NiPd / Al2O3 catalyst as well as preparation method and application thereof
By preparing NiPd/Al2O3 catalyst, the problem of low selectivity of existing catalysts was solved, and the complete conversion of biphenyl into dicyclohexane under mild conditions was achieved, and the catalyst activity and stability were significantly improved.
Patent Information
- Application Number
- CN202510810203.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-17
- Publication Date
- 2025-10-17
Smart Images
Figure CN120790172A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of catalyst preparation, and particularly relates to a NiPd / Al2O3 catalyst and a preparation method and application thereof. BACKGROUND
[0002] Fossil fuels in low reactivity industrial applications will be accompanied by a large number of high-toxic aromatic compounds emissions, which will cause great threat to the environment and human health. Therefore, how to realize the high-value and harmless conversion of aromatic compounds and complete the emission reduction of aromatic compounds has become a research hotspot. Biphenyl, as one of the compounds that are difficult to hydrogenate in aromatic compounds, is widely present in coal tar, crude oil and natural gas, and direct emission will cause great damage to the environment, but its hydrogenation products cyclohexylbenzene and bicyclohexane are important chemical products with high added value. Among them, bicyclohexane is the product of complete hydrogenation of biphenyl, which has the advantages of low toxicity, high dehydrogenation efficiency, high quality hydrogen storage density and high volume hydrogen storage density, and is a very promising hydrogen storage material.
[0003] Some scholars use Rh / C and Ru / C catalysts for catalytic hydrogenation of biphenyl in supercritical carbon dioxide medium, which can make the yield of BCH reach more than 99%, but the reaction system pressure is as high as 20MPa, which requires high equipment. Some people also use strong electrostatic adsorption method to synthesize Ru / SiO2 catalyst for hydrogenation of biphenyl to bicyclohexane with high activity and good stability, but the preparation method is complex and needs to accurately control the concentration and pH value of the nanoparticles in the solution. Therefore, it is of great significance to develop a high-efficiency catalyst with simple preparation method and capable of realizing complete hydrogenation of biphenyl under mild conditions for the production of bicyclohexane and hydrogenation dealkylation of other aromatic compounds. SUMMARY
[0004] The technical problem to be solved by the present application is to provide a NiPd / Al2O3 catalyst and a preparation method and application thereof, so as to solve the technical problem of low selectivity of existing catalysts to bicyclohexane.
[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is to provide a preparation method of a NiPd / Al2O3 catalyst, comprising the following steps: S1, dissolving nickel salt, aluminum salt, palladium salt and precipitant in water, so that the molar ratio of Ni, Al and Pd elements in the reaction system is 40-60:40-60:0.5-1.5; then condensing and refluxing at 110-140 DEG C for 5-7h, and then aging the obtained precipitate at room temperature for 10-14h, and then washing and drying to obtain a precursor; the precipitant is urea, ammonia or sodium hydroxide, and the molar ratio of the precipitant and the metal salt is 6-8:1-1.2; the prepared precursor has a two-dimensional layered nanosheet structure, which is beneficial to the uniform dispersion of Ni and Pd active metals, promotes the contact between the reactants and the active components, and thus improves the hydrogenation activity of the catalyst; S2, calcining the precursor at 480-520 DEG C for 2.5-3.5h, cooling to room temperature, and then reducing in a reducing atmosphere at 450-500 DEG C for 2.5-3.5h to obtain a NiPd / Al2O3 catalyst; the precursor still maintains a good layered nanosheet structure after calcination and reduction, and the moderate calcination is beneficial to the growth of Ni crystal grains and the dispersion of metal particles, and the reduction effectively promotes the exposure of active metals Ni and Pd, and the process can significantly improve the stability and reaction activity of the catalyst.
[0006] Based on the technical scheme, the application can be further improved as follows: Further, the nickel salt is Ni(NO3)2.6H2O, Ni(CH3COO)2 or NiSO4.6H2O, the aluminum salt is Al(NO3)3.9H2O or Al2(SO4)3.18H2O, and the palladium salt is PdCl2 or Pd(NO3)2.
[0007] Further, the molar ratio of Ni, Al and Pd elements in the reaction system is 50:50:1.
[0008] Further, the drying temperature is 70-90 DEG C, and the drying time is 8-12h.
[0009] Further, the heating rate of calcination and reduction is 3-7 DEG C / min.
[0010] Further, the gas used in the reducing atmosphere is H2, and the gas flow rate is 25-30mL / min.
[0011] The application also discloses a NiPd / Al2O3 catalyst prepared by the preparation method.
[0012] The application also discloses application of the NiPd / Al2O3 catalyst in a biphenyl hydrogenation reaction.
[0013] Based on the technical scheme, the application can be further improved as follows: Further, the application comprises the following steps: mixing biphenyl, NiPd / Al2O3 catalyst and solvent in a ratio of 0.4-0.6 g: 0.05-0.1 g: 25-35 mL, reacting at 1.5-2.5 MPa of hydrogen pressure and 140-160 ℃ for 1.5-2.5 h, separating by filtration under reduced pressure to obtain a liquid product, wherein the selectivity of bicyclohexane is up to 85%.
[0014] Further, the solvent is cyclohexane, n-hexane or isopropanol.
[0015] The NiPd / Al2O3 catalyst prepared by the application has a developed pore structure and a large specific surface area, the active metals Ni and Pd are uniformly dispersed on the surface of nanosheets, and there is a strong interaction between the metals and the carrier, which is conducive to improving the activity and stability of the catalyst. The preparation process is simple, and the prepared catalyst has good hydrogenation performance and can realize complete conversion of biphenyl under mild conditions, and the selectivity of bicyclohexane can be as high as 99%. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 It is a scanning electron microscope image of the NiPd / Al2O3 catalyst; Figure 2 It is an element mapping image of the NiPd / Al2O3 catalyst; Figure 3 It is a N2 adsorption-desorption curve of the NiPd / Al2O3 catalyst; Figure 4 It is a pore size distribution graph of the NiPd / Al2O3 catalyst; Figure 5 It is an XRD spectrum of the NiPd / Al2O3 catalyst. DETAILED DESCRIPTION
[0017] The specific embodiments of the application are described below to facilitate the understanding of the application by those skilled in the art, and the specific conditions are not specified in the examples, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer, and the reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market. But it should be clear that the application is not limited to the scope of the specific embodiments, and for those skilled in the art, it is obvious that all kinds of changes within the spirit and scope of the application defined and determined by the appended claims are obvious, and all the inventions and creations utilizing the concept of the application are within the scope of protection.
[0018] Example 1 A preparation method of a NiPd / Al2O3 catalyst comprises the following steps: S1, 1.5 g Ni(CH3COO)2, 3.5 g Al(NO3)3.9H2O and 8.4 g urea were mixed, then Pd(NO3)2 solution was added to make the molar ratio of Ni and Pd elements in the reaction system 40:1.5, then 120 mL of deionized water was added and ultrasonic dispersion was dissolved for 10 min; then it was condensed and refluxed at 110°C for 7 h, the obtained precipitate was aged at room temperature for 10 h, and finally it was washed and vacuum dried at 90°C for 8 h to obtain a light blue solid powder, i.e. a precursor (NiPdAl hydroxide); S2, the precursor was placed in a tube furnace, then the temperature was raised from room temperature to 480°C at a heating rate of 3°C / min, calcined in air atmosphere for 3.5 h, and after cooling, a gray-green NiPdAl oxide powder was obtained; then the NiPdAl oxide powder was placed in a fixed bed, while the temperature was raised from room temperature to 450°C at a heating rate of 3°C / min, reduced in H2 atmosphere with a flow rate of 25 mL / min for 3.5 h, and after cooling to room temperature, a black magnetic powder, i.e. a NiPd / Al2O3 catalyst, was obtained.
[0019] Example 2 A preparation method of a NiPd / Al2O3 catalyst, comprising the following steps: S1, 1.5 g Ni(CH3COO)2, 3.5 g Al(NO3)3.9H2O and 8.4 g urea were mixed, then Pd(NO3)2 solution was added to make the molar ratio of Ni and Pd elements in the reaction system 40:1.5, then 120 mL of deionized water was added and ultrasonic dispersion was dissolved for 10 min; then it was condensed and refluxed at 110°C for 7 h, the obtained precipitate was aged at room temperature for 10 h, and finally it was washed and vacuum dried at 90°C for 8 h to obtain a light blue solid powder, i.e. a precursor (NiPdAl hydroxide); S2, the precursor was placed in a tube furnace, then the temperature was raised from room temperature to 480°C at a heating rate of 3°C / min, calcined in air atmosphere for 3.5 h, and after cooling, a gray-green NiPdAl oxide powder was obtained; then the NiPdAl oxide powder was placed in a fixed bed, while the temperature was raised from room temperature to 450°C at a heating rate of 3°C / min, reduced in H2 atmosphere with a flow rate of 25 mL / min for 3.5 h, and after cooling to room temperature, a black magnetic powder, i.e. a NiPd / Al2O3 catalyst, was obtained.
[0020] Example 3 A preparation method of a NiPd / Al2O3 catalyst, comprising the following steps: S1. Mix 2.91 g Ni(NO3)2·6H2O, 3.75 g Al(NO3)3·9H2O, and 8.4 g urea, then add PdCl2 solution to make the molar ratio of Ni and Pd elements in the reaction system 50:1, then add 120 mL of deionized water, and ultrasonically disperse and dissolve for 10 minutes; then condense and reflux at 125°C for 6 hours, and let the resulting precipitate stand and age at room temperature for 12 hours, finally wash, and vacuum dry at 80°C for 10 hours to obtain a light blue solid powder, i.e., the precursor (NiPdAl hydroxide); S2. Place the precursor in a tube furnace, then increase the temperature from room temperature to 500°C at a heating rate of 5°C / min, calcine in an air atmosphere for 3 hours, and obtain gray-green NiPdAl oxide powder after cooling; then place the NiPdAl oxide powder in a fixed bed, and at the same time increase the temperature from room temperature to 480°C at a heating rate of 5°C / min, reduce it in a H2 atmosphere with a flow rate of 28 mL / min for 3 hours, and obtain magnetic black powder, i.e., NiPd / Al2O3 catalyst, after cooling to room temperature.
[0021] The following experiments were conducted using the NiPd / Al2O3 catalyst prepared in Example 3 as a sample.
[0022] Experimental Example 1 Catalyst Characterization The prepared NiPd / Al2O3 catalyst was observed by scanning electron microscopy. Figure 1 As shown in the figure, the morphology of the catalyst is a cluster flower structure, which is composed of disordered nanosheets stacked together, showing a two-dimensional layered nanosheet stacking structure, and spherical particles are evenly distributed on the surface. Figure 2 ) found that the Ni and Pd active metals of the catalyst were highly dispersed and evenly distributed on the nanosheets.
[0023] Figure 3 The N2 adsorption-desorption curve of NiPd / Al2O3 catalyst shows a typical IV-type curve. An H3-type hysteresis loop appears at a relative pressure of 0.4-1.0, indicating the coexistence of micropores and mesopores in the catalyst. The specific surface area of NiPd / Al2O3 is as high as 198.62 m 2 g -1 .like Figure 4 As shown in the pore size distribution diagram of the catalyst, the pore size distribution of NiPd / Al2O3 is relatively concentrated, and mainly exists in the form of 2-10nm mesopores.
[0024] The NiPd / Al2O3 catalyst was further analyzed by X-ray diffraction. Figure 5As shown, strong diffraction peaks appeared at 44.5°, 51.8° and 76.3°, corresponding to the (110), (200) and (220) crystal planes of the Ni standard card (PDF #04-0850) respectively. The Ni diffraction peak is thin and high, indicating that the crystallinity of elemental Ni in the NiPd / Al2O3 catalyst is good, and the Ni atoms are arranged in order.
[0025] Experimental Example 2 Catalyst performance evaluation By changing the amount of NiPd / Al2O3 catalyst and the reaction temperature, the effect on the hydrogenation of diphenyl was explored. Specifically, 0.5 g of diphenyl, NiPd / Al2O3 catalyst and 30 mL of cyclohexane were added to a high-pressure reaction kettle. The air in the kettle was replaced with N2 for 3 times, and then the gas in the kettle was replaced with H2 for 3 times. H2 was introduced into the kettle to 2 MPa, the stirring speed was set to 900 rpm, and the reaction time was 2 h. After the reaction, the reaction liquid and the catalyst were separated by reduced pressure filtration, the catalyst was washed with cyclohexane and stored, the liquid product was detected by GC-MS to obtain the relative concentration of each component in the product, and then the conversion rate A of diphenyl and the selectivity B of bicyclohexane were calculated. The specific calculation formula is as follows: ; ; Wherein, A is the conversion rate of diphenyl, %; B is the selectivity of bicyclohexane, %; c0 is the concentration of diphenyl in the reaction system before the reaction starts, mol / L; c1 is the concentration of diphenyl in the reaction system after the reaction ends, mol / L; c2 is the concentration of bicyclohexane in the reaction system after the reaction ends, mol / L.
[0026] The parameter settings and catalytic performance data of the four experimental groups are shown in Table 1.
[0027] Table 1 Reaction parameter settings and catalytic performance data
[0028] As can be seen from Table 1, the four experimental groups can all achieve complete conversion of diphenyl, and the selectivity of bicyclohexane is more than 88%. By optimizing the reaction conditions, the selectivity of bicyclohexane can be further improved. When the catalyst dosage is 0.05 g, as the reaction temperature increases from 140°C to 160°C, the selectivity of bicyclohexane increases from 88.4% to 98.4%, indicating that appropriately increasing the temperature is beneficial to improving the selectivity of bicyclohexane. Further, when the reaction temperature is 160°C, the catalyst dosage is increased to 0.1 g, and the selectivity of bicyclohexane is increased to 100%, indicating that under this condition, the hydrogenation of diphenyl is completely converted into bicyclohexane.
Claims
1. A method for preparing a NiPd / Al2O3 catalyst, characterized in that: The following steps are involved: S1. Dissolving nickel salt, aluminum salt, palladium salt and a precipitant in water so that the molar ratio of Ni, Al and Pd elements in the reaction system is 40-60:40-60:0.5-1.5; then condensing and refluxing at 110-140° C. for 5-7 hours, allowing the obtained precipitate to stand and age at room temperature for 10-14 hours, and then washing and drying to obtain a precursor; the precipitant is urea, ammonia water or sodium hydroxide, and the molar ratio of the precipitant to the metal salt is 6-8:1-1.2; S2. calcining the precursor at 480-520° C. for 2.5-3.5 h, cooling it to room temperature, and then placing it in a reducing atmosphere and reducing it at 450-500° C. for 2.5-3.5 h to obtain a NiPd / Al2O3 catalyst.
2. The method for preparing the NiPd / Al2O3 catalyst according to claim 1, wherein: The nickel salt is Ni(NO3)2·6H2O, Ni(CH3COO)2 or NiSO4·6H2O, the aluminum salt is Al(NO3)3·9H2O or Al2(SO4)3·18H2O, and the palladium salt is PdCl2 or Pd(NO3)2.
3. The method for preparing the NiPd / Al2O3 catalyst according to claim 1, wherein: The molar ratio of Ni, Al and Pd elements in the reaction system is 50:50:
1.
4. The method for preparing the NiPd / Al2O3 catalyst according to claim 1, wherein: The drying temperature is 70-90° C., and the drying time is 8-12 hours.
5. The method for preparing the NiPd / Al2O3 catalyst according to claim 1, wherein: The heating rates of the calcination and reduction are both 3-7°C / min.
6. The method for preparing the NiPd / Al2O3 catalyst according to claim 1, wherein: The gas used in the reducing atmosphere is H2, and the gas flow rate is 25-30 mL / min.
7. A NiPd / Al2O3 catalyst, characterized in that The method is prepared according to any one of claims 1 to 6.
8. Use of the NiPd / Al2O3 catalyst according to claim 7 in biphenyl hydrogenation reaction.
9. The use according to claim 8, characterized in that The method comprises the following steps: mixing biphenyl, NiPd / Al2O3 catalyst and solvent in a ratio of 0.4-0.6 g: 0.05-0.1 g: 25-35 mL, reacting at a hydrogen pressure of 1.5-2.5 MPa and 140-160° C. for 1.5-2.5 h, and filtering and separating under reduced pressure to obtain a liquid product.
10. The use according to claim 9, characterized in that The solvent is cyclohexane, n-hexane or isopropanol.