Preparation method of Pd-coated H-ZSM-22-P catalyst and application of Pd-coated H-ZSM-22-P catalyst in long-chain alkane hydroisomerization

Abstract

The invention discloses a preparation method of a Pd-coated H-ZSM-22-P catalyst and application of the Pd-coated H-ZSM-22-P catalyst in long-chain alkane hydroisomerization, and relates to the technical field of catalysis and long-chain alkane hydroisomerization. The preparation method comprises the following steps: firstly, carrying out hydrothermal synthesis on a ZSM-22-P zeolite molecular sieve carrier by adopting a seed crystal induction method; then, an impregnation method is adopted to promote N atoms and metal Pd salt to be uniformly dispersed on the surface of the carrier to obtain a catalyst precursor, the catalyst Pd-coated H-ZSM-22-P is prepared under the programmed low-temperature reduction condition, and efficient hydroisomerization of long-chain alkane can be achieved under the mild condition. According to the catalyst disclosed by the invention, the completion of catalytic hydroisomerization of long-chain alkane at a relatively low temperature is realized through the cooperation of Pd nanoclusters and strong acid sites, the metal Pd is dispersed on H-ZSM-22-P in the form of nanoclusters, the self-generated electron structure of the catalyst is effectively changed through N doping, and the atom utilization efficiency of the catalyst in a catalytic hydroisomerization reaction is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of catalysis and hydroisomerization technology of long-chain alkanes, and particularly to a method for preparing a Pd@H-ZSM-22-P catalyst and its application in the hydroisomerization of long-chain alkanes. Background Technology

[0002] In recent years, the demand for high-quality petrochemical products has been increasing. Normal long-chain alkanes, through catalytic hydroisomerization, yield isoalkanes of varying chain lengths, which are widely used in aviation, aerospace, and submarine fuels. With the development trend of molecular refining, employing mild catalytic hydroisomerization technology to selectively obtain long-chain isoalkanes and reduce the cracking efficiency of normal long-chain alkanes is of great significance for the upgrading and development of the traditional petrochemical industry.

[0003] Specifically, catalyst performance is influenced by factors such as the distribution of catalytic active sites, the accessibility of substrate molecules to catalytic sites, and diffusion between bulk and guest molecules. From a molecular catalysis perspective, developing catalysts with atomic clusters dispersed in a two-dimensional porous support with high-flux diffusion can enhance the accessibility of substrate molecules to catalytic sites, effectively reduce secondary cracking side reactions to improve the selectivity of isomerization reactions, and avoid localized violent reactions under mild conditions to effectively reduce catalyst lifetime shortening caused by carbon deposition. Based on this, highly active catalysts with synergistic metal-solid acid interactions are the best choice for the efficient isomerization of n-chain alkanes. Summary of the Invention

[0004] To address the aforementioned problems in molecular refining, this invention discloses a method for preparing a Pd@H-ZSM-22-P catalyst and its application in the hydroisomerization of long-chain alkanes. First, this method employs a seed-induced hydrothermal synthesis of a ZSM-22-P zeolite molecular sieve support, which possesses strong accessibility to long-chain alkane macromolecules, highly acidic and uniformly distributed catalytic sites, and significant surface defect sites. Next, an impregnation method is used to uniformly disperse N atoms and metallic Pd salt on the support surface to obtain a catalyst precursor. Under programmed low-temperature reduction conditions, a highly active catalyst, Pd@H-ZSM-22-P, is prepared, enabling efficient hydroisomerization of long-chain alkanes under mild conditions. The catalyst Pd@H-ZSM-22-P prepared in this invention combines the synergistic effect of Pd nanoclusters and strong acid sites to achieve catalytic hydroisomerization of long-chain alkanes at lower temperatures. Metallic Pd is dispersed on H-ZSM-22-P in the form of nanoclusters. N doping effectively changes the self-generated electronic structure of the catalyst, significantly improving the atom utilization efficiency of the catalyst in the catalytic hydroisomerization reaction and ensuring the stability of the catalyst.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The preparation method of Pd@H-ZSM-22-P catalyst includes the following steps:

[0007] a. Preparation of H-ZSM-22-P vector

[0008] a1. KOH, deionized water, Al2SO4·18H2O, ethylenediamine and industrial ZSM-22 zeolite molecular sieve were mixed in proportion, stirred evenly at room temperature, and then gaseous SiO2 was added. After aging by stirring in a sealed container, a sol-gel mixture was obtained.

[0009] a2. The sol-gel mixture was transferred to a self-generated pressure hydrothermal synthesis vessel, sealed and placed in a forced-air drying oven for crystallization, then cooled to room temperature, washed with ethanol until pH=7, dried and placed in an O2 atmosphere tube furnace for calcination, cooling and grinding to obtain a solid powder.

[0010] a3. Take solid powder, perform ion exchange in NH4Cl solution, and then centrifuge to obtain solid precipitate;

[0011] a4. The solid precipitate was placed in a tube furnace under an O2 atmosphere and heated to calcine. After cooling to room temperature, it was ground to obtain solid powder H-ZSM-22-P carrier.

[0012] b. Preparation of Pd@H-ZSM-22-P catalyst precursor

[0013] At room temperature, urea and Pd salt were fully dissolved in deionized water, and H-ZSM-22-P solid powder was added. The mixture was then sealed and sonicated to ensure the support was wetted. After vacuum drying, Pd@H-ZSM-22-P catalyst precursor was obtained, which was then ground and ready for use.

[0014] c. Preparation of Pd@H-ZSM-22-P catalyst

[0015] c1. The Pd@H-ZSM-22-P catalyst precursor was placed in a tube furnace under N2 atmosphere for calcination.

[0016] c2. After naturally cooling to 50℃, switch the N2 in the tubular furnace to H2, raise the temperature to 100~200℃ to perform a first reduction of the Pd@H-ZSM-22-P catalyst precursor, maintain for a certain time, and after the tubular furnace naturally cools to room temperature, raise the temperature to 300~400℃ to perform a second reduction of the Pd@H-ZSM-22-P catalyst precursor, maintain for a certain time, and cool to room temperature to obtain the target catalyst Pd@H-ZSM-22-P.

[0017] Optionally, in step a1, industrial ZSM-22 zeolite molecular sieve is used as a seed crystal to induce secondary crystal growth, and the Si / Al ratio of industrial ZSM-22 zeolite molecular sieve is 70.

[0018] Optionally, in step a1, the mass ratio of KOH, industrial ZSM-22 zeolite molecular sieve, gaseous SiO2, Al2SO4·18H2O and ethylenediamine is 15:7~8:60:5:20, and the aging time is 2~4h.

[0019] Optionally, in step a2, the crystallization temperature is 160~180℃, the crystallization time is 48h; the drying temperature is 90℃, the drying time is 12h; and the heating rate is 8℃·min. -1 Heat to 600℃ and roast for 5 hours.

[0020] Optionally, in step a3, the concentration of the NH4Cl solution is 0.5~1.0 mol·L⁻¹. -1 The ion exchange temperature is 30~50℃, and the number of exchanges is 2~4 times.

[0021] Optionally, in step a4, the heating rate is 8°C·min. -1 Heat to 600℃ and roast for 3 hours.

[0022] Optionally, in step b, the molar ratio of Pd salt to urea is 1:10, and the solid mass ratio of Pd salt to H-ZSM-22-P is 1:60.

[0023] Optionally, in step c1, the N2 flow rate is 2 mL·min. -1 The heating rate is 1.5℃·min. -1 Heat to 400-500℃ and maintain for 2-3 hours; in step c2, the H2 flow rate is 6 mL / min. -1 In one reduction, the heating rate is 2℃·min. -1 The holding time is 1~2 hours, and the heating rate during the secondary reduction is 3℃·min. -1 The duration is 3-4 hours.

[0024] A second aspect of the present invention provides a Pd@H-ZSM-22-P catalyst prepared using the above method.

[0025] A third aspect of the present invention provides the application of the catalyst Pd@H-ZSM-22-P.

[0026] In an alternative embodiment, the catalyst Pd@H-ZSM-22-P is used for the catalytic hydroisomerization of long-chain alkanes under mild conditions.

[0027] The beneficial effects of this invention are:

[0028] 1. The H-ZSM-22-P support prepared in this invention is generated by seed-induced industrial ZSM-22 zeolite molecular sieve and hydrothermal crystallization in situ crystallization to produce H-ZSM-22-P. The accessibility of long-chain n-alkanes to solid acidic catalytic sites is significantly improved, the pore structure is optimized, and the diffusion performance of the guest macromolecule is enhanced.

[0029] 2. The accessibility of the long-chain n-alkane to the solid acidic catalytic site and the pore structure of the H-ZSM-22-P support prepared in this invention can be controlled by adjusting the external driving force such as the aging temperature and time of the sol-gel and the crystallization time and temperature during the hydrothermal synthesis process.

[0030] 3. In the Pd@H-ZSM-22-P catalyst precursor prepared in this invention, the ratio of urea, Pd salt and H-ZSM-22-P support needs to be strictly controlled to ensure that in a complex system, a small amount of N element doping is achieved by micro-etching the H-ZSM-22-P crystal framework, and the Pd salt is uniformly distributed in the form of clusters on the surface and in the pores of the H-ZSM-22-P support, maintaining the integrity of the H-ZSM-22-P framework structure.

[0031] 4. The Pd@H-ZSM-22-P catalyst prepared in this invention employs a two-stage reduction process (first and second stage) to achieve high dispersion of metallic Pd nanoclusters, thereby enhancing catalytic activity by improving atom utilization efficiency. The low-temperature first-stage reduction promotes the uniform dispersion of Pd salt on the support in the form of smaller particles, while the second-stage slow reduction enables bonding between the metallic Pd nanoclusters and the H-ZSM-22-P support, improving the catalyst's stability.

[0032] 5. The Pd@H-ZSM-22-P catalyst prepared in this invention can achieve the hydroisomerization reaction of long-chain n-alkanes at a relatively low reaction temperature. At 320℃ and a WHSV of 3 h⁻¹, the reaction can achieve this effect. -1 At a hydrogen pressure of 2 MPa, the conversion rate of n-nonane hydroisomerization was 91.4%; the yield of the target product was 76.6%; and the conversion rate was achieved at 320 °C and a WHSV of 3 h⁻¹. -1 At a hydrogen pressure of 2 MPa, the conversion rate of n-heptane hydroisomerization was 89.6%; the yield of the target product was 78.4%.

[0033] 6. The Pd@H-ZSM-22-P catalyst prepared in this invention has high activity and strong stability. After 1000 hours of continuous reaction, the activity of the hydroisomerization reaction is basically not reduced. Attached Figure Description

[0034] Figure 1The XRD patterns of the H-ZSM-22-P support and Pd@H-ZSM-22-P catalyst prepared in Example 1 of this invention are shown below.

[0035] Figure 2 The NH3-TPD diagram of the Pd@H-ZSM-22-P catalyst prepared in Example 1 of this invention is shown.

[0036] Figure 3 This is a SEM image of the Pd@H-ZSM-22-P catalyst prepared in Example 1 of this invention;

[0037] Figure 4 This is a graph showing the change in activity of the Pd@H-ZSM-22-P catalyst prepared in Example 1 of this invention during continuous reaction. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] The preparation method of Pd@H-ZSM-22-P catalyst is as follows:

[0041] 1. KOH, deionized water, Al2SO4·18H2O, ethylenediamine and industrial ZSM-22 zeolite molecular sieve were placed in a beaker at a mass ratio of 15:7.5:60:5:20. After stirring evenly at room temperature, gaseous SiO2 was added. After aging for 3 hours with sealed stirring, a sol-gel mixture was obtained.

[0042] 2. The sol-gel mixture was transferred to a self-generated pressure hydrothermal synthesis vessel, sealed, and placed in a forced-air drying oven for crystallization at 170℃ for 48 hours. After cooling to room temperature, it was washed until pH=7 to obtain a white solid precipitate. The white solid precipitate was dried at 90℃ for 12 hours to obtain ZSM-22-P solid powder. After drying, it was placed in an O2 atmosphere tube furnace for calcination at 8℃·min. -1The temperature was increased to 600℃ at a certain rate, calcined for 5 hours, cooled and ground to 300 mesh to obtain a solid powder;

[0043] 3. Place the solid powder in a 1.0 mol·L⁻¹ solution. -1 In an NH4Cl solution, three ion exchanges were performed at a temperature of 40℃, followed by filtration and drying to obtain a solid precipitate.

[0044] 4. Place the solid precipitate in an O2 atmosphere tube furnace at 8°C / min. -1 The temperature was increased to 600℃ at a certain rate, calcined for 3 hours, and then ground to 300 mesh after cooling to room temperature in a tube furnace to obtain H-ZSM-22-P powder. Its XRD diffraction pattern is shown below. Figure 1 As shown;

[0045] 5. At room temperature, urea and Pd salt were fully dissolved in deionized water at a molar ratio of 1:10. After adding H-ZSM-22-P solid powder, the mixture was sealed and sonicated. The mass ratio of Pd salt to H-ZSM-22-P solid was 1:60 to ensure the support was in a wetted state. After vacuum drying, Pd@H-ZSM-22-P catalyst precursor was obtained, ground, and ready for use.

[0046] 6. The Pd@H-ZSM-22-P catalyst precursor was calcined in a tube furnace under a N2 atmosphere. The calcination conditions were: N2 flow rate of 2 mL / min. -1 The heating rate is 1.5℃·min. -1 Heat to 500℃ and maintain for 3 hours;

[0047] 7. After allowing the atmosphere tube furnace to cool naturally to 50℃, switch the N2 in the atmosphere tube furnace to H2, with an H2 flow rate of 6 mL·min. -1 , at 2℃·min -1 The Pd@H-ZSM-22-P catalyst precursor was reduced once by heating to 200℃ at a rate of 2 h; after the tube furnace cooled naturally to room temperature, the H2 flow rate was kept constant and the catalyst was heated at 3℃·min. -1 The Pd@H-ZSM-22-P catalyst precursor was subjected to a secondary reduction at a rate of 400℃. After maintaining the temperature for 4 hours, it was cooled to room temperature to obtain the target catalyst Pd@H-ZSM-22-P.

[0048] like Figure 1 As shown, the skeletal structure of the catalyst support H-ZSM-22-P remains intact during the metal loading process. Figure 2 The H2-TPR diagram of Pd@H-ZSM-22-P shows that the catalyst has good performance in adsorbing and activating H2 at lower temperatures. Figure 3The SEM image of Pd@H-ZSM-22-P further demonstrates that the catalyst possesses the morphological characteristics of two-dimensional small fragments, which is beneficial for the diffusion of the guest reactants and products, reduces the probability of secondary reactions, and improves the selectivity of the target product. Figure 4 As shown, the Pd@H-ZSM-22-P catalyst prepared in Example 1 has high activity and strong stability. After 1000 hours of continuous reaction, the activity of the hydroisomerization reaction basically did not decrease.

[0049] Comparative Example 1

[0050] The difference from Example 1 is that ammonia is used instead of ethylenediamine.

[0051] Comparative Example 2

[0052] The difference from Example 1 is that the mass ratio of KOH, industrial ZSM-22 zeolite molecular sieve, gaseous SiO2, Al2SO4·18H2O and ethylenediamine is 25:3:60:10:20.

[0053] Comparative Example 3

[0054] The difference from Example 1 is that the crystallization temperature is 220°C.

[0055] Comparative Example 4

[0056] The difference from Example 1 is that the crystallization time is 72 hours.

[0057] Comparative Example 5

[0058] The difference from Example 1 is that the molar ratio of Pd salt to urea is 1:20, and the solid mass ratio of Pd salt to H-ZSM-22-P is 1:80.

[0059] Comparative Example 6

[0060] The difference from Example 1 is that in step 6, the atmosphere in the tubular furnace is air, and the duration is 1 hour.

[0061] Application Example 1

[0062] The catalysts prepared in Example 1 and Comparative Examples 1 to 6 were respectively applied to the hydroisomerization reaction of n-nonane.

[0063] Reaction conditions: The catalyst was evaluated using a single-channel fully automated catalyst evaluation device.

[0064] Using n-nonane as a long-chain n-alkane model compound, the catalyst loading was 50 mg. The catalyst was first reduced in situ at 400 °C under a H2 atmosphere and 0.1 MPa for 3 h, with a heating rate of 10 °C / min. When the reactor temperature reached 240 °C, a n-nonane / H2 mixture was uniformly distributed into the reactor through a capillary column. The reaction was carried out at 320 °C with a weight hourly space velocity (WHSV) of 3 h⁻¹. -1 The reaction was initiated at a hydrogen pressure of 2 MPa in the reactor. This was used to evaluate the catalytic hydroisomerization capabilities of the catalysts in Example 1 and Comparative Examples 1 to 6.

[0065] Analysis of hydroisomerization products: The composition of the catalytic hydrogenation conversion products was analyzed in detail using an Agilent 7890 / 5973 quadrupole gas chromatograph / mass spectrometer. The chromatographic column was a 60m × 0.25mm × 0.25μm HP-5MS capillary cross-linked column. The chromatograms were obtained from the NIST20 library. The products were quantitatively analyzed using an Agilent 7890 gas chromatograph with a 60m × 0.25mm × 0.25μm HP-5 capillary cross-linked column.

[0066] Under the same conditions, the catalytic hydrogenation conversion performance of n-nonane was evaluated, and the conversion rate of n-nonane and the molar yield of isononane are shown in Table 1.

[0067] Table 1. Application of different implementation examples in the hydroisomerization reaction of n-nonane.

[0068]

[0069] In Table 1, the evaluation of the catalytic hydroisomerization of the model compound n-nonane shows that the catalyst Pd@H-ZSM-22-P, with the synergistic effect of Pd nanoclusters and strong acid sites, enables the catalytic hydroisomerization of long-chain alkanes at a lower temperature. Metallic Pd is dispersed on H-ZSM-22-P in the form of nanoclusters. N doping effectively changes the self-generated electronic structure of the catalyst, significantly improving the atom utilization efficiency of the catalyst in the catalytic hydroisomerization reaction and ensuring the stability of the catalyst, thus showing broad prospects for practical application.

[0070] Application Example 2

[0071] The catalysts prepared in Example 1 and Comparative Examples 1 to 6 were respectively applied to the hydroisomerization reaction of n-heptane.

[0072] Reaction conditions: The catalyst was evaluated using a single-channel fully automated catalyst evaluation device.

[0073] Using n-heptane as a long-chain n-alkane model compound, the catalyst loading was 50 mg. The catalyst was first reduced in situ at 400 °C under a H2 atmosphere and 0.1 MPa for 3 h, with a heating rate of 10 °C / min. After the reactor temperature reached 240 °C, the n-heptane / H2 mixture was uniformly distributed into the reactor through a capillary column. The reaction was carried out at 320 °C with a weight hourly space velocity (WHSV) of 3 h⁻¹. -1 The reaction was initiated at a hydrogen pressure of 2 MPa in the reactor. This was used to evaluate the catalytic hydroisomerization capabilities of the catalysts in Examples 1 and Comparative Examples 1 to 6.

[0074] Analysis of hydroisomerization products: The composition of the catalytic hydrogenation conversion products was analyzed in detail using an Agilent 7890 / 5973 quadrupole gas chromatograph / mass spectrometer. The chromatographic column was a 60m × 0.25mm × 0.25μm HP-5MS capillary cross-linked column. The chromatograms were obtained from the NIST20 library. The products were quantitatively analyzed using an Agilent 7890 gas chromatograph with a 60m × 0.25mm × 0.25μm HP-5 capillary cross-linked column.

[0075] Under the same conditions, the catalytic hydrogenation conversion performance of n-heptane was evaluated, and the conversion rates of n-heptane and the molar yields of isoheptane are shown in Table 2.

[0076] Table 2. Application of different implementation examples in the hydroisomerization reaction of n-heptane.

[0077]

[0078] In Table 2, the evaluation of the catalytic hydroisomerization of the model compound n-heptane shows that the catalyst Pd@H-ZSM-22-P, with the synergistic effect of Pd nanoclusters and strong acid sites, enables the catalytic hydroisomerization of long-chain alkanes at a lower temperature. Metallic Pd is dispersed on H-ZSM-22-P in the form of nanoclusters. N doping effectively changes the self-generated electronic structure of the catalyst, significantly improving the atom utilization efficiency of the catalyst in the catalytic hydroisomerization reaction and ensuring the stability of the catalyst, thus showing broad prospects for practical application.

[0079] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing Pd@H-ZSM-22-P catalyst, characterized in that, Includes the following steps: a. Preparation of H-ZSM-22-P vector a1. KOH, deionized water, Al2SO4·18H2O, ethylenediamine and industrial ZSM-22 zeolite molecular sieve were mixed in proportion, stirred evenly at room temperature, and then gaseous SiO2 was added. After aging by stirring in a sealed container, a sol-gel mixture was obtained. a2. The sol-gel mixture was transferred to a self-generated pressure hydrothermal synthesis vessel, sealed and placed in a forced-air drying oven for crystallization, then cooled to room temperature, washed with ethanol until pH=7, dried and placed in an O2 atmosphere tube furnace for calcination, cooling and grinding to obtain a solid powder. a3. Take the solid powder, perform ion exchange in NH4Cl solution, and then centrifuge to obtain a solid precipitate; a4. The solid precipitate was placed in a tube furnace under an O2 atmosphere and heated to calcine. After cooling to room temperature, it was ground to obtain solid powder H-ZSM-22-P carrier. b. Preparation of Pd@H-ZSM-22-P catalyst precursor At room temperature, urea and Pd salt were fully dissolved in deionized water, and then H-ZSM-22-P solid powder was added. The mixture was then sealed and ultrasonically treated, and vacuum dried to obtain the Pd@H-ZSM-22-P catalyst precursor, which was then ground and ready for use. c. Preparation of Pd@H-ZSM-22-P catalyst c1. The Pd@H-ZSM-22-P catalyst precursor was placed in a tube furnace under N2 atmosphere for calcination. c2. After naturally cooling to 50℃, switch the N2 in the tubular furnace to H2, raise the temperature to 100~200℃ to perform a first reduction of the Pd@H-ZSM-22-P catalyst precursor, and after the tubular furnace naturally cools to room temperature, raise the temperature to 300~400℃ to perform a second reduction of the Pd@H-ZSM-22-P catalyst precursor, and cool to room temperature to obtain the target catalyst Pd@H-ZSM-22-P.

2. The method for preparing the Pd@H-ZSM-22-P catalyst as described in claim 1, characterized in that, In step a1, industrial ZSM-22 zeolite molecular sieve is used as a seed crystal to induce secondary crystal growth, and the Si / Al ratio of industrial ZSM-22 zeolite molecular sieve is 70.

3. The preparation method of the Pd@H-ZSM-22-P catalyst as described in claim 1, characterized in that, In step a1, the mass ratio of KOH, industrial ZSM-22 zeolite molecular sieve, gaseous SiO2, Al2SO4·18H2O and ethylenediamine is 15:7~8:60:5:20, and the aging time is 2~4h.

4. The preparation method of the Pd@H-ZSM-22-P catalyst as described in claim 1, characterized in that, In step a2, the crystallization temperature is 160~180℃, the crystallization time is 48h; the drying temperature is 90℃, the drying time is 12h; and the heating rate is 8℃·min. -1 Heat to 600℃ and roast for 5 hours.

5. The preparation method of the Pd@H-ZSM-22-P catalyst as described in claim 1, characterized in that, In step a3, the concentration of the NH4Cl solution is 0.5~1.0 mol·L⁻¹. -1 The ion exchange temperature is 30~50℃, and the number of exchanges is 2~4 times.

6. The preparation method of the Pd@H-ZSM-22-P catalyst as described in claim 1, characterized in that, In step a4, the heating rate is 8°C·min. -1 Heat to 600℃ and roast for 3 hours.

7. The method for preparing the Pd@H-ZSM-22-P catalyst as described in claim 1, characterized in that, In step b, the molar ratio of Pd salt to urea is 1:10, and the solid mass ratio of Pd salt to H-ZSM-22-P is 1:

60.

8. The method for preparing the Pd@H-ZSM-22-P catalyst as described in claim 1, characterized in that, In step c1, the N2 flow rate is 2 mL·min -1 The heating rate is 1.5℃·min. -1 Heat to 400-500℃ and maintain for 2-3 hours; in step c2, the H2 flow rate is 6 mL / min. -1 In one reduction cycle, the heating rate is 2℃·min. -1 The holding time is 1~2 hours, and the heating rate during the secondary reduction is 3℃·min. -1 The duration is 3-4 hours.

9. A Pd@H-ZSM-22-P catalyst prepared by the method according to any one of claims 1 to 8.

10. The application of the Pd@H-ZSM-22-P catalyst as described in claim 9 in the hydroisomerization of long-chain alkanes under mild conditions.

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