A metal-coated multi-level pore ZSM-5 catalyst for hydrocyclization of aviation coal carbon chain precursor substances

Abstract

The application discloses a metal-coated multi-level hole ZSM-5 catalyst for hydroisomerization of aviation kerosene carbon chain precursor substances and belongs to the technical field of catalyst preparation. A preparation method is as follows: one or two or more of iron salt, platinum salt and nickel salt are impregnated on a ZSM-5 carrier, and a supported metal oxide / ZSM-5 is obtained after calcination; then, tetrapropylammonium hydroxide and a sodium hydroxide solution are added to the supported metal oxide / ZSM-5, after reaction and calcination, ion exchange is carried out through ammonium chloride, and finally reduction is carried out to obtain metal@MHS-Z5. The product is composed of a multi-level hole hollow ZSM-5 carrier and one or more of metal components Fe, Ni or Pt, is used for hydroisomerization of aviation kerosene carbon chain precursor substances, has good catalytic stability, and can maintain the aviation kerosene long-chain alkane cyclization isomerization activity at a lower temperature.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a method for preparing a metal-coated hierarchical porous ZSM-5 catalyst for the hydrogenation cyclization isomerization of aviation kerosene carbon chain precursors and its application. Background Technology

[0002] With the rapid development of the aviation industry, the energy demands of modern aircraft are increasing daily, and the requirements for the composition of aviation kerosene are becoming increasingly stringent. Aviation fuel must not only possess high energy density to meet the needs of long-duration, high-load flights, but also exhibit excellent combustion stability, anti-knock properties, and low-temperature fluidity under a wide range of temperature and pressure conditions. However, the high proportion of straight-chain alkanes in traditional aviation kerosene has some shortcomings. Although straight-chain alkanes have high energy density, their anti-knock properties are poor, easily causing knocking in the engine, thus reducing fuel efficiency and affecting engine safety. Furthermore, straight-chain alkanes have poor fluidity at low temperatures, easily leading to fuel condensation under the frigid conditions of high-altitude flight, thereby affecting the normal operation of the fuel supply system. Their thermal stability is also relatively low, easily forming deposits under high-temperature conditions, shortening engine life. Therefore, in the aviation fuel production process, isomerizing straight-chain alkanes into branched-chain alkanes or generating cycloalkanes through cyclization has become an effective optimization method.

[0003] Branched alkanes, due to their branched structure, exhibit higher anti-knock properties and more stable combustion performance, while cycloalkanes offer good low-temperature fluidity and high thermal stability. These features not only enhance the anti-knock performance of aviation fuels but also significantly improve their low-temperature performance and thermal stability, meeting the stringent fuel requirements of modern aero-engines and thus improving flight efficiency and safety. Therefore, developing catalysts for the efficient preparation of branched alkanes and cyclization into cycloalkanes at lower temperatures is of great significance.

[0004] ZSM-5 possesses advantages such as abundant pores, good hydrothermal stability, and easily tunable acidity. By controlling the pore structure, metal loading, and acidity, it can easily achieve various functionalities, thus its application as a catalyst or catalyst support is already widespread. However, when used for the cyclization and isomerization of aviation kerosene, the large size of the reactant molecules and the small pore size and poor mass transfer of the original ZSM-5 make it unsuitable for industrial production. Some researchers have chosen to add strong basic substances and template agents, such as a combination of sodium hydroxide, potassium hydroxide, and tetrapropylammonium hydroxide, to ZSM-5 to transform it into a hollow, hierarchical porous material, MHS-Z5. The introduction of mesopores greatly enhances the mass transfer effect of macromolecules. Since MHS-Z5 itself only possesses acidity and lacks the ability to activate hydrogen, loading noble metals or some transition metals onto the surface or interior of MHS-Z5 allows the loaded MHS-Z5 to possess both acidity and the ability to activate hydrogen, making it an excellent catalyst for the hydrogenation and cyclization isomerization of precursors with suitable carbon chain lengths. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a metal-coated hierarchical porous ZSM-5 catalyst for the hydrogenation cyclization and isomerization of carbon chain precursors in aviation kerosene, addressing the shortcomings of the prior art.

[0006] A metal-coated hierarchical porous ZSM-5 catalyst for the hydrogenation cyclization isomerization of aviation kerosene carbon chain precursors is prepared by the following steps:

[0007] Step 1: Dissolve one or more of the following salts in deionized water in a certain proportion: iron salt, platinum salt, and nickel salt to obtain mixed solution A;

[0008] The iron salt contains 1–5 wt% Fe, the platinum salt contains 1–5 wt% Pt, the nickel salt contains 1–5 wt% Ni, and the remainder is deionized water.

[0009] The nickel salt is one or a combination of two or more of nickel nitrate, nickel acetate, and nickel chloride; the iron salt is one or a combination of two or more of ferric nitrate, ferric chloride, ferric nitrate, ferric oxalate, and ferric acetate, preferably ferric nitrate or ferric chloride; the platinum salt is one or a combination of two or more of platinum chloride, chloroplatinic acid, and platinum nitrate.

[0010] Step 2: Add mixed solution A to type H ZSM-5 and add a magnetic stir bar. Stir vigorously on a magnetic stirrer at room temperature until the compound is fully impregnated into the ZSM-5 support.

[0011] The soaking time is 3 to 10 hours, with a preferred time of 5 to 8 hours.

[0012] Step 3: Dry and calcine the impregnated material to obtain supported metal oxide / ZSM-5;

[0013] The drying temperature is 80–120℃; the calcination temperature is 400–550℃, and the calcination time is 6 hours.

[0014] Step 4: Add tetrapropylammonium hydroxide and sodium hydroxide solution to the supported metal oxide / ZSM-5, and after stirring, hydrothermal treatment, centrifugation, drying and calcination, obtain sodium-type metal oxide coated hierarchical porous catalyst metal oxide@MHS-Z5;

[0015] The mass fraction of tetrapropylammonium hydroxide is 25 wt%, and the molar ratio of tetrapropylammonium hydroxide to sodium hydroxide is 1-12:1, preferably 1-8:1; the hydrothermal reaction temperature is 110-200℃, and the time is 48-96 h; the filter cake drying temperature is 60-120℃; the calcination temperature is 500-700℃, the heating rate is 4-10℃ / min, and the calcination time is 4-8 h.

[0016] Step 5: Disperse the metal oxide @MHS-Z5 powder in an aqueous solution of ammonium chloride and stir to carry out ion exchange.

[0017] After drying and calcination, H-type metal oxide @MHS-Z5 was obtained;

[0018] Add one gram of metal oxide @MHS-Z5 powder to 30-60 ml of ammonium chloride solution;

[0019] The ammonium chloride concentration is 0.5–2 M, the stirring time is 2–4 h, and the ion exchange is repeated 2–3 times.

[0020] The drying temperature is 60–100℃, the calcination temperature is 300–600℃, and the calcination time is 4–7 hours.

[0021] Step 6: Reduce the H-type metal oxide @MHS-Z5 in an H2 / Ar environment at 300℃~500℃ to obtain the reduced metal @MHS-Z5.

[0022] A metal-coated hierarchical porous ZSM-5 catalyst for the hydrogenation cyclization isomerization of carbon chain precursors in aviation kerosene comprises a hierarchical hollow ZSM-5 support and one or more metal components selected from Fe, Ni, or Pt. The metal components are present in the amounts of 1–5 wt% Ni, 1–5 wt% Fe, and 1–5 wt% Pt. The specific surface area of ​​the hierarchical hollow ZSM-5 support is 402–440 μm. 2 / g, with a pore volume of 0.43 to 0.21 ml / g and a B acidity of 12 to 26 mmol / g.

[0023] The metal-coated hierarchical porous ZSM-5 catalyst is used for the hydrogenation, cyclization, and isomerization of aviation kerosene carbon chain precursors containing 10–15 carbon atoms. The product contains 30–50% cycloalkanes or isoalkanes, and the total product of cycloalkanes and isoalkanes is 50–70%.

[0024] The advantages and beneficial effects of this invention are as follows:

[0025] (1) The hydrogenation cyclization and isomerization catalyst for aviation kerosene carbon chain precursors prepared by the present invention has high cyclization activity and isomerization activity, and good catalytic stability.

[0026] (2) When the hydrogenation cyclization isomerization catalyst of the aviation kerosene carbon chain precursor prepared in this invention is used for the hydrogenation cyclization isomerization reaction, the reaction temperature is low, and the cyclization isomerization activity of aviation kerosene long chain alkane can be maintained at a low temperature.

[0027] (3) The preparation method of the hydrogenation cyclization isomerization catalyst of the carbon chain precursor of aviation kerosene of the present invention has readily available equipment, controllable reaction conditions, and higher production efficiency. Attached Figure Description

[0028] Figure 1 This is a comparison chart showing the results of using the catalysts prepared in Examples 1-4 for hydrogenation cyclization isomerization reactions;

[0029] Figure 2 The image shows the TEM characterization of the A4 catalyst prepared in Example 4.

[0030] Figure 3 This is a comparison chart showing the results of using the catalysts prepared in Examples 5-8 for hydrogenation cyclization isomerization reactions;

[0031] Figure 4 The following are the powder diffraction characterization patterns of the catalysts prepared in Examples 5-8;

[0032] Figure 5 The image shows a transmission electron microscopy (TEM) scan of the B2 catalyst prepared in Example 6.

[0033] Figure 6 This is a comparison chart showing the results of using the catalysts prepared in Examples 9-11 for the hydrogenation cyclization isomerization reaction;

[0034] Figure 7 The following are the powder diffraction characterization patterns of the catalysts prepared in Examples 9-11;

[0035] Figure 8 The image shows a transmission electron microscopy (TEM) scan of the C3 catalyst prepared in Example 11.

[0036] Figure 9This is a comparison diagram of the products of hydrogenation of the catalysts prepared in Examples 3, 6, 11 and Comparative Example 1 under the same conditions. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0038] The technical solution of the present invention will be further illustrated below with reference to specific embodiments, but these are not intended to limit the scope of protection of the present invention.

[0039] The feedstock for the hydrogenation cyclization isomerization of jet fuel is an oxygen-containing precursor containing 10–15 carbon atoms. The synthesis method includes the following steps:

[0040] (1) After mixing furfural and sodium levulinate solution, add an appropriate amount of alkaline solid oxide and react under vigorous stirring;

[0041] The molar ratio of furfural to sodium levulinate is 0.5 to 2:1, preferably 0.8 to 1:1.

[0042] The alkaline solid oxide is calcium oxide, magnesium oxide, or barium oxide, preferably magnesium oxide, and is used as a catalyst. The mass ratio of furfural to oxide is 2 to 3:1.

[0043] The reaction temperature is 60–90℃, and the reaction time is 5–10 hours;

[0044] (2) After the reaction is complete, the mixture is rapidly cooled with water and the magnesium oxide is separated by centrifugation or filtration.

[0045] (3) The filtrate was added dropwise to an excess of dilute hydrochloric acid, resulting in a large amount of precipitate;

[0046] (4) Let the mixture stand at room temperature for 3–6 hours. A brown, oily substance insoluble in water will appear on the beaker wall. Transfer the clear liquid to other beakers and dry the oily substance on the beaker wall at 30–50°C. Collect the dried brown solid, grind it, dry it again, and store it; this is the C15 precursor.

[0047] (5) The clear liquid was refrigerated at low temperature, and a large number of yellow crystals precipitated on the cup wall. The yellow crystals were collected and dried at low temperature.

[0048] Low-temperature refrigeration is carried out at a temperature of 4–10°C for 8–12 hours; low-temperature drying is carried out at a temperature of 40–60°C for 8–12 hours.

[0049] (6) After the dried product is dissolved in water again, repeat the low-temperature refrigeration and low-temperature drying of (5) 1 to 3 times, and wash the precipitate.

[0050] (7) After washing, the resulting yellow product is ground and stored, which is the C10 precursor substance.

[0051] This invention prepares a metal-coated hierarchical porous ZSM-5 catalyst for the hydrogenation cyclization and isomerization of the aforementioned precursors.

[0052] Example 1

[0053] (1) Dissolve the calculated amount of chloroplatinic acid (1wt% Pt) in deionized water and add it to hydrothermal synthesized or commercially available H-type ZSM-5;

[0054] (2) Stir the mixture vigorously at room temperature for 6 hours and then impregnate it onto the ZSM-5 carrier;

[0055] (3) The material impregnated in step (2) was dried at 85°C and calcined at 500°C for 6 hours to obtain the supported catalyst PtO2 / ZSM-5.

[0056] (4) The calculated amount of TPAOH (25wt%):NaOH:H2O mixed solution with a mass ratio of 1:0.024:5.157 was added to the PtO2 / ZSM-5 prepared in step (3). After stirring, it was hydrothermally heated in an oven at 170℃ for 72 hours, centrifuged, dried at 85℃ for 12 hours, and calcined at 550℃ for 6 hours to obtain sodium-type metal oxide coated hierarchical porous catalyst PtO2@Na-MHS-Z5;

[0057] (5) Disperse the PtO2@Na-MHS-Z5 powder obtained in step (4) in an aqueous solution of 1 mol / L ammonium chloride, stir vigorously at 60°C to carry out ion exchange, repeat the ion exchange 3 times, dry at 85°C for 12 h, and calcine at 550°C for 6 h to obtain H-type PtO2@MHS-Z5.

[0058] (6) The PtO2@MHS-Z5 from step (5) was reduced for 4 h at 350 °C in a 5% H2 / Ar environment to obtain the reduced cyclization isomerization catalyst Pt@MHS-Z5. The active metal Pt had a mass fraction of 1% and was named catalyst A1.

[0059] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a reactor at 200–300 °C. This reaction has no specific requirements for the reactor; batch reactors, fixed-bed reactors, and flow-through reactors are all suitable. After the reaction, samples were taken, and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0060] Example 2

[0061] The operation steps are the same as in Example 1, except that in step (1), the raw material is changed to chloroplatinic acid (2wt% Pt), and subsequent steps are carried out after impregnation. A 2Pt@MHS-Z5 catalyst with a Pt mass fraction of 2% is obtained and named catalyst A2.

[0062] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0063] Example 3

[0064] The operation steps are the same as in Example 1, except that in step (1), the raw material is changed to chloroplatinic acid (3wt% Pt), and subsequent steps are carried out after impregnation. A 1Pt@MHS-Z5 catalyst with a Pt mass fraction of 3% is obtained and named catalyst A3.

[0065] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0066] Example 4

[0067] The operation steps are the same as in Example 1, except that in step (1), the raw material is changed to chloroplatinic acid (5wt% Pt), and subsequent steps are performed after impregnation. A 5Pt@MHS-Z5 catalyst with a Pt mass fraction of 5% is obtained and named catalyst A4.

[0068] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0069] Example 5

[0070] The operation steps are the same as in Example 1, except that in step (1), the raw material is changed to nickel nitrate (3wt% Ni), and subsequent steps are performed after impregnation. In step (6), the H2 reduction catalyst temperature is adjusted to 500℃ to obtain a 3Ni@MHS-Z5 catalyst with a Ni mass fraction of 3%, which is named catalyst B1.

[0071] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0072] Example 6

[0073] The operation steps are the same as in Example 1, except that in step (1), the raw materials are changed to chloroplatinic acid (1wt% Pt) and nickel nitrate (2wt% Ni), and the subsequent steps are carried out after impregnation. In step (6), the H2 reduction catalyst temperature is adjusted to 500℃ to obtain a 2Ni1Pt@MHS-Z5 catalyst with a Ni mass fraction of 2% and a Pt mass fraction of 1%, which is named catalyst B2.

[0074] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0075] Example 7

[0076] The operation steps are the same as in Example 1, except that in step (1), the raw materials are changed to chloroplatinic acid (1.5 wt% Pt) and nickel nitrate (1.5 wt% Ni), and the subsequent steps are carried out after impregnation. In step (6), the H2 reduction catalyst temperature is adjusted to 500℃ to obtain a 1.5Ni1.5Pt@MHS-Z5 catalyst with a Ni mass fraction of 1.5% and a Pt mass fraction of 1.5%, which is named catalyst B3.

[0077] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0078] Example 8

[0079] The operation steps are the same as in Example 1, except that in step (1), the raw materials are changed to chloroplatinic acid (2wt% Pt) and nickel nitrate (1wt% Ni), and the subsequent steps are carried out after impregnation. In step (6), the H2 reduction catalyst temperature is adjusted to 500℃ to obtain a 1Ni2Pt@MHS-Z5 catalyst with a Ni mass fraction of 1% and a Pt mass fraction of 2%, which is named catalyst B4.

[0080] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0081] Example 9

[0082] The operation steps are the same as in Example 1, except that in step (1), the raw materials are changed to ferric nitrate (1 wt% Fe) and chloroplatinic acid (2 wt% Pt), and the subsequent steps are carried out after impregnation. In step (6), the H2 reduction catalyst temperature is adjusted to 500℃ to obtain a 1Fe2Pt@MHS-Z5 catalyst with a Pt mass fraction of 3%, which is named catalyst C1.

[0083] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0084] Example 10

[0085] The operation steps are the same as in Example 1, except that in step (1), the raw materials are changed to ferric nitrate (2wt% Fe) and chloroplatinic acid (1wt% Pt), and the subsequent steps are carried out after impregnation. In step (6), the H2 reduction catalyst temperature is adjusted to 500℃ to obtain a 2Fe1Pt@MHS-Z5 catalyst with a Fe mass fraction of 2% and a Pt mass fraction of 2%, which is named catalyst C2.

[0086] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0087] Example 11

[0088] The operation steps are the same as in Example 1, except that in step (1), the raw materials are changed to ferric nitrate (1 wt% Fe), chloroplatinic acid (1 wt% Pt), and nickel nitrate (1 wt% Ni), and then impregnated before proceeding to the subsequent steps. In step (6), the H2 reduction catalyst temperature is adjusted to 500℃ to obtain a 1Fe1Ni1Pt@MHS-Z5 catalyst with a mass fraction of 1% Fe, 1% Ni, and 1% Pt, which is named catalyst C3.

[0089] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0090] Comparative Example 1

[0091] Pt / NbOPO4 exhibits excellent performance in hydrogenation and is used as a comparative example in this invention. Its synthesis method is as follows:

[0092] (1) Dissolve 1.32 g of diammonium hydrogen phosphate in 20 ml of water, and then adjust the pH to 2 with phosphoric acid. Under vigorous stirring, add 20 ml of 0.M niobium oxalate (pH = 2) to the above solution;

[0093] (2) Dissolve 1.0 g of hexadecyltrimethylammonium bromide (CTAB) in 15 mL of distilled water, and then add the mixed solution dropwise to the CTAB aqueous solution. The final pH value of the solution is approximately 2;

[0094] (3) Stir at 35°C for 60 minutes, then age the solution in a Teflon-lined autoclave at 160°C for 24 hours. After cooling, filter the solid, wash with distilled water, and then dry at 50°C overnight. Calcine at 500°C for 5 hours;

[0095] (4) After impregnation with Pt salt (3% wt), the product was dried at 100℃ for 12 h and calcined at 500℃ for 3 h to obtain the hydrogenation catalyst PtO2 / NbOPO4.

[0096] (5) Reduce Pt O2 / NbOPO4 in step (4) at 350℃ in a 5% H2 / Ar environment for 4h to obtain hydrogenation catalyst Pt / NbOPO4, which is named catalyst D.

[0097] C10 reactants and catalyst were added to cyclohexane at a mass ratio of 1:0.75, and H2 was introduced at 2–5 MPa. The hydrogenation cyclization-isomerization reaction was carried out in a high-pressure reactor at 200–300 °C. After the reaction, samples were taken and the components were analyzed using a Shimadzu TQ2010 gas chromatography-mass spectrometry system. The catalyst performance and selectivity for cycloalkanes and isoalkanes are shown in Table 1.

[0098] Table 1. Components of catalysts in Examples 1-11 and products after reaction in Comparative Example 1

[0099]

[0100] Examples 1-4 involve coating different amounts of Pt metal inside hierarchical ZSM-5 cells to investigate the effect of Pt metal loading on the hydrogenation of C10 precursors. Figure 1 Table 1 shows the hydrogenation results of four catalyst groups: A1, A2, A3, and A4. Catalyst A3, with a Pt loading of 3%, achieved the highest alkane yield, with complete hydrogenation of the precursor to alkanes. At lower loadings, catalysts A1 and A2 both showed low alkane yields, with incompletely converted alkanes consisting of a large amount of undeoxygenated and unhydrogenated products and a large amount of unsaturated C=C products. In deoxygenation and hydrogenation reactions, the noble metal Pt can not only provide activated hydrogen atoms for saturating unsaturated double bonds but also synergistically work with Brønsted acids to remove oxygen from the precursor. In group A1, the low Pt loading resulted in poor activity in both deoxygenation and hydrogenation reactions. With a further increased loading, all products underwent oxygen removal, but a large number of unsaturated C=C bonds remained. This indicates that while this catalyst has good activity for deoxygenation, its ability to activate hydrogen is poor, hindering effective hydrogenation. The A3 catalyst exhibited excellent deoxygenation and hydrogenation performance, achieving complete conversion of precursors and a high-value cycloalkanes yield of 30%. However, the A4 catalyst, with further increased Pt loading, did not perform as expected, showing a significant decrease in activity. This is related to the fact that at higher loadings, the metal tends to form large metal clusters during calcination, resulting in poor dispersion and a decrease in activity. Figure 2 The image shows a TEM image of the A4 catalyst after transmission electron microscopy (TEM). It reveals a large number of Pt clusters on the catalyst, exhibiting poor dispersion and failing to effectively provide metal active sites. Experimental results indicate that the A3 catalyst, with a suitable loading, can synergistically cooperate with Brønsted acid to complete the deoxygenation reaction and effectively provide activated hydrogen to promote the hydrogenation reaction, achieving a high cycloalkane yield. However, this catalyst also has significant drawbacks: the supported single-metal Pt is prone to agglomeration, and due to the high cost of Pt, the catalyst cost is high. Introducing appropriate amounts of transition metals can mitigate this problem.

[0101] Examples 5-8 are hydrogenation results obtained by introducing Ni, a transition metal, into the catalyst of Example 3 while maintaining a constant total metal loading of 3%, to gradually or completely replace Pt. In Examples 5-8, the Ni loading decreased sequentially to 3%, 2%, 1.5%, and 1%, respectively. Figure 3 This comparison shows the hydrogenation results after the introduction of Ni. In Example 5, the B1 catalyst was loaded with 3% pure Ni. Ni's activation ability for hydrogen is much weaker than that of Pt, and a concentration above 5% is usually required for a good effect; therefore, the catalytic effect of B1 was poor. In Examples 6-8, by adjusting different Ni-Pt ratios, good catalytic effects were observed. Among them, the B2 catalyst in Example 6, loaded with 1% Pt and 2% Ni, achieved the best results. The introduction of Ni not only changed the dispersion of Pt, allowing Pt to fully activate hydrogen, but also changed the B / L acid ratio in the catalyst. After the introduction of Ni, the B / L ratio in the catalyst decreased, thus the selectivity for cycloalkanes also decreased significantly, but excellent isomerization ability was still retained. Figure 4 The powder diffraction characterization of the catalysts used in Examples 5-8 shows that when only Ni is loaded, a Ni diffraction peak appears at 43.1°, and a metallic peak appears at low loading, indicating that Ni forms metal particles >4 nm. In the powder diffraction patterns of B3 and B4 catalysts with Pt loadings of 1.5% and 2%, a Pt peak appears at 39.5°, while in the test results of the B2 catalyst, neither Pt nor Ni peaks appear, indicating uniform metal dispersion, which is the reason why Example 6 shows the best results. Figure 5 These are transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) images of the B2 catalyst. The metal particles are small, primarily Ni, while Pt particles are uniformly distributed throughout the catalyst. The B2 catalyst exhibits good isomerization ability, with uniform Pt metal dispersion. However, due to its relatively high B / L acid ratio, excessive carbon chain breakage occurs, resulting in 9.5% of non-C8-C16 alkanes (excluding those from aviation kerosene). Further introduction of other metals to alter the B / L acid ratio will be investigated to observe the catalytic activity of different metals.

[0102] In Examples 9-11, different amounts of Fe were introduced into the catalysts. With a total metal loading of 3%, the active metal components of the C1, C2, and C3 catalysts were 1%Fe + 2%Pt, 2%Fe + 1%Pt, and 1%Fe + 1%Ni + 1%Pt, respectively. Figure 6 This is a comparison of the hydrogenation results in Examples 9-11. When only Fe and Pt are loaded, the catalytic effect is poor, with alkane yields of 14% and 32%, respectively. The undeoxygenated hydrogenated components in the product composition are mainly undeoxygenated unsaturated products and undeoxygenated products, respectively. Figure 7The XRD characterization of catalysts C1, C2, and C3 is shown. With a loading of 1% Fe and 2% Pt, no Fe peak appeared in the XRD, but a large bulge appeared around 39.5 nm, corresponding to a Pt peak. The flattened peak indicates that Pt agglomerates into small particles, likely forming alloy agglomerates with Fe. Poor dispersibility resulted in a high amount of undeoxygenated and unhydrogenated products in Example 9. Fe's ability to activate hydrogen is poor; compared to 2% Ni and 1% Pt in Example 6, the activity of 2% Fe and 1% Pt for hydrogenation was significantly reduced. Catalyst C3 retained the high activity of catalyst B2 and further reduced the B / L ratio, thus producing fewer non-jet fuel components C8-C16. Figure 8 These are transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) scans of the C3 catalyst. After replacing 1% Ni with 1% Fe, the three metals showed good dispersion and were uniformly distributed within the catalyst.

[0103] Table 2 shows the infrared test results of catalysts pyridine in Examples 3, 6, 11 and Comparative Example 1.

[0104]

[0105] Comparative Example 1 is a catalyst with excellent performance currently under development. Hydrogenation was performed under the same conditions, and its performance was compared with that of catalysts A3, B2, and C3, which also showed good results in this invention. Table 2 shows the pyridine infrared and BET test results for A3, B2, C3, and D. After introducing other metals, the B / L acid ratio decreased significantly. Compared with catalyst D, the catalyst developed in this invention has a much larger specific surface area, which is beneficial for mass transfer during the reaction. Catalysts A3, B2, and C3 encapsulate the metal within ZSM-5, providing stronger metal confinement compared to catalyst D, thus ensuring a longer catalyst lifespan. Figure 9 The hydrogenation products of Examples 3, 6, and 11 are compared with those of Comparative Example 1. Figure 9 The distribution of components in the products after catalysis by three example catalysts (A3, B2, and C3) and the comparative catalyst D was compared. Compared with the hydrogenation results of Pt / NbOPO4, which has excellent hydrogenation capabilities, the three metal-coated hollow hierarchical porous ZSM-5 catalysts prepared in this invention exhibit good cyclization and isomerization capabilities. After the reaction, the selectivity for isomeric cyclized hydrocarbons was 56%–67%, significantly higher than the 30.6% total selectivity for isoalkanes and cycloalkanes in the Pt / NbOPO4 hydrogenation results. High selectivity in the preparation of isomeric alkanes and cyclized hydrocarbons was achieved at a relatively low temperature.

[0106] As can be seen from the data in Table 1, the metal-coated hierarchical ZSM-5 catalyst prepared according to the present invention, with hollow hierarchical ZSM-5 as the support and 1 to 3 active metal components of Fe, Ni, and Pt, for the cyclization and isomerization of long-chain alkanes in aviation kerosene, has high isomerization activity and cyclization ability, good catalytic stability, and low reaction temperature, and can maintain the cyclization and isomerization activity of long-chain alkanes in aviation kerosene at a low temperature.

[0107] Example 12

[0108] (1) Dissolve the calculated amounts of chloroplatinic acid (5wt% Pt), nickel nitrate (5wt% Ni) and ferric nitrate (5wt% Fe) in deionized water and add them to commercially available H-type ZSM-5;

[0109] (2) Stir the mixture vigorously at room temperature for 10 hours and then impregnate it onto the ZSM-5 carrier;

[0110] (3) The material impregnated in step (2) was dried at 80°C and calcined at 550°C for 6 hours to obtain the supported catalyst PtO2NiOFe2O3 / ZSM-5.

[0111] The impregnated metal salts are decomposed by calcination. Under common atmospheric conditions, nickel salts decompose at 170-300℃, iron salts at 150-350℃, and platinum salts at 200-400℃.

[0112] (4) The calculated amount of TPAOH (25wt%):NaOH mixed solution with a molar ratio of 1:1 was added to the PtO2NiOFe2O3 / ZSM-5 prepared in step (3). After stirring, it was hydrothermally heated in an oven at 200℃ for 48 hours, centrifuged, dried at 120℃ for 12 hours, and calcined at 500℃ for 8 hours. The heating rate was 4℃ / min to obtain the sodium-type metal oxide coated hierarchical porous catalyst PtO2NiOFe2O3@Na-MHS-Z5.

[0113] Calcination is primarily for the decomposition of tetrapropylammonium hydroxide, which mainly occurs within the temperature range of 250-350℃. Typically, the calcination temperature is 500-600℃, but sometimes it can be increased to 550-650℃ depending on the specific type of molecular sieve. Within this temperature range, not only is the template agent completely decomposed and burned off, but the molecular sieve framework is also stabilized.

[0114] (5) The PtO2NiOFe2O3@Na-MHS-Z5 powder obtained in step (4) was dispersed in a 0.5 mol / L ammonium chloride aqueous solution, and ion exchange was carried out by vigorous stirring at 60°C for 4 h, and repeated twice; after drying at 60°C for 12 h, and calcining at 600°C for 4 h, H-type PtO2NiOFe2O3@MHS-Z5 was obtained;

[0115] (6) The PtO2NiOFe2O3@MHS-Z5 from step (5) was reduced at 500℃ in a 5% H2 / Ar environment to obtain the reduced cyclization isomerization catalyst PtNiFe@MHS-Z5. The mass fractions of the active metals Pt, Ni, and Fe were all 5%.

[0116] Example 13

[0117] (1) Dissolve the calculated amounts of chloroplatinic acid (3wt% Pt), nickel nitrate (3wt% Ni) and ferric nitrate (3wt% Fe) in deionized water and add them to commercially available H-type ZSM-5;

[0118] (2) Stir the mixture vigorously at room temperature for 3 hours and then impregnate it onto the ZSM-5 carrier;

[0119] (3) The material impregnated in step (2) was dried at 120°C and calcined at 400°C for 6 hours to obtain the supported catalyst PtO2NiOFe2O3 / ZSM-5.

[0120] (4) The calculated amount of TPAOH (25wt%):NaOH mixed solution with a molar ratio of 1:12 was added to the PtO2NiOFe2O3 / ZSM-5 prepared in step (3). After stirring, it was hydrothermally heated in an oven at 110℃ for 96 hours, centrifuged, dried at 60℃ for 24 hours, and calcined at 700℃ for 4 hours. The heating rate was 10℃ / min to obtain the sodium-type metal oxide coated hierarchical porous catalyst PtO2NiOFe2O3@Na-MHS-Z5.

[0121] (5) The PtO2NiOFe2O3@Na-MHS-Z5 powder obtained in step (4) was dispersed in a 2 mol / L ammonium chloride aqueous solution, and ion exchange was carried out by vigorous stirring at 60°C for 2 h, and repeated 3 times; after drying at 100°C for 12 h, and calcining at 300°C for 7 h, H-type PtO2NiOFe2O3@MHS-Z5 was obtained;

[0122] (6) The PtO2NiOFe2O3@MHS-Z5 from step (5) was reduced at 500℃ in a 5% H2 / Ar environment to obtain the reduced cyclization isomerization catalyst PtNiFe@MHS-Z5. The mass fractions of the active metals Pt, Ni, and Fe were all 3%.

[0123] In Example 13, the large metal loading resulted in large metal particles. Although this significantly reduced the utilization rate of the active metal sites, the abundance of active metal components still provided some deoxygenation and hydrogenation capacity. More than 30% of the product failed to fully saturate the C=C and C=O bonds, which is related to the decreased utilization rate of the metal sites. In Example 12, the highest metal loading was achieved in the hierarchical ZSM-5 encapsulation, with each of the Pt, Fe, and Ni active metal components at 5%, resulting in a total metal loading of 15%. The formed metal particles were the largest, with some large metal blocks detaching from the support. These excessively large metal blocks reduced the efficiency of metal-activated hydrogen. Furthermore, the high metal loading significantly increased the amount of Li acid in the catalyst while significantly decreasing the amount of Beta acid, resulting in a low B / L acid ratio that failed to achieve deoxygenation. The obtained product not only contained a large amount of unsaturated double bonds but also a significant amount of oxygen-containing substances, with an overall alkane yield of less than 10%. This demonstrates that a suitable metal ratio has a significant impact on the activity, selectivity, and structure of the catalyst.

[0124] The present invention has been described above by way of specific embodiments. Those skilled in the art should understand that the present disclosure is not limited to the embodiments described above, and various changes, modifications and substitutions can be made without departing from the scope of the present invention.

Claims

1. A metal-coated hierarchical porous ZSM-5 catalyst for the hydrogenation cyclization isomerization of aviation kerosene carbon chain precursors, characterized in that, The material consists of a hierarchical porous hollow ZSM-5 support and metallic components Fe, Ni, and Pt, with the metals encapsulated within the ZSM-5 support. The metal components are present in 1 wt% Ni, 1 wt% Fe, and 1 wt% Pt. The specific surface area of ​​the hierarchical porous hollow ZSM-5 support is 402.2 μm. 2 / g, pore volume is 0.21~0.43 ml / g, and B acidity is 30mmol / g.

2. A method for preparing a metal-coated hierarchical porous ZSM-5 catalyst for the hydrogenation cyclization isomerization of aviation kerosene carbon chain precursors, used to generate the catalyst of claim 1, characterized in that, It includes the following steps: Step 1: Dissolve iron salt, platinum salt and nickel salt in deionized water in a certain proportion to obtain mixed solution A; Step 2: Add mixed solution A to type H ZSM-5, add a magnetic stir bar, and stir vigorously on a magnetic stirrer until the compound is fully impregnated into the ZSM-5 support; The soaking time is 3 to 10 hours; Step 3: Dry and calcine the impregnated material to obtain supported metal oxide / ZSM-5; Step 4: Add tetrapropylammonium hydroxide and sodium hydroxide solution to the supported metal oxide / ZSM-5, and after stirring, hydrothermal treatment, centrifugation, drying and calcination, obtain sodium-type metal oxide coated hierarchical porous catalyst metal oxide@MHS-Z5; The mass fraction of tetrapropylammonium hydroxide is 25 wt%, and the molar ratio of tetrapropylammonium hydroxide to sodium hydroxide is 1~12:1; Step 5: Disperse the metal oxide @MHS-Z5 powder in an aqueous solution of ammonium chloride, stir to carry out ion exchange, and after drying and calcination, obtain H-type metal oxide @MHS-Z5; Add one gram of metal oxide @MHS-Z5 powder to 30~60 ml of ammonium chloride solution; Step 6: Reduce the H-type metal oxide @MHS-Z5 in an H2 / Ar environment at 300℃~500℃ to obtain the reduced metal @MHS-Z5.

3. The preparation method according to claim 2, characterized in that, The nickel salt is one or a combination of two or more of nickel nitrate, nickel acetate, and nickel chloride; the iron salt is one or a combination of two or more of ferric nitrate, ferric chloride, ferric nitrate, ferric oxalate, and ferric acetate; and the platinum salt is one or a combination of two or more of platinum chloride, chloroplatinic acid, and platinum nitrate.

4. The preparation method according to claim 2, characterized in that, The soaking time is 5 to 8 hours.

5. The preparation method according to claim 2, characterized in that, The calcination temperature in step three is 400~550℃, and the calcination time is 6h, so that the metal salts in the impregnated material decompose.

6. The preparation method according to claim 2, characterized in that, The hydrothermal reaction in step four is carried out at a temperature of 110-200℃ for 48-96 hours; the filter cake drying temperature is 60-120℃; the calcination temperature is 500-700℃, the heating rate is 4-10℃ / min, and the calcination time is 4-8 hours, in order to decompose tetrapropylammonium hydroxide and stabilize the molecular sieve framework.

7. The preparation method according to claim 2, characterized in that, The ion exchange in step five is repeated 2 to 3 times; the drying temperature is 60 to 100°C, the calcination temperature is 300 to 600°C, and the calcination time is 4 to 7 hours.

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