Sulfur-doped porous carbon loaded platinum fully-exposed cluster catalyst as well as preparation method and application thereof

Abstract

The invention discloses a sulfur-doped porous carbon loaded platinum fully-exposed cluster catalyst and a preparation method and application thereof, platinum in the catalyst is loaded on the surface of a carbon carrier in an atomic-scale dispersion form, the carbon carrier is sulfur-doped porous carbon, the loading amount of platinum is 0.1 wt%-3wt%, and the doping amount of sulfur is 3.2-9.5%. The fully-exposed platinum cluster catalyst is prepared by using a traditional wet chemical impregnation method, the catalytic active center of the catalyst is generally a nanocluster composed of metal atoms with a limited number, the metal atoms are completely exposed on the surface of a carrier, and the catalyst has a metal atom utilization rate close to 100% and has abundant surface active sites. The catalyst material shows good activity and selectivity in selective reaction of 4-nitrostyrene. The preparation cost is low, and the preparation method has universality, is simple to operate and is easy for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a fully exposed platinum cluster catalyst, a preparation method and use thereof. Background Art

[0002] Ultra-small nanocluster catalysts have attracted widespread attention from scientists in recent years due to their special geometric structure, electronic structure and high atomic utilization efficiency. When the particle size is less than 1nm, almost all atoms in the metal particles are fully exposed, that is, fully exposed cluster catalysts (FECCs). Fully exposed platinum cluster catalysts have the dual advantages of heterogeneous catalysts and homogeneous catalysts and have great potential utilization value in many important catalytic fields. Compared with single-atom catalysts, the atomic utilization rates of both are close to 100%, while single-atom catalysts have some disadvantages in many fields. For example, the dissociation of H2 often requires two adjacent metal atoms to be realized; in some reaction systems, multiple metal active sites need to be activated synergistically to make the reaction efficient, which single-atom catalysts often cannot achieve in this case. FECCs have adjacent metal active sites. This feature allows multiple sites to work synergistically, perfectly solving the need for multi-active site synergistic catalysis that single-atom catalysts cannot meet. In fully exposed platinum cluster catalysts, metal particles exist in the form of extremely small clusters, and all atoms in the clusters are in a coordination unsaturated state, which gives them extremely high reactivity, enables rapid response to reactants, and achieves efficient catalysis. Therefore, theoretically speaking, fully exposed platinum cluster catalysts are the most ideal type of catalyst.

[0003] 4-Alkenylaniline is an important chemical raw material and intermediate, widely used in dyes, adhesives, crosslinking agents, sensors and other fields, and can also be used as an additive to improve the mechanical strength and chemical resistance of materials. This type of substance can be obtained by selective hydrogenation of 4-nitrostyrene. Its disadvantage is that the highly active Pd and Pt catalysts have strong hydrogenation capabilities for both nitro functional groups and olefin functional groups. While hydrogenating the nitro functional group, the olefin functional group is also hydrogenated. The obtained product needs to be further purified, making its process complicated. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a fully exposed cluster catalyst of platinum supported by sulfur-doped porous carbon. The fully exposed platinum cluster catalyst selectively hydrogenates nitro functional groups while retaining olefin functional groups by changing its coordination environment. The nitro functional groups can be selectively hydrogenated in the selective hydrogenation reaction of 4-nitrostyrene, thereby greatly improving the yield and reducing the process procedures.

[0005] To this end, the technical solution of the present invention is as follows: a fully exposed cluster catalyst of platinum supported by sulfur-doped porous carbon, in which platinum is loaded on the surface of a carbon carrier in an atomically dispersed form, the carbon carrier is sulfur-doped porous carbon, the platinum loading is 0.1wt% to 3wt%, and the sulfur doping amount is 3.25-9.5%.

[0006] The method for preparing the sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst comprises the following steps:

[0007] S1) mixing the sulfur-doped porous carbon support and the platinum-containing precursor in a solvent, and then drying by rotary evaporation to obtain a dry powder mixture; the solvent may be water or ethanol, and when the platinum precursor is an inorganic salt, the solvent may be water, and when the platinum precursor is an organic salt, the solvent is preferably ethanol;

[0008] S2) subjecting the dry powder mixture to reduction heat treatment in a hydrogen reducing atmosphere to obtain a fully exposed platinum cluster catalyst; the reduction heat treatment temperature is 200 to 1000°C.

[0009] Furthermore, the hydrogen reducing atmosphere is a mixture of H2 / Ar, H2 / N2 or H2 / He, wherein the volume content of hydrogen is 3 to 50%.

[0010] Furthermore, the heating rate of the reduction heat treatment is 1 to 20° C. / min, and the reduction heat treatment time is 1 to 5 hours.

[0011] Furthermore, the uniform mixing in step S1 specifically comprises: ultrasonic mixing followed by vigorous stirring; the ultrasonic time is 0.5 to 2 hours, and the vigorous stirring time is 6 to 15 hours.

[0012] Furthermore, in step S1, the rotary evaporation drying temperature is 80-100° C., preferably 30-60° C.

[0013] Furthermore, the method for preparing the sulfur-doped porous carbon carrier comprises the following steps:

[0014] S1-1) Mix the sulfur-containing organic matter, carbon material and cobalt salt in a solvent, ultrasonically, stir, and rotary evaporate, dry and then calcine at high temperature in a nitrogen or argon atmosphere to obtain a carbon material; the calcination temperature is 600-1000°C; the sulfur-containing organic matter is one or more of thiophene, sulfide, and thiol, the carbon material is one of commercial carbon black, carbon nanotubes, and activated carbon, the cobalt salt is hexahydrated cobalt nitrate, and the mass ratio of the sulfur-containing organic matter, carbon material and cobalt salt is 2:1:1; commercial carbon black includes EC-300J, BP-2000, XC-72R, etc.; the addition of transition metal cobalt salt is to prevent the decomposition of small molecular thiophene in the sulfur-containing organic matter and improve the carbonization rate. The role of the carbon material is to provide a template to form a layer of sulfur-doped carbon on the surface of the original carbon material. The atmosphere during high-temperature calcination is nitrogen or argon, the purpose of which is to prevent the sulfur-doped carbon material from burning at high temperature.

[0015] S1-2) etching the carbon material with sulfuric acid to remove the cobalt particles in the carrier, washing the carbon material, and then drying the washed carbon material in an oven at 100° C. to obtain a sulfur-doped porous carbon material.

[0016] The use of the sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst obtained by the present invention is that the fully exposed cluster catalyst can be used in the selective hydrogenation reaction of 4-nitrostyrene to catalyze hydrogenation to generate 4-alkenylaniline.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention uses a simple wet chemical impregnation method to prepare a fully exposed platinum cluster catalyst. The platinum precursor is impregnated into the pores of porous carbon in a solvent. The preparation cost is low, the preparation method is universal, the operation is simple, and it is easy to industrialize.

[0019] 2. Use sulfur-containing small molecule materials and carbon materials to mix and heat-treat to obtain sulfur-doped carbon materials; the catalytic active center of this type of catalyst is usually a nanocluster composed of a limited number of metal atoms, and the metal atoms are completely exposed on the surface of the carrier. Compared with metal nanoparticles, fully exposed metal cluster catalysts have unique advantages: this type of catalyst has a metal atom utilization rate of nearly 100%, and has abundant surface active sites. Platinum atoms have a strong coordination effect with sulfur-doped porous carbon, and the active site is Pt n / SC, which can avoid sintering during the preparation and use process.

[0020] 3. The present invention synthesizes different fully exposed platinum cluster catalysts by regulating the ratio between the doped sulfur and the carbon material and the type of the doped sulfur. The catalyst material exhibits good activity and selectivity in the selective reaction of 4-nitrostyrene. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Characterization and performance study of the 0.3% Pt / SC catalyst (Pt loading 0.3 wt%) prepared in Example 1 of the present invention. (a) High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image; (b) Mapping image. (c) XRD pattern of the SC carrier; (d) XRD pattern of the 0.3% Pt / SC catalyst. Comparison of the catalytic activities of the catalysts at three temperatures: (e) 120°C; (f) 100°C; (g) 80°C. (h) Relationship between 1 / T and ln(TOF) value and the activation energy (E) of the hydrogenation of the nitro group in 4-nitrostyrene calculated from this. a ).

[0022] Figure 2 XRD patterns of the samples prepared in Example 4. (a) SC support; (b) Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0023] Figure 3 XRD patterns of the samples prepared in Example 5. (a) SC support; (b) Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0024] Figure 4 This is the XRD pattern of the Pt / Al2O3 catalyst prepared in Example 6 with a loading amount of 0.3 wt% of Pt nanoparticles.

[0025] Figure 5 The figures are comparative diagrams of the selective hydrogenation performance of 4-nitrostyrene catalyzed by different catalysts. (a) Example 2; (b) Example 3; (c) Example 4; (d) Example 5.

[0026] Figure 6 The comparison chart of hydrogenation performance of catalysts after anti-sulfur poisoning experiment: (a) 100ppm thiophene; (b) 300ppm thiophene; (c) 500ppm thiophene.

[0027] Figure 7 The selective hydrogenation activity comparison diagram of 0.3% Pt / Al2O3 catalyst and 0.3% Pt / SC catalyst. (a) Catalytic activity curve of 0.3% Pt / Al2O3; (b) Catalytic activity curve of 0.3% Pt / SC.

[0028] Figure 8 The relationship between 1 / T and ln(TOF) values ​​at three temperatures in Example 10 and the activation energy (E) of double bond hydrogenation in 4-alkenylaniline calculated therefrom are shown in FIG. a ). DETAILED DESCRIPTION

[0029] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0030] The present application also provides a method for preparing the above-mentioned fully exposed platinum cluster catalyst material, comprising the following steps:

[0031] The sulfur-doped porous carbon and the platinum-containing precursor solution are mixed uniformly in a solvent, stirred, rotary evaporated, and dried to obtain a dry powder mixture of the Pt precursor supported on the sulfur-doped carbon (SC) carrier;

[0032] The obtained dry powder mixture is then transferred to a tubular furnace and reduced at high temperature for a certain period of time in a mixed gas containing H2, and then naturally cooled to room temperature to obtain a Pt-loaded catalyst.

[0033] According to the present invention, the metal salt may be any of the following common metal salts, such as platinum nitrate, platinum chloride, platinum acetate, platinum (II) acetylacetonate, etc. There is no particular limitation on the salt form of the metal element. Those skilled in the art may be familiar with the metal salt. If the metal salt is unevenly dispersed in an aqueous solution, ethanol may be used instead of water.

[0034] The high-temperature reduction temperature is 200-1000°C, depending on the specific situation. The heating rate is controlled at 1-20°C / min, not too fast, and is kept warm for 1-6 hours. The reducing gas is usually a mixed gas such as H2 / Ar, H2 / N2 or H2 / He (the hydrogen content is 3-50vol%).

[0035] The loading amount of the metal atoms is 0.1wt% to 3wt%. In the present application, the fully exposed platinum cluster catalyst is loaded on the SC carrier in the form of extremely small clusters with a size of about 1nm, and there is a strong coordination effect between the fully exposed platinum cluster catalyst and the sulfur-doped porous carbon.

[0036] Specifically, in the process of preparing the fully exposed platinum cluster catalyst, the present application first mixes the sulfur-doped porous carbon and the cobalt salt in an aqueous solution, and obtains an initial mixture after impregnation, rotary evaporation, and drying; this process is a mixing process of the sulfur-doped porous carbon and the metal salt; for the raw sulfur-doped porous carbon, the type of raw sulfur is not too limited, and the preparation method thereof can be prepared according to a method well known to those skilled in the art. More specifically, the preparation method of the sulfur-doped porous carbon is as follows:

[0037] The sulfur-containing organic matter, carbon material and cobalt salt are mixed and dissolved in an organic solvent, stirred, rotary evaporated, dried and then calcined at high temperature, the metal particles in the material are etched with acid, and dried to obtain the SC material;

[0038] In the above-mentioned process of preparing sulfur-doped porous carbon, the sulfur-containing organic matter is selected from sulfur-containing small molecules well known to those skilled in the art, including diphenyl sulfide, 2,2'-bithiophene, 2,2':5',2"-terthiophene, benzenethiol, etc.; the metal salt is also selected from cobalt-containing metal salts well known to those skilled in the art. For example, in the present application, the cobalt salt is selected from cobalt nitrate hexahydrate, and the solvent can be selected from tetrahydrofuran (THF), ethyl acetate, etc. The mass ratio of the sulfur-containing organic matter, the carbon material and the cobalt salt is 2:2:1; the calcination temperature is 600-1000°C. The preparation method of the above-mentioned sulfur-doped porous carbon can be prepared according to the method well known to those skilled in the art, and this application does not impose any special restrictions on this. In the subsequent etching process, sulfuric acid etches the metal particles in the carbon material to finally obtain sulfur-doped porous carbon.

[0039] In the process of obtaining the initial mixture, the solvent can be selected according to the type of metal salt precursor added. For example, water is usually used as the solvent for inorganic metal salts (H2PtCl6·6H2O), and ethanol is usually used as the solvent for organic metal salts. In this process, the main purpose of the solvent is to fully mix without chemical reaction.

[0040] According to the present invention, after the initial mixture is obtained, it is subjected to reduction heat treatment to obtain a Pt single metal catalyst; this process is a reduction process of a metal salt, and the metal salt can be reduced by hydrogen in a hydrogen mixed gas atmosphere. The specific process is:

[0041] The initial mixture is transferred to a quartz crucible or a corundum crucible, placed in a tube furnace, and then heated to 200-800°C at a rate of 1-20°C / min using a mixture of hydrogen and inert gas as a reducing atmosphere, kept warm for 1-6 hours, and then naturally cooled to room temperature; during this process, the tube furnace is kept at normal pressure. The above-mentioned inert atmosphere is an argon atmosphere; the above-mentioned hydrogen mixture is selected from a mixture of hydrogen and helium. In the above process, the rate is 2-10°C / min in a specific embodiment; the above-mentioned heating rate is too fast, which will cause the metal elements to form metal particles.

[0042] This application uses impregnation and chemical coordination regulation to accurately synthesize fully exposed platinum cluster catalysts. The composite material improves the stability of the catalyst through the strong interaction between metal atoms and sulfur in the carrier.

[0043] The Pt single metal catalyst provided in the present application can be used as a catalyst for catalytic hydrogenation, and specifically can be used as a catalyst for the reaction of 4-nitrostyrene; the catalyst shows excellent selectivity.

[0044] In order to further understand the present invention, the fully exposed platinum cluster catalyst provided by the present invention, its preparation method and its application in the selective hydrogenation of 4-nitrostyrene are described in detail below in combination with the examples. The protection scope of the present invention is not limited by the following examples.

[0045] Example 1

[0046] a. Dissolve 1g 2,2'-bithiophene, 1g EC~300J, and 0.5g Co(NO3)2·6H2O in THF and stir for 10~14h, remove the solvent by rotary evaporation to obtain a uniform dry powder mixture; transfer the obtained dry powder mixture to a quartz boat, put it into a tube furnace, and then introduce nitrogen as a protective gas, heat the tube furnace to 800℃ at a rate of 5~10℃ / min, keep it warm for 2h, and naturally cool it to room temperature to obtain a sulfur-doped carbon material;

[0047] b. The carbon material obtained above was placed in a round-bottom flask, 100 mL of 0.5 mol / L sulfuric acid solution was added, and acid etching was performed at 80 ° C for 4 to 6 h, followed by filtration, washing three times, drying in an oven at 100 ° C, and then grinding to obtain a sulfur-doped porous carbon material; the sulfur content was 7.3%;

[0048] c. Take 50 mg of the SC carrier obtained by drying above and 0.1 mL of 1.5087 mg / mL H2PtCl6 solution and transfer them together to a 100 mL round-bottom flask, dilute with water (the total volume is kept at 30-50 mL) to obtain a mixture, ultrasonicate the mixture for 0.5 h, stir for 12 h, and rotary evaporate at 50-60 ° C to obtain catalyst precursor-1.

[0049] d. Place the catalyst precursor-1 obtained above into a crucible, introduce 5 vol% H2 / Ar gas, heat the tube furnace to 300-1000°C at a rate of 5-10°C / min, and maintain for 1-3 hours; cool naturally to room temperature to obtain a Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0050] e. The 0.3% Pt / SC catalyst obtained in Example 1 was used in a high-pressure reactor for the hydrogenation reaction of 4-nitrostyrene; the reaction conditions were 5 mg Pt / SC catalyst, 50 mL of 0.01 mol / L 4-nitrostyrene, reaction time 2 h, reaction pressure 1.5 MPa, temperature 80°C, 100°C, 120°C.

[0051] Figure 1 This is the characterization and performance study of the 0.3% Pt / SC catalyst prepared in Example 1 of the present invention.

[0052] From the high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image in Figure (a) and the mapping image in Figure (b), it can be seen that the platinum nanoclusters are uniformly dispersed on the surface of the SC carrier and the size is about 1 nm.

[0053] From the XRD pattern of the SC carrier in Figure (c) and the XRD pattern of the 0.3% Pt / SC catalyst in Figure (d), it can be clearly seen that there are no diffraction peaks of platinum, indicating that no large-sized nanoparticles are formed in the catalyst.

[0054] From the comparison of the catalytic activities of the catalysts at three temperatures: (e), (f), and (g), it can be seen that as the temperature increases, the selectivity and activity of the catalyst for 4-alkenylaniline gradually increase.

[0055] From the relationship between 1 / T and lnTOF value in Figure (h), the activation energy E of nitro hydrogenation in 4-nitrostyrene can be calculated. a =41 kJ / mol.

[0056] Example 2

[0057] The synthesis steps of the aS-C carrier are the same as those in Example 1, but the source of the raw sulfur is different. 1 g of 2,2':5',2"-terthiophene, 1 g of EC~300J, and 0.5 g of Co(NO3)2·6H2O are dissolved in THF and stirred for 10 to 14 h, and the solvent is removed by rotary evaporation to obtain a uniform dry powder mixture; the obtained dry powder mixture is transferred to a quartz boat, placed in a tube furnace, and then nitrogen is introduced as a protective gas, and the tube furnace is heated to 800°C at a rate of 5°C / min, kept warm for 1 to 3 h, and naturally cooled to room temperature to obtain a sulfur-doped carbon material;

[0058] b. The porous carbon material obtained above was placed in a round-bottom flask, 100 mL of 0.5 mol / L sulfuric acid solution was added, acid-etched at 80 ° C for 4 to 6 h, then filtered, washed three times, dried in an oven at 100 ° C, and then ground to obtain a sulfur-doped porous carbon material; the sulfur content was 9.5%;

[0059] c. The remaining synthesis steps are the same as step c and step d in Example 1 to obtain a Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0060] Example 3

[0061] The synthesis steps of the aS-C carrier are the same as those in Example 1, but the source of the raw sulfur is different. 1g of diphenyl sulfide, 1g of EC~300J, and 0.5g of Co(NO3)2·6H2O are dissolved in THF and stirred for 10-14h, and the solvent is removed by rotary evaporation to obtain a uniform dry powder mixture; the obtained dry powder mixture is transferred to a quartz boat, placed in a tube furnace, and then nitrogen is introduced as a protective gas, and the tube furnace is heated to 800℃ at a rate of 5℃ / min, kept warm for 1-3h, and naturally cooled to room temperature to obtain a sulfur-doped carbon material;

[0062] b. The carbon material obtained above was placed in a round-bottom flask, 100 mL of 0.5 mol / L sulfuric acid solution was added, acid-etched at 80 ° C for 4 to 6 h, then filtered, washed three times, dried in an oven at 100 ° C, and then ground to obtain a SC carrier; the sulfur content was 3.2%;

[0063] c. The remaining synthesis steps are the same as step c and step d in Example 1 to obtain a Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0064] Example 4

[0065] The synthesis steps of the aS-C carrier are the same as those in Example 1, but the mass ratio of the raw sulfur to the carbon material is different. 1 g of 2,2'-bithiophene, 2 g of EC~300J, and 0.5 g of Co(NO3)2·6H2O are dissolved in THF and stirred for 10 to 14 h, and the solvent is removed by rotary evaporation to obtain a uniform dry powder mixture; the obtained dry powder mixture is transferred to a quartz boat, placed in a tube furnace, and then nitrogen is introduced as a protective gas, and the tube furnace is heated to 800°C at a rate of 5 to 10°C / min, kept warm for 1 to 3 h, and naturally cooled to room temperature to obtain a sulfur-doped carbon material;

[0066] b. The carbon material obtained above was placed in a round-bottom flask, 100 mL of 0.5 mol / L sulfuric acid solution was added, acid-etched at 80 ° C for 4 to 6 h, then filtered, washed three times, dried in an oven at 100 ° C, and then ground to obtain a SC carrier; the sulfur content was 5.8%;

[0067] c. The remaining synthesis steps are the same as step c and step d in Example 1 to obtain a Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0068] Figure 2 XRD patterns of the samples prepared in Example 4. (a) SC support; (b) Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0069] Example 5

[0070] The synthesis steps of the aS-C carrier are the same as those in Example 1, but the mass ratio of the raw sulfur to the carbon material is different. 2g 2,2'-bithiophene, 1g EC~300J, and 0.5g Co(NO3)2·6H2O are dissolved in THF and stirred for 10-14h, and the solvent is removed by rotary evaporation to obtain a uniform dry powder mixture; the obtained dry powder mixture is transferred to a quartz boat, placed in a tube furnace, and then nitrogen is introduced as a protective gas, and the tube furnace is heated to 800°C at a rate of 5-10°C / min, kept warm for 1-3h, and naturally cooled to room temperature to obtain a sulfur-doped carbon material;

[0071] b. The carbon material obtained above was placed in a round-bottom flask, 100 mL of 0.5 mol / L sulfuric acid solution was added, acid-etched at 80 ° C for 4 to 6 h, then filtered, washed three times, dried in an oven at 100 ° C, and then ground to obtain a SC carrier;

[0072] c. The remaining synthesis steps are the same as step c and step d in Example 1, and a Pt / SC catalyst with a Pt loading of 0.3 wt% and a sulfur content of 8.8% is obtained;

[0073] Figure 3 XRD patterns of the samples prepared in Example 5. (a) SC support; (b) Pt / SC catalyst with a Pt loading of 0.3 wt%.

[0074] Example 6

[0075] a. Preparation of Pt nanoparticles: 39.2 mg Pt(acac)2 and 12 mL oleylamine were added to a three-necked flask, heated to 100°C, kept warm for 20 min, then 3 mL oleylamine containing 160 mg tetrabutylammonium borohydride was added, heated to 130°C, kept warm for 2 h. Finally, the mixture was washed several times with ethanol and ethanol / cyclohexane mixture (centrifugal washing, suction filtration is not acceptable), and then dispersed in a volumetric flask with cyclohexane.

[0076] b. Take 50 mg of Al2O3 carrier and 390 μL of 0.3890 mg / mL Pt nanoparticle solution and transfer them to a 100-mL round-bottom flask. Disperse them with cyclohexane (the total volume is kept at 30-50 mL) to obtain a mixture. Ultrasonicate the mixture for 0.5 h, stir it for 12 h, and rotary evaporate it at 50-60°C to obtain catalyst precursor-4.

[0077] c. Place the catalyst precursor-4 obtained above into a crucible, introduce 5 vol% H2 / Ar gas, heat the tube furnace to 300-1000°C at a rate of 5-10°C / min, and maintain for 1-3 hours; cool naturally to room temperature to obtain a Pt / Al2O3 catalyst with a Pt nanoparticle loading of 0.3 wt%.

[0078] Figure 4 The XRD pattern of the Pt / Al2O3 catalyst with a loading of 0.3 wt% of Pt nanoparticles prepared in Example 6. Figure 4 It can be seen that there is a platinum diffraction peak at 40°, corresponding to the (111) plane of Pt.

[0079] Example 7

[0080] The catalysts prepared in Example 1 and Examples 2, 3, 4, and 5 were used for the hydrogenation reaction of 4-nitrostyrene in a high-pressure reactor, respectively. The reaction conditions were 5 mg Pt / SC catalyst, 50 mL of 0.01 mol / L 4-nitrostyrene, reaction time 2 h, reaction pressure 1.5 MPa, and temperature 120° C.

[0081] Figure 5 The following is a comparison of the performance of 4-nitrostyrene selective hydrogenation catalyzed by different catalysts. (a) Example 2; (b) Example 3; (c) Example 4; (d) Example 5. After comparing the five examples, it can be seen that the catalytic performance of the catalyst synthesized according to the preparation method of Example 1 is the best.

[0082] Example 8

[0083] The 0.3% Pt / SC catalyst obtained in Example 1 was used in an anti-sulfur poisoning experiment in a high-pressure reactor. Reaction conditions: 5 mg Pt / SC catalyst, 50 mL 0.01 mol / L 4-nitrostyrene, 100 ppm, 300 ppm, 500 ppm thiophene were added respectively; reaction time 2 h, reaction pressure 1.5 MPa, temperature 120°C.

[0084] Figure 6 The comparison chart of hydrogenation performance of catalysts after sulfur poisoning test: (a) 100 ppm thiophene; (b) 300 ppm thiophene; (c) 500 ppm thiophene.

[0085] Depend on Figure 6 It can be seen that the activity slightly decreased when 100 ppm was added, but still maintained above 90%. As the concentration of thiophene increased, the selectivity of the catalyst increased slightly, and the activity decreased with the increase of thiophene concentration.

[0086] Example 9

[0087] The Pt / Al2O3 prepared in Example 6 with a Pt loading of 0.3 wt% was used for the hydrogenation reaction of 4-nitrostyrene in a high-pressure reactor; the reaction conditions were 5 mg Pt / Al2O3 catalyst, 50 mL of 0.01 mol / L 4-nitrostyrene, reaction time 2 h, reaction pressure 1.5 MPa, and temperature 120°C.

[0088] Figure 7 The hydrogenation performance comparison diagram of 0.3% Pt / Al2O3 catalyst and 0.3% Pt / SC catalyst of Example 1. (a) Catalytic activity curve of 0.3% Pt / Al2O3; (b) Catalytic activity curve of 0.3% Pt / SC.

[0089] Depend on Figure 7 It can be seen that the selectivity of the catalyst 0.3% Pt / SC is significantly higher than the selectivity of the catalyst 0.3% Pt / Al2O3.

[0090] Example 10

[0091] The 0.3% Pt / SC catalyst obtained in Example 1 was used in a high-pressure reactor for the hydrogenation experiment of 4-alkenylaniline.

[0092] a. The reaction conditions are 10 mg Pt / SC catalyst, 50 mL of 0.01 mol / L 4-vinylaniline, reaction pressure 1.5 MPa, reaction temperature 130°C, and reaction time 6 h.

[0093] b. The reaction conditions are 10 mg Pt / SC catalyst, 50 mL of 0.01 mol / L 4-vinylaniline, reaction pressure 1.5 MPa, reaction temperature 140°C, and reaction time 3 h.

[0094] c. The reaction conditions are 10 mg Pt / SC catalyst, 50 mL of 0.01 mol / L 4-vinylaniline, reaction pressure 1.5 MPa, reaction temperature 150°C, and reaction time 3 h.

[0095] Figure 8 The relationship between 1 / T and lnTOF value at three temperatures in Example 10 and the E of hydrogenation of carbon-carbon double bond in 4-alkenylaniline calculated therefrom are shown in FIG. a =82kJ / mol.

[0096] The present invention uses the catalytic hydrogenation reduction of 4-nitrostyrene to 4-vinylaniline as a probe reaction to evaluate the catalytic activity of the catalyst, and the reaction equation is as follows:

[0097]

[0098] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that those skilled in the art can make other changes within the spirit of the present invention, and these changes made according to the spirit of the present invention should be included in the scope of protection claimed by the present invention.

Claims

1. A fully exposed cluster catalyst of platinum supported on sulfur-doped porous carbon, characterized in that: The platinum in the catalyst is loaded on the surface of a carbon carrier in an atomically dispersed form. The carbon carrier is sulfur-doped porous carbon. The platinum loading is 0.1wt%-3wt%, and the sulfur doping amount is 3.2-9.5%.

2. The method for preparing the sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 1 is characterized in that it comprises the following steps: S1) mixing the sulfur-doped porous carbon support and the platinum-containing precursor in a solvent, and then drying by rotary evaporation to obtain a dry powder mixture; S2) performing a reduction heat treatment on the dry powder mixture in a hydrogen reducing atmosphere to obtain a fully exposed platinum cluster catalyst; the reduction heat treatment temperature is 200-1000°C.

3. The method for preparing a sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 2, characterized in that: The hydrogen reducing atmosphere is a mixture of H2 / Ar, H2 / N2 or H2 / He, wherein the volume content of hydrogen is 3-50 vol%.

4. The method for preparing a sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 2, characterized in that: The heating rate of the reduction heat treatment is 1-20°C / min, and the reduction heat treatment time is 1-5 h.

5. The method for preparing a sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 2, characterized in that: The uniform mixing in step S1 specifically comprises: ultrasonic mixing followed by vigorous stirring; the ultrasonic time is 0.5 to 2 h, and the vigorous stirring time is 10 to 12 h.

6. The method for preparing a sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 3, characterized in that: The rotary evaporation drying temperature in step S1 is 80-100°C.

7. The method for preparing a sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 6, characterized in that: The rotary evaporation drying temperature is 30-60°C.

8. The method for preparing a sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 2, characterized in that: The method for preparing the sulfur-doped porous carbon carrier comprises the following steps: S1-1) Mixing sulfur-containing organic matter, carbon material and cobalt salt in a solvent, ultrasonically treating, stirring, rotary evaporating, drying, and then calcining at high temperature in a nitrogen or argon atmosphere to obtain a sulfur-doped carbon material; the calcination temperature is 600-1000°C; S1-2) etching the carbon material with sulfuric acid to remove the cobalt particles in the carrier, washing the carbon material, and then drying the washed carbon material in an oven at 100° C. to obtain a sulfur-doped porous carbon material.

9. The method for preparing a sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 8, characterized in that: The sulfur-containing organic matter is one or more of thiophene, sulfide, and thiol; the carbon material is one of commercial carbon black, carbon nanotubes, and activated carbon; the cobalt salt is cobalt nitrate hexahydrate; and the mass ratio of the sulfur-containing organic matter, the carbon material, and the cobalt salt is 2:1:

1.

10. The sulfur-doped porous carbon-supported platinum fully exposed cluster catalyst according to claim 1, wherein the fully exposed cluster catalyst is used in the selective hydrogenation reaction of 4-nitrostyrene to catalyze hydrogenation to produce 4-vinylaniline.

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