A nano core-shell type catalyst and a preparation method and application thereof

Abstract

The application discloses a kind of nano core-shell catalyst and its preparation method and application.The nano core-shell catalyst includes: carbon carrier and nano particle cluster loaded on the surface of the carbon carrier, the nano particle cluster is formed by palladium-in-situ tin core-shell nanoparticle, the palladium-in-situ tin core-shell nanoparticle includes the palladium metal core as core structure and the tin shell layer as shell structure, and the tin shell layer can at least partially wrap palladium metal core.Pd in the nano core-shell catalyst of the application has high activity and selectivity to halogenated nitrobenzene hydrogenation to halogenated aniline under the action of Sn promoter, and the preparation of the nano core-shell catalyst in the application innovatively uses high-frequency ultrasonic assisted reduction method, which is simple and easy to operate, and provides a new idea for Pd-based catalyst in the field of selective catalytic preparation of corresponding halogenated aniline by catalytic hydrogenation of halogen-containing nitrobenzene.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology and thermocatalysis application, and relates to a nano core-shell catalyst, its preparation method and application, especially a nano core-shell catalyst for the catalytic hydrogenation of halonitrobenzene to haloaniline under normal pressure and temperature conditions, its preparation method and application. Background Technology

[0002] Halogenated anilines are important organic intermediates in the synthesis of industrial fine chemicals such as dyes, pesticides, and pharmaceuticals. Traditionally, halogenated anilines are mainly prepared by the direct reduction of the corresponding halonitrobenzenes using metal acids or hydride reagents. However, this route generates harmful chemical waste, leading to serious environmental problems. Currently, the strategy of selectively hydrogenating halonitrobenzenes using H2 on a heterogeneous metal catalyst is considered an efficient, economical, and environmentally friendly alternative for the preparation of halogenated anilines. Noble metals, such as Pt, Pd, Au, and Rh, exhibit high activity in the hydrogenation of halonitrobenzenes due to their excellent hydrogen (H2) dissociation capabilities. However, due to the inevitable hydrogenolysis of the carbon-halogen bond, these single-metal particles are difficult to obtain with high selectivity for halogenated anilines.

[0003] Compared to Pt-based catalysts, Pd-based catalysts offer the advantage of lower cost while maintaining the same catalytic efficiency. However, while Pd catalysts possess high activity, they inevitably suffer from low selectivity. To address this incompatibility between selectivity and activity, considerable research has been conducted. Examples include establishing strong metal-support interactions, synergistic effects between noble metals and metal oxides, and constructing bimetallic alloy structures. However, these strategies suffer from drawbacks: improving selectivity may reduce the catalyst's own activity, making a balance impossible; the preparation process is complex; and there are few bimetallic catalytic interfaces. Therefore, providing a catalyst with both high selectivity and high activity is a pressing issue. Summary of the Invention

[0004] The main objective of this invention is to provide a nano-core-shell catalyst, its preparation method, and its application, in order to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a nano-core-shell catalyst, comprising: a carbon support and a cluster of nanoparticles supported on the surface of the carbon support. The cluster of nanoparticles is formed by tin-coated palladium core-shell nanoparticles. The tin-coated palladium core-shell nanoparticles include a palladium metal core as the core structure and a tin shell layer as the shell structure, and the tin shell layer can at least partially encapsulate the palladium metal core.

[0007] This invention also provides a method for preparing the aforementioned core-shell nanocatalyst, comprising:

[0008] A suspension is formed by mixing a palladium source, a tin source, a dispersant, a reducing agent, and a carbon support.

[0009] Furthermore, the suspension is subjected to ultrasonic treatment to obtain the nano-core-shell catalyst.

[0010] The present invention also provides the use of the aforementioned nano-core-shell catalyst in the catalytic hydrogenation of halonitrobenzenes to prepare haloanilines.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] (1) The synergistic effect of the Pd core and Sn shell in the nano core-shell catalyst of the present invention improves the adsorption capacity of the reaction substrate and the adsorption and dissociation capacity of H2, thereby improving the catalytic activity;

[0013] (2) The nano core-shell catalyst provided in this invention effectively reduces the amount of precious metal palladium used, saving costs;

[0014] (3) The Sn shell in the nano core-shell catalyst of the present invention changes its substrate adsorption environment and electronic state structure, thereby improving the selectivity of catalytic preparation of halonitrobenzene to haloaniline; at the same time, the nano core-shell catalyst of the present invention innovatively adopts the ultrasonic-assisted reduction method, which is simple and easy to implement. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a transmission electron microscope image of the Pd2@Sn catalyst prepared in Example 5 of this invention;

[0017] Figure 2 This is the XRD pattern of the Pd2@Sn catalyst prepared in Example 5 of this invention;

[0018] Figures 3-4 This is a mapping diagram of the Pd2@Sn catalyst prepared in Example 5 of the present invention. Detailed Implementation

[0019] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] Specifically, as one aspect of the technical solution of the present invention, a nano-core-shell catalyst includes: a carbon support and a cluster of nanoparticles supported on the surface of the carbon support. The cluster of nanoparticles is formed by tin-coated palladium core-shell nanoparticles. The tin-coated palladium core-shell nanoparticles include a palladium metal core as the core structure and a tin shell layer as the shell structure, and the tin shell layer can at least partially encapsulate the palladium metal core.

[0021] In some preferred embodiments, the nano-core-shell catalyst of the present invention is a supported catalyst, with Cabot conductive carbon spherical particles as the support. The active component is distributed on the surface of the Cabot conductive carbon spherical particles as nanoparticle clusters (also referred to as: nanoparticle soft clusters). The nanoparticle clusters are formed by tin-coated palladium core-shell nanoparticles (referred to as: Pd@Sn core-shell nanoparticles). The structure of the Pd@Sn core-shell nanoparticles is that the palladium nanoparticles serve as the core, which is tightly wrapped by the surface tin shell layer. However, the tin shell layer does not completely cover all Pd active sites (this is because there are differences in the reduction potential of the metals themselves, and palladium is more easily reduced to the metallic state, thus preferentially forming nucleation sites). In addition, the active center of the catalyst is considered to be the Pt-Sn interface. The introduction of the tin shell layer improves the performance of Pd in ​​the selective catalytic hydrogenation of halonitrobenzenes.

[0022] In some preferred embodiments, the thickness of the tin shell layer is less than 3 nm.

[0023] In some preferred embodiments, the particle size of the tin-coated palladium core-shell nanoparticles is less than 5 nm.

[0024] In some preferred embodiments, the particle size of the nanoparticle clusters is 10–30 nm.

[0025] In some preferred embodiments, the palladium content in the nano-core-shell catalyst is 0.15 wt% to 1.0 wt%.

[0026] In some preferred embodiments, the tin content in the nano-core-shell catalyst is 0.005 wt% to 1.0 wt%.

[0027] In some preferred embodiments, the carbon support includes, but is not limited to, Cabot conductive carbon supports.

[0028] Furthermore, the Cabot conductive carbon carrier includes, but is not limited to, Cabot conductive carbon particles.

[0029] Another aspect of the present invention provides a method for preparing the aforementioned core-shell nanocatalyst, comprising:

[0030] A suspension is formed by mixing a palladium source, a tin source, a dispersant, a reducing agent, and a carbon support.

[0031] Furthermore, the suspension is subjected to ultrasonic treatment to obtain the nano-core-shell catalyst.

[0032] In some preferred embodiments, the preparation method specifically includes:

[0033] The palladium source, tin source, dispersant, and reducing agent are ultrasonically mixed to form a first mixed solution;

[0034] The carbon support is added to the first mixed solution and dispersed to form a suspension;

[0035] Furthermore, the suspension is subjected to ultrasonication, washing, and drying to obtain the nano-core-shell catalyst.

[0036] Furthermore, the palladium source includes an organic palladium salt.

[0037] Furthermore, the organic palladium salt includes, but is not limited to, palladium acetylacetonate and / or palladium acetate.

[0038] Furthermore, the tin source includes any one or more combinations of tin chloride, stannous chloride, and tin ethylhexanoate, and is not limited thereto.

[0039] Furthermore, the dispersant includes any one or more combinations of oleylamine, octadecene, and oleic acid; preferably oleylamine.

[0040] Furthermore, the reducing agent includes any one or more combinations of glucose, polyols, and ascorbic acid; preferably glucose.

[0041] Furthermore, the carbon support includes, but is not limited to, Cabot conductive carbon supports.

[0042] Furthermore, the ratio of the palladium source, tin source, reducing agent, and dispersant is 1 mol: 0.1–5 mol: 5–20 mol: 5–20 mL.

[0043] Furthermore, the preparation method specifically includes: ultrasonically treating the suspension at an ultrasonic frequency of 1000Hz to 8000Hz for 10 to 50 minutes; wherein the ultrasonic treatment adopts a two-stage cyclic treatment: ultrasonic output for 10s to 100s, and pause for 0s to 50s.

[0044] Furthermore, the washing liquid used in the washing process includes, but is not limited to, acetone.

[0045] Furthermore, the drying process is carried out at a temperature of 30–60°C.

[0046] In some preferred embodiments, the preparation method of the rice core-shell type catalyst specifically includes:

[0047] (1) Mix palladium acetylacetonate, SnCl4 tin chloride, oleylamine and glucose, and sonicate until homogeneous to prepare solution A;

[0048] (2) Add a certain amount of Cabot conductive carbon to solution A and disperse it evenly to form suspension B;

[0049] (3) Place suspension B in a cell disruption sonicator, place the probe in suspension B, set the frequency to 1000Hz~8000Hz, and the continuous reaction time to 10 minutes~50 minutes.

[0050] (4) Cool the reaction suspension B to room temperature, wash with acetone and dry to obtain the catalyst.

[0051] Furthermore, in step (1), the ratio and mass of palladium acetylacetone and tin chloride can be adjusted to the Sn shell thickness that is most suitable for the corresponding reaction.

[0052] Furthermore, the amount of carbon support added in step (2) is such that the Pd loading is controlled between 0.15 wt% and 1 wt%.

[0053] Furthermore, in step (3), the ultrasonic output time during the reaction duration is 10s to 100s, and the pause is 0s to 50s. These two stages are repeated sequentially until the total time ends.

[0054] Furthermore, the drying temperature in step (4) is 30–60°C.

[0055] The preparation method of the nano-core-shell catalyst in this invention innovatively adopts a high-frequency ultrasonic-assisted reduction method, which is simple and easy to implement.

[0056] Another aspect of the present invention provides the use of the aforementioned nano-core-shell catalyst in the catalytic hydrogenation of halonitrobenzenes to prepare haloanilines.

[0057] In this invention, the catalytic test is used to evaluate the efficiency of the catalyst. The reaction conditions are atmospheric pressure H2 atmosphere and reaction temperature of 25℃.

[0058] The design of the nano-core-shell catalyst in this invention achieves unexpected improvements in the selective hydrogenation of halonitrobenzenes by Pd-based catalysts. This is because the Pd core and Sn shell have a significant synergistic effect, and the catalytic effect can be controlled by adjusting the thickness of the Sn shell through changing the Pt / Sn input ratio. Effective control of the tin shell thickness will enable the Pd@Sn core-shell nanocatalyst to exhibit high activity and excellent selectivity in the selective hydrogenation of halonitrobenzenes.

[0059] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0060] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0061] In the ultrasonic-assisted reduction of the catalyst in the embodiments of the present invention, the reaction duration includes a 20-second output of 7000Hz ultrasonic waves followed by a 10-second pause, and these two phases are repeated sequentially until the total time is 10 minutes.

[0062] In the catalyst tests of the embodiments of this invention, p-chloronitrobenzene was used as a model catalyst for halonitrobenzenes, a typical type of halonitrobenzene. However, the application of this catalyst can be directed towards the selective hydrogenation of other halonitrobenzenes. The reaction conditions used in the tests were set as follows: atmospheric pressure H2 atmosphere; temperature 25°C; catalyst loading of 1 wt%; catalyst mass / p-chloronitrobenzene mass ratio of 30:1; and high rotational speed to eliminate diffusion effects.

[0063] The method for calculating the selectivity of p-chloroaniline in the preparation of p-chloronitrobenzene is as follows: the content of p-chloroaniline in the product is obtained by gas chromatography analysis, which is the selectivity.

[0064] Example 1

[0065] The preparation process of a Pd catalyst involved in this embodiment includes the following steps:

[0066] (1) Mix palladium acetylacetone, oleylamine and glucose, sonicate until homogeneous, and prepare solution A.

[0067] (2) Add a certain amount of Cabot conductive carbon (control the Pd loading to 1wt%) to solution A and disperse it evenly to form suspension B.

[0068] (3) Place the suspension B into the cell disruption sonicator, place the probe in the suspension B, set the frequency to 7000Hz, and the continuous reaction time to 10 minutes.

[0069] (4) Cool the reaction suspension B to room temperature, wash with acetone, and dry at 30°C to obtain the Pd catalyst.

[0070] (5) Evaluation of the reaction of preparing p-chloroaniline from p-chloronitrobenzene using a catalyst.

[0071] Example 2

[0072] This embodiment involves a Pd 24 The preparation process of @Sn catalyst includes the following steps:

[0073] (1) Mix palladium acetylacetonate, tin tetrachloride (the molar ratio of palladium acetylacetonate to tin tetrachloride is 1:24), oleylamine, and glucose, and sonicate until homogeneous to prepare solution A.

[0074] (2) Add a certain amount of Cabot conductive carbon (control the Pd loading to 1wt%) to solution A and disperse it evenly to form suspension B.

[0075] (3) Place the suspension B into the cell disruption sonicator, place the probe in the suspension B, set the frequency to 7000Hz, and the continuous reaction time to 10 minutes.

[0076] (4) Cool the reaction suspension B to room temperature, wash with acetone, and dry at 30°C to obtain Pd. 24 @Sn catalyst.

[0077] (5) Evaluation of the reaction of preparing p-chloroaniline from p-chloronitrobenzene using a catalyst.

[0078] Example 3

[0079] This embodiment involves a Pd 12 The preparation process of @Sn catalyst includes the following steps:

[0080] (1) Mix palladium acetylacetonate, tin tetrachloride (the molar ratio of palladium acetylacetonate to tin tetrachloride is 1:12), oleylamine, and glucose, and sonicate until homogeneous to prepare solution A.

[0081] (2) Add a certain amount of Cabot conductive carbon (control the Pd loading to 1wt%) to solution A and disperse it evenly to form suspension B.

[0082] (3) Place the suspension B into the cell disruption sonicator, place the probe in the suspension B, set the frequency to 7000Hz, and the continuous reaction time to 10 minutes.

[0083] (4) Cool the reaction suspension B to room temperature, wash with acetone, and dry at 30°C to obtain Pd. 12 @Sn catalyst.

[0084] (5) Evaluation of the reaction of preparing p-chloroaniline from p-chloronitrobenzene using a catalyst.

[0085] Example 4

[0086] The preparation process of a Pd8@Sn catalyst involved in this embodiment includes the following steps:

[0087] (1) Mix palladium acetylacetonate, tin tetrachloride (the molar ratio of palladium acetylacetonate to tin tetrachloride is 1:8), oleylamine, and glucose, and sonicate until homogeneous to prepare solution A.

[0088] (2) Add a certain amount of Cabot conductive carbon (control the Pd loading to 1wt%) to solution A and disperse it evenly to form suspension B.

[0089] (3) Place the suspension B into the cell disruption sonicator, place the probe in the suspension B, set the frequency to 7000Hz, and the continuous reaction time to 10 minutes.

[0090] (4) Cool the reaction suspension B to room temperature, wash with acetone, and dry at 30°C to obtain the Pd8@Sn catalyst.

[0091] (5) Evaluation of the reaction of preparing p-chloroaniline from p-chloronitrobenzene using a catalyst.

[0092] Example 5

[0093] The preparation process of a Pd2@Sn catalyst involved in this embodiment includes the following steps:

[0094] (1) Mix palladium acetylacetonate, tin tetrachloride (the molar ratio of palladium acetylacetonate to tin tetrachloride is 1:2), oleylamine, and glucose, and sonicate until homogeneous to prepare solution A.

[0095] (2) Add a certain amount of Cabot conductive carbon (control the Pd loading to 1wt%) to solution A and disperse it evenly to form suspension B.

[0096] (3) Place the suspension B into the cell disruption sonicator, place the probe in the suspension B, set the frequency to 7000Hz, and the continuous reaction time to 10 minutes.

[0097] (4) The reaction suspension B was cooled to room temperature, washed with acetone, and dried at 30°C to obtain the Pd2@Sn catalyst. The transmission electron microscopy (TEM) image of the Pd2@Sn catalyst prepared in this example is shown below. Figure 1 As shown, the XRD pattern is as follows Figure 2 As shown, the mapping diagram of the Pd2@Sn catalyst is as follows. Figures 3-4 As shown in the mapping diagram, Pd is more enriched, while Sn exhibits a shell-like state.

[0098] (5) Evaluation of the reaction of preparing p-chloroaniline from p-chloronitrobenzene using a catalyst.

[0099] Performance characterization:

[0100] The Pd catalysts and Pd catalysts prepared in Examples 1-5 24 @Sn catalyst, Pd 12 Catalytic performance tests were conducted on @Sn, Pd8@Sn, and Pd2@Sn catalysts, using p-chloronitrobenzene as a model catalyst for halonitrobenzene. The reaction conditions were set as follows: ambient pressure H2 atmosphere; temperature 25℃; catalyst loading 1 wt%; catalyst mass / p-chloronitrobenzene mass ratio 30:1; high rotation speed to eliminate diffusion effects. The selectivity for the preparation of p-chloroaniline from p-chloronitrobenzene was calculated by gas chromatography analysis of the product, with the p-chloroaniline content in the product representing the selectivity. The test results are shown in Table 1.

[0101] Table 1. Catalytic performance results of the catalysts prepared in Examples 1-5

[0102]

[0103] As shown in Table 1, in all embodiments, the catalyst activity exhibits a volcano-like structure with the amount of Sn added. Before the Sn precursor addition ratio reaches 1:12, the catalyst activity increases with increasing Sn shell thickness (increased Sn addition); subsequently, it gradually decreases, as the Sn shell covers too many Pd active site centers. In terms of selectivity, it continuously increases with increasing Sn shell thickness. Therefore, considering both selectivity and activity, the catalyst performance is optimal when the Sn:Pd ratio is 1:8.

[0104] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0105] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. The use of a nano-core-shell catalyst in the catalytic hydrogenation of halonitrobenzene to prepare haloaniline, characterized in that, The preparation method of the nano-core-shell catalyst includes: A palladium source, a tin source, a dispersant, and a reducing agent are ultrasonically mixed to form a first mixed solution; wherein, the palladium source is an organic palladium salt; the organic palladium salt is palladium acetylacetonate; the reducing agent is glucose; the molar ratio of the tin source to the palladium source is 1:8; and the dispersant is selected from any one or more combinations of oleylamine, octadecene, and oleic acid. A carbon support is added to the first mixed solution and dispersed to form a suspension; the carbon support is a Cabot conductive carbon support; the Cabot conductive carbon support is Cabot conductive carbon particles; Furthermore, the suspension is ultrasonically treated at an ultrasonic frequency of 1000Hz to 8000Hz for 10 to 50 minutes, followed by washing and drying to obtain a nano-core-shell catalyst; wherein the ultrasonic treatment adopts a two-stage cyclic treatment: ultrasonic output for 10s to 100s, pause for 0s to 50s; the drying temperature is 30 to 60℃. The core-shell nanocatalyst comprises a carbon support and a cluster of nanoparticles supported on the surface of the carbon support. The nanoparticle clusters are formed by tin-coated palladium core-shell nanoparticles. Each tin-coated palladium core-shell nanoparticle comprises a palladium metal core as the core structure and a tin shell layer as the shell structure, wherein the tin shell layer partially encapsulates the palladium metal core. The thickness of the tin shell layer is less than 3 nm. The particle size of the tin-coated palladium core-shell nanoparticles is less than 5 nm. The particle size of the nanoparticle clusters is 10-30 nm. The tin content in the core-shell nanocatalyst is 0.005 wt% to 1.0 wt%. The palladium content in the core-shell nanocatalyst is 0.15 wt% to 1.0 wt%.

2. The use according to claim 1, characterized in that: The tin source is selected from any one or a combination of tin chloride, stannous chloride, and tin ethylhexanoate.

3. The use according to claim 1, characterized in that: The washing solution used in the washing process includes acetone.

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