A palladium-cobalt bimetallic catalyst, a preparation method and application thereof

Abstract

The application discloses a palladium-cobalt bimetal catalyst and a preparation method and application thereof, and comprises a carrier and an active component, wherein the active component is loaded on the surface of the carrier, the carrier is a metal-doped silicon oxide carrier, and the active component is a bimetal nanoparticle of palladium and cobalt elements. The metal-doped mesoporous silicon oxide carrier can better interact with the active component, enhance the anchoring capacity of the active component, and inhibit the loss and aggregation of the active component; the active component is selected from palladium and cobalt, cobalt is used as an additive to control the charge distribution of palladium, and the hydrogenation of a C=C bond has good catalytic conversion activity and selectivity.

Description

TECHNICAL FIELD

[0001] The application relates to a palladium-cobalt bimetallic catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts. BACKGROUND

[0002] With the development of society, the waste and exhaustion of natural resources prompt people to synthesize a large number of artificial chemicals to meet the demand. In these organic syntheses, the selective hydrogenation of unsaturated organic substances plays an irreplaceable role. However, it is challenging to hydrogenate the target functional group while avoiding the hydrogenation reduction of other functional groups under mild reaction conditions, and a catalyst with high selectivity for the target functional group is needed. According to the current relevant literature reports, Pd-based catalysts are often applied to selective hydrogenation reactions due to their unique electronic structure, ability to adsorb and activate hydrogen and unsaturated substrates. However, Pd NPs in traditional Pd-based catalysts are thermodynamically unstable and tend to undergo self-polymerization, resulting in a decrease in catalytic performance. Therefore, it is necessary to select a suitable support material to disperse Pd NPs and improve the catalytic performance. SUMMARY

[0003] The purpose of the application is to use metal-doped mesoporous silica as a support for catalysts to anchor and disperse metal nanoparticles, prevent their agglomeration and loss, and further adjust the electronic structure and geometric structure of the active sites of the catalysts by utilizing the synergistic effect between palladium and cobalt, thereby regulating the catalytic performance.

[0004] According to one aspect of the application, a palladium-cobalt bimetallic catalyst is provided, comprising a support and an active component loaded on the surface of the support.

[0005] The support is a metal-doped silica support.

[0006] The active component is a bimetallic nanoparticle of palladium and cobalt elements.

[0007] The mesoporous silica support used in the palladium-cobalt bimetallic catalyst has a high specific surface area and pore volume, which is more conducive to the adsorption and dispersion of metal salt solutions by the impregnation method, avoiding the addition of acid or alkaline organic polymers required by deposition-precipitation or other complex methods. The inherent porosity provides more positions for the support to load the active component.

[0008] Optionally, in the palladium-cobalt bimetallic catalyst,

[0009] The content of the support is 82-94 wt%, and the content of the active component is 6-18 wt%.

[0010] In the active component, the content of the palladium element is 5.8-7 wt% of the mass of the catalyst.

[0011] The content of the cobalt element is 0.2-11wt% of the mass of the catalyst.

[0012] Optionally, the carrier is nanospherical, and the diameter of the carrier is 80-160nm.

[0013] The diameter of the bimetallic nanoparticles is 5-10nm.

[0014] Optionally, the diameter of the carrier is selected from any value or a range between two values selected from 80nm, 100nm, 116nm, 140nm, 160nm.

[0015] The diameter of the bimetallic nanoparticles is selected from any value or a range between two values selected from 5nm, 7.3nm, 10nm.

[0016] Optionally, the metal-doped silicon oxide carrier is selected from at least one of mesoporous silicon oxide nanospheres, mesoporous niobium-silicon nanospheres, mesoporous aluminum-silicon nanospheres, mesoporous zirconium-silicon nanospheres.

[0017] In another aspect of the present application, a preparation method of a palladium-cobalt bimetallic catalyst is provided, comprising the following steps:

[0018] (a) adding a solution I containing a palladium source and a cobalt source to a carrier, impregnating, to obtain a catalyst precursor solution;

[0019] (b) adding an aqueous solution containing a reducing agent to the catalyst precursor solution prepared in step (a) to obtain a mixture II, reducing, to obtain the palladium-cobalt bimetallic catalyst;

[0020] The carrier is a metal-doped silicon oxide carrier.

[0021] Optionally, the concentration of the palladium source in the solution I is 2-4mol / L, in terms of the molar amount of palladium element in the palladium source;

[0022] The concentration of the cobalt source in the solution I is 0.05-0.7mol / L, in terms of the molar amount of cobalt element in the cobalt source.

[0023] In step a), the mass of the carrier to the volume of solution I is 0.1g: 90-300μl.

[0024] Optionally, the concentration of the palladium source in the solution I is selected from any value or a range between two values selected from 2mol / L, 3mol / L, 4mol / L.

[0025] Optionally, the concentration of the cobalt source in the solution I is selected from any value or a range between two values of 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.7 mol / L.

[0026] Optionally, in step a), the mass of the carrier to the volume of the solution I is selected from any value or a range between two values of 0.1 g: 50 μL, 0.1 g: 100 μL, 0.1 g: 200 μL, 0.1 g: 300 μL.

[0027] Optionally, the concentration of the reducing agent in the mixed solution II is 0.03-0.1 mol / L, calculated by the molar mass of the reducing agent itself.

[0028] In step b), the mass of the carrier to the volume of the aqueous solution containing the reducing agent is 0.1 g: 5-30 ml.

[0029] Optionally, the concentration of the reducing agent in the mixed solution II is selected from any value or a range between two values of 0.03 mol / L, 0.05 mol / L, 0.75 mol / L, 0.1 mol / L.

[0030] Optionally, in step b), the mass of the carrier to the volume of the aqueous solution containing the reducing agent is selected from any value or a range between two values of 0.1 g: 5 mL, 0.1 g: 10 mL, 0.1 g: 15 mL, 0.1 g: 20 mL, 0.1 g: 30 mL.

[0031] Optionally, the metal-doped silicon oxide carrier is selected from at least one of mesoporous silicon oxide nanospheres, mesoporous niobium silicon nanospheres, mesoporous aluminum silicon nanospheres, mesoporous zirconium silicon nanospheres.

[0032] The palladium source is selected from at least one of palladium chloride, palladium acetate.

[0033] The cobalt source is selected from at least one of cobalt chloride, cobalt acetate.

[0034] The reducing agent is selected from at least one of sodium borohydride, ascorbic acid.

[0035] Optionally, the reduction conditions are: the reduction temperature is 20-30 °C, and the reduction time is 10-30 min.

[0036] Optionally, the reduction temperature is selected from any value or a range between two values of 20 °C, 24 °C, 25 °C, 26 °C, 30 °C.

[0037] Optionally, the reduction time is selected from any value or a range between two values of 10 min, 15 min, 20 min, 25 min, 30 min.

[0038] Optionally, the impregnation condition is that the impregnation temperature is 20-30℃ and the impregnation time is 12-24h.

[0039] Optionally, the impregnation temperature is selected from any value or a range value between two values selected from 20℃, 24℃, 25℃, 26℃ and 30℃.

[0040] Optionally, the impregnation time is selected from any value or a range value between two values selected from 12h, 16h, 20h and 24h.

[0041] As a specific embodiment, the preparation method of the palladium-cobalt bimetallic catalyst is as follows:

[0042] A mixed aqueous solution containing palladium chloride and cobalt chloride is configured, a metal-doped mesoporous silica carrier is added, and impregnation is performed after standing to obtain a catalyst precursor;

[0043] An aqueous solution containing sodium borohydride is added to the catalyst precursor, and the mixed solution is reduced;

[0044] The mixed solution is centrifuged, washed, dried, and the palladium-cobalt bimetallic catalyst is obtained.

[0045] The use amount ratio of the metal-doped mesoporous silica carrier, the aqueous solution containing palladium chloride and the aqueous solution containing cobalt chloride is 0.1g: 90-110μL: 10-100μL.

[0046] In the metal-doped mesoporous silica carrier, the atom ratio of the doped metal to silicon is 0.01:1-0.05:1.

[0047] After the mixed solution is mixed with the carrier, stirring and ultrasonic treatment are performed, and then impregnation is performed.

[0048] According to another aspect of the present application, the application of the palladium-cobalt bimetallic catalyst is provided, and a method for selectively hydrogenating 3-nitrostyrene includes the following steps:

[0049] The raw materials containing 3-nitrostyrene, an alcohol solvent and a catalyst are subjected to a hydrogenation reaction in a hydrogen atmosphere to obtain 3-ethyl nitrobenzene.

[0050] Optionally, the alcohol solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol and n-butanol.

[0051] Optionally, the reaction conditions of the hydrogenation reaction are that the reaction temperature is 40-60℃, the reaction time is 8-30min, and the reaction pressure is 1-3bar.

[0052] Optionally, the reaction conditions of the hydrogenation reaction are that the reaction temperature is 40-60℃, the reaction time is 8-30min, and the reaction pressure is 1-3bar.

[0053] The reaction temperature is selected from any value or a range between two values selected from 40℃, 45℃, 50℃, 55℃, 60℃;

[0054] The reaction time is selected from any value or a range between two values selected from 8min, 12min, 15min, 20min, 30min;

[0055] The reaction pressure is selected from any value or a range between two values selected from 1bar, 2bar, 3bar.

[0056] Optionally, the concentration of 3-nitrostyrene in the raw material is 0.09-0.2mol / L.

[0057] Optionally, the concentration of 3-nitrostyrene in the raw material is selected from any value or a range between two values selected from 0.09mol / L, 0.1mol / L, 0.15mol / L, 0.2mol / L.

[0058] Optionally, the mass ratio of 3-nitrostyrene to catalyst in the raw material is 1:(0.03-0.04).

[0059] Optionally, the mass ratio of 3-nitrostyrene to catalyst in the raw material is selected from any value or a range between two values selected from 1:0.03, 1:0.037, 1:0.04.

[0060] The beneficial effects that can be produced by the present application include:

[0061] 1) The palladium-cobalt bimetallic catalyst provided by the present application is selected from metal-doped mesoporous silica as a carrier, and the metal-doped mesoporous silica contains transition metal heteroatoms, which can better interact with the loaded active components, improve the catalytic performance, and to some extent, enhance the anchoring ability of the active components, and inhibit the loss and aggregation of the active components.

[0062] 2) The palladium-cobalt bimetallic catalyst provided by the present application uses metal palladium as an active site, and another metal cobalt as an additive to regulate the charge distribution of palladium, and has better catalytic conversion activity and selectivity for the hydrogenation of C=C bonds.

[0063] 3) The preparation method of the palladium-cobalt bimetallic catalyst provided by the present application is reduced at normal temperature and pressure in a liquid phase, the preparation method is simple, the experimental conditions are mild, the prepared catalyst has good cycle stability and universality, and is conducive to further application and large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 SEM and TEM images of the metal Nb-doped mesoporous silica carrier described in Example 2 of the present application, wherein a) is an SEM image; and b) is a TEM image.

[0065] Figure 2 SEM and TEM images of the palladium-cobalt bimetallic catalyst 8 described in Example 12, wherein a) is the SEM image; b) is the TEM image. DETAILED DESCRIPTION

[0066] The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

[0067] The raw materials in the examples of the present application are all purchased through commercial channels unless otherwise specified.

[0068] The analysis method in the examples of the present application is as follows:

[0069] The SEM images of the metal Nb-doped mesoporous silica support were obtained using a JEOL JSM-7800F scanning electron microscope;

[0070] The TEM images of the metal Nb-doped mesoporous silica support and the palladium-cobalt bimetallic catalyst 8 were obtained using a JEOL JEM-2000EX transmission electron microscope;

[0071] Quantitative analysis was performed using HPLC (Waters).

[0072] The conversion rate of the substrate and the product distribution in the examples of the present application were calculated by the following methods:

[0073] Conversion rate = (n0-n) / n0x100%

[0074] Selectivity = n x / (n0-n)x100%

[0075] In the formula, n0 is the amount of substance (mol) of the substrate added before the reaction, n is the amount of substance (mol) of the substrate remaining after the reaction, and n x is the amount of substance (mol) of one product after the reaction.

[0076] Preparation of the support:

[0077] Example 1

[0078] Take a 500 mL beaker, weigh 0.58 g of cetyltrimethylammonium bromide (CTAB) into it, add 288 g of deionized water and 12 g of ammonia water in turn, then place the beaker in a 50°C water bath, stir at 400 rpm for 10 min, quickly add 5 mL of 0.2M tetraethyl orthosilicate (TEOS) ethanol solution, continue to stir at a stirring speed of 400 rpm for 5 h to form the crystal nucleus of silica. Then increase the stirring speed to 600 rpm, add 5 mL of 1.0M TEOS ethanol solution dropwise, continue to stir for 1 h, then stop stirring, and then transfer to a 60°C oven and continue to age for 24 h. Centrifugal separation at 15000 rpm, wash with deionized water and ethanol in turn until neutral, then dry in an 80°C oven overnight, and finally calcine in a muffle furnace at 550°C for 10 h to obtain MSN.

[0079] Example 2

[0080] Take a 500 mL beaker, weigh 0.58 g of cetyltrimethylammonium bromide (CTAB) into it, add 288 g of deionized water and 12 g of ammonia water in turn, then place the beaker in a 50°C water bath, stir at 400 rpm for 10 min, quickly add 5 mL of 0.2M tetraethyl orthosilicate (TEOS) ethanol solution, continue to stir at a stirring speed of 400 rpm for 5 h to form the crystal nucleus of silica. Then increase the stirring speed to 600 rpm, add 5 mL of 1.0M TEOS ethanol solution dropwise, continue to stir for 1 h, then stop stirring, and then transfer to a 60°C oven and continue to age for 24 h. Centrifugal separation at 15000 rpm, wash with deionized water and ethanol in turn until neutral, then dry in an 80°C oven overnight, and finally calcine in a muffle furnace at 550°C for 10 h to obtain MSN.

[0081] Figure 1 SEM and TEM images of the metal Nb-doped mesoporous silica Nb-MSN described in Example 2; in the figure, a) is the SEM image; b) is the TEM image.

[0082] As can be seen from Figure 1 , the Nb-MSN is uniformly dispersed nanospheres with a particle size of about 116 nm, and has ordered hexagonal mesoporous channels.

[0083] Example 3

[0084] The experimental steps of Example 3 are similar to those of Example 2, and Al(O iC3H7)3 as the aluminum source, except that the amount of CTAB added was 0.15 g, and the pH value was not adjusted with hydrochloric acid, and the atomic ratio of Si:Al added was 1:0.05. An Al-MSN was obtained.

[0085] Example 4

[0086] The experimental steps of Example 4 were similar to those of Example 2, using Zr(O n C3H7)4 as the zirconium source, except that the amount of CTAB added was 0.15 g, and the pH value was not adjusted with hydrochloric acid, and the atomic ratio of Si:Zr added was 1:0.05, and Zr(O n C3H7)4 was added to the system after the ethanol solution of Zr(O

[0087] Preparation of the catalyst:

[0088] Example 5

[0089] In a 10 mL beaker, 0.0110 g of PdCl2 and 0.0010 g of CoCl2 were weighed, 0.3 mL of water was added, and the mixture was completely dissolved by ultrasonic treatment and mixed by stirring. Then, 0.1 g of Nb-MSN was added, and the mixture was stirred at 500 rpm for 10 min and ultrasonically treated for 5 min. The resulting muddy mixture was left to stand at room temperature for 24 h of impregnation, and a catalyst precursor was obtained. Under stirring at 500 rpm, 10 mL of a 0.05 M NaBH4 solution was added to the catalyst precursor, and the resulting mixture was collected after reduction at room temperature for 20 min. The mixture was then washed 3 times by centrifugation and deionized water. A light black catalyst was obtained after vacuum drying at 40°C for 12 h. It was labeled as Pd1-Co 0.07 / Nb-MSN catalyst 1.

[0090] Example 6

[0091] The experimental steps of Example 6 were the same as those of Example 5, except that the carrier Nb-MSN was replaced by Al-MSN. It was labeled as Pd1-Co 0.07 / Al-MSN catalyst 2.

[0092] Example 7

[0093] The experimental steps of Example 7 were the same as those of Example 5, except that the carrier Nb-MSN was replaced by Zr-MSN. It was labeled as Pd1-Co 0.07 / Zr-MSN catalyst 3.

[0094] Example 8

[0095] The experimental steps of Example 8 were the same as those of Example 5, except that the amount of CoCl2 added was changed to 0.0030 g. It was labeled as Pd1-Co0.2 Pd-Co NPs / Nb-MSN catalyst 4.

[0096] Example 9

[0097] The experimental procedure of Example 9 is the same as that of Example 5, except that the amount of CoCl2added is changed to 0.0089 g, which is labeled as Pd1-Co / Nb-MSN catalyst 5. 0.6 Pd-Co NPs / Nb-MSN catalyst 5.

[0098] Example 10

[0099] The experimental procedure of Example 10 is the same as that of Example 5, except that the amount of CoCl2added is changed to 0.0148 g, which is labeled as Pd1-Co1 / Nb-MSN catalyst 6.

[0100] Example 11

[0101] The experimental procedure of Example 11 is the same as that of Example 5, except that the amount of CoCl2added is changed to 0.0296 g, which is labeled as Pd1-Co2 / Nb-MSN catalyst 7.

[0102] Example 12

[0103] The experimental procedure of Example 12 is the same as that of Example 5, except that the amount of CoCl2added is changed to 0.0370 g, which is labeled as Pd1-Co3 / Nb-MSN catalyst 8. 2.5 Pd-Co NPs / Nb-MSN catalyst 8.

[0104] Figure 2 SEM and TEM images of catalyst 8 described in Example 12; in the figure, a) is a SEM image; b) is a TEM image.

[0105] As can be seen from Figure 2 , the Pd-Co NPs are mainly loaded on the outer surface of the support Nb-MSN, and the average particle size is about 7.3 nm.

[0106] Comparative Example 1

[0107] In a 10 mL beaker, 0.0110 g of PdCl2and 0.0148 g of CoCl2were weighed, 0.3 mL of water was added, and they were completely dissolved by ultrasonic treatment. After stirring to mix thoroughly, 0.1 g of Nb-MSN was added, and the mixture was stirred at 500 rpm for 10 min and ultrasonically treated for 5 min. The obtained muddy mixture was left to stand at room temperature for 24 h of impregnation to obtain a catalyst precursor. The catalyst precursor was dried at 110 °C overnight, and the catalyst precursor was reduced in a tube furnace at a temperature of 200 °C for 4 h under hydrogen gas, with a heating rate of 4 °C / min and a hydrogen flow rate of 30 mL / min. It is labeled as Pd1-Co1 / Nb-MSN(200) catalyst 9.

[0108] Comparative Example 2

[0109] The experimental procedure of Comparative Example 2 is the same as Comparative Example 1, except that the reduction temperature is changed to 300°C, which is marked as Pd1-Co1 / Nb-MSN(300) catalyst 10.

[0110] Comparative Example 3

[0111] The experimental procedure of Comparative Example 3 is the same as Comparative Example 1, except that the reduction temperature is changed to 400°C, which is marked as Pd1-Co1 / Nb-MSN(400) catalyst 11.

[0112] Comparative Example 4

[0113] The experimental procedure of Comparative Example 4 is the same as Example 5, except that the support Nb-MSN is changed to MSN. It is marked as Pd1-Co1 / MSN catalyst 12. 0.07

[0114] Application Test Examples

[0115] Test Example 1

[0116] 0.45 mmol of 3-nitrostyrene, 2.5 mg of catalyst 1 and 5 ml of solvent ethanol are all added to a high-pressure reaction kettle, after sealing, flushing with hydrogen gas for 3 times, then flushing into 3 bar hydrogen gas, and then placed in an oil bath with a temperature of 50°C and a stirring speed of 500 rpm. After 20 min of reaction, the reaction kettle is taken out and cooled in an ice water bath. The quantitative analysis of the product uses HPLC.

[0117] Test Examples 2-3

[0118] The experimental procedure of Test Example 2 is the same as Test Example 1, except that catalyst 1 is changed to catalyst 2.

[0119] The experimental procedure of Test Example 3 is the same as Test Example 1, except that catalyst 1 is changed to catalyst 3.

[0120] Test Example 4

[0121] 0.45 mmol of 3-nitrostyrene, 2.5 mg of catalyst 6 and 5 ml of solvent methanol are all added to a high-pressure reaction kettle, after sealing, flushing with hydrogen gas for 3 times, then flushing into 1 bar hydrogen gas, and then placed in an oil bath with a temperature of 50°C and a stirring speed of 500 rpm. After 15 min of reaction, the reaction kettle is taken out and cooled in an ice water bath. The quantitative analysis of the product uses HPLC.

[0122] Test Examples 5-18

[0123] The experimental procedure of Test Example 5 is the same as Test Example 4, except that catalyst 6 is changed to catalyst 4 and the reaction solvent is changed to ethanol.​

[0124] The experimental procedure of Test Example 6 is the same as that of Test Example 4, except that catalyst 6 is replaced by catalyst 5 and the reaction solvent is replaced by ethanol.

[0125] The experimental procedure of Test Example 7 is the same as that of Test Example 4, except that catalyst 6 is replaced by catalyst 7 and the reaction solvent is replaced by ethanol.

[0126] The experimental procedure of Test Example 8 is the same as that of Test Example 4, except that catalyst 6 is replaced by catalyst 8 and the reaction solvent is replaced by ethanol.

[0127] The experimental procedure of Test Example 9 is the same as that of Test Example 4, except that the reaction solvent is replaced by ethanol.

[0128] The experimental procedure of Test Example 10 is the same as that of Test Example 4, except that the reaction solvent is replaced by n-propanol.

[0129] The experimental procedure of Test Example 11 is the same as that of Test Example 4, except that the reaction solvent is replaced by isopropanol.

[0130] The experimental procedure of Test Example 12 is the same as that of Test Example 4, except that the reaction solvent is replaced by n-butanol.

[0131] The experimental procedure of Test Example 13 is the same as that of Test Example 4, except that the reaction time is replaced by 8 min.

[0132] The experimental procedure of Test Example 14 is the same as that of Test Example 4, except that the reaction time is replaced by 10 min.

[0133] The experimental procedure of Test Example 15 is the same as that of Test Example 4, except that the reaction time is replaced by 12 min.

[0134] The experimental procedure of Test Example 16 is the same as that of Test Example 4, except that the reaction time is replaced by 20 min.

[0135] The experimental procedure of Test Example 17 is the same as that of Test Example 4, except that the reaction temperature is replaced by 40 °C.

[0136] The experimental procedure of Test Example 18 is the same as that of Test Example 4, except that the reaction temperature is replaced by 45 °C.

[0137] Comparative Test Examples 1-4

[0138] The experimental procedure of Comparative Test Example 1 is the same as that of Test Example 4, except that catalyst 6 is replaced by catalyst 9.

[0139] The experimental procedure of Comparative Test Example 2 is the same as that of Test Example 4, except that catalyst 6 is replaced by catalyst 10.

[0140] The experimental procedure of Comparative Test Example 3 is the same as that of Test Example 4, except that catalyst 6 is replaced by catalyst 11.

[0141] The experimental steps of Comparative Test Example 4 are the same as those of Test Example 1, except that catalyst 6 is replaced by catalyst 12.

[0142] The reaction conversion rate and selectivity of 3-nitrostyrene catalyzed by the above-mentioned metal-doped mesoporous silica supported palladium-cobalt bimetallic catalyst are shown in Table 1:

[0143] Table 1

[0144]

[0145]

[0146] According to Table 1, it can be seen from the comparison of Test Examples 1, 2, 3 and Comparative Test Example 4 that the palladium-cobalt catalyst prepared by using a metal-doped mesoporous silica support and a mesoporous silica support without doping metal has better conversion rate of 3-nitrostyrene and higher catalytic activity.

[0147] From Test Examples 5 to 9, it can be seen that the mass ratio of the active components palladium and cobalt has a great influence on the performance of the catalyst, and when the mass ratio of palladium to cobalt is 1:1, the catalytic performance is the best.

[0148] From the comparison of Test Example 4 and Comparative Test Examples 1 to 3, it can be seen that the catalyst obtained by liquid reduction has better catalytic performance than the catalyst obtained by high-temperature reduction under hydrogen atmosphere, and has higher conversion rate of 3-nitrostyrene and selectivity of 3-ethyl nitrobenzene.

[0149] From Test Example 4 and Test Examples 9 to 12, it can be seen that the reaction solvent has a great influence on the test results in the method of selectively hydrogenating 3-nitrostyrene, and when the reaction solvent is methanol, the conversion rate of 3-nitrostyrene and the selectivity of 3-ethyl nitrobenzene are better.

[0150] From Test Example 4 and Test Examples 13 to 16, it can be seen that as the reaction time increases, the conversion rate of 3-nitrostyrene and the selectivity of 3-ethyl nitrobenzene are better.

[0151] From Test Example 4 and Test Examples 17 to 18, it can be seen that the reaction temperature has a great influence on the test results, and the higher the reaction temperature, the greater the activity of catalyzing the hydrogenation of 3-nitrostyrene.

[0152] In summary, the preparation of the metal-doped mesoporous silica supported palladium-cobalt bimetallic catalyst described in the present application is simple, the experimental conditions are relatively mild, the prepared catalyst has good cycle stability and universality, and is conducive to large-scale production. The metal-doped mesoporous silica is selected as the carrier, the metal-doped mesoporous silica contains transition metal heteroatoms, which can better interact with the supported active phase, improve the catalytic performance, and to some extent enhance the anchoring ability to the active phase, inhibit the loss and aggregation of the active components.

[0153] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed above, the present application is not limited thereto. Any person skilled in the art can make some changes or modifications to the above disclosed technical contents without departing from the scope of the technical solutions of the present application, and such changes or modifications are equivalent to equivalent embodiments, and are within the scope of the technical solutions.

Claims

1. A palladium-cobalt bimetallic catalyst, characterized in that, It includes a carrier and an active component, wherein the active component is loaded on the surface of the carrier; The carrier is a metal-doped silicon oxide carrier, selected from at least one of mesoporous niobium-silicon nanospheres, mesoporous aluminum-silicon nanospheres, and mesoporous zirconium-silicon nanospheres; the carrier is in the form of nanospheres, and the diameter of the carrier is 80~160nm; the content of the carrier is 82~94 wt%, and the content of the active component is 6~18 wt%. In the active component, the palladium content is 5.8~7 wt% of the catalyst mass. The cobalt content is 0.2~11 wt% of the catalyst mass; the active component is bimetallic nanoparticles of palladium and cobalt, and the diameter of the bimetallic nanoparticles is 5~10 nm.

2. The palladium-cobalt bimetallic catalyst according to claim 1, characterized in that, The diameter of the carrier is 100~140nm.

3. A method for preparing a palladium-cobalt bimetallic catalyst according to any one of claims 1 to 2, characterized in that, Includes the following steps: (a) A solution containing palladium and cobalt sources is added to a support and impregnated to obtain a catalyst precursor solution; (b) Add an aqueous solution containing a reducing agent to the catalyst precursor solution prepared in step (a) to obtain mixture II, reduce, and obtain the palladium-cobalt bimetallic catalyst; The carrier is a metal-doped silicon oxide carrier.

4. The preparation method according to claim 3, characterized in that, The concentration of the palladium source in solution I is 2~4 mol / L, based on the molar amount of palladium in the palladium source; The concentration of the cobalt source in solution I is 0.05~0.7 mol / L, based on the molar amount of cobalt element in the cobalt source; In step a), the mass ratio of the carrier to the volume of solution I is 0.1 g: 90~300 μL; Preferably, the concentration of the reducing agent in the mixture II is 0.03~0.1 mol / L, based on the molar mass of the reducing agent itself; In step b), the mass ratio of the carrier to the volume ratio of the aqueous solution containing the reducing agent is 0.1 g: 5~30 ml.

5. The preparation method according to claim 3, characterized in that, The metal-doped silicon oxide support is selected from at least one of mesoporous niobium silicon nanospheres, mesoporous aluminum silicon nanospheres, and mesoporous zirconium silicon nanospheres. The palladium source is selected from at least one of palladium chloride and palladium acetate; The cobalt source is selected from at least one of cobalt chloride and cobalt acetate; The reducing agent is selected from at least one of sodium borohydride and ascorbic acid.

6. The preparation method according to claim 3, characterized in that, The reduction conditions are: reduction temperature of 20~30℃ and reduction time of 10~30 min; The impregnation conditions are: impregnation temperature of 20~30 ℃ and impregnation time of 12~24 h.

7. A method for the selective hydrogenation of catalytically 3-nitrostyrene, characterized in that, Includes the following steps: A raw material containing 3-nitrostyrene, an alcohol solvent, and a catalyst is subjected to a selective hydrogenation reaction under a hydrogen atmosphere to obtain 3-ethylnitrobenzene. The catalyst is selected from any one of the palladium-cobalt bimetallic catalysts according to any one of claims 1 to 2 or palladium-cobalt bimetallic catalysts prepared by the preparation method according to any one of claims 3 to 6.

8. The method for selective hydrogenation of catalytically 3-nitrostyrene according to claim 7, characterized in that, The alcohol solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, and n-butanol.

9. The method for selective hydrogenation of catalytically 3-nitrostyrene according to claim 7, characterized in that, The reaction conditions for the hydrogenation reaction are: reaction temperature of 40~60 ℃, reaction time of 8~30 min, and reaction pressure of 1~3 bar.

10. The method for selective hydrogenation of catalytically 3-nitrostyrene according to claim 7, characterized in that, The concentration of 3-nitrostyrene in the raw material is 0.09~0.2 mol / L; The mass ratio of 3-nitrostyrene to catalyst in the raw materials is 1:(0.03~0.04).

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