Monoatom and cluster coexisting Pt-Ni2P / Beta n-hexane hydroisomerization catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of petrochemical engineering, and relates to a single atom and cluster coexisting Pt-Ni2P / Beta n-hexane hydroisomerization catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving nickel nitrate hexahydrate in water, dropwise adding nitric acid to adjust acidity, and adding diammonium hydrogen phosphate to obtain a Ni-P precursor solution; a Beta molecular sieve is impregnated in the Ni-P precursor solution in an equivalent volume mode, and Ni2P / Beta is prepared through air drying, drying, air calcination and hydrogen reduction; and dissolving platinum acetylacetonate in acetone to prepare a platinum precursor solution, carrying out equivalent-volume impregnation on Ni2P / Beta, carrying out air drying, drying, calcining in air, and carrying out hydrogen reduction to obtain the single atom and cluster coexisting Pt-Ni2P / Beta catalyst. The method is easy and convenient to operate and mild in condition, the hydrogen activation capacity and isomerization selectivity are remarkably improved through the synergistic effect of Ni2P and trace Pt single atoms / clusters, and efficient hydroisomerization of n-hexane is achieved while the use amount of precious metal and the preparation cost of the catalyst are reduced.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals, specifically relating to a Pt-Ni2P / Beta n-hexane hydroisomerization catalyst with coexisting single atoms and clusters, its preparation method, and its application. Background Technology

[0002] With the continuous improvement of automotive industry and refined oil quality standards, the requirements for the research octane number (RON) of gasoline are gradually increasing. Traditional methods of increasing octane number by blending aromatics, olefins, or oxygen-containing compounds (such as MTBE and alcohol ethers) are no longer sufficient to simultaneously meet the environmental requirements and engine compatibility needs under National VI and subsequent stricter standards. Light, straight-chain alkanes, represented by n-hexane, are present in high concentrations in gasoline fractions but have low octane numbers. Without deep isomerization, they severely limit the overall quality of finished gasoline. Hexane hydroisomerization can convert straight-chain alkanes into multi-branched isoalkanes under mild conditions, significantly increasing the gasoline octane number while avoiding the problem of excessive aromatic content caused by aromatization. Therefore, it is considered one of the core processes for producing clean, high-octane gasoline.

[0003] Pt / Cl commonly used in industry - Catalytic systems such as Al2O3 and Pt / SO2-4-ZrO2, while exhibiting high activity, also present several challenges: First, chlorine and sulfur additives are corrosive and environmentally hazardous, easily causing equipment corrosion and increasing the burden of waste treatment. Second, an excessive number of strong acid centers on the support can induce side reactions such as cracking, reducing isomer selectivity and exacerbating carbon deposition and deactivation. Third, the large amount of precious metal Pt required results in high costs, and under high temperature and impurity conditions, metal particles are prone to sintering and growth, which is detrimental to the long-term stable operation of the equipment. Traditional isomerization catalysts typically consist of two parts: a solid acid component responsible for framework rearrangement and a metal component serving as hydrogenation centers. Many isomerization catalysts inevitably require a high loading of the precious metal Pt as the metal component. How to prepare low-cost catalysts with high hydrogenation activity to completely convert n-hexane into isoalkanes and increase the octane number has long been a research hotspot in the petrochemical field. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a Pt-Ni2P / Beta n-hexane hydroisomerization catalyst with coexisting single atoms and clusters and its preparation method, so as to solve the shortcomings of existing catalysts such as high amount of noble metal Pt, insufficient synergistic effect between metal and acid center and poor stability.

[0005] The second technical problem to be solved by the present invention is to provide a method for preparing a Pt-Ni2P / Beta n-hexane hydroisomerization catalyst in which single atoms and clusters coexist.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for preparing a Pt-Ni2P / Beta n-hexane hydroisomerization catalyst in which single atoms and clusters coexist, comprising the following steps:

[0008] (1) Dissolve the nickel precursor in water, stir until homogeneous, adjust the solution to acidity, add the phosphorus precursor, and stir until homogeneous to obtain a Ni-P precursor mixed solution.

[0009] (2) The Ni-P precursor mixed solution obtained in step (1) was added to the Beta molecular sieve by the equal volume impregnation method. After stirring, it was air-dried, baked, calcined, cooled to room temperature and then reduced to obtain Ni2P / Beta.

[0010] (3) Dissolve the platinum precursor in an organic solvent and stir until homogeneous to obtain a platinum precursor solution. Then, add the platinum precursor solution to the Ni2P / Beta obtained in step (2) using an equal volume impregnation method. After stirring, air dry, bake dry, calcine, cool to room temperature, and then reduce to obtain the final product.

[0011] In some embodiments, in step (1), the nickel precursor is any one of nickel nitrate, nickel chloride, or nickel acetate (preferably nickel nitrate); and / or, the acidity is achieved by adjusting the pH of the solution to 1-3 (preferably 3) using nitric acid solution; and / or, the mass fraction of the nitric acid solution is 65-68 wt.%; and / or, the phosphorus precursor is any one of diammonium hydrogen phosphate, sodium hypophosphite, or ammonium dihydrogen phosphate (preferably diammonium hydrogen phosphate); and / or, the molar ratio of the nickel precursor to the phosphorus precursor is 1:1-3 (preferably 1:2).

[0012] In some embodiments, in step (2), the Beta molecular sieve is an H-type Beta molecular sieve with a silica-alumina ratio of 10 to 40:1 (preferably 25:1).

[0013] In some embodiments, in step (2), the mass ratio of nickel in the nickel precursor to the Beta molecular sieve is 1% to 5% (preferably 2%).

[0014] In some embodiments, in step (2), the stirring time is 10-20 min (preferably 10 min); and / or, the air drying time is 8-24 h (preferably 12 h) at room temperature; and / or, the drying time is 70-90 °C (preferably 80 °C) at 8-10 h (preferably 8 h); and / or, the calcination time is 400-500 °C (preferably 450 °C) at 2-6 h (preferably 4 h); and / or, the reduction is hydrogen reduction at 550-650 °C (preferably 600 °C) at 1-4 h (preferably 2 h).

[0015] In some embodiments, in step (3), the platinum precursor is any one of platinum acetylacetonate, chloroplatinic acid, or platinum nitrate (preferably platinum acetylacetonate); the organic solvent is any one of acetone, dichloromethane, or ethanol (preferably acetone).

[0016] In some embodiments, in step (3), the mass ratio of platinum in the platinum precursor to the Beta molecular sieve is 0.1 to 0.5%.

[0017] In some embodiments, in step (3), the stirring time is 10-20 min (preferably 10 min); and / or, the air drying time is 8-24 h (preferably 12 h) at room temperature; and / or, the drying time is 70-90 °C (preferably 80 °C) at 4-6 h (preferably 4 h); and / or, the calcination time is 400-550 °C (preferably 500 °C) at 1-4 h (preferably 2 h); and / or, the reduction is hydrogen reduction at 300-400 °C (preferably 360 °C) at 1-4 h (preferably 2 h).

[0018] The Pt-Ni2P / Beta n-hexane hydroisomerization catalyst prepared by the above method, which contains both single atoms and clusters, is also within the scope of protection of this invention.

[0019] The application of the Pt-Ni2P / Beta n-hexane hydroisomerization catalyst, which contains both single atoms and clusters, in the n-hexane hydroisomerization catalytic reaction is also within the scope of protection of this invention.

[0020] Beneficial effects:

[0021] (1) The preparation process adopts conventional steps such as equal volume impregnation-drying-calcination-reduction. The conditions are mild and the operation is simple. The metal species in the catalyst are firmly bonded to the support, and the catalyst has excellent anti-sintering and anti-carbon deposition properties. It is suitable for industrial scale-up preparation and long-term stable operation.

[0022] (2) By constructing the Ni2P phase on the Beta molecular sieve and dispersing trace Pt in the form of single atoms and small clusters on the Ni2P / Beta surface, a metal-phosphide-acid multi-interface structure with hydrogen overflow effect is formed. Under the premise of significantly reducing the amount of noble metal Pt, the hydrogen activation ability and metal-acid synergy are significantly improved, resulting in higher n-hexane conversion rate and isomer selectivity, and cracking side reactions are effectively suppressed. Attached Figure Description

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0025] Figure 1 The attached image shows the XRD pattern of the Pt-Ni2P / Beta n-hexane hydroisomerization catalyst prepared in Example 1.

[0026] Figure 2 The attached figure shows the NH3-TPD catalyst for the Pt-Ni2P / Beta n-hexane hydroisomerization prepared in Example 1.

[0027] Figure 3 The attached figure shows the Py-FTIR of the Pt-Ni2P / Beta n-hexane hydroisomerization catalyst prepared in Example 1;

[0028] Figure 4 The attached TEM image shows the Pt-Ni2P / Beta n-hexane hydroisomerization catalyst prepared in Example 1.

[0029] Figure 5 The graph shows the yield of n-hexane isomerization catalyzed by the Pt-Ni2P / Beta n-hexane hydroisomerization catalyst and the Ni2P / Beta catalyst prepared in Example 1. Detailed Implementation

[0031] The following embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described herein. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

[0032] Evaluation and analysis methods:

[0033] XRD measurements were performed on a Bruker diffractometer. A Cu target Kα light source (λ = 0.15432 nm), a graphite monochromator, a tube voltage of 40 kV, and a tube current of 40 mA were used. The XRD values ​​ranged from 5 to 80 nm.o The scanning speed within the interval is 7 o / min. Qualitative analysis was performed using JCPDS (Junior High-Pressure Cryometry Data Sheets).

[0034] NH3-TPD experiment: Acidity test was performed using the calcined catalyst. The catalyst was pressed into tablets under a pressure of 1.5-2.0 MPa in a dry state, sieved into 40-60 mesh particles, purged under a helium atmosphere, and adsorbed with 10% ammonia and helium at 120℃. Then the temperature was raised to 800℃ to investigate the content of different acid strengths.

[0035] Py-IR Experiment: Pyridine infrared (Py-IR) spectra were recorded using a Thermo Fisher Scientific NICOLET iS20 Fourier transform infrared spectrometer. The 1545 cm⁻¹... -1 The characteristic peak at 1455 cm⁻¹ corresponds to Brønsted acid. -1 The characteristic peak at that location corresponds to a Lewis acid.

[0036] Source of raw materials or equipment: including raw material name, specifications, and manufacturer.

[0037]

[0038] Example 1

[0039] (1) At 25°C, 0.198 g of nickel nitrate hexahydrate calculated according to the required loading amount was first dissolved in deionized water and stirred to obtain a clear solution; then nitric acid solution (mass fraction of 65~68wt.%) was added dropwise to adjust the pH value of the solution to 3, and 0.18 g of diammonium hydrogen phosphate precursor was added under stirring to completely dissolve it without producing a precipitate. Stirring was continued for 1 h to obtain a Ni-P precursor mixed solution.

[0040] (2) Take 2g of H-type Beta molecular sieve and place it in a crucible. Then add the above Ni-P precursor mixed solution dropwise and stir for 10min to make it reach the same volume impregnation state. Then let it stand at room temperature and air dry for 12h. After drying at 80℃ for 8h, calcine at 450℃ in air atmosphere for 4h. After cooling to room temperature, reduce at 600℃ in hydrogen atmosphere (50 mL / min) for 2h to obtain Ni2P / Beta.

[0041] (3) At 25°C, 0.010 g of platinum acetylacetonate was dissolved in acetone and stirred to obtain a clear solution. The platinum acetylacetonate solution was added dropwise to the above Ni2P / Beta and stirred for 10 min to achieve an equal volume impregnation state. Then, it was allowed to stand at room temperature and air-dried for 12 h. After drying at 80°C for 4 h, it was calcined at 500°C for 2 h in an air atmosphere. After cooling to room temperature, it was reduced at 360°C for 2 h in a hydrogen atmosphere (50 mL / min) to obtain Pt-Ni2P / Beta.

[0042] 1 g of Pt-Ni2P / Beta catalyst was packed into a fixed-bed reactor and reduced at 330 °C for 2 h in a hydrogen atmosphere (38 mL / min). The temperature was then lowered to 300 °C, and hexane model oil was injected using a metering pump at a flow rate of 0.051 mL / min and a hydrogen / oil molar ratio of 4:1 under 2.0 MPa conditions for 2 h. After the reaction, the product was collected from the outlet, condensed, and separated. The concentration of hexane in the model oil was analyzed by gas chromatography. The calculated hexane conversion rate was 79%, and the isomer selectivity was 97%, achieving efficient hydroisomerization of hexane.

[0043] The Pt-Ni2P / Beta catalyst prepared in Example 1 was subjected to XRD testing, and the results are as follows: Figure 1 As shown, all samples exhibited characteristic diffraction peaks corresponding to the BEA topology at 2θ around 7–8°, 22–23°, and 25°, indicating that the Beta molecular sieve framework structure remained intact after the introduction of Ni2P and subsequent loading of Pt and reduction treatment, without any phase transformation or severe collapse. Furthermore, no characteristic diffraction peaks attributable to Ni2P or Pt crystal phase particles were observed within the tested 2θ range, suggesting that Ni2P and Pt species exist at a highly dispersed nanoscale, with grain sizes smaller than the XRD detection limit.

[0044] The Pt-Ni2P / Beta prepared in Example 1 was analyzed by NH3-TPD and Py-FTIR. Figure 2 As shown, after introducing the active component, the catalyst exhibits two main desorption peaks distinguishable between 100-200 °C and 400-650 °C, corresponding to weak acid sites and strong acid sites, respectively. This indicates that Pt-Ni2P / Beta possesses abundant weak acid and strong acid sites. Furthermore, combined with... Figure 3 As shown, Py-FTIR at 1450 cm⁻¹ -1 1490cm -1 and 1540 cm -1 The peaks at 1450 cm⁻¹ correspond to the characteristic peaks of Lewis acid, B / L common peak, and Brønsted acid, respectively. -1 The peak intensity is significantly higher than 1540 cm⁻¹ -1This indicates that the Pt-Ni2P / Beta surface is dominated by Lewis acid while retaining a certain number of Brønsted acid sites, providing the necessary acidic structural basis for metal-acid co-isomerization.

[0045] TEM experiments were performed on the Pt-Ni2P / Beta catalyst prepared in Example 1, such as... Figure 4 As shown, since heavy materials have high brightness in dark-field transmission electron microscopy, single atoms and clusters of Pt are uniformly loaded on the surface of Ni2P nanoparticles. Furthermore, there is a certain distance between Ni2P particles, and they are uniformly dispersed on the surface of the molecular sieve.

[0046] Example 2

[0047] (1) At 25°C, 0.297 g of nickel nitrate hexahydrate calculated according to the required loading amount was first dissolved in deionized water and stirred to obtain a clear solution; then nitric acid solution (mass fraction of 65~68wt.%) was added dropwise to adjust the pH value of the solution to 3, and 0.27 g of phosphorus precursor diammonium hydrogen phosphate was added under stirring to completely dissolve it without producing a precipitate. Stirring was continued for 1 h to obtain a Ni-P precursor mixed solution.

[0048] (2) Take 3g of H-type Beta molecular sieve and place it in a crucible. Then add the above Ni-P precursor mixed solution dropwise and stir for 15min to make it reach the state of equal volume impregnation. Then let it stand at room temperature and air dry for 10h. After drying at 80℃ for 8h, calcine at 450℃ for 4h in air atmosphere. After cooling to room temperature, reduce at 600℃ for 2h in hydrogen atmosphere (50 mL / min) to obtain Ni2P / Beta.

[0049] (3) At 25°C, 0.015 g of platinum acetylacetonate was dissolved in acetone and stirred to obtain a clear solution. The platinum acetylacetonate solution was added dropwise to the above Ni2P / Beta and stirred for 15 min to achieve an equal volume impregnation state. The solution was allowed to stand at room temperature for 10 h, dried at 80°C for 4 h, calcined at 500°C for 2 h in air atmosphere, cooled to room temperature, and reduced at 360°C for 2 h in hydrogen atmosphere (50 mL / min) to obtain Pt-Ni2P / Beta.

[0050] One g of Pt-Ni2P / Beta catalyst was loaded into a fixed-bed reactor and reduced at 330 °C for 2 h in a hydrogen atmosphere (38 mL / min). The temperature was then lowered to 310 °C, and hexane model oil was injected using a metering pump at a flow rate of 0.051 mL / min and a hydrogen / oil molar ratio of 4:1 under 2.0 MPa conditions for 2 h. After the reaction, the product was collected from the outlet, condensed, and separated. Gas chromatography was used to analyze the concentration of hexane in the model oil, calculating a hexane conversion rate of 79% and an isomer selectivity of 95%, achieving efficient hydroisomerization of hexane.

[0051] Example 3

[0052] (1) At 25°C, 0.396 g of nickel nitrate hexahydrate calculated according to the required loading amount was first dissolved in deionized water and stirred to obtain a clear solution; then nitric acid solution (mass fraction of 65~68wt.%) was added dropwise to adjust the pH value of the solution to 3, and 0.36 g of phosphorus precursor diammonium hydrogen phosphate was added under stirring to completely dissolve it without producing a precipitate. Stirring was continued for 1 h to obtain a Ni-P precursor mixed solution.

[0053] (2) Take 4g of H-type Beta molecular sieve and place it in a crucible. Then add the above Ni-P precursor mixed solution dropwise and stir for 15min to make it reach the state of equal volume impregnation. Then let it stand at room temperature and air dry for 12h. After drying at 80℃ for 8h, calcine at 450℃ for 4h in air atmosphere. After cooling to room temperature, reduce at 600℃ for 2h in hydrogen atmosphere (50 mL / min) to obtain Ni2P / Beta.

[0054] (3) At 25°C, 0.020 g of platinum acetylacetonate was dissolved in acetone and stirred to obtain a clear solution. The platinum acetylacetonate solution was added dropwise to the above Ni2P / Beta and stirred for 10 min to achieve an equal volume impregnation state. Then, it was allowed to stand at room temperature and air-dried for 12 h. After drying at 80°C for 4 h, it was calcined at 500°C for 2 h in an air atmosphere. After cooling to room temperature, it was reduced at 360°C for 2 h in a hydrogen atmosphere (50 mL / min) to obtain Pt-Ni2P / Beta.

[0055] 1 g of Pt-Ni2P / Beta catalyst was loaded into a fixed-bed reactor and reduced at 330 °C for 2 h in a hydrogen atmosphere (38 mL / min). The temperature was then lowered to 320 °C, and hexane model oil was injected using a metering pump at a flow rate of 0.051 mL / min and a hydrogen / oil molar ratio of 4:1 under 2.0 MPa conditions for 2 h. After the reaction, the product was collected from the outlet, condensed, and separated. The concentration of hexane in the model oil was analyzed by gas chromatography. The calculated hexane conversion rate was 81%, and the isomer selectivity was 90%, achieving efficient hydroisomerization of hexane.

[0056] Example 4

[0057] (1) At 25°C, 0.495 g of nickel nitrate hexahydrate calculated according to the required loading amount was first dissolved in deionized water and stirred to obtain a clear solution; then nitric acid solution (mass fraction of 65~68wt.%) was added dropwise to adjust the pH value of the solution to 3, and 0.45 g of diammonium hydrogen phosphate precursor was added under stirring to completely dissolve it without producing a precipitate. Stirring was continued for 1 h to obtain a Ni-P precursor mixed solution.

[0058] (2) Take 5g of H-type Beta molecular sieve and disperse it in an appropriate amount of deionized water. Then add the above Ni-P precursor mixed solution dropwise and stir for 10min to make it reach the same volume impregnation state. Then let it stand at room temperature and air dry for 12h. After drying at 80℃ for 8h, calcine at 450℃ for 4h in air atmosphere. After cooling to room temperature, reduce at 600℃ for 2h in hydrogen atmosphere (50 mL / min) to obtain Ni2P / Beta.

[0059] (3) At 25°C, 0.025 g of platinum acetylacetonate was dissolved in acetone and stirred to obtain a clear solution. The platinum acetylacetonate solution was added dropwise to the above Ni2P / Beta and stirred for 10 min to achieve an equal volume impregnation state. Then, it was allowed to stand at room temperature and air-dried for 12 h. After drying at 80°C for 4 h, it was calcined at 500°C for 2 h in an air atmosphere. After cooling to room temperature, it was reduced at 360°C for 2 h in a hydrogen atmosphere (50 mL / min) to obtain Pt-Ni2P / Beta.

[0060] Two g of Pt-Ni2P / Beta catalyst was loaded into a fixed-bed reactor and reduced at 330 °C for 2 h in a hydrogen atmosphere (76 mL / min). The temperature was then lowered to 300 °C, and hexane model oil was introduced using a metering pump at a flow rate of 0.102 mL / min and a hydrogen / oil molar ratio of 4:1 under 2.0 MPa conditions for 2 h. After the reaction, the product was collected from the outlet, condensed, and separated. Gas chromatography was used to analyze the concentration of hexane in the model oil, calculating a hexane conversion rate of 79% and an isomer selectivity of 97%, achieving efficient hydroisomerization of hexane.

[0061] Example 5

[0062] (1) At 25°C, 0.594 g of nickel nitrate hexahydrate calculated according to the required loading amount was first dissolved in deionized water and stirred to obtain a clear solution; then nitric acid solution (mass fraction of 65~68wt.%) was added dropwise to adjust the pH value of the solution to 3, and 0.54 g of diammonium hydrogen phosphate precursor was added under stirring to completely dissolve it without producing a precipitate. Stirring was continued for 1 h to obtain a Ni-P precursor mixed solution.

[0063] (2) Take 6g of H-type Beta molecular sieve and place it in a crucible. Then add the above Ni-P precursor mixed solution dropwise and stir for 10min to make it reach the same volume impregnation state. Then let it stand at room temperature and air dry for 12h. After drying at 80℃ for 8h, calcine at 450℃ for 4h in air atmosphere. After cooling to room temperature, reduce at 600℃ for 2h in hydrogen atmosphere (50 mL / min) to obtain Ni2P / Beta.

[0064] (3) At 25°C, 0.030 g of platinum acetylacetonate was dissolved in acetone and stirred to obtain a clear solution. The platinum acetylacetonate solution was added dropwise to the above Ni2P / Beta and stirred for 10 min to achieve an equal volume impregnation state. Then, it was allowed to stand at room temperature and air-dried for 12 h. After drying at 80°C for 4 h, it was calcined at 500°C for 2 h in an air atmosphere. After cooling to room temperature, it was reduced at 360°C for 2 h in a hydrogen atmosphere (50 mL / min) to obtain Pt-Ni2P / Beta.

[0065] Four g of Pt-Ni2P / Beta catalyst was packed into a fixed-bed reactor and reduced at 330 °C for 2 h in a hydrogen atmosphere (152 mL / min). The temperature was then lowered to 310 °C, and hexane model oil was injected using a metering pump at a flow rate of 0.204 mL / min and a hydrogen / oil molar ratio of 4:1 under 2.0 MPa conditions for 2 h. After the reaction, the product was collected from the outlet, condensed, and separated. Gas chromatography was used to analyze the concentration of hexane in the model oil, calculating a hexane conversion rate of 79% and an isomer selectivity of 95%, achieving efficient hydroisomerization of hexane.

[0066] This invention constructs a Ni2P phase on a Beta molecular sieve and introduces trace amounts of Pt, allowing Pt to be dispersed on the surfaces of Ni2P and Beta molecular sieves in the form of both single atoms and small-sized clusters. This forms a metal-phosphide-acid multi-interface structure with strong electronic coupling and hydrogen spillover effects. Under the premise of significantly reducing the amount of Pt, it improves the hydrogen activation capacity and the metal-acid synergistic level, thereby improving the hexane conversion rate and isomer selectivity, suppressing cracking side reactions, and improving the catalyst's resistance to coking and sintering. It has significant industrial application value.

[0067] Comparative Example 1

[0068] At 25℃, 0.198g of nickel nitrate hexahydrate, calculated according to the required loading, was first dissolved in deionized water and stirred to obtain a clear solution. Then, nitric acid solution (mass fraction of 65~68wt.%) was added dropwise to adjust the pH of the solution to 3. 0.18g of diammonium hydrogen phosphate, a phosphorus precursor, was added under stirring until it was completely dissolved without precipitation. Stirring was continued for 1 hour to obtain a Ni-P precursor mixed solution.

[0069] Take 2g of H-type Beta molecular sieve and place it in a crucible. Then add the above Ni-P precursor mixed solution dropwise and stir for 10min to achieve an equal volume impregnation state. Then let it stand at room temperature and air dry for 12h. After drying at 80℃ for 8h, calcine at 450℃ in air atmosphere for 4h. After cooling to room temperature, reduce at 600℃ in hydrogen atmosphere (50 mL / min) for 2h to obtain Ni2P / Beta.

[0070] 1 g of Ni₂P / Beta catalyst was loaded into a fixed-bed reactor and reduced at 330 °C for 2 h in a hydrogen atmosphere (38 mL / min). The temperature was then lowered to 300 °C, and hexane model oil was injected using a metering pump at a feed rate of 0.051 mL / min and a hydrogen / oil molar ratio of 4:1 under 2.0 MPa conditions for 2 h. After the reaction, the product was collected from the outlet, condensed, and separated. The concentration of hexane in the model oil was analyzed by gas chromatography. Figure 5 As shown, the isomerization yield of the Ni2P / Beta group is much lower than that of the Pt-Ni2P / Beta group in Example 1, and the isomerization yield of Pt-Ni2P / Beta can reach 62% at 280°C.

[0071] This invention provides a Pt-Ni2P / Beta n-hexane hydroisomerization catalyst with coexisting single atoms and clusters, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing a Pt-Ni2P / Beta n-hexane hydroisomerization catalyst in which single atoms and clusters coexist, characterized in that, Includes the following steps: (1) Dissolve the nickel precursor in water, stir until homogeneous, adjust the solution to acidity, add the phosphorus precursor, and stir until homogeneous to obtain a Ni-P precursor mixed solution. (2) The Ni-P precursor mixed solution obtained in step (1) was added to the Beta molecular sieve by the equal volume impregnation method. After stirring, it was air-dried, baked, calcined, cooled to room temperature and then reduced to obtain Ni2P / Beta. (3) Dissolve the platinum precursor in an organic solvent and stir until homogeneous to obtain a platinum precursor solution. Then, add the platinum precursor solution to the Ni2P / Beta obtained in step (2) using an equal volume impregnation method. After stirring, air dry, bake dry, calcine, cool to room temperature, and then reduce to obtain the final product.

2. The preparation method according to claim 1, characterized in that, In step (1), the nickel precursor is any one of nickel nitrate, nickel chloride, or nickel acetate; and / or, the acidity is achieved by adjusting the pH of the solution to 1-3 using a nitric acid solution, wherein the mass fraction of the nitric acid solution is 65-68 wt.%. And / or, the phosphorus precursor is any one of diammonium hydrogen phosphate, sodium hypophosphite, or ammonium dihydrogen phosphate; and / or, the molar ratio of the nickel precursor to the phosphorus precursor is 1:1 to 3.

3. The preparation method according to claim 1, characterized in that, In step (2), the Beta molecular sieve is an H-type Beta molecular sieve with a silica-alumina ratio of 10 to 40:

1.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of nickel in the nickel precursor to the Beta molecular sieve is 1% to 5%.

5. The preparation method according to claim 1, characterized in that, In step (2), the stirring time is 10-20 min; and / or the air drying time is 8-24 h at room temperature; and / or the drying time is 70-90 °C for 8-10 h; and / or the calcination time is 400-500 °C for 2-6 h; and / or the reduction time is 550-650 °C for 1-4 h.

6. The preparation method according to claim 1, characterized in that, In step (3), the platinum precursor is any one of platinum acetylacetonate, chloroplatinic acid, or platinum nitrate; the organic solvent is any one of acetone, dichloromethane, or ethanol.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of platinum in the platinum precursor to the Beta molecular sieve is 0.1 to 0.5%.

8. The preparation method according to claim 1, characterized in that, In step (3), the stirring time is 10-20 min; and / or the air drying time is 8-24 h at room temperature; and / or the drying time is 70-90 °C for 4-6 h; and / or the calcination time is 400-550 °C for 1-4 h; and / or the reduction time is 300-400 °C for 1-4 h.

9. The Pt-Ni2P / Beta n-hexane hydroisomerization catalyst with coexisting single atoms and clusters prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the single-atom and cluster coexisting Pt-Ni2P / Beta n-hexane hydroisomerization catalyst according to claim 9 in the n-hexane hydroisomerization catalytic reaction.

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