A supported PtNi dual-site adiponitrile hydrogenation catalyst, a preparation method and application thereof

Abstract

The application discloses a supported PtNi b-site adiponitrile hydrogenation catalyst and a preparation method and application thereof, and belongs to the technical field of thermal catalysis. The preparation method comprises the following steps: (1) dispersing ammonium tungsten oxide pentahydrate in water, adding an acidic solution, condensing and refluxing, heating and reacting, centrifugal filtering and drying the precipitate to prepare tungsten oxide nanorod carriers; (2) dispersing the tungsten oxide nanorod carriers in a solvent, adding a platinum salt solution, stirring, evaporating the solvent, and calcining the solid to prepare a catalyst precursor; and (3) dispersing the catalyst precursor in a solvent, adding a nickel salt solution, stirring, evaporating the solvent, and calcining the solid to prepare the catalyst. The application introduces Pt and Ni on the reducible WO3 carrier to construct a bimetallic active site catalyst, and the bimetallic active site catalyst can catalyze the reaction of adiponitrile hydrogenation to prepare primary amine under mild conditions, has the characteristics of low noble metal loading, high activity and high selectivity, and has important industrial application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal catalysis, in particular to a supported PtNi b-site adiponitrile hydrogenation catalyst, its preparation method and application. BACKGROUND

[0002] The hydrogenation of nitriles to the corresponding primary amines is one of the most active research topics in the field of bulk chemicals and fine chemicals. Primary amines are important chemical raw materials and fine chemical intermediates, which can be widely used in the synthesis of plastics, detergents, textile auxiliaries, flotation agents, antistatic agents and preservatives, etc. However, in the process of nitrile hydrogenation to primary amine, the hydrogenation and condensation of unsaturated-C≡N bond can occur simultaneously. Therefore, the formation of primary amine is often accompanied by by-products such as secondary amine and tertiary amine. Therefore, the key step to improve the selectivity of primary amine is to inhibit the formation of the above by-products. Therefore, it is of great significance to construct a suitable catalytic system to realize the high selective preparation of primary amine from nitrile under mild conditions.

[0003] The hydrogenation of adiponitrile (ADN) to primary amine is the most effective and reasonable reaction route. Since ADN is highly unsaturated, it contains two-C≡N functional groups, so the hydrogenation reaction includes semi-hydrogenation (6-aminocapronitrile, ACN) and complete hydrogenation (1,6-hexanediamine, HDA) products. In addition, imine as a highly active intermediate, intramolecular condensation to form the by-product cyclohexylamine (ACH). Among them, ACN and HMDA are important chemical intermediates, the former is used to prepare epsilon-caprolactam (CPL), which is a very important organic chemical intermediate and is also the main raw material for the synthesis of nylon-6 fiber, nylon-6 engineering plastic and film, and the latter is used to prepare nylon-66. As shown in Figure 1 ADN hydrogenation is a complex process with different reaction pathways. First, ADN semi-hydrogenation generates highly active imine, which can be further hydrogenated to primary amine ACN and HDA. The intermediate imine of CAN continues to hydrogenate and can also react with primary amine to form 1-(alkylamine)alk-1-amine (intermolecular condensation) and azacycloheptane-2-amine (intermolecular condensation) by nucleophilic addition of primary amine to the alpha-carbon of aldehyde amine, and further deamination to form N-substituted imine (tertiary amine). Then hydrogenation generates the main by-product 1-azacycloheptane (ACH) of secondary amine.

[0004] The reported ADN hydrogenation catalysts include Raney catalyst, Ziegler catalyst, amorphous alloy catalyst, non-supported and supported nickel-based catalyst, Ru or Rh noble metal catalyst. The Raney catalyst has problems of fragmentation, spontaneous combustion, and the need for a large amount of ammonia and alkali solution to inhibit side reactions. The Ru complex homogeneous catalyst and the Rh supported catalyst have high conversion rate and selectivity of ADN to ACN and HDA in the liquid phase hydrogenation process, but these catalysts have complex preparation process, high cost, and the need for a large amount of ammonia and alkali solution to inhibit the generation of by-products. A catalyst with low noble metal loading, high activity, high selectivity, stable structure and easy recycling, and capable of catalyzing the hydrogenation of adiponitrile to prepare primary amine under mild conditions is urgently needed to be developed. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide a supported PtNi b-site adiponitrile hydrogenation catalyst and its preparation method and application, so as to solve the problems of fragmentation, spontaneous combustion, the need for a large amount of ammonia and alkali solution to inhibit side reactions, complex preparation process, high cost and other problems of the existing adiponitrile hydrogenation catalyst.

[0006] The technical solution of the present application to solve the above technical problems is as follows:

[0007] A preparation method of a supported PtNi b-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0008] (1) Preparation of tungsten oxide nanorod carrier: disperse tungsten oxide ammonium pentahydrate in water, add an acidic solution, condense and reflux, heat the reaction, centrifuge and filter the precipitate, and dry to obtain;

[0009] (2) Preparation of catalyst precursor: disperse the tungsten oxide nanorod carrier obtained in step (1) in a solvent, add a platinum salt solution, stir, evaporate the solvent, and calcine the solid to obtain;

[0010] (3) Preparation of supported PtNi b-site adiponitrile hydrogenation catalyst: disperse the catalyst precursor obtained in step (2) in a solvent, add a nickel salt solution, stir, evaporate the solvent, and calcine the solid to obtain.

[0011] The present application has the following advantages: the present application introduces Pt and Ni bimetallic active sites on the tungsten oxide nanorod carrier by using the traditional impregnation method, the loading amount of Pt is very low, and Pt exists in the form of single atom, and Ni exists in the form of particles, which realizes the spatial separation of bimetallic sites, breaks the contradiction of the linear scale limitation of the traditional supported catalyst, and thus improves the adiponitrile hydrogenation catalytic activity and the selectivity of the target product, the preparation method is simple, the loading amount of noble metal is low, the cost is low, and a large amount of ammonia and alkali solution is not needed to inhibit side reactions, which has high industrial value.

[0012] Further, the molar volume ratio of the ammonium tungsten oxide pentahydrate, water and the acidic solution in step (1) is 1-5 mmol: 30-50 mL: 5-15 mL; the acidic solution is nitric acid solution, and the concentration is 2-3 mol / L.

[0013] Preferably, the molar volume ratio of the ammonium tungsten oxide pentahydrate, water and the acidic solution in step (1) is 2.5 mmol: 40 mL: 10 mL; the acidic solution is nitric acid solution, and the concentration is 2.5 mol / L.

[0014] Further, the temperature of the condensation reflux in step (1) is 80-90℃, and the time is 30-90 min; the temperature of the heating reaction is 120-200℃, and the time is 10-15 h; the temperature of the drying is 40-80℃, and the time is 5-12 h.

[0015] Preferably, the temperature of the condensation reflux in step (1) is 85℃, and the time is 60 min; the temperature of the heating reaction is 160℃, and the time is 12 h; the temperature of the drying is 60℃, and the time is 8 h.

[0016] The beneficial effects of the above further technical solutions are that the tungsten oxide nanorod carrier is prepared by using the ammonium tungsten oxide pentahydrate as a raw material, and the surface of the carrier is rich in oxygen defects, which not only provides sufficient active sites for the subsequent Pt and Ni bimetallic loading, but also provides the possibility of hydrogen overflow as a reducible carrier.

[0017] Further, the mass-volume ratio of the oxide nanorod carrier, the solvent and the platinum salt solution in step (2) is 200-400 mg: 10-50 mL: 4-8 μL; the solvent is ethanol; and the platinum salt solution is aqueous platinum nitrate solution, and the concentration is 3-7 mg / mL.

[0018] Preferably, the mass-volume ratio of the oxide nanorod carrier, the solvent and the platinum salt solution in step (2) is 300 mg: 30 mL: 6 μL; the solvent is ethanol; and the platinum salt solution is aqueous platinum nitrate solution, and the concentration is 5 mg / mL.

[0019] Further, the stirring time in step (2) is 30-90 min, and the rotating speed is 300-500 rpm; the calcination condition is that the temperature is increased to 300-700℃ at a rate of 3-7℃ / min in the mixed gas of hydrogen and rare gas, and the temperature is kept for 1-3 h, wherein the volume fraction of hydrogen in the mixed gas is 1-10%.

[0020] The beneficial effects of the above further technical solutions are that the Pt is loaded on the tungsten oxide nanorod carrier by the traditional impregnation method, so that the Pt exists in the form of single atom, and plays a catalytic role in the hydrogenation reaction of adiponitrile as the adsorption and activation site of hydrogen.

[0021] Further, the mass / volume ratio of the catalyst precursor, the solvent and the nickel salt solution in step (3) is 200-400 mg: 10-50 mL: 1-10 mL; the solvent is ethanol; the nickel salt solution is an aqueous nickel nitrate solution with a concentration of 3-7 mg / mL.

[0022] Further, the stirring time in step (3) is 30-90 min, and the stirring speed is 300-500 rpm; the calcination condition is that the temperature is raised to 300-700 DEG C at a rate of 3-7 DEG C / min in a mixed gas of hydrogen and rare gas, and the temperature is kept for 1-3 h, wherein the volume fraction of hydrogen in the mixed gas is 1-10%.

[0023] The beneficial effect of the above further technical solution is that the Ni is loaded on the tungsten oxide nanorod carrier by the traditional impregnation method, so that the Ni exists in the form of particles, the spatial separation of the bimetallic site is realized, the contradiction of the linear scale limitation of the traditional supported catalyst is broken, and the bimetallic site serves as an activation site of the -C≡N bond to catalyze the adiponitrile hydrogenation reaction.

[0024] A supported PtNi bimetallic site adiponitrile hydrogenation catalyst is prepared by the above preparation method.

[0025] The above supported PtNi bimetallic site adiponitrile hydrogenation catalyst is used in the preparation of primary amine by catalyzing the adiponitrile hydrogenation reaction.

[0026] A method for preparing primary amine by catalyzing the adiponitrile hydrogenation reaction, the above supported PtNi bimetallic site adiponitrile hydrogenation catalyst, a reaction solvent, an alkaline solution and adiponitrile are mixed, and the reaction is carried out at 80-120 DEG C under a hydrogen pressure of 1-3 MPa to prepare primary amine.

[0027] The mass ratio of the catalyst and the adiponitrile is 10-30 mg: 50-150 mg.

[0028] Further, the mass / volume ratio of the catalyst, the reaction solvent and the alkaline solution is 10-30 mg: 1-3 mL: 10-100 μL; the reaction solvent is ethanol; and the alkaline solution is any one of a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution with a concentration of 3-7 mol / L.

[0029] The beneficial effect of the present application is that the present application provides a method for preparing primary amine by catalyzing the adiponitrile hydrogenation reaction by using the supported PtNi bimetallic site adiponitrile hydrogenation catalyst, hydrogen gas is selected as the hydrogen ion source, which conforms to the development concept of green, pollution-free and environment-friendly, the catalytic reaction condition is mild, the yield of primary amine is high, the selectivity is high, the utilization rate of the catalyst is high, the stability is good, and the method has important industrial application value.

[0030] The present application has the following beneficial effects:

[0031] (1) The present application provides a preparation method of a supported PtNi b-site adiponitrile hydrogenation catalyst, which can be obtained by a traditional impregnation method, is simple and efficient, ensures that noble metal ions are completely loaded on a tungsten oxide carrier, the loading amount of Pt is very low, Pt exists in the form of a single atom, Ni exists in the form of a particle, spatial separation of bimetallic sites is realized, the contradiction of the linear scale limitation of the traditional supported catalyst is broken, and therefore the adiponitrile hydrogenation catalytic activity and the selectivity of the target product are improved.

[0032] (2) In the prepared supported PtNi b-site adiponitrile hydrogenation catalyst, Pt and Ni respectively serve as adsorption sites and activation sites of hydrogen and activation sites of a -C≡N bond, and a WO3 carrier with a surface rich in oxygen defects serves as a reducible carrier to provide a possibility for hydrogen spillover. H2 molecules are activated at Pt sites to produce activated hydrogen atoms (*H), adiponitrile molecules are adsorbed on the surface of Ni particles through a -C≡N bond, and *H reaches the surface of the Ni particle through spillover on the surface of WO3, thereby realizing the hydrogenation of adiponitrile to generate primary amines (hexamethylene diamine and 6-aminocapronitrile).

[0033] (3) The present application provides a method for preparing primary amines by catalyzing the hydrogenation of adiponitrile with a supported PtNi b-site adiponitrile hydrogenation catalyst, which selects hydrogen as a hydrogen ion source, conforms to the development concept of green, pollution-free and environment-friendly, and is widely used in industry. The catalytic reaction conditions are mild, the yield of primary amines is high, the selectivity is high, the utilization rate of the catalyst is high, the stability is good, and the method has important industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a reaction path diagram for the hydrogenation of adiponitrile;

[0035] Figure 2 It is the experimental results of the catalytic hydrogenation reaction of adiponitrile to generate primary amines in the test example, wherein a is a b-site hydrogenation reaction schematic diagram, b is the conversion rate of different catalysts, c is the selectivity of different catalysts to the product, d is the relationship between the loading amount of Ni and the reaction rate, e is the H2-TPR graph of different catalysts, and f is the TOF value of different catalysts;

[0036] Figure 3 It is the experimental results of the reaction mechanism research of the catalytic hydrogenation of adiponitrile to generate primary amines in the test example, wherein a is the W 5+ X-ray photoelectron spectroscopy, b is the H2-TPR graph of the catalyst prepared at different calcination temperatures, c is the conversion rate and selectivity of the catalyst prepared at different calcination temperatures in the catalytic hydrogenation reaction of adiponitrile to generate primary amines; d is the relationship between the hydrogen spillover rate and the reaction rate of the catalyst prepared at different calcination temperatures;

[0037] Figure 4 The primary amine selectivity in the experimental examples and the Ni content on the surface of the Pt-Ni / WO3 catalyst at different reduction temperatures 0 The experimental results are shown in the figure. In this figure, a represents the X-ray photoelectron spectra of Ni elemental catalysts prepared at different calcination temperatures; b represents the d-band center test results; and c represents the Ni elemental surface of the catalyst. 0 The graph shows the relationship between quantity and selectivity, where d represents the relationship between binding energy and selectivity, and e represents the relationship between binding energy and reaction rate. Detailed Implementation

[0038] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0039] Example 1:

[0040] A method for preparing a supported PtNi two-site adiponitrile hydrogenation catalyst includes the following steps:

[0041] (1) Preparation of tungsten oxide nanorod (NR-WO3) support

[0042] First, add 2.5 mmol (3.06 g) (NH4). 10 W 12 O4·5H2O was placed in a round-bottom flask, 40 mL of deionized water was added and stirred; then 10 mL of 2.5 mol / L dilute nitric acid solution was slowly added dropwise to the suspension, and the mixture was refluxed at 85 °C for 1 h; then the precipitate was poured into a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner and heated at 160 °C for 12 h, cooled to room temperature, centrifuged and filtered to obtain the precipitate, and washed three times with deionized water; finally, it was dried at 60 °C overnight to obtain light yellow tungsten oxide powder (oxide nanorod carrier).

[0043] (2) Preparation of Pt1 / NR-WO3 catalyst precursor

[0044] The 300 mg of the NR-WO3 powder obtained in step (1) was dispersed in 30 mL of ethanol at room temperature by ultrasonic and stirring. 6 μL of 5 mg / mL aqueous solution of platinum nitrate was added dropwise into the dispersion, and the ethanol was completely evaporated by heating after stirring at 400 rpm for 1 h. The solid powder was heated to 350 ℃ at a rate of 5 ℃ / min in a mixed gas of hydrogen and argon (the volume fraction of hydrogen in the mixed gas was 5%), and calcined for 2 h to obtain the Pt1 / NR-WO3 catalyst precursor, in which the loading mass fraction of Pt metal was 0.01%.

[0045] (3) Preparation of the Pt1-Ni / NR-WO3 catalyst:

[0046] The 300 mg of the Pt1 / NR-WO3 catalyst precursor obtained in step (2) was dispersed in 30 mL of ethanol at room temperature by ultrasonic and stirring. 3 mL of 5 mg / mL aqueous solution of nickel nitrate was added dropwise into the dispersion, and the ethanol was completely evaporated by heating after stirring for 1 h. The solid powder was heated to 350 ℃ at a rate of 5 ℃ / min in a mixed gas of hydrogen and argon (the volume fraction of hydrogen in the mixed gas was 5%), and calcined for 2 h to obtain the Pt1-Ni / NR-WO3 catalyst, in which the loading mass fraction of Ni metal was 5%, and the catalyst was named as Pt-Ni / WO3-350.

[0047] Example 2:

[0048] A preparation method of a supported PtNi dual-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0049] The preparation method was the same as that in Example 1, except that the amount of the aqueous solution of nickel nitrate added in step (3) was changed to 1.2 mL, and the loading mass fraction of Ni metal in the obtained catalyst was 2%.

[0050] Example 3:

[0051] A preparation method of a supported PtNi dual-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0052] The preparation method was the same as that in Example 1, except that the amount of the aqueous solution of nickel nitrate added in step (3) was changed to 1.8 mL, and the loading mass fraction of Ni metal in the obtained catalyst was 3%.

[0053] Example 4:

[0054] A preparation method of a supported PtNi dual-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0055] The preparation method is same as example 1, except that the adding amount of the aqueous nickel nitrate solution in step (3) is modified to 2.4 mL, at this time the loading mass fraction of the metal Ni of the obtained catalyst is 4%.

[0056] Example 5:

[0057] A preparation method of a supported PtNi b-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0058] The preparation method is same as example 1, except that the calcination temperature of step (2) and step (3) is modified to 450℃, and the catalyst is named as Pt-Ni / WO3-450.

[0059] Example 6:

[0060] A preparation method of a supported PtNi b-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0061] The preparation method is same as example 1, except that the calcination temperature of step (2) and step (3) is modified to 550℃, and the catalyst is named as Pt-Ni / WO3-550.

[0062] Example 7:

[0063] A preparation method of a supported PtNi b-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0064] The preparation method is same as example 1, except that the calcination temperature of step (2) and step (3) is modified to 600℃, and the catalyst is named as Pt-Ni / WO3-600.

[0065] Example 8:

[0066] A preparation method of a supported PtNi b-site adiponitrile hydrogenation catalyst, comprising the following steps:

[0067] The preparation method is same as example 1, except that the calcination temperature of step (2) and step (3) is modified to 650℃, and the catalyst is named as Pt-Ni / WO3-650.

[0068] Comparative example 1:

[0069] A preparation method of a supported Pt unit point adiponitrile hydrogenation catalyst, comprising the following steps:

[0070] (1) Preparation of tungsten oxide nanorod (NR-WO3) carrier

[0071] First, 2.5 mmol (3.06 g) (NH4)2WO4 and 0.5 mL of 30% H2O2 were dissolved in 50 mL of deionized water, and then 0.5 mL of 30% H2O2 was added dropwise under stirring. 10 W 12O4·5H2O was placed in a round-bottom flask, 40 mL of deionized water was added and stirred; then 10 mL of 2.5 mol / L dilute nitric acid solution was slowly added dropwise to the suspension, and the mixture was refluxed at 85 °C for 1 h; then the precipitate was poured into a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner and heated at 160 °C for 12 h, cooled to room temperature, centrifuged and filtered to obtain the precipitate, and washed three times with deionized water; finally, it was dried at 60 °C overnight to obtain light yellow tungsten oxide powder (oxide nanorod carrier).

[0072] (2) Preparation of Pt / WO3 supported Pt single-point adiponitrile hydrogenation catalyst

[0073] At room temperature, 300 mg of NR-WO3 powder obtained in step (1) was first uniformly dispersed in 30 mL of ethanol by ultrasound and stirring; then 6 μL of 5 mg / mL platinum nitrate aqueous solution was added dropwise to the dispersion, stirred at 400 rpm for 1 h, and then heated to completely evaporate the ethanol to obtain solid powder. Finally, the solid powder was heated to 350 °C at a rate of 5 °C / min in a mixture of hydrogen and argon (the volume fraction of hydrogen in the mixture was 5%) and calcined for 2 h to obtain the supported Pt unit point adiponitrile hydrogenation catalyst Pt / WO3, named Pt / WO3, at which time the mass fraction of Pt metal loading was 0.01%.

[0074] Comparative Example 2:

[0075] A method for preparing a supported Ni single-point adiponitrile hydrogenation catalyst includes the following steps:

[0076] (1) Preparation of tungsten oxide nanorod (NR-WO3) support

[0077] First, add 2.5 mmol (3.06 g) (NH4). 10 W 12 O4·5H2O was placed in a round-bottom flask, 40 mL of deionized water was added and stirred; then 10 mL of 2.5 mol / L dilute nitric acid solution was slowly added dropwise to the suspension, and the mixture was refluxed at 85 °C for 1 h; then the precipitate was poured into a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner and heated at 160 °C for 12 h, cooled to room temperature, centrifuged and filtered to obtain the precipitate, and washed three times with deionized water; finally, it was dried at 60 °C overnight to obtain light yellow tungsten oxide powder (oxide nanorod carrier).

[0078] (2) Preparation of Ni / WO3 supported Ni-type adiponitrile hydrogenation catalyst:

[0079] The NR-WO3 powder obtained in step (1) was dispersed in 30 mL of ethanol by ultrasonic and stirring at room temperature; 3 mL of 5 mg / mL nickel nitrate aqueous solution was added dropwise into the dispersion, and the ethanol was completely evaporated by heating after stirring for 1 h to obtain a solid powder; finally, the solid powder was calcined in a mixed gas of hydrogen and argon (the volume fraction of hydrogen in the mixed gas was 5%) at a rate of 5°C / min to 350°C, and the calcination was performed for 2 h to prepare a supported Ni unit point adiponitrile hydrogenation catalyst Ni / WO3, which was named as Ni / WO3, wherein the loading mass fraction of metal Ni was 5%.

[0080] Comparative Example 3:

[0081] A preparation method of a supported Ni unit point adiponitrile hydrogenation catalyst, comprising the following steps:

[0082] The preparation method was the same as that of Comparative Example 2, except that the amount of nickel nitrate aqueous solution added in step (2) was changed to 1.2 mL, and the loading mass fraction of metal Ni in the catalyst was 2%.

[0083] Comparative Example 4:

[0084] A preparation method of a supported Ni unit point adiponitrile hydrogenation catalyst, comprising the following steps:

[0085] The preparation method was the same as that of Comparative Example 2, except that the amount of nickel nitrate aqueous solution added in step (2) was changed to 1.8 mL, and the loading mass fraction of metal Ni in the catalyst was 3%.

[0086] Comparative Example 5:

[0087] A preparation method of a supported Ni unit point adiponitrile hydrogenation catalyst, comprising the following steps:

[0088] The preparation method was the same as that of Comparative Example 2, except that the amount of nickel nitrate aqueous solution added in step (2) was changed to 2.4 mL, and the loading mass fraction of metal Ni in the catalyst was 4%.

[0089] Comparative Example 6:

[0090] A preparation method of a supported PtNi dual site adiponitrile hydrogenation catalyst, comprising the following steps:

[0091] (1) Preparation of tungsten oxide nanorod (NR-WO3) carrier

[0092] First, 2.5 mmol (3.06 g) of (NH4)2WO4 was dissolved in 50 mL of deionized water, and 0.5 mL of 0.1 mol / L H2C2O4 aqueous solution was added dropwise into the solution under stirring; then, 0.5 mL of 0.1 mol / L Na2CO3 aqueous solution was added dropwise into the solution under stirring; finally, the solution was heated to 95°C and kept for 2 h, and the product was collected by centrifugation and washing with deionized water to obtain the NR-WO3 carrier. 10 W 12O4·5H2O was placed in a round-bottom flask, 40 mL of deionized water was added and stirred; then 10 mL of 2.5 mol / L dilute nitric acid solution was slowly added dropwise into the above suspension, and condensed refluxed at 85℃ for 1 h; then the precipitate after reaction was poured into a stainless steel hydrothermal kettle with a polytetrafluoroethylene lining, heated at 160℃ for 12 h, cooled to room temperature, centrifuged, filtered to obtain the precipitate, and the precipitate was washed with deionized water for 3 times; finally, it was dried at 60℃ overnight to obtain a light yellow tungsten oxide powder (oxide nanorod carrier).

[0093] (2) Preparation of Pt1 / NR-WO3 catalyst precursor

[0094] At room temperature, 300 mg of NR-WO3 powder obtained in step (1) was uniformly dispersed in 30 mL of ethanol by ultrasonic and stirring; then 6 μL of 5 mg / mL aqueous solution of platinum nitrate was added dropwise into the dispersion, and after stirring at 400 rpm for 1 h, the ethanol was completely evaporated by heating to obtain a solid powder of Pt1 / NR-WO3 catalyst precursor.

[0095] (3) Preparation of Pt1-Ni / NR-WO3 catalyst:

[0096] At room temperature, 300 mg of Pt1 / NR-WO3 catalyst precursor obtained in step (2) was uniformly dispersed in 30 mL of ethanol by ultrasonic and stirring; then 3 mL of 5 mg / mL aqueous solution of nickel nitrate was added dropwise into the dispersion, and after stirring for 1 h, the ethanol was completely evaporated by heating to obtain a solid powder of Pt1-Ni / NR-WO3 catalyst, which was named as PtNi / WO3.

[0097] Test example:

[0098] I. Experiment of catalyzing hydrogenation of adiponitrile to generate primary amine

[0099] (1) Experimental method

[0100] 20 mg of catalyst was dispersed in a glass reaction bottle containing 2 mL of ethanol, and then transferred into a 500 mL autoclave, 50 μL of 5 mol / L sodium hydroxide solution and 1 mmol of adiponitrile were added, and then washed with 1 MPa hydrogen gas for three times, and then reacted in 2 MPa hydrogen gas atmosphere, and the reaction temperature was 100℃. After the reaction, the content of primary amine in the liquid phase was quantitatively analyzed by gas chromatograph, and subsequent analysis was carried out.

[0101] The catalysts of examples 1-4, comparative examples 1-5, and the mixture of comparative example 1 and comparative example 2 with a mass ratio of 1:1 were used as experimental catalyst samples for experiments.

[0102] (2) Experimental results

[0103] The experimental results are as follows:Figure 2 As shown.

[0104] in, Figure 2 Figure a is a schematic diagram of the two-site hydrogenation reaction of the supported PtNi two-site adiponitrile hydrogenation catalyst prepared in this invention. Figure 2 Figures b and c show the catalytic hydrogenation performance of different catalysts under hydrogen conditions of 100℃ and 2MPa. According to the experimental results, the catalyst sample Pt-Ni / WO3-350 prepared in Example 1 of this invention exhibits excellent catalytic activity and the highest primary amine selectivity (>95%). Figure 2 Figure d shows catalysts with different Ni metal loadings (i.e., catalysts prepared in Examples 1-4 and Comparative Examples 1-4). According to the experimental data in the figure, as the Ni loading increases from 2% to 5%, the rate ratios of Pt-Ni / WO3 and Ni / WO3 catalysts increase by 5.6 times and 3.5 times, respectively, which fully demonstrates that the overflow hydrogen provided by Pt enhances the reactivity of Ni. Figure 2 The figure shows that, according to H2-TPR testing, both Pt / WO3 and Ni / WO3 samples exhibited obvious characteristic peaks, with Ni showing the most significant peak. 2+ Reduced to Ni 0 The temperature was 384℃. When metals Pt and Ni form a bisite, the reduction temperature of Ni in Pt-Ni / WO3 (290℃) is lower than that of Ni / WO3, confirming that hydrogen spillover occurs between the Pt and Ni bimetals. Specifically, H2 is activated and dissociated into activated hydrogen species *H on the single-atom Pt, and then spills over onto the WO3 support surface to promote Ni reduction. 2+ Reduced to Ni 0 Furthermore, according to Figure 2 As shown in Figure f, under the same catalytic conditions, the Pt-Ni / WO3-350 catalyst prepared in Example 1 of this invention not only has a much higher hydrogenation reaction rate than the catalyst prepared in the comparative example, but also achieves a primary amine selectivity of over 95% and a TOF value as high as 519.1 h⁻¹. -1 It is 5.5 times the amount of NiWO3 obtained in Comparative Example 2.

[0105] II. Study on the reaction mechanism of catalytic hydrogenation of adiponitrile to primary amine

[0106] The catalysts prepared in Examples 1 and 5-8 were used in experiments. The number of oxygen vacancies on the catalyst surface was characterized by X-ray photoelectron spectroscopy and H2-TPR spectra. W... 5+ The amount of oxygen defect was used to replace the oxygen defect concentration, and experiments were conducted to detect the conversion (Conv.) and selectivity (Sel.) of the catalytic hydrogenation reaction of adiponitrile to primary amine.

[0107] Experimental results are as follows Figure 3 As shown, Figure 3As shown in Figures a and b, the number of Ov on the catalyst surface gradually increases with the increase of calcination temperature during preparation. Furthermore, according to the H2-TPR spectrum, the characteristic fraction between 50-200℃ can be attributed to hydrogen overflow between Pt and Ni metals on the Pt-Ni / WO3 catalyst surface, with the lowest hydrogen overflow temperature of 65℃ observed in the Pt-Ni / WO3-550 sample. Figure 3 As shown in Figures c and d, under the same experimental conditions, the Pt-Ni / WO3-550 catalyst exhibits the highest activity and the lowest reduction temperature, indicating that the hydrogen overflow rate is greater than that of other catalysts. Further increasing the calcination temperature to 600℃ and 650℃ causes a sharp decrease in the reaction rate, presumably because the OH groups formed by the overflow of *H on the WO3 surface are restricted.

[0108] III. Primary Amine Selectivity and Ni Surface of Pt-Ni / WO3 Catalysts at Different Calcination Temperatures 0 Relationship

[0109] The catalysts prepared in Examples 1 and 5-8 were used in experiments. X-ray photoelectron spectroscopy was used for analysis to investigate the relationship between primary amine selectivity and the Ni content on the surface of the Pt-Ni / WO3 catalyst at different calcination temperatures. 0 The relationship.

[0110] Experimental results are as follows Figure 4 As shown. According to Figure 4 It can be seen that as the calcination temperature increases, the Ni on the catalyst surface... 0 The increasing number of samples and the enhanced desorption capacity of the catalyst for the product by testing the d-band center provide a good explanation for the improved selectivity of primary amines.

[0111] In summary, this invention constructs a bimetallic active site catalyst by introducing Pt and Ni onto a reducible WO3 support. This catalyst can catalyze the hydrogenation of adiponitrile to primary amines under mild conditions. Specifically, single-atom Pt serves as the activation site for H2, and the overflow of *H on the WO3 surface enables adiponitrile molecules adsorbed on the surface of Ni particles to complete the hydrogenation process. This achieves high activity of the Pt-Ni / WO3 catalyst and high selectivity for primary amines.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Use of a supported PtNi bi-site adiponitrile hydrogenation catalyst in the preparation of a primary amine by catalytic hydrogenation of adiponitrile, characterized in that, The preparation method of the supported PtNi dual-site adiponitrile hydrogenation catalyst comprises the following steps: (1) Preparation of tungsten oxide nanorod carrier: disperse tungsten oxide ammonium pentahydrate in water, add an acidic solution, condense and reflux, heat the reaction, centrifuge and filter the precipitate, and dry the precipitate to obtain the tungsten oxide nanorod carrier; (2) Preparation of catalyst precursor: disperse the tungsten oxide nanorod carrier obtained in step (1) in a solvent, add a platinum salt solution, stir, evaporate the solvent, and calcine the solid to obtain the catalyst precursor; (3) Preparation of supported PtNi dual-site adiponitrile hydrogenation catalyst: disperse the catalyst precursor obtained in step (2) in a solvent, add a nickel salt solution, stir, evaporate the solvent, and calcine the solid to obtain the supported PtNi dual-site adiponitrile hydrogenation catalyst; In the catalyst precursor obtained in step (2), the mass fraction of Pt metal is 0.01%. The calcination conditions in step (2) are as follows: in a mixture of hydrogen and rare gas, the temperature is increased to 300-700 ℃ at a rate of 3-7 ℃ / min, and the temperature is maintained for 1-3 h, wherein the volume fraction of hydrogen in the mixed gas is 1-10%. The calcination conditions in step (3) are as follows: in a mixture of hydrogen and rare gas, the temperature is increased to 300-700 ℃ at a rate of 3-7 ℃ / min, and the temperature is maintained for 1-3 h, wherein the volume fraction of hydrogen in the mixed gas is 1-10%.

2. Use of the supported PtNi bi-site adiponitrile hydrogenation catalyst according to claim 1 for the production of primary amines by catalytic hydrogenation of adiponitrile, characterized in that, In step (1), the molar volume ratio of tungsten oxide ammonium pentahydrate, water and acidic solution is 1-5 mmol: 30-50 mL: 5-15 mL; the acidic solution is nitric acid solution with a concentration of 2-3 mol / L.

3. Use of the supported PtNi bi-site adiponitrile hydrogenation catalyst according to claim 1 for the production of primary amines by catalytic hydrogenation of adiponitrile, characterized in that, In step (1), the condensation reflux temperature is 80-90 ℃, the time is 30-90 min; the heating reaction temperature is 120-200 ℃, the time is 10-15 h; the drying temperature is 40-80 ℃, and the time is 5-12 h.

4. Use of the supported PtNi bi-site adiponitrile hydrogenation catalyst according to claim 1 for the production of primary amines by catalytic hydrogenation of adiponitrile, characterized in that, In step (2), the mass-volume ratio of tungsten oxide nanorod carrier, solvent and platinum salt solution is 200-400 mg: 10-50 mL: 4-8 μL; the solvent is ethanol; and the platinum salt solution is an aqueous platinum nitrate solution with a concentration of 3-7 mg / mL.

5. Use of the supported PtNi bi-site adiponitrile hydrogenation catalyst according to claim 1 for the production of primary amines by catalytic hydrogenation of adiponitrile, characterized in that, In step (2), the stirring time is 30-90 min, and the rotating speed is 300-500 rpm.

6. Use of the supported PtNi bi-site adiponitrile hydrogenation catalyst according to claim 1 for the production of primary amines by catalytic hydrogenation of adiponitrile, characterized in that, In step (3), the mass-volume ratio of catalyst precursor, solvent and nickel salt solution is 200-400 mg: 10-50 mL: 1-10 mL; the solvent is ethanol; and the nickel salt solution is an aqueous nickel nitrate solution with a concentration of 3-7 mg / mL.

7. Use of the supported PtNi bi-site adiponitrile hydrogenation catalyst according to claim 1 for the production of primary amines by catalytic hydrogenation of adiponitrile, characterized in that, In step (3), the stirring time is 30-90 min, and the rotating speed is 300-500 rpm.

8. Use of the supported PtNi bi-site adiponitrile hydrogenation catalyst according to claim 1 for the production of primary amines by catalytic hydrogenation of adiponitrile, characterized in that, The supported PtNi dual-site adiponitrile hydrogenation catalyst, a reaction solvent, a basic solution and adiponitrile are mixed, and the mixture is reacted at 80-120 ℃ under a hydrogen pressure of 1-3 MPa to obtain a primary amine. In the reaction, the mass ratio of catalyst to adiponitrile is 10-30 mg: 50-150 mg.

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