Method for hydrogenation of nitrile rubber by using magnetically supported catalyst

Abstract

The invention discloses a method for hydrogenation of nitrile rubber by using a magnetically supported catalyst. The method comprises the following steps: in the presence of a magnetically supported catalyst, hydrogenating nitrile rubber by adopting a solvent method, and then carrying out post-treatment to obtain hydrogenated nitrile rubber, wherein the magnetically supported catalyst comprises a magnetic carrier and an active component supported on the surface of the magnetic carrier; the magnetic carrier is of a core-shell structure and comprises a magnetic core and at least one compact coating layer coating the outer surface of the magnetic core. According to the method, the magnetic supported catalyst is adopted, the noble metal active component of the magnetic supported catalyst is low in supporting capacity and high in activity, complete separation and recovery can be achieved, the cost of the catalyst is greatly reduced, and the prepared hydrogenated butadiene-acrylonitrile rubber is high in purity.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts and preparation thereof, and in particular to a method for hydrogenating nitrile rubber by utilizing a magnetically supported catalyst. Background Art

[0002] Nitrile rubber (NBR) is a copolymer of butadiene and acrylonitrile. It is widely used in the fields of automobile, aviation, navigation, oil extraction, etc. due to its good air tightness, water resistance, oil resistance, temperature resistance and wear resistance. In the polymer chain structure of nitrile rubber (NBR), there are C=C and C≡N; the presence of C≡N makes the rubber have excellent properties such as oil resistance, high tensile strength and high modulus, while the presence of C=C double bond will cause hidden dangers in the rubber in terms of aging resistance and chemical corrosion resistance.

[0003] In order to improve the performance and application scope of acrylonitrile-butadiene rubber, the conventional catalytic hydrogenation method eliminates C=C double bonds, but how to remove the noble metal catalyst after hydrogenation and purify the hydrogenation product, then need to use one or more method combinations such as centrifugal, filtration and extraction and ion exchange, the process is quite cumbersome, and it is difficult to remove cleanly, not only causing the loss and waste of noble metals, and can have adverse effects on the service life and safety of hydrogenated acrylonitrile-butadiene rubber (HNBR). How to achieve efficient selective hydrogenation and carry out reliable removal of catalyst at the same time, has always been the research hotspot of large-scale production of hydrogenated acrylonitrile-butadiene rubber.

[0004] CN101703936A discloses a method for preparing a magnetically supported catalyst by loading a magnetic carrier and an active component on a long-chain organic polymer. From the preparation process, a large amount of active components are wrapped into 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 by Fe3O4@S / M; wherein Fe3O4 is a core layer, S is a shell layer carrier, and M is a main active metal and / or auxiliary metal loaded on the shell layer carrier; the active metal is one or more of Ru, Ni, Ir, Pd and Pt, and the loading amount is 1-50wt% 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 has a porous structure and a large active component loading amount, but the mesopores are easily blocked by the rubber liquid during the hydrogenation process, thereby causing most of the active components to lose their catalytic activity, so the porous system is not suitable for the hydrogenation process of nitrile rubber.

[0006] CN104785301A discloses a magnetic palladium composite catalyst and its preparation method and use. The magnetic palladium composite catalyst uses superparamagnetic Fe3O4@SiO2 microspheres as carriers, and the surface is covalently modified with amino Pd (II) particles. It is prepared by sequentially preparing Fe3O4 nanoparticles, core-shell magnetic nano microspheres Fe3O4@SiO2, Fe3O4@SiO2@APTES, and finally by loading Pd (II) particles to obtain Fe3O4@SiO2@APTES@Pd catalyst. The surface structure of the catalyst is still a porous structure, and the mesopores are easily blocked by the glue during the hydrogenation process, so that most of the active components lose their catalytic activity, so the porous system is not suitable for the hydrogenation process of nitrile rubber. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of low selective hydrogenation efficiency and difficulty in separation of nitrile rubber hydrogenation catalysts in the prior art, and to provide a magnetic-supported catalyst and a preparation method thereof and an application thereof in nitrile rubber hydrogenation. The magnetic-supported catalyst has low noble metal loading, high activity, high selectivity and high separation efficiency, and greatly reduces the cost of the catalyst.

[0008] In order to achieve the above-mentioned purpose, the present invention provides a method for hydrogenating nitrile rubber using a magnetic-supported catalyst, the method comprising: in the presence of a magnetic-supported catalyst, hydrogenating the nitrile rubber by a solvent method, and then performing post-treatment to obtain hydrogenated nitrile rubber; wherein the magnetic-supported catalyst comprises a magnetic carrier and an active component supported on the surface of the magnetic carrier; the magnetic carrier is a core-shell structure, comprising a magnetic core and at least one dense coating layer coated on the outer surface of the magnetic core.

[0009] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0010] (1) The catalyst of the present invention is a heterogeneous and recyclable magnetically supported catalyst. The magnetic carrier of the catalyst is a core-shell structure, including a magnetic core and at least one dense coating layer coated on the outer surface of the magnetic core. The coating layer is a dense non-porous structure. The active components are supported on the coating layer. The dense coating layer will not wrap a large amount of active components into the interior of the pores. The loading amount is low, but the activity is high, which greatly reduces the cost of the catalyst. Moreover, the magnetically supported catalyst of the present invention can be reused, is easy to recycle, and has a high separation efficiency.

[0011] (2) The magnetically supported catalyst prepared by the present invention can achieve highly selective hydrogenation of nitrile rubber while greatly reducing the cost of the catalyst. The prepared hydrogenated nitrile rubber contains low active components and has a long service life. At the same time, the catalyst can be efficiently separated by an external magnetic field, with high separation efficiency and simple operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a TEM image of the Fe3O4@C@PVP@Pd magnetically supported catalyst prepared in Preparation Example 2 of the present invention;

[0013] Figure 2 This is a TEM image of the Fe3O4@PDA@Pd magnetically supported catalyst prepared in Preparation Example 16 of the present invention. DETAILED DESCRIPTION

[0014] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0015] The present invention provides a method for hydrogenating nitrile rubber using a magnetically supported catalyst, the method comprising: in the presence of a magnetically supported catalyst, subjecting the nitrile rubber to a hydrogenation reaction to obtain a reaction liquid, and then subjecting the reaction liquid to post-treatment to obtain hydrogenated nitrile rubber; wherein the magnetically supported catalyst comprises a magnetic carrier and an active component supported on the surface of the magnetic carrier; wherein the magnetic carrier is a core-shell structure, comprising a magnetic core and at least one dense coating layer coated on the outer surface of the magnetic core.

[0016] The catalyst of the present invention is a heterogeneous and recyclable magnetically supported catalyst. The magnetic carrier of the catalyst is a core-shell structure, including a magnetic core and at least one dense coating layer coated on the outer surface of the magnetic core. The coating layer is a dense pore-free structure. The active components are supported on the coating layer. The dense coating layer will not wrap a large amount of active components into the pores. Under the premise of a low active component loading, it still has an excellent hydrogenation effect. Under the condition of the same hydrogenation activity, the cost of the catalyst is reduced.

[0017] The magnetically supported catalyst of the present invention can be reused, is convenient to recycle, and has high separation efficiency.

[0018] In the present invention, a dense coating layer is coated on the surface of the magnetic core, and then active sites are formed in situ on the dense coating layer through chemical bonding between the coating and the active component elements to support the noble metal active hydrogenation component. The catalyst carrier of the present invention is a dense non-porous structure, not a conventional porous structure, so that the content of active components supported by the catalyst is low. However, since the particle size of the catalyst is nanometer-level, the hydrogenation effect is close to that of conventional catalysts, which greatly reduces the cost of the catalyst.

[0019] In some embodiments of the present invention, the coating layer is selected from polydopamine and / or polyvinyl pyrrolidone.

[0020] The coating of the present invention includes at least one layer, which can be a single coating layer, for example, a polydopamine coating layer or a polyvinyl pyrrolidone coating layer; or a multi-layer coating layer, such as a two-layer coating layer, the first layer is polydopamine, and the second layer is polyvinyl pyrrolidone.

[0021] In some embodiments of the present invention, the coating layer has a dense non-porous structure.

[0022] The coating layer of the magnetically supported catalyst of the present invention is a dense non-porous structure, and the active components are supported on the dense coating layer, which does not cause a large amount of active components to enter the interior of the carrier, thereby reducing the catalyst efficiency. The prepared catalyst has a low loading amount of noble metal active components, but due to its nano-distribution, it has high activity, which greatly reduces the cost of the catalyst.

[0023] The coating layer of the present invention has a dense surface structure. Transmission electron microscopy has proved that the coating layer has a dense non-porous structure, which can reduce the entry of active components or other components into the pores, saving costs and preventing other components from entering the pores to cause pore blockage, thereby affecting catalytic efficiency.

[0024] In some embodiments of the present invention, the coating layer has a thickness of 10-50 nm, preferably 10-30 nm.

[0025] In the present invention, the magnetic core is selected from a substance having magnetism, and there is no special limitation here. Any substance that can provide magnetism and is beneficial to improving separation efficiency can be used in the present invention, and preferably a substance having ferromagnetism.

[0026] In some embodiments of the present invention, an activated carbon layer is further contained between the magnetic core and the coating layer.

[0027] In the present invention, the addition of the activated carbon layer is used to adjust the final density of the catalyst to achieve uniform distribution of catalyst particles during the hydrogenation process.

[0028] In some embodiments of the present invention, the magnetic core is selected from one or more of Fe3O4, Fe3S4 and FeNi.

[0029] In the present invention, the magnetic core is a magnetic nanoparticle.

[0030] In some embodiments of the present invention, the average particle size of the selected magnetic core is 50-500 nm, preferably 60-400 nm.

[0031] In some embodiments of the present invention, the content of the active component is 0.01-1 wt %, preferably 0.02-0.5 wt %, based on the total amount of the magnetically supported catalyst.

[0032] In some embodiments of the present invention, the active component includes a noble metal component and an optional non-noble metal component, wherein the noble metal component is selected from one or more of Pd, Rh, Pt and Ru, and the non-noble metal component is selected from Ni and / or Mo.

[0033] In some embodiments of the present invention, the mass ratio of the precious metal component to the non-precious metal component is 1:0-1.

[0034] In some embodiments of the present invention, the average particle size of the magnetically supported catalyst is 50-500 nm, preferably 200-400 nm.

[0035] In some embodiments of the present invention, the specific surface area of ​​the magnetic carrier is 45-100m 2 / g, preferably 50-90m 2 / g.

[0036] In some embodiments of the present invention, the bulk density of the magnetic carrier is 0.6-1.25 g / cm 3 , preferably 0.7-1.1 g / cm 3 .

[0037] In some embodiments of the present invention, the method for preparing the magnetically supported catalyst comprises:

[0038] Coating at least one dense coating layer on the surface of the magnetic nanoparticles to obtain a magnetic carrier with a core-shell structure, wherein the magnetic nanoparticles are cores and the coating layer is a shell;

[0039] An active component precursor is loaded on the outer surface of the dense coating layer in the magnetic carrier to obtain a catalyst precursor, which is then reduced to obtain a magnetically supported catalyst.

[0040] The method of the present invention uses nano magnetic particles such as Fe3O4 as a magnetic core, then prepares a dense coating layer on the surface of the magnetic core, and then forms active sites on the dense coating layer through chemical bonding between the coating layer and the active component elements to load the precious metal active hydrogenation component. The loading amount is low, but the activity is high, the dosage is low, the catalyst can be completely recovered, and the cost of the catalyst is greatly reduced.

[0041] The coating method of the present invention is not specifically limited, and any preparation method that can ultimately form a densely structured coating layer on the surface of the magnetic core can be adopted. Different methods can be used according to different coating layers, including but not limited to: hydrolysis method, reduction method or layered assembly method.

[0042] According to a particularly preferred embodiment of the present invention, the specific coating steps of the coating method of the present invention are described by taking homemade or commercially available 50-300 nm Fe3O4 as a magnetic core as an example. The coating methods are as follows:

[0043] Preparation of Fe3O4@PDA: Tris was dissolved in deionized water to prepare a buffer solution with a pH of 8-9, and Fe3O4 was added for ultrasonic dispersion; dopamine hydrochloride was then added to form a mixed solution, and the solution was stirred at room temperature for reaction; after the reaction, the solution was separated from the solid by a magnet, and the obtained black solid was washed three times with deionized water and twice with ethanol, dried at 40-80°C, and then treated at 350-400°C under argon protection to obtain polydopamine-coated Fe3O4.

[0044] Preparation of Fe3O4@PVP: Polyvinyl pyrrolidone and Fe3O4 were dissolved in deionized water, first stirred at high speed, then stirred at low speed, and then stirred at high speed, washed three times with deionized water, then washed twice with ethanol, dried at 40-80°C, and then treated at 350-420°C under argon protection to obtain Fe3O4 coated with polyvinyl pyrrolidone.

[0045] The above coating method can be scaled up, and in addition to the above coating method, other well-known preparation methods can also be used.

[0046] In the present invention, when the coating layer is two or more layers, a layer-by-layer coating method is adopted, that is, the first layer is coated and then the second layer is coated, and the steps of the second layer are the same as those of the first layer.

[0047] Before coating the dense coating layer, the preparation method of the present invention further comprises: coating at least one activated carbon layer on the surface of the magnetic nanoparticles. The method is described by taking Fe3O4 magnetic core as an example. The specific steps are as follows:

[0048] Preparation of Fe3O4@C: Fe3O4 and glucose are added to deionized water and ultrasonically mixed; the mixed solution is transferred to a reactor and reacted at 160-200°C; after the reactor is cooled to room temperature, the black solid is separated by magnetic separation; finally, the black solid is washed three times with deionized water and twice with ethanol, dried at 40-80°C, and then carbonized at 450-550°C under argon protection to obtain activated carbon-coated Fe3O4, namely Fe3O4@C.

[0049] After coating the activated carbon, a dense coating layer is coated to obtain Fe3O4@C@PDA or Fe3O4@C@PVP. For details, please refer to the above coating method and will not be repeated here.

[0050] The present invention combines the coating process of Fe3O4 or Fe3O4@C with PDA or PVP once or multiple times, and then performs a heat treatment of the obtained powder at 150-400°C according to the concentration of the colloid to be hydrogenated, so that a final dense structure with a suitable specific surface area and a bulk density can be formed. The appropriate particle size and bulk density are crucial for the uniform dispersion of the catalyst in a stirred tank or a slurry tank. Too small or too large a particle size and bulk density are particularly important for the distribution of the catalyst in the entire reaction zone during the hydrogenation process, which can be reflected in the following preparation examples and comparative examples.

[0051] The loading method of the present invention is not specifically limited, and any preparation method that can ultimately form active points of several nanometers to tens of nanometers on the surface of the dense coating layer can be adopted. Different methods can be used according to different supports, including but not limited to: in-situ synthesis method, in-situ reduction method or impregnation method, and in-situ synthesis method or in-situ reduction method is preferred.

[0052] The method of the present invention can obtain a catalyst with a dense structure, so that the loading amount of the noble metal is reduced by several times or dozens of times compared with that of the porous supported catalyst, thereby greatly reducing the cost of the catalyst.

[0053] In some embodiments of the present invention, the loading method is an in-situ synthesis method, specifically comprising: washing Fe3O4@PDA with hydrochloric acid, deionized water and ethanol respectively; then adding ethanol and stirring evenly; then adding palladium chloride solution to the mixture at a ratio of 1:15-20 under stirring, and continuing to stir evenly; then adding ascorbic acid to the mixture at a ratio of 1:50-70, continuing the reaction, separating with a magnet to obtain a solid phase and a liquid phase; then washing the solid phase and vacuum drying to obtain a magnetic palladium catalyst.

[0054] In some preferred embodiments of the present invention, the loading of the active component specifically includes: dispersing the densely coated magnetic carrier into an inorganic solvent or an organic solvent, adding an active component precursor, adding a pH adjuster, stirring evenly, heating to 30-120°C, reacting for 4-10 hours, cooling to 12-35°C, and after the reaction is completed, separating and recovering with a magnet, washing and freeze-drying to obtain a solid powder, which is the desired magnetically supported catalyst.

[0055] It should be emphasized that if a non-rhodium catalyst is used as the active component, a 200-400°C hydrogen reduction step is required. This is a well-known operation and is not specifically described here.

[0056] In some embodiments of the present invention, the reduction treatment conditions include: using hydrogen as the reducing gas, the reducing pressure is 0.5-1.5 MPa, and the reducing temperature is 250-400°C.

[0057] Before the reduction treatment, the method further includes: re-separating and recovering the catalyst precursor, washing and freeze-drying the catalyst precursor.

[0058] In some embodiments of the present invention, the active component precursor includes a noble metal component precursor and an optional non-noble metal component precursor.

[0059] Preferably, the noble metal component precursor is selected from one or more soluble salts of Pd, Rh, Pt and Ru.

[0060] Preferably, the non-noble metal component precursor is selected from one or more soluble salts of Ni and Mo.

[0061] In the present invention, soluble salts include but are not limited to hydrochlorides, nitrates, acetates and sulfates, for example, the precious metal component precursor can be selected from palladium chloride, rhodium chloride, chloroplatinic acid, ruthenium chloride; the non-precious metal component precursor can be selected from nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, molybdenum chloride, molybdenum nitrate, molybdenum acetate, molybdenum sulfate and molybdate.

[0062] The invention provides a convenient method for preparing hydrogenated nitrile rubber by hydrogenating nitrile rubber using a magnetically supported noble metal catalyst.

[0063] The magnetically supported catalyst of the present invention can be used to meet the different requirements of different brands of nitrile rubber on the catalyst system by utilizing the different formulations and the particle sizes of the catalyst, and can efficiently separate and reuse the catalyst through an external magnetic field while realizing the highly selective hydrogenation of the olefin double bonds of the nitrile rubber. The magnetically supported catalyst of the present invention has a dense coating layer, and the loading amount of the active component is greatly reduced. However, since the active component of the catalyst is only a few or a dozen nanometers, and the catalyst is evenly distributed in the rubber solution, the catalyst cost is low; at the same time, since the separation efficiency of the catalyst is high, the residue is low or even no residue, the obtained hydrogenated nitrile rubber (HNBR) product is of high quality.

[0064] In some embodiments of the present invention, the weight ratio of the nitrile rubber to the magnetically supported catalyst is 1-2:1, preferably 1-1.5:1.

[0065] In some embodiments of the present invention, the conditions of the hydrogenation reaction include: hydrogen pressure of 0.5-16MPa, preferably 2-10MPa, more preferably 4-8MPa; reaction temperature of 50-120°C, preferably 60-110°C, more preferably 70-100°C; reaction time of 2-12h, preferably 2-8h, more preferably 2-4h.

[0066] In some embodiments of the present invention, the hydrogenation reaction is carried out under stirring conditions, and the stirring speed is 180-600 rpm, preferably 200-450 rpm.

[0067] In the present invention, the hydrogenation method is carried out in an organic solvent, and the organic solvent is selected from one or more of chlorinated aromatics, ketones and ethers, preferably chlorinated aromatics and ketones. Among them, chlorinated aromatics include but are not limited to: chlorobenzene; ketones include but are not limited to: acetone, butanone, pentanone, etc.

[0068] In some embodiments of the present invention, the post-treatment includes: magnetically separating the reaction liquid, recovering and reusing the separated catalyst; and obtaining a hydrogenated nitrile rubber product by precipitating, deliquoring and curing the separated rubber liquid.

[0069] The present invention can recover and separate the catalyst by applying an external magnetic field, and the efficiency of magnetic separation can reach more than 98%.

[0070] In some embodiments of the present invention, the degree of hydrogenation of the hydrogenated nitrile rubber is above 95%.

[0071] The present invention is described in detail below through preparation examples and examples, but the protection scope of the present invention is not limited to the following description.

[0072] In the following preparation examples, embodiments and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if no manufacturer is specified, are conventional products that can be obtained through commercial channels.

[0073] Preparation Example 1

[0074] A method for preparing a supported Fe3O4@C@PVP@Pd magnetic catalyst comprises the following steps:

[0075] (1) Preparation of magnetic carrier: 1 g of Fe3O4 nanopowder with an average particle size of 400 nm and 2.7 g of glucose were added to 120 mL of deionized water and mixed by ultrasonication for 10 min. The obtained mixture was transferred to a 200 mL reactor and reacted at 180°C for 4 h. After the reactor was cooled to room temperature, the black solid was separated by magnetic separation. Finally, the black solid was washed three times with deionized water and twice with ethanol, and dried at 60°C to obtain the product. Then, it was carbonized at 500°C for 4 h under argon protection to obtain Fe3O4@C. 1 g of polyvinyl pyrrolidone and 1.6 g of Fe3O4@C were weighed and dissolved in 300 mL of deionized water, and stirred at 800 rpm for 1 h. Subsequently, after continuing to stir at 300 rpm for 3 h, the mixture was washed three times with deionized water and twice with ethanol, dried at 60 °C, and treated at 390 °C for 4 h under argon protection to obtain a Fe3O4@C@PVP magnetic carrier.

[0076] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@C@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 10 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, perform ultrasonication for 10 min, and then place the impregnated sample at 60°C to dry. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@C@PVP@Pd magnetic catalyst. The TEM image of the catalyst is as follows: Figure 1 As shown, from Figure 1 It can be seen that the particle size of the magnetically supported catalyst is about 500 nm, the thickness of the coating layer is about 30 nm, and the active component particles are about 5-10 nm, which are evenly distributed on the coating surface.

[0077] The Fe3O4@C@PVP@Pd magnetic catalyst has a coating layer of polyvinyl pyrrolidone, the thickness of which is about 30 nm; the active component is Pd, and the content of Pd is 0.01 wt%. The average particle size of the magnetic catalyst is 500 nm, and the specific surface area is 69.1 m 2 / g; bulk density is 0.86g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0078] Preparation Example 2

[0079] A method for preparing a supported Fe3O4@C@PVP@Pd magnetic catalyst comprises the following steps:

[0080] (1) Preparation of magnetic carrier: 1 g of Fe3O4 nanopowder with an average particle size of 200 nm and 2.3 g of glucose were added to 120 mL of deionized water and mixed by ultrasonication for 10 min. The resulting mixture was transferred to a 200 mL reactor and reacted at 180°C for 4 h. After the reactor was cooled to room temperature, the black solid was separated by magnetic separation. Finally, the black solid was washed three times with deionized water and twice with ethanol, and dried at 60°C to obtain the product. Then, the product was carbonized at 550°C for 4 h under argon protection to obtain Fe3O4@C. 1 g of polyvinyl pyrrolidone and 1.2 g of Fe3O4@C were weighed and dissolved in 250 mL of deionized water and stirred at 700 rpm for 1 h. Subsequently, after continuing to stir at 300 rpm for 3 h, the mixture was washed three times with deionized water and twice with ethanol, dried at 60 °C, and treated at 380 °C for 4 h under argon protection to obtain a Fe3O4@C@PVP magnetic carrier.

[0081] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@C@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 50 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1.5 MPa and 250°C for 1.5 h to obtain a supported Fe3O4@C@PVP@Pd magnetic catalyst.

[0082] The Fe3O4@C@PVP@Pd magnetic catalyst has a coating layer of polyvinyl pyrrolidone with a thickness of 40 nm, an active component of Pd with a Pd content of 0.5 wt %. The average particle size of the magnetic catalyst is 260 nm and the specific surface area is 65.2 m 2 / g; bulk density is 0.89g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0083] Preparation Example 3

[0084] A method for preparing a supported Fe3O4@C@PVP@Pd magnetic catalyst comprises the following steps:

[0085] (1) Preparation of magnetic carrier: 1 g of Fe3O4 with an average particle size of 50 nm and 1.5 g of glucose were added to 120 mL of deionized water and mixed evenly by ultrasonication for 10 min; the obtained mixed solution was transferred to a 200 mL reactor and reacted at 180°C for 4 h; after the reactor was cooled to room temperature, the black solid was separated by magnetic separation; finally, the black solid was washed three times with deionized water and twice with ethanol, and dried at 60°C to obtain the product, which was then carbonized and densified to obtain Fe3O4@C; 1 g of Fe3O4@C was weighed and dispersed in 350 mL of distilled water, 1.25 g of polyvinyl pyrrolidone was added, and the mixed reactants were added to the reactor, heated at 180°C for 4 h, cooled to 25°C, separated and recovered by magnet after the reaction, washed, freeze-dried, and then heat-treated at 400°C for 1 h under nitrogen protection, and finally densified to obtain Fe3O4@C@PVP magnetic carrier;

[0086] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@C@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 100 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 0.5 MPa and 400°C for 2 h to obtain a supported Fe3O4@C@PVP@Pd magnetic catalyst.

[0087] The Fe3O4@C@PVP@Pd magnetic catalyst has a coating layer of polyvinyl pyrrolidone with a thickness of 50 nm, an active component of Pd with a Pd content of 1 wt %. The average particle size of the magnetic catalyst is 110 nm and the specific surface area is 90.1 m 2 / g; bulk density is 0.63g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0088] Preparation Example 4

[0089] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of polyvinyl pyrrolidone added in step (1) was different, which was 0.8 g of polyvinyl pyrrolidone in this example.

[0090] The Fe3O4@C@PVP@Pd magnetic catalyst has a coating layer of polyvinyl pyrrolidone with a thickness of 20 nm, an active component of Pd with a Pd content of 0.01 wt %. The average particle size of the magnetic catalyst is 490 nm, the Pd content is 0.01 wt %, and the specific surface area is 78.2 m 2 / g; bulk density is 0.79g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0091] Preparation Example 5

[0092] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of polyvinyl pyrrolidone added in step (1) was different, which was 1.5 g polyvinyl pyrrolidone in this example.

[0093] The Fe3O4@C@PVP@Pd magnetic catalyst has a coating layer of polyvinyl pyrrolidone with a thickness of 50nm; the active component is Pd with a Pd content of 0.01wt%. The average particle size of the catalyst is 520nm, the Pd content is 0.01wt%, and the specific surface area is 69.2m 2 / g; bulk density is 0.82g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0094] Preparation Example 6

[0095] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of polyvinyl pyrrolidone added in step (1) was different, which was 0.5 g of polyvinyl pyrrolidone in this example.

[0096] The Fe3O4@C@PVP@Pd magnetic catalyst has a coating layer of polyvinyl pyrrolidone with a thickness of 10 nm, an active component of Pd with a Pd content of 0.01 wt %. The average particle size of the catalyst is 480 nm, the Pd content is 0.01 wt %, and the specific surface area is 70.8 m 2 / g; bulk density is 0.83g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0097] Preparation Example 7

[0098] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 20 mL of 0.01 mol / L palladium chloride was added dropwise to the aforementioned dispersion.

[0099] The active component of the magnetic catalyst is Pd, and the content of Pd is 0.02wt%. The specific surface area of ​​the catalyst is 67.4m 2 / g; bulk density is 0.85g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0100] Preparation Example 8

[0101] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 100 mL of 0.01 mol / L palladium chloride was added dropwise to the aforementioned dispersion.

[0102] The active component of the magnetic catalyst is Pd, and the content of Pd is 0.1wt%. The specific surface area of ​​the catalyst is 69.2m 2 / g; bulk density is 0.86g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0103] Preparation Example 9

[0104] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 500 mL of 0.01 mol / L palladium chloride was added dropwise to the aforementioned dispersion.

[0105] The active component of the magnetic catalyst is Pd, and the content of Pd is 0.5wt%. The specific surface area of ​​the catalyst is 72.5m 2 / g; bulk density is 0.83g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0106] Preparation Example 10

[0107] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 1 L of 0.01 mol / L palladium chloride was added dropwise to the aforementioned dispersion.

[0108] The active component of the magnetic catalyst is Pd, and the content of Pd is 1wt%. The specific surface area of ​​the catalyst is 71.5m 2 / g; bulk density is 0.82g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0109] Preparation Example 11

[0110] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 50 mL of 0.01 mol / L palladium chloride was added dropwise to the aforementioned dispersion.

[0111] The active component of the magnetic catalyst is Pd, and the content of Pd is 0.05wt%. The specific surface area of ​​the catalyst is 73.4m 2 / g; bulk density is 0.86g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0112] Preparation Example 12

[0113] The supported Fe3O4@C@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 2 L of 0.01 mol / L palladium chloride was added dropwise to the aforementioned dispersion.

[0114] The active component of the magnetic catalyst is Pd, and the content of Pd is 2wt%. The specific surface area of ​​the catalyst is 73.5m 2 / g; bulk density is 0.89g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0115] Preparation Example 13

[0116] A supported magnetic catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 20 mL of 0.01 mol / L rhodium chloride was added dropwise to the aforementioned dispersion. At the same time, a certain amount of triphenylphosphine was added during hydrogen reduction, and the added amount was Fe3O4@C@PVP@Rh:triphenylphosphine = 1:1, to obtain a supported Fe3O4@C@PVP@Rh magnetic catalyst.

[0117] The active component of the magnetic catalyst is Rh, and the content of Rh is 0.02wt%. The specific surface area of ​​the catalyst is 71.2m 2 / g; bulk density is 0.83g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0118] Preparation Example 14

[0119] The magnetically supported catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 10 mL of 0.01 mol / L platinum chloride was added dropwise to the aforementioned dispersion to obtain a supported Fe3O4@C@Pt magnetically supported catalyst.

[0120] The active component of the magnetic catalyst is Pt, and the content of Pt is 0.02wt%. The specific surface area of ​​the catalyst is 72.6m 2 / g; bulk density is 0.82g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0121] Preparation Example 15

[0122] The magnetically supported catalyst was prepared according to the method of Preparation Example 1, except that the amount of palladium chloride added in step (2) was different. In this example, 20 mL of 0.01 mol / L ruthenium chloride was added dropwise to the aforementioned dispersion to obtain a supported Fe3O4@C@PVP@Ru magnetically supported catalyst.

[0123] The active component of the magnetic catalyst is Ru, and the content of Ru is 0.02wt%. The specific surface area of ​​the catalyst is 73.5m 2 / g; bulk density is 0.81g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0124] Preparation Example 16

[0125] A method for preparing a supported Fe3O4@PDA@Pd magnetic catalyst comprises the following steps:

[0126] (1) Preparation of magnetic carrier: 1.2 g of tris(hydroxymethyl)aminomethane (Tris) was weighed and added to 600 mL of deionized water to dissolve to prepare a pH = 8.5 buffer solution, and 1 g of Fe3O4 with an average particle size of 390 nm was added and ultrasonically dispersed for 2 h; then 1.2 g of dopamine hydrochloride was added to form a mixed solution, which was stirred at room temperature for 6 h; after the reaction was completed, the solution and the solid were separated by a magnet, and the obtained black solid was washed three times with deionized water and twice with ethanol, dried at 60°C, and treated at 380°C for 2 h under argon to obtain Fe3O4@PDA magnetic carrier;

[0127] (2) Preparation of catalyst: 1 g of the Fe3O4@PDA magnetic carrier prepared in step (1) was weighed and dispersed in acetone, 20 mL of 0.01 mol / L palladium chloride was added dropwise to the above dispersion, ultrasonicated for 10 min, and then the impregnated sample was dried at 60°C; the dried sample was reduced with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@PDA@Pd magnetic catalyst. The TEM image of the catalyst is as follows: Figure 2 As shown, from Figure 2 It can be seen that the particle size of the magnetically supported catalyst is about 500 nm, the thickness of the coating layer is about 50 nm, and the active component particles are about 10 nm, which are evenly distributed on the coating surface.

[0128] The coating layer of the magnetic catalyst is polydopamine, the thickness of the coating layer is 50nm, the active component is Pd, and the content of Pd is 0.02wt%. The average particle size of the catalyst is 450nm, and the specific surface area is 69.1m 2 / g; bulk density is 0.83g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0129] Preparation Example 17

[0130] A method for preparing a supported Fe3O4@PVP@Pd magnetic catalyst comprises the following steps:

[0131] (1) Preparation of magnetic carrier: 1 g of polyvinyl pyrrolidone and 1.6 g of Fe3O4 with an average particle size of 400 nm were weighed and dissolved in 300 mL of deionized water, and stirred at 800 rpm for 1 h. Subsequently, after stirring at 300 rpm for 3 h, the mixture was washed three times with deionized water and twice with ethanol, dried at 60 ° C, and treated at 390 ° C for 4 h under argon protection to obtain Fe3O4@PVP magnetic carrier;

[0132] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@PVP@Pd magnetic catalyst.

[0133] The coating layer of the magnetic catalyst is polyvinyl pyrrolidone, the thickness of the coating layer is 50nm, the active component is Pd, and the content of Pd is 0.02wt%. The average particle size of the catalyst is 430nm, and the specific surface area is 71.2m 2 / g; bulk density is 0.83g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0134] Preparation Example 18

[0135] A method for preparing a supported Fe3O4@C@PDA@Pd magnetic catalyst comprises the following steps:

[0136] (1) Preparation of magnetic carrier: First, Fe3O4@C was prepared according to step (1) of the method of Preparation Example 1; 1 g of Fe3O4@C was weighed and dispersed in acetone, and then 1.2 g of tris(hydroxymethyl)aminomethane (Tris) was weighed and added to 600 mL of deionized water to dissolve to prepare a pH=8.5 buffer solution; then 1.2 g of dopamine hydrochloride was added to form a mixed solution, and stirred at room temperature for 6 h; after the reaction was completed, the solution and the solid were separated by a magnet, and the obtained black solid was washed three times with deionized water and twice with ethanol, dried at 60°C, and treated at 380°C for 2 h under argon to obtain Fe3O4@C@PDA magnetic carrier;

[0137] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@C@PDA magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@C@PDA@Pd magnetic catalyst.

[0138] The coating layer of the magnetic catalyst is polydopamine (PDA), the thickness of the coating layer is 30nm, the active component is Pd, and the content of Pd is 0.02wt%. The average particle size of the catalyst is 410nm, and the specific surface area is 72.6m 2 / g; bulk density is 0.79g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0139] Preparation Example 19

[0140] A method for preparing a supported Fe3O4@C@PVP@Pd magnetic catalyst comprises the following steps:

[0141] (1) Preparation of magnetic carrier: First, Fe3O4@C was prepared according to step (1) of the method of Preparation Example 1; 1 g of Fe3O4@C was weighed and dispersed in acetone, 1 g of polyvinyl pyrrolidone and 1.6 g of Fe3O4@C were weighed and dissolved in 300 mL of deionized water, and stirred at 800 rpm for 1 h. Subsequently, after stirring at 300 rpm for 3 h, the mixture was washed three times with deionized water and twice with ethanol, dried at 60°C, and treated at 390°C for 4 h under argon protection to obtain Fe3O4@C@PVP magnetic carrier;

[0142] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@C@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@C@PVP@Pd magnetic catalyst.

[0143] The coating layer of the magnetic catalyst is polyvinyl pyrrolidone (PVP), the thickness of the coating layer is 20nm, the active component is Pd, and the content of Pd is 0.02wt%. The average particle size of the catalyst is 400nm, and the specific surface area is 73.4m 2 / g; bulk density is 0.78g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0144] Preparation Example 20

[0145] A method for preparing a supported Fe3S4@C@PDA@Pd magnetic catalyst comprises the following steps:

[0146] (1) Preparation of magnetic carrier: 1 g Fe3S4 and 3 g glucose were added to 150 mL deionized water and mixed by ultrasonic for 10 min; the obtained mixed solution was transferred to a 200 mL reactor and reacted at 180°C for 4 h; after the reactor was cooled to room temperature, a black solid was separated by magnetic separation; finally, the black solid was washed three times with deionized water and twice with ethanol, and dried at 60°C to obtain a product, which was then carbonized at 500°C for 4 h under argon protection, and then PDA surface densification coating was performed according to the steps of Preparation Example 18 to obtain Fe3S4@C@PDA magnetic carrier;

[0147] (2) Preparation of catalyst: Weigh 1 g of the Fe3S4@C@PDA magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3S4@C@PDA@Pd magnetic catalyst.

[0148] The magnetic core of the magnetic catalyst is Fe3S4 with an average particle size of 350nm; the coating layer is polydopamine with a thickness of 40nm; the active component is Pd with a Pd content of 0.02wt%. The average particle size of the catalyst is 430nm and the specific surface area is 72.1m 2 / g; bulk density is 0.82g / cm3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0149] Preparation Example 21

[0150] A method for preparing a supported Fe3S4@PDA@Pd magnetic catalyst comprises the following steps:

[0151] (1) Preparation of magnetic carrier: 1.2 g of tris(hydroxymethyl)aminomethane (Tris) was weighed and added to 600 mL of deionized water to dissolve to prepare a pH = 8.5 buffer solution, and 1 g of Fe3S4 was added and ultrasonically dispersed for 2 h; then 1.3 g of dopamine hydrochloride was added to form a mixed solution, which was stirred at room temperature for 6 h; after the reaction was completed, the solution and the solid were separated by a magnet, and the obtained black solid was washed three times with deionized water and twice with ethanol, dried at 60°C, and treated at 380°C for 2 h under argon to obtain Fe3S4@PDA magnetic carrier;

[0152] (2) Preparation of catalyst: Weigh 1 g of the Fe3S4@PDA magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3S4@PDA@Pd magnetic catalyst.

[0153] The magnetic core of the magnetic catalyst is Fe3S4 with an average particle size of 350nm; the coating layer is polydopamine with a thickness of 30nm; the active component is Pd with a Pd content of 0.02wt%. The average particle size of the catalyst is 410nm and the specific surface area is 71.6m 2 / g; bulk density is 0.82g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0154] Preparation Example 22

[0155] A method for preparing a supported FeNi@C@PVP@Pd magnetic catalyst comprises the following steps:

[0156] (1) Preparation of magnetic carrier: 1 g FeNi and 2.6 g glucose were added to 120 mL deionized water and mixed by ultrasonic for 10 min; the obtained mixed solution was transferred to a 200 mL reactor and reacted at 180° C. for 4 h; after the reactor was cooled to room temperature, a black solid was separated by magnetic separation; finally, the black solid was washed three times with deionized water and twice with ethanol, and dried at 60° C. to obtain a product, which was then carbonized at 500° C. for 4 h under argon protection to obtain FeNi@C; and then PVP densification was performed according to the steps of Preparation Example 19 to obtain a FeNi@C@PVP magnetic carrier;

[0157] (2) Preparation of catalyst: Weigh 1 g of the FeNi@C@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported FeNi@C@PVP@Pd magnetic catalyst.

[0158] The magnetic core of the magnetic catalyst is FeNi, with an average particle size of 400nm; the coating layer is polyvinyl pyrrolidone, with a thickness of 40nm; the active component is Pd, and the content of Pd is 0.02wt%. The average particle size of the magnetic catalyst is 480nm, and the specific surface area is 70.6m 2 / g; bulk density is 0.82g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0159] Preparation Example 23

[0160] A method for preparing a supported Fe3O4@C@PVP@Pd+Ni magnetic catalyst comprises the following steps:

[0161] (1) Preparation of magnetic carrier: First, Fe3O4@C@PVP magnetic carrier was prepared according to step (1) of the method of Preparation Example 1;

[0162] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@C@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 18 mL of 0.01 mol / L palladium chloride and 3.6 mL of 0.01 mol / L nickel chloride dropwise into the above dispersion. Ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@C@PVP@Pd+Ni magnetic catalyst.

[0163] The magnetic core of the magnetic catalyst is Fe3O4 with an average particle size of 360nm; the coating layer is activated carbon and polyvinyl pyrrolidone with a thickness of 20nm; the active components are Pd and Ni, and the total content of Pd and Ni is 0.02wt%, wherein the mass ratio of Pd to Ni is 9:1. The average particle size of the catalyst is 400nm and the specific surface area is 73.2m 2 / g; bulk density is 0.0.79g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0164] Preparation Example 24

[0165] A method for preparing a supported Fe3O4@PDA@Pd+Ni magnetic catalyst comprises the following steps:

[0166] (1) Preparation of magnetic carrier: First, Fe3O4@PDA magnetic carrier was prepared according to step (1) of the method of Preparation Example 16;

[0167] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@PDA magnetic carrier prepared in step (1) and disperse it in acetone. Add 10 mL of 0.01 mol / L palladium chloride and 18 mL of 0.01 mol / L nickel chloride dropwise into the above dispersion. Ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@PDA@Pd+Ni magnetic catalyst.

[0168] The magnetic core of the magnetic catalyst is Fe3O4 with an average particle size of 350nm; the coating layer is polydopamine (PDA) with a thickness of 20nm; the active components are Pd and Ni, and the total content of Pd and Ni is 0.02wt%, wherein the mass ratio of Pd to Ni is 1:1. The average particle size of the catalyst is 390nm, and the specific surface area is 73.8m 2 / g; bulk density is 0.78g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0169] Comparative Example 1

[0170] The supported magnetic catalyst was prepared according to the method of Preparation Example 6, except that the magnetic carrier was not coated, to obtain a supported Fe3O4@Pd magnetic catalyst, which specifically includes the following steps:

[0171] Weigh 1 g of Fe3O4 nanopowder with an average particle size of 400 nm as a magnetic carrier and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion and ultrasonicate for 10 min. Then, dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@Pd magnetic catalyst.

[0172] The magnetic core of the magnetic catalyst is Fe3O4, the average particle size is 400nm, the active component is Pd, and the content of Pd is 0.02wt%. The specific surface area of ​​the catalyst is 105m 2 / g; bulk density is 2.89g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0173] Comparative Example 2

[0174] The supported Fe3O4@C@Pd magnetic catalyst was prepared according to the method of Preparation Example 6, except that Fe3O4@C was not coated with polyvinyl pyrrolidone. The specific steps are as follows:

[0175] (1) Preparation of magnetic carrier: 1 g of Fe3O4 nanopowder with an average particle size of 400 nm and 2.7 g of glucose were added to 120 mL of deionized water and mixed by ultrasonication for 10 min. The obtained mixed solution was transferred to a 200 mL reactor and reacted at 180°C for 4 h. After the reactor was cooled to room temperature, the black solid was separated by magnetic separation. Finally, the black solid was washed three times with deionized water and twice with ethanol, and dried at 60°C to obtain the product. Then, the product was carbonized at 500°C for 4 h under argon protection to obtain Fe3O4@C magnetic carrier.

[0176] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@C magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.0 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@C@Pd magnetic catalyst.

[0177] The active component of the magnetic catalyst is Pd, and the content of Pd is 0.02wt%. The average particle size of the magnetic catalyst is 450nm, and the specific surface area is 71.4m 2 / g; bulk density is 0.81g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0178] Comparative Example 3

[0179] The magnetic catalyst is prepared according to the method of Preparation Example 6, except that SiO2 is used to coat the magnetic carrier to obtain a supported Fe3O4@SiO2@Pd magnetic catalyst, including the following steps:

[0180] (1) Preparation of magnetic carrier: 110.8 mL of water, 333.3 mL of anhydrous ethanol and 1 g of Fe3O4 were added to the reactor in proportion, ultrasonically dispersed for 30 min, 4.7 mL of TEOS and 5.6 mL of ammonia water were added, and stirred at 100 r / min for 3 h at room temperature. After the reaction, solid particles were obtained by magnetic separation, washed with ethanol twice and then washed with water three times to obtain Fe3O4@SiO2 magnetic carrier;

[0181] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@SiO2 magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@SiO2@Pd magnetic catalyst.

[0182] The magnetic core of the magnetic catalyst is 50nm Fe3O4, the coating layer is SiO2, the thickness of the coating layer is 10nm; the active component is Pd, and the content of Pd is 0.02wt%. The average particle size of the catalyst is 70nm, and the specific surface area is 208m 2 / g; bulk density is 0.46g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0183] Comparative Example 4

[0184] The supported Fe3O4@PVP@Pd magnetic catalyst was prepared according to the method of Preparation Example 17, except that the Fe3O4@PVP was not subjected to densification treatment and the coating layer was in the original state of PDA. The specific steps were as follows:

[0185] (1) Preparation of magnetic carrier: 1 g of polyvinyl pyrrolidone and 1.6 g of Fe3O4 with an average particle size of 360 nm were weighed and dissolved in 300 mL of deionized water, and stirred at 800 rpm for 1 h. Subsequently, after stirring at 300 rpm for 3 h, the mixture was washed three times with deionized water and twice with ethanol, and dried at 60°C to obtain Fe3O4@PVP magnetic carrier;

[0186] (2) Preparation of catalyst: Weigh 1 g of the Fe3O4@PVP magnetic carrier prepared in step (1) and disperse it in acetone. Add 20 mL of 0.01 mol / L palladium chloride dropwise into the above dispersion, ultrasonicate for 10 min, and then dry the impregnated sample at 60°C. Reduce the dried sample with hydrogen at a hydrogen pressure of 1 MPa and 380°C for 2 h to obtain a supported Fe3O4@PVP@Pd magnetic catalyst.

[0187] The magnetic core of the magnetic catalyst is Fe3O4, the average particle size is 400nm, and no dense coating layer is formed; the active component is Pd, and the content of Pd is 0.02wt%. The average particle size of the catalyst is 460nm, and the specific surface area is 202m 2 / g; bulk density is 0.58g / cm 3 The degree of hydrogenation and recovery rate are shown in Table 1.

[0188] Hydrogenation degree evaluation 1

[0189] Weigh 1 g of commercially available NBR with a brand name of 3304, add it to 201 g of acetone solution, stir thoroughly to completely dissolve the NBR, and then transfer the glue solution to a high-pressure reactor; add 0.93 g of the catalysts obtained in Preparation Examples 1-24 and Comparative Examples 1-4 to the high-pressure reactor respectively; introduce 0.4 MPa nitrogen gas 3 times to replace the air in the reactor, and 2 MPa H2 to replace it twice; raise the temperature to 80°C, increase the hydrogen pressure to 5 MPa at this temperature, and react for 4 hours at a stirring rate of 400 r / min; after the reaction is completed, cool the reactor to room temperature, slowly vent it, and after venting the hydrogen gas, open the reactor and take samples to obtain samples S1-S24 and D1-D4, respectively.

[0190] The above samples were separated by magnetic separation to obtain solid catalyst and glue solution, and the recovery rate of the catalyst was measured. The results are shown in Table 1; the glue solution was collected in a reagent bottle to obtain a mixture of HNBR and acetone, and the hydrogenation degree of HNBR was determined by infrared analysis. The results are shown in Table 1.

[0191] Table 1 Catalyst addition amount, hydrogenation degree and recovery rate of each preparation example

[0192]

[0193]

[0194] It can be seen from the results in Table 1 that, from the perspective of hydrogenation effect evaluation under the same conditions, the degree of hydrogenation and recovery rate of the catalyst obtained in Preparation Examples 1-24 are better than those in Comparative Examples 1-4.

[0195] Comparative Example 1 prepared Fe3O4@Pd magnetic catalyst without coating its carrier. The hydrogenation effect was evaluated under the same conditions as Preparation Example 6. Under the premise of the same active components, the hydrogenation activity was equivalent to that of Preparation Example 6. However, after the hydrogenation reaction, 87% of the active component Pd fell off from the surface of Fe3O4 and entered the gel solution. It requires extremely complex separation steps to separate it, which increases the catalytic cost.

[0196] Comparative Example 2 prepared Fe3O4@C@Pd magnetically supported catalyst, whose Fe3O4 carrier surface was activated carbon, and the hydrogenation effect was evaluated under the same conditions as Preparation Example 6, and the hydrogenation activity was much lower than that of Preparation Example 6. This is because the activated carbon on the surface of the Fe3O4 carrier is a porous structure, and some active components enter the porous structure of the activated carbon. At the same time, the rough surface of the catalyst easily causes adhesion with the glue, resulting in difficulty in the final catalyst recovery. Moreover, for high-viscosity systems such as NBR, it is easy to cause clogging of the porous in the coating layer.

[0197] After the Fe3O4 is coated with SiO2, the Fe3O4@SiO2@Pd magnetically supported catalyst prepared in Comparative Example 3 has a porous coating layer because the surface cannot be densified. The hydrogenation effect was evaluated under the same conditions as in Preparation Example 6, and the hydrogenation activity was much lower than that in Preparation Example 6. After analysis, it was found that although the loading amount of the active component Pd in ​​Comparative Example 3 was the same as that in Preparation Example 6, both were 0.02wt%, the active components in the pores were easily blocked by the glue and could not play the due catalytic role. Therefore, the hydrogenation effect was not good. In addition, 23.5% of the active component Pd fell off into the glue, and it required extremely complicated separation steps to separate it, which increased the catalytic cost.

[0198] The Fe3O4@PVP@Pd magnetic catalyst prepared in Comparative Example 4 has no densification treatment on the surface of the carrier PVP, and the coating layer is in the original state of PVP. The hydrogenation effect is evaluated under the same conditions as Preparation Example 17, and the hydrogenation activity is much lower than that of Preparation Example 17. This is because the surface of the coating layer of the catalyst has not been densified, and some active components are wrapped in the surface coating layer. At the same time, the rough surface of the catalyst is easy to cause adhesion with the glue, resulting in difficulty in the final catalyst recovery. Moreover, for high-viscosity systems such as NBR, it is easy to cause clogging of the porous coating layer.

[0199] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for hydrogenating nitrile rubber using a magnetically supported catalyst, characterized in that: The method comprises: in the presence of a magnetically supported catalyst, hydrogenating nitrile rubber by a solvent method, and then performing post-treatment to obtain hydrogenated nitrile rubber; wherein the magnetically supported catalyst comprises a magnetic carrier and an active component supported on the surface of the magnetic carrier; the magnetic carrier is a core-shell structure, comprising a magnetic core and at least one dense coating layer coated on the outer surface of the magnetic core.

2. The method according to claim 1, wherein: The coating layer is selected from polydopamine and / or polyvinyl pyrrolidone; and / or the coating layer has a dense non-porous structure; And / or, the coating layer has a thickness of 10-50 nm, preferably 10-30 nm.

3. The method according to claim 1 or 2, wherein: An activated carbon layer is also contained between the magnetic core and the coating layer.

4. The method according to claim 1, wherein: The magnetic core is selected from one or more of Fe3O4, Fe3S4 and FeNi; And / or, the average particle size of the magnetic core is 50-500 nm, preferably 60-400 nm.

5. The method according to claim 1, wherein: Based on the total amount of the magnetically supported catalyst, the content of the active component is 0.01-1wt%, preferably 0.02-0.5wt%; And / or, the active component includes a noble metal component and an optional non-noble metal component, the noble metal component is selected from one or more of Pd, Rh, Pt and Ru, and the non-noble metal component is selected from Ni and / or Mo.

6. The method according to claim 5, wherein: The mass ratio of the noble metal component to the non-noble metal component is 1:0-1.

7. The method according to claim 1, wherein: The average particle size of the magnetically supported catalyst is 50-500 nm; And / or, the specific surface area of ​​the magnetic carrier is 45-100m 2 / g; And / or, the bulk density of the magnetic carrier is 0.6-1.25 g / cm 3 .

8. The method according to claim 1, wherein: The preparation method of the magnetic-supported catalyst comprises: At least one dense coating layer is coated on the surface of the magnetic nanoparticles to obtain a magnetic carrier with a core-shell structure, wherein the magnetic nanoparticles are cores and the coating layer is a shell; An active component precursor is loaded on the outer surface of the dense coating layer in the magnetic carrier to obtain a catalyst precursor, which is then reduced to obtain a magnetically supported catalyst.

9. The method according to claim 8, wherein: The coating method is selected from a hydrolysis method, a reduction method or a layered assembly method.

10. The method according to claim 8, wherein: The reduction treatment conditions include: using hydrogen as the reduction gas, the reduction pressure is 0.5-1.5 MPa, and the reduction temperature is 250-400°C.

11. The method according to claim 8, wherein: The active component precursor includes a noble metal component precursor and an optional non-noble metal component precursor.

12. The method according to claim 11, wherein: The noble metal component precursor is selected from one or more soluble salts of Pd, Rh, Pt and Ru; The non-noble metal component precursor is selected from one or more soluble salts of Ni and Mo.

13. The method according to claim 1, wherein: The weight ratio of the nitrile rubber to the magnetically supported catalyst is 1-2:1, preferably 1-1.5:

1.

14. The method according to claim 1, wherein: The conditions of the hydrogenation reaction include: hydrogen pressure of 0.5-16 MPa; reaction temperature of 50-120° C.; reaction time of 2-12 h.

15. The method according to claim 1, wherein: The method further comprises: magnetically separating the reaction liquid, recovering the catalyst from the separated solid and reusing it; and precipitating, deliquoring and solidifying the separated liquid to obtain a hydrogenated nitrile rubber product.

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