for 3 hours, and then a second 20 nm layer of polyvinylpyrrolidone coating followed by heat treatment at 370 °C for 1 hour. The active component is Pd, resulting in the Fe3S4@C@PVP@Pd magnetic supported catalyst.

[0145] The specific preparation process includes:

[0146] 1) Carbon coating:

[0147] 1.75 g of Fe3S4 with a particle size of 150 nm was ultrasonically dispersed in 300 mL of water; 2.1 g of polyvinylpyrrolidone with a weight average molecular weight of 40,000 was weighed and added to 200 mL of deionized water, and stirred at 25 °C for 2 hours. The two solutions were then mixed and stirred for another 2 hours. Afterward, the Fe3S4@polyvinylpyrrolidone was separated and recovered using a magnet, washed, and freeze-dried. The dried Fe3S4@polyvinylpyrrolidone was then carbonized at 600 °C for 3 hours under argon protection to obtain Fe3S4 nanoparticles coated with a 15 nm thick C layer.

[0148] 2) Coating with a dense polymer layer:

[0149] 1.1g of carbonized magnetic nanoparticles were weighed and dispersed again in 350mL of distilled water. 1.25g of polyvinylpyrrolidone was added, and the well-mixed reactants were added to a reaction vessel. The mixture was heated at 180℃ for 4 hours and then cooled to 25℃. After the reaction was completed, the nanoparticles were separated and recovered using a magnet, washed, freeze-dried, and then subjected to heat treatment at 370℃ for 1 hour under argon protection to complete the densification process. The thickness of the dense polymer layer was about 20 nanometers.

[0150] 3) Loaded active components:

[0151] Weigh 1g of the double-layer coated nanoparticles prepared above and add them to 250mL of 25% ethanol aqueous solution. Add 0.21g of the active component precursor palladium acetate, stir evenly, heat to 60℃, react for 4 hours, cool to 15℃, separate and recover using a magnet, wash, freeze dry to obtain the magnetically supported catalyst, denoted as Fe3S4@C@PVP@Pd.

[0152] 4) Hydrogenation reduction:

[0153] The obtained nanoparticles were reduced with hydrogen at 280℃ for 2 hours to finally obtain the supported magnetic catalyst Fe3S4@C@PVP@Pd with hydrogenation activity.

[0154] The catalyst was found to have a particle size of approximately 240 nm, contain 0.1 wt% Pd, and have a specific surface area of ​​73 m². 2 / g; bulk density is 0.88g / cm³ 3 .

[0155] 5) Evaluation of hydrogenation degree:

[0156] 1.01 g of 3305 NBR adhesive, 200 g of acetone solution, and 0.99 g of Fe3S4@C@PVP@Pd catalyst were added to a reactor. The reactor was purged three times with 0.4 MPa nitrogen and twice with 2 MPa H2. The reaction was carried out at 95 °C, hydrogen pressure of 8 MPa, and stirring rate of 389 r / min for 10 h. The catalyst recovery rate and degree of hydrogenation are shown in Table 1.

[0157] Example 4

[0158] The magnetic core used in the catalyst preparation of this embodiment is a commercially available 200nm FeNi; the active components are Pd and Ni, and the active precursors are 0.02g palladium chloride (PdCl2·2H2O) and 1.24g nickel chloride (NiCl2·2H2O). The coating process is as follows: first, a 25nm glucose carbonization layer is coated, followed by a 30nm polyvinylpyrrolidone layer. Then, Fe3O4@C is heat-treated at 500℃ for 1 hour under an argon atmosphere, resulting in the final FeNi@C@PVP@Pd+Ni magnetic supported catalyst.

[0159] The specific preparation process includes:

[0160] 1) Carbon coating:

[0161] 1.5 g of FeNi with a particle size of 200 nm was ultrasonically dispersed in 300 mL of water; 2.1 g of polyvinylpyrrolidone with a weight average molecular weight of 40,000 was weighed and added to 200 mL of deionized water, and stirred at 25 °C for 2 hours. The two solutions were then mixed and stirred for another 2 hours. Afterward, the FeNi@polyvinylpyrrolidone was separated and recovered using a magnet, washed, and freeze-dried. The dried FeNi@polyvinylpyrrolidone was then carbonized at 600 °C for 3 hours under argon protection to obtain FeNi nanoparticles coated with a 15 nm thick C layer.

[0162] 2) Coating with a dense polymer layer:

[0163] 1.1g of carbonized magnetic nanoparticles were weighed and dispersed again in 350mL of distilled water. 1.25g of polyvinylpyrrolidone was added, and the well-mixed reactants were added to a reaction vessel. The mixture was heated at 180℃ for 4 hours and then cooled to 25℃. After the reaction was completed, the nanoparticles were separated and recovered using a magnet, washed, freeze-dried, and then subjected to heat treatment at 370℃ for 1 hour under argon protection to complete the densification process. The thickness of the dense polymer layer was about 20 nanometers.

[0164] 3) Loaded active components:

[0165] Weigh 1g of the double-layer coated nanoparticles prepared above and add them to 250mL of 25% ethanol aqueous solution. Add 0.02g of the active component precursor palladium chloride and 1.24g of nickel chloride to 10mL of 0.1mol dilute hydrochloric acid, stir evenly, add ethanol aqueous solution, react for 4 hours, separate and recover with a magnet, wash, freeze dry to obtain the magnetically supported catalyst, denoted as FeNi@C@PVP@Pd+Ni.

[0166] 4) Hydrogenation reduction:

[0167] The obtained nanoparticles were reduced with hydrogen at 280℃ for 2 hours to finally obtain the supported magnetic catalyst FeNi@C@PVP@Pd+Ni with hydrogenation activity.

[0168] The catalyst has a particle size of 310 nm, contains 0.01 wt% Pd and 0.3 wt% Ni, and has a specific surface area of ​​67 m². 2 / g; bulk density is 0.95g / cm³ 3 .

[0169] 5) Evaluation of hydrogenation degree:

[0170] Weigh 1g of NBR (grade 3304) and add it to 200g of acetone solution. Stir thoroughly until completely dissolved. Then, add 1g of FeNi@C@Pd+Ni to a high-pressure reactor. Replace the reactor three times with 0.4MPa nitrogen and twice with 2MPa H2. The reaction is carried out at 70℃, hydrogen pressure of 16MPa, and stirring rate of 380r / min for 12h. Catalyst recovery and degree of hydrogenation are shown in Table 1.

[0171] Example 5

[0172] The magnetic core used in the preparation of the catalyst in this embodiment is a commercially available 500nm Fe3O4; the active component is Pd. Due to the large particle size of the magnetic core, in order to obtain a suitable density, the magnetic core was coated with glucose once with a coating thickness of 10nm, and coated with polyvinylpyrrolidone twice with coating thicknesses of 20nm and 25nm, respectively. The heat treatment temperatures after the two polyvinylpyrrolidone coatings were 480℃ and 400℃ for 1 hour each.

[0173] Referring to the specific coating process in Examples 1-4, the specific preparation process includes:

[0174] First, a 10 nm layer of glucose was coated onto the surface of Fe3O4. After carbonization by heat treatment at 500℃ for 1 hour under an argon atmosphere, a 20 nm layer of polyvinylpyrrolidone (PVP) was applied, followed by treatment at 480℃ for 1 hour under an argon atmosphere. Then, a 25 nm layer of PVP was applied, followed by treatment at 400℃ for 1 hour under an argon atmosphere. Finally, the prepared double-layer coated nanoparticles were added to 250 mL of 25% ethanol aqueous solution, along with 0.13 g of the active component precursor palladium acetate. The mixture was stirred until homogeneous, heated to 60℃, and reacted for 4 hours. After cooling to 15℃, the nanoparticles were separated and recovered using a magnet, washed, and freeze-dried. The resulting nanoparticles were then reduced with hydrogen at 280℃ for 2 hours. This yielded a supported magnetic catalyst with hydrogenation activity, denoted as Fe3O4@C@PVP@PVP@Pd magnetic catalyst.

[0175] The catalyst was found to have a particle size of 610 nm, contain 6 wt% Pd, and have a specific surface area of ​​45.2 m². 2 / g; bulk density is 1.25g / cm³ 3 .

[0176] Weigh 1.5g of NBR (grade 3304) and add it to 201g of acetone solution. Stir thoroughly until completely dissolved. Then, add 1g of Fe3O4@C@PVP@PVP@Pd to a high-pressure reactor. The reactor is purged three times with 0.4MPa nitrogen and twice with 2MPa H2. The temperature is raised to 85℃, the hydrogen pressure is 2MPa, and the stirring rate is 380r / min. The catalyst recovery rate and degree of hydrogenation are shown in Table 1.

[0177] Example 6

[0178] In this embodiment, the magnetic core used in the catalyst preparation is commercially available Fe3S4 with a particle size of 150 nm; the active components are rhodium and ruthenium, and the active precursors are 0.39 g of rhodium chloride (RhCl3·3H2O) and 0.64 g of ruthenium chloride (RuCl3·3H2O). The reaction is carried out in a 25% aqueous ethanol solution. After the reaction, Fe3S4@PDA@Rh+Ru magnetic supported catalyst is obtained. The coating process is to first coat a 5 nm carbon layer, and then coat a 20 nm polyvinylpyrrolidone layer. The heat treatment temperature after coating is 340 °C.

[0179] Referring to the specific coating process in Examples 1-4, the specific preparation process includes:

[0180] First, a 5nm layer of glucose was coated onto the surface of 150nm Fe3S4, and then carbonized by heat treatment at 500℃ for 1 hour under an argon atmosphere. Next, a 20nm layer of polyvinylpyrrolidone was applied, followed by treatment at 340℃ for 1 hour under an argon atmosphere. Finally, the prepared double-layer coated nanoparticles were added to 250mL of 25% ethanol aqueous solution, along with 0.39g of rhodium chloride and 0.64g of ruthenium chloride. The pH was adjusted to 9.0, and the mixture was stirred at room temperature for 8 hours. The nanoparticles were then separated and recovered using a magnet, washed, and freeze-dried. This yielded a supported magnetic catalyst with hydrogenation activity, denoted as Fe3S4@C@PVP@Rh+Ru magnetic catalyst.

[0181] The catalyst has a particle size of approximately 200 nm, contains 0.1 wt% Rh and 0.3 wt% Ru, and has a specific surface area of ​​81 m². 2 / g; bulk density is 0.84g / cm³ 3 .

[0182] Weigh 2g of NBR (grade 3304) and add it to 200g of acetone solution. Stir thoroughly until completely dissolved. Then, transfer 1.01g of Fe3S4@C@PVP@Rh+Ru and the gel solution to a high-pressure reactor, and simultaneously add 10mL of a 1mol / L triphenylphosphine acetone solution. The reactor is purged three times with 0.4MPa nitrogen and twice with 2MPa H2. The temperature is raised to 120℃, the hydrogen pressure is 6MPa, and the stirring rate is 380r / min. The reaction is carried out for 4h. The catalyst recovery rate and degree of hydrogenation are shown in Table 1.

[0183] Example 7

[0184] In this embodiment, the magnetic core used in the catalyst preparation is a commercially available 200nm FeNi; the active component is Pd, and the active precursor is 3.5g palladium chloride (PdCl2·2H2O). The coating process is as follows: first, a 25nm layer of glucose is coated and carbonized, followed by a 30nm layer of polyvinylpyrrolidone coating. Then, FeNi@C is heat-treated at 500℃ for 1 hour under an argon atmosphere, resulting in the final FeNi@C@PVP@Pd magnetic support catalyst.

[0185] Referring to the specific coating process in Examples 1-4, the specific preparation process includes:

[0186] First, a 25nm glucose layer was coated onto a 150nm FeNi surface, followed by carbonization at 500℃ for 1 hour under an argon atmosphere. Then, a 20nm polyvinylpyrrolidone layer was applied. 1g of the double-layered coated nanoparticles was added to 250mL of 25% ethanol aqueous solution. 0.27g of the active component precursor palladium chloride was added to 10mL of 0.1mol dilute hydrochloric acid, stirred thoroughly, and then the ethanol aqueous solution was added. The reaction was carried out for 4 hours. The nanoparticles were separated and recovered using a magnet, washed, and freeze-dried. Finally, the obtained nanoparticles were reduced with hydrogen at 280℃ for 2 hours. The resulting supported magnetic catalyst with hydrogenation activity was obtained, denoted as FeNi@C@PVP@Pd.

[0187] The catalyst has a particle size of 310 nm, a Pd content of 2.1 wt%, and a specific surface area of ​​66 m². 2 / g; bulk density is 0.98g / cm³ 3 .

[0188] Weigh 1g of NBR (grade 3304) and add it to 200g of acetone solution. Stir thoroughly until completely dissolved. Then, add 1g of FeNi@C@PVP@Pd to a high-pressure reactor. Replace the reactor three times with 0.4MPa nitrogen and twice with 2MPa H2. The reaction is carried out at 90℃, hydrogen pressure of 5MPa, and stirring rate of 380r / min for 2 hours. Catalyst recovery and degree of hydrogenation are shown in Table 1.

[0189] Comparative Example 1

[0190] This comparative example tested a Fe3O4@C@Pd type porous magnetic catalyst. Compared with Example 1, this catalyst coated Fe3O4 with a 20 nm layer of glucose and carbonized it at 800 °C to form a porous surface structure, but no polymer dense layer was subsequently coated on it.

[0191] Because the surface was not densified, the loading of the active component Pd accounted for as high as 4.8 wt% of the catalyst weight. As shown in Table 1, despite the high loading of the active component, the hydrogenation activity was not good, only 79.6%, and 24.5% of the active component detached and entered the colloidal solution (HNBRZ). The analysis results indicate that the portion of the active component that entered the pores was encapsulated by the colloidal solution and did not play its intended role; a small portion also dissolved into the colloidal solution after hydrogenation. Therefore, although the nominal loading was high, the hydrogenation effect was not good.

[0192] Comparative Example 2

[0193] This comparative example tested a Fe3O4@C@PVP@Pd type magnetic catalyst. Compared with Example 1, this catalyst, after coating Fe3O4 with a 30nm layer of polyvinylpyrrolidone, was only dried at 60°C without high-temperature densification treatment. Table 1 shows the hydrogenation degree evaluation results, indicating a high loading of Pd active component (3wt%). However, the hydrogenation activity was not good, only 88.3%, and 8.5% of the active component detached and entered the gel. The analysis results indicate that the active component was partially encapsulated and did not play its intended role, and a small portion dissolved into the hydrogenated gel. Therefore, although the nominal loading was high, the hydrogenation effect was not good.

[0194] Comparative Example 3

[0195] This comparative example attempted to modify Example 1 by using Fe3O4 magnetic cores with an average particle size of 40 nm. Table 1 shows the hydrogenation degree evaluation results. For the 3604NBR high-viscosity system, although the hydrogenation activity was very high, reaching 99.5%, the catalyst recovery rate was only 80%. Even after several recovery attempts, it only reached 91%. This is because some magnetic core particles were too small, and due to the high viscosity of the solution, they remained in the solution, ultimately leading to a low catalyst recovery rate.

[0196] Therefore, neither porous supports nor undensified coatings can achieve the same effect as surface-densified magnetically supported catalysts. In addition, for the NBR hydrogenation process in high-viscosity systems, there is an optimal particle size for the catalyst.

[0197] Table 1 Results of hydrogenation and magnetic separation

[0198]

[0199]

[0200] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A magnetically supported catalyst, wherein, The magnetic carrier catalyst comprises a magnetic core, a compact coating layer coated on the magnetic core, and an active component supported on the compact coating layer; The compact coating layer comprises at least one compact polymer layer; The compact polymer layer is formed by coating and compacting treatment of polyvinylpyrrolidone; and the compacting treatment is a heat treatment at 180-500°C under a protective atmosphere.

2. The magnetic catalyst of claim 1, wherein, The compact coating layer comprises at least one carbon layer and at least one compact polymer layer, and the outermost layer of the compact coating layer is the compact polymer layer; The carbon layer is formed by coating and carbonization treatment of a carbon source; and the carbonization treatment is high-temperature carbonization at 600-800°C under a protective atmosphere.

3. The magnetic catalyst of claim 2, wherein, The carbon source is polyvinylpyrrolidone.

4. The magnetic catalyst support of any one of claims 1-3, wherein, The magnetic carrier catalyst has a particle size of 60 nm to 610 nm, a specific surface area of 45 m 2 / g to 95 m 2 / g, and a bulk density of 0.6 g / cm 3 to 1.25 g / cm 3 .

5. The magnetically supported catalyst of any one of claims 1-3, wherein, The loading amount of the active component accounts for 0.01wt%-6wt% of the catalyst.

6. The supported catalyst of any one of claims 1-3, wherein, The active component is selected from at least one of Pd, Rh, Ru, Ni, and Mo.

7. The supported catalyst of any of claims 1-3, wherein, The magnetic core is selected from at least one of Fe3O4, Fe3S4, and FeNi.

8. The magnetically supported catalyst of any one of claims 1-3, wherein, The particle size of the magnetic core is 50 nm-500 nm.

9. The magnetic catalyst of claim 2, wherein, The carbon source is selected from at least one of glucose, citric acid, polyacrylic acid, and polyvinyl alcohol.

10. A process for the preparation of the supported catalyst of any one of claims 1 to 9, wherein, The preparation method comprises the following steps: The magnetic core is coated with a carbon source, and then high-temperature carbonization at 600-800°C under a protective atmosphere is performed to form a carbon layer; then polyvinylpyrrolidone is coated and heat treatment at 180-500°C under a protective atmosphere is performed to form a compact polymer layer; when the particle size and density of the catalyst cannot meet the hydrogenation requirements, the coating of the carbon layer and / or the compact polymer layer is repeated for multiple times, and the outermost layer is the compact polymer layer; When the compact coating layer does not comprise the carbon layer, the step of coating the carbon layer by the carbon source is not included; The active component is supported to obtain the magnetic carrier catalyst.

11. The production method according to claim 10, wherein When the carbon source is glucose, the coating formation process of the carbon layer comprises: An organic coating layer is formed on the surface of the magnetic core by glucose hydrolysis reaction, and then high-temperature carbonization at 600-800°C for 2-4 hours under a protective atmosphere is performed to form the carbon layer.

12. The production method according to claim 11, wherein The process of forming the organic coating layer on the surface of the magnetic core by glucose hydrolysis reaction comprises: The magnetic core is added into deionized water, and then glucose is added for hydrolysis at 18-180°C for 16-24 hours; after the reaction is completed, the precipitate is separated and recovered by a magnet, and then washed and dried.

13. The production method according to claim 11 or 12, wherein, The mass ratio of the magnetic core to glucose is 1:(0.5-2.0).

14. The production method according to claim 10, wherein The coating formation process of the compact polymer layer comprises: The magnetic core or the magnetic core coated with the carbon layer is dispersed in deionized water, polyvinylpyrrolidone is added, and heating reaction is performed at 25-180°C for 2-4 hours; after being cooled to room temperature, the precipitate is separated and recovered by a magnet, and then washed and dried; and then heat treatment at 180-500°C for 1-2 hours under a protective atmosphere is performed to form the compact polymer layer.

15. The method of manufacturing according to claim 14, wherein, The mass ratio of the magnetic core or the magnetic core coated with the carbon layer to the polyvinylpyrrolidone is 1:(0.1-2).

16. The method of manufacturing according to claim 10, wherein, The loading process of the active component comprises: The magnetic core coated with a dense polymer layer is dispersed into a solvent, a precursor of an active component is added for reaction, and after the reaction, the solid is separated and recovered by a magnet, washed and dried, and the obtained solid powder is the magnetic carrier catalyst.

17. The method of making according to claim 16, wherein, The precursor of the active component is at least one of acetate, halide or ammonium salt of Pd, Rh, Ru, Ni or Mo.

18. Use of the magnetic carrier catalyst according to any one of claims 1-9 in the hydrogenation of a polymer containing unsaturated olefinic double bonds.

19. Use according to claim 18, wherein, The magnetic carrier catalyst is used in the hydrogenation of nitrile rubber.

20. The use according to claim 19, wherein, The weight ratio of nitrile rubber to the magnetic carrier catalyst is (1-2):

1.

21. The use according to claim 19, wherein, The hydrogenation is carried out in a stirred tank or slurry tank, the hydrogenation temperature is 70-120℃, the hydrogen pressure is 2-16 MPa, and the reaction time is 4-12 hours.

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