Method for preparing high-density aviation fuel by one-pot degradation of waste PC plastic

Abstract

The application discloses a method for preparing high-density aviation fuel by one-pot degradation of waste PC plastic, which comprises the following steps: taking waste PC plastic as raw material, and adding a double-function synergistic catalyst in a high-pressure reaction kettle; under the joint action of a metal-supported catalyst and a solid superacid additive, the reaction steps of ester bond breaking, intermediate hydrogenation, aromatic ring saturation and hydrogenation deoxidization are continuously completed by one-pot method in the high-pressure reaction kettle, and high-density aviation fuel is prepared with high selectivity. The method avoids the complicated intermediate separation step in the traditional multi-step conversion process, the aviation fuel obtained is mainly propane-2,2-diyl dicyclohexane (C15), the selectivity of which is greater than or equal to 95%, the yield is as high as 95%, the density of the aviation fuel obtained is greater than 0.90 g / mL, the combustion heat is greater than 40 MJ / kg, the freezing point is lower than-35 DEG C, and the aviation fuel has excellent combustion performance and low-temperature performance. The application provides a green and efficient solution for the high-value upgrading and recycling of waste PC plastic, and meets the development strategy of circular economy.

Description

Technical Field

[0001] This invention belongs to the field of plastic recycling and energy chemical technology, specifically relating to a method for one-pot degradation of waste PC plastic to prepare high-density aviation fuel. Background Technology

[0002] Polycarbonate (PC) plastics, especially bisphenol A polycarbonate, are widely used in electronics, automotive manufacturing, medical devices, and building materials due to their excellent heat resistance, corrosion resistance, insulation, and impact resistance, making it one of the five major engineering plastics. However, with the increasing consumption of PC plastics year by year, the problem of waste disposal has become increasingly prominent. Traditional disposal methods such as incineration and landfill not only waste resources but also cause serious environmental pollution. PC plastics have a stable chemical structure and are not easily biodegradable. Therefore, developing efficient and green chemical recycling technologies for waste PC plastics to convert them into high-value-added chemicals, especially aviation fuel with broad market demand, has become a research hotspot in the field of circular economy.

[0003] PC plastic's molecular structure is rich in bisphenol A units and carbonate bonds. Theoretically, by breaking the ester bonds in its molecules and hydrogenating and deoxygenating the resulting aromatic ring structure, PC plastic can be converted into bicycloalkanes. These compounds have high density and high volumetric calorific value, making them ideal components for high-performance aviation fuels. Traditional waste plastic pyrolysis for oil production technology, while feasible to some extent, generally suffers from high reaction temperatures (>400℃), high energy consumption, complex product composition (hydrocarbon mixtures with poor selectivity), and numerous gaseous and coke byproducts, leading to difficulties in subsequent separation and poor economic efficiency.

[0004] In recent years, catalytic hydrogenolysis / hydrodeoxygenation strategies have attracted attention. Some studies have attempted to convert PC plastics into fuels through a two-step method: first, PC plastics are depolymerized to obtain bisphenol A monomers through hydrolysis or alcoholysis, and then bisphenol A is subjected to catalytic hydrodeoxygenation. However, this multi-step route is complex, the intermediate separation and purification costs are high, and it requires the use of large amounts of acid and base catalysts, which is environmentally unfriendly.

[0005] Currently, there is no mature one-pot co-catalytic system in existing technologies that can directly and efficiently convert waste PC plastic into high-purity C15 bicycloalkane aviation fuel under mild conditions. This process suffers from technical bottlenecks such as high complexity, demanding reaction conditions, poor selectivity of the target product, and insufficient product performance. Therefore, developing a mild, efficient, low-cost, and highly selective one-pot degradation process for waste PC plastic to prepare high-density aviation fuel has significant academic value and industrialization prospects. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing waste PC plastic fuel conversion technologies, such as high energy consumption, cumbersome processes, low product selectivity, numerous byproducts, and difficulty in industrialization. This invention provides a one-pot degradation method for waste PC plastic to prepare high-density aviation fuel. By constructing a dual synergistic catalytic system of metal hydrogenation catalysis and solid superacid, this invention achieves multi-stage reaction coupling of PC plastic depolymerization, hydrogenation, and deoxygenation. The entire process requires no intermediate separation, is simple, operates under mild conditions, and exhibits extremely high selectivity for the target product. The resulting aviation fuel has performance far exceeding that of traditional petroleum-based fuels, making it suitable for high-end aerospace applications.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0008] A one-pot degradation method for producing high-density aviation fuel from waste PC plastic involves placing waste PC plastic, a specific metal-supported catalyst, and a specific solid superacid additive in a high-pressure reactor under a hydrogen atmosphere and carrying out a one-pot reaction under suitable solvent and reaction conditions. In this process, the waste PC plastic requires no pretreatment and directly undergoes ester bond cleavage and aromatic ring hydrogenation and deoxygenation reactions under the synergistic effect of the two catalysts, transforming it in one step into high-density aviation fuel whose main component is propane-2,2-dimethyldicyclohexane (C15H28).

[0009] The "one-pot method" described in this invention refers to the continuous completion of all chemical reaction steps from the addition of raw materials to the generation of the target product in the same reaction vessel, without any product separation or catalyst transfer operations in between.

[0010] Specifically, the method of the present invention includes the following steps:

[0011] Waste PC plastic, reaction solvent, metal-supported catalyst, and solid superacid additive are added to a reactor. Hydrogen gas is introduced to displace the air inside the reactor, maintaining a hydrogen pressure of 1-5 MPa. The temperature is raised to 160-220°C, and the reaction is stirred for 6-12 hours. After the reaction is complete, it is cooled to room temperature and the pressure is released. The reaction mixture is filtered to remove the solid catalyst, and the filtrate is distilled or subjected to vacuum distillation to remove the solvent, thus obtaining the high-density aviation fuel product.

[0012] The key to this invention lies in the selection and synergistic effect of the catalytic system, which consists of a metal-supported catalyst and a solid superacid additive.

[0013] Metal-supported catalysts, denoted as X / Y, catalyze the hydrogenation saturation of aromatic rings and the hydrogenation deoxygenation of intermediates. The active component X is a noble or non-noble metal with excellent hydrogenation activity, selected from one or a mixture of at least two of Pd, Ni, and Pt, preferably Pd or Pt. The support Y is used to support and disperse the active component and provide suitable pore structure and surface properties, selected from one or a mixture of at least two of γ-Al₂O₃, Nb₂O₅, C, SiO₂, and MgO. Experiments have shown that the catalyst with Pd supported on γ-Al₂O₃ (Pd / γ-Al₂O₃) exhibits optimal hydrogenation activity and selectivity.

[0014] The preparation method of the metal-supported catalyst X / Y adopts the equal-volume impregnation method, specifically including:

[0015] (1) Carrier pretreatment: Carrier Y is calcined in a muffle furnace at 80-550℃ for 2-4 hours to remove moisture and impurities and to regulate the number of hydroxyl groups on its surface.

[0016] (2) Equal-volume impregnation: Prepare a soluble salt solution of active component X (such as palladium nitrate, chloroplatinic acid, nickel nitrate, etc.). Based on the saturated water absorption capacity of carrier Y determined in previous experiments, add the pretreated carrier Y to the calculated amount of soluble salt solution, ensuring that the solution is just completely absorbed by the carrier. Impregnate at a mass ratio of active component X to carrier Y of (0.01-0.1):1, preferably 0.05:1. Stir at 60°C for 4-8 hours to ensure uniform loading of the active component precursor.

[0017] (3) Drying and calcination: After impregnation, the sample is dried overnight at 80-160℃ to remove the solvent; then calcined at 200-500℃ in air for 2-8 hours to decompose the active component precursor into metal oxide.

[0018] (4) Reduction Activation: The calcined catalyst must be reduced before use to convert the metal oxide into a zero-valent metal element with catalytic activity. The reduction treatment is carried out in a tube furnace under the following conditions: hydrogen pressure 0.1-2.0 MPa (preferably atmospheric pressure), hydrogen space velocity 100-5000 h⁻¹, reduction temperature 200-550℃ (preferably 300-400℃), and reduction time 3-8 hours. After the reduction is completed, as the hydrogen atmosphere cools to room temperature, a low concentration of oxygen (such as 1% O2 / N2) can be introduced for passivation treatment to prevent the active metal from spontaneously combusting in air.

[0019] Solid superacid additive, selected from phosphomolybdic acid (H3[P(Mo3O4]2) 10 )4]), phosphotungstic acid (H3PW) 12 O 40 ), silicotungstic acid (H4SiW) 12 O40 It is a mixture of one or at least two of the following, preferably phosphomolybdic acid. This type of heteropolyacid possesses extremely strong acidity, enabling it to efficiently catalyze the breaking of carbonate bonds in PC plastic molecules, generating bisphenol A intermediates. Simultaneously, its unique acidity and redox properties may participate in the deoxygenation process, forming a synergistic effect with metal catalysts.

[0020] Catalyst dosage and ratio: To ensure efficient reaction, the synergistic effect of the metal-supported catalyst and the solid superacid additive is crucial. The mass ratio of the two affects the reaction pathway and product distribution. When the proportion of the metal-supported catalyst is too high, excessive hydrogenation activity may lead to over-cracking or over-cyclization; when the proportion of the solid superacid is too high, it may lead to side reactions such as polymerization and coking. Preferably, the mass ratio of the metal-supported catalyst to the solid superacid additive is (0.5-2):1, and most preferably 2:1 (e.g., Pd / γ-Al2O3:phosphomolybdic acid = 2:1). The total amount of both is 10-50 wt% of the mass of the waste PC plastic, preferably 30-45 wt%.

[0021] Reaction temperature: If the temperature is too low (<160℃), the PC plastic will not degrade completely; if the temperature is too high (>220℃), the side reactions will be aggravated, leading to the cracking or coking of C15 products. The optimal reaction temperature is 190-210℃.

[0022] Hydrogen pressure: Hydrogen is the hydrogen source for the hydrodeoxygenation reaction and is also key to inhibiting carbon deposit formation. If the pressure is too low, hydrogenation will be unsaturated, easily forming oxygen-containing compounds or aromatic intermediates; if the pressure is too high, it places high demands on equipment and increases costs. The optimal hydrogen pressure is 2-4 MPa.

[0023] Reaction time: If the time is too short, the reaction will be incomplete; if the time is too long, the product yield will stabilize or decrease slightly. The optimal reaction time is 6-10 hours.

[0024] Reaction solvent: The reaction is carried out in an organic solvent to provide a good mass and heat transfer environment. Preferably, it is an inert solvent with good solubility for hydrogen and reactants, such as cyclohexane, n-hexane, or decahydronaphthalene. Cyclohexane is most preferred, and its amount is 20-100 times the mass of the waste PC plastic.

[0025] The beneficial effects of this invention are:

[0026] (1) The present invention provides a one-pot process that integrates complex steps such as ester bond breaking, aromatic ring hydrogenation and deoxygenation of waste PC plastic into the same reactor for continuous completion. No intermediates need to be separated, which greatly simplifies the process flow, significantly reduces production costs and equipment investment, and is easy to scale up industrially.

[0027] (2) It achieves synergistic enhancement of dual-function catalysis by innovatively using a metal-supported catalyst and a solid superacid composite system, which work together to achieve precise conversion from polymer to target fuel molecules. Under optimal conditions, the yield of the C15 target product is as high as 95%, with almost single selectivity, far exceeding existing technologies.

[0028] (3) The product has excellent performance. The resulting aviation fuel is mainly propane-2,2-dimethyldicyclohexane with a density >0.93 g / mL, a volumetric heat of combustion >40 MJ / L, and a freezing point below -35℃. Its comprehensive performance is better than that of traditional petroleum-based aviation fuel and it can be used as a high-energy additive or special fuel. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below through specific embodiments. The described embodiments are merely some embodiments of the present invention, intended to explain the present invention, and not to limit the scope of the present 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.

[0030] I. Catalyst Preparation Examples

[0031] Example 1: Preparation of 5% Pd / γ-Al2O3 catalyst

[0032] 5.0 g of γ-Al₂O₃ support was pretreated in a muffle furnace at 550 °C for 3 hours to obtain a pretreated support. 0.66 g of Pd(NO₃)₂·2H₂O (equivalent to 0.25 g Pd) was weighed and dissolved in an appropriate amount of deionized water to prepare a solution with a volume of exactly 5.0 mL (the saturated water absorption of 5.0 g γ-Al₂O₃ was determined to be 5.0 mL in previous experiments). The pretreated γ-Al₂O₃ support was slowly added to the palladium nitrate solution while stirring to ensure uniform impregnation. The solution was stirred and impregnated in a 60 °C water bath for 6 hours. Afterward, it was transferred to an oven and dried overnight at 120 °C. The dried solid was transferred to a muffle furnace and calcined at 400 °C for 4 hours at a rate of 5 °C / min. The calcined catalyst was then reduced and activated in a tube furnace under atmospheric pressure (0.1 MPa) with a hydrogen gas flow (space velocity 500 h⁻¹). -1 In the process, the temperature was increased to 300℃ at 5℃ / min and reduced at a constant temperature for 4 hours. After reduction, the mixture was cooled to room temperature in a hydrogen stream, and then passivated with a 1% O2 / N2 mixed gas for 2 hours to obtain a 5% Pd / γ-Al2O3 catalyst (Pd loading of 5 wt%).

[0033] Example 2: Preparation of 5% Pt / γ-Al2O3 catalyst

[0034] The Pd(NO3)2·2H2O in Example 1 was replaced with 0.41 g H2PtCl6·6H2O (equivalent to 0.25 g Pt), and the rest of the operation was the same as in Example 1, to obtain a 5% Pt / γ-Al2O3 catalyst.

[0035] Example 3: Preparation of 5% Ni / γ-Al2O3 catalyst

[0036] The Pd(NO3)2·2H2O in Example 1 was replaced with 1.24 g Ni(NO3)2·6H2O (equivalent to 0.25 g Ni), and the rest of the operation was the same as in Example 1, to obtain a 5% Ni / γ-Al2O3 catalyst.

[0037] Example 4: Preparation of Pd / Nb2O5 catalyst

[0038] The γ-Al2O3 support in Example 1 was replaced with an equal mass of Nb2O5, and the remaining operations were the same as in Example 1, to obtain a 5% Pd / Nb2O5 catalyst.

[0039] Example 5: Preparation of Pd / SiO2 catalyst

[0040] The γ-Al2O3 support in Example 1 was replaced with an equal mass of SiO2, and the remaining operations were the same as in Example 1, to obtain a 5% Pd / SiO2 catalyst.

[0041] Example 6: Preparation of Pd / C catalyst

[0042] The γ-Al2O3 support in Example 1 was replaced with an equal mass of activated carbon (C). Note that the activated carbon did not require high-temperature pretreatment in a muffle furnace (it was dried in a 120°C oven for 4 hours instead). The remaining impregnation, drying, calcination (carbonization treatment at 400°C under an inert atmosphere) and reduction operations were the same as in Example 1, resulting in a 5% Pd / C catalyst.

[0043] Example 7: Preparation of Pd / MgO catalyst

[0044] The γ-Al2O3 support in Example 1 was replaced with an equal mass of MgO hydrotalcite-derived composite oxide, and the remaining operations were the same as in Example 1, to obtain a 5% Pd / MgO catalyst.

[0045] II. Examples of Degrading Waste PC Plastics to Prepare Aviation Fuel

[0046] Example 8 (Comparative): Pd / γ-Al2O3 catalyst alone

[0047] In a 50 mL high-pressure reactor, 0.1 g of waste PC plastic (derived from discarded CDs, pulverized to a particle size <1 mm), 5 mL of cyclohexane, and 0.03 g of the Pd / γ-Al₂O₃ catalyst prepared in Example 1 were added sequentially. The reactor was sealed, purged three times with hydrogen, and then purged with hydrogen to an initial pressure of 3.5 MPa. The temperature was raised to 200 °C, and the reaction was stirred for 6 hours. After the reaction was completed, the reactor was allowed to cool naturally to room temperature and the pressure was released. The catalyst was removed by filtration, and the filtrate was subjected to qualitative and quantitative analysis by GC (gas chromatography). The results showed that the yield of C15 (propane-2,2-dimethyldicyclohexane) was 80%, with a small amount of C8 / C9 cycloalkanes (approximately 9%).

[0048] Example 9: Pt / γ-Al2O3 catalyst alone

[0049] The Pd / γ-Al₂O₃ catalyst in Example 8 was replaced with an equal mass of the Pt / γ-Al₂O₃ catalyst prepared in Example 2, with all other conditions remaining unchanged. GC analysis showed that the C15 yield was only 11%, and the C8 / C9 cycloalkane yield was 12%. This indicates that the Pt-based catalyst exhibits significantly lower activity for PC plastic degradation under these conditions compared to the Pd-based catalyst.

[0050] Example 10: Ni / γ-Al2O3 catalyst alone

[0051] The Pd / γ-Al₂O₃ catalyst in Example 8 was replaced with an equal mass of the Ni / γ-Al₂O₃ catalyst prepared in Example 3, with all other conditions remaining unchanged. GC analysis showed that almost no target product was formed, and the yields of C15 and C8 / C9 were both 0. This indicates that the hydrogenation activity of non-noble metal Ni is insufficient under these mild conditions.

[0052] Example 11: Pd / Nb2O5 catalyst alone

[0053] The Pd / γ-Al₂O₃ catalyst in Example 8 was replaced with an equal mass of the Pd / Nb₂O₅ catalyst prepared in Example 4, with all other conditions remaining unchanged. GC analysis showed that no target product was formed. This indicates that the support properties have a decisive influence on the performance of the Pd catalyst, and the Nb₂O₅ support may fail to proceed due to excessive acidity or insufficient exposure of hydrogenation active sites.

[0054] Example 12 (Comparative): Pd / SiO2 catalyst alone

[0055] The Pd / γ-Al₂O₃ catalyst in Example 8 was replaced with an equal mass of the Pd / SiO₂ catalyst prepared in Example 5, with all other conditions remaining unchanged. GC analysis showed that no target product was formed.

[0056] Example 13 (Comparative): Pd / C catalyst alone

[0057] The Pd / γ-Al₂O₃ catalyst in Example 8 was replaced with an equal mass of the Pd / C catalyst prepared in Example 6, with all other conditions remaining unchanged. GC analysis showed that the C15 yield was 8%, and the C8 / C9 yield was 21%. This indicates that although Pd / C has certain hydrogenation activity, the increased proportion of low-carbon cycloalkanes in the products may be due to cracking side reactions caused by the microporous structure of the activated carbon support.

[0058] Example 14 (Comparative): Pd / MgO catalyst alone

[0059] The Pd / γ-Al₂O₃ catalyst in Example 8 was replaced with an equal mass of the Pd / MgO catalyst prepared in Example 7, with all other conditions remaining unchanged. GC analysis showed that no target product was formed.

[0060] Example 15: Pd / γ-Al2O3 + phosphomolybdic acid (1:1 mass ratio)

[0061] In a 50 mL high-pressure reactor, 0.1 g of waste PC plastic, 5 mL of cyclohexane, 0.03 g of the Pd / γ-Al2O3 catalyst prepared in Example 1, and 0.03 g of phosphomolybdic acid (H3[P(Mo3O4]2)) were added sequentially. 10 )4). The remaining conditions were the same as in Example 8. GC analysis showed that the C15 yield increased significantly to 92%, and the C8 / C9 yield was 7%. This indicates that the addition of the solid superacid phosphomolybdic acid formed a highly efficient synergistic catalytic effect with Pd / γ-Al2O3, significantly improving the yield of the target product.

[0062] Example 16: Pd / γ-Al2O3 + phosphotungstic acid (1:1 mass ratio)

[0063] In Example 15, phosphomolybdic acid was replaced with an equal mass of phosphotungstic acid (H3PW). 12 O 40 With all other conditions unchanged, GC results showed that the C15 yield was 12% and the C8 / C9 yield was 28%. This indicates that the synergistic effect of phosphotungstic acid was far worse than that of phosphomolybdic acid, leading to more product cracking.

[0064] Example 17: Pd / γ-Al2O3 + silicotungstic acid (1:1 mass ratio)

[0065] In Example 15, phosphomolybdic acid was replaced with an equal mass of silicotungstic acid (H4SiW). 12 O 40 With all other conditions unchanged, GC results showed that the yield of C15 was 11%, and the yield of C8 / C9 was 21%. This indicates that the synergistic effect of silicotungstic acid is not as good as that of phosphomolybdic acid.

[0066] Example 18: Pd / γ-Al2O3 + phosphomolybdic acid (1:1 mass ratio), total catalyst amount insufficient.

[0067] The amounts of Pd / γ-Al₂O₃ and phosphomolybdic acid in Example 15 were each reduced to 0.01 g (total catalyst 0.02 g), while other conditions remained unchanged. GC results showed that no target product was formed. This indicates that the total amount of catalyst needs to reach a certain threshold to effectively initiate and maintain the reaction.

[0068] Example 19: Pd / γ-Al2O3 + phosphomolybdic acid (1:2 mass ratio)

[0069] In a 50 mL high-pressure reactor, 0.01 g of Pd / γ-Al₂O₃ and 0.02 g of phosphomolybdic acid (mass ratio 1:2) were added, with the remaining conditions the same as in Example 8. GC results showed that the C15 yield was 69%, and the C8 / C9 yield was 6%. This indicates that increasing the proportion of solid superacid is beneficial for ester bond breaking, but excessive acid content may lead to side reactions of some hydrogenation intermediates, resulting in a decrease in the C15 yield compared to 1:1 (92%).

[0070] Example 20: Pd / γ-Al2O3 + phosphomolybdic acid (1:3 mass ratio)

[0071] In a 50 mL high-pressure reactor, 0.01 g of Pd / γ-Al₂O₃ and 0.03 g of phosphomolybdic acid (mass ratio 1:3) were added, with the remaining conditions the same as in Example 8. GC results showed that the C15 yield decreased to 22%, and the C8 / C9 yield was 0. This indicates a severe excess of solid acid, triggering excessive acid-catalyzed side reactions (such as isomerization, cracking, and coking), resulting in a significant decrease in C15 selectivity.

[0072] Example 21: Pd / γ-Al2O3 + phosphomolybdic acid (1:1 mass ratio), total catalyst 0.03g

[0073] In a 50 mL high-pressure reactor, 0.015 g of Pd / γ-Al₂O₃ and 0.015 g of phosphomolybdic acid (total weight 0.03 g, mass ratio 1:1) were added, with other conditions the same as in Example 8. GC results showed that the yield of C15 was 80%, and the yield of C8 / C9 was 7%. Compared with Example 15 (total weight 0.06 g), this indicates that, under the same ratio, increasing the total amount of catalyst is beneficial to improving the yield.

[0074] Example 22: Pd / γ-Al2O3 + phosphomolybdic acid (2:1 mass ratio)

[0075] In a 50 mL high-pressure reactor, 0.02 g of Pd / γ-Al₂O₃ and 0.01 g of phosphomolybdic acid (mass ratio 2:1) were added, with the remaining conditions the same as in Example 8. GC results showed that the C15 yield reached the highest level of 95%, and no byproducts such as C8 / C9 were detected, indicating extremely high selectivity for the target product.

[0076] Example 23: Pd / γ-Al2O3 + phosphomolybdic acid (5:1 mass ratio)

[0077] In a 50 mL high-pressure reactor, 0.025 g of Pd / γ-Al₂O₃ and 0.005 g of phosphomolybdic acid (mass ratio 5:1) were added, with other conditions the same as in Example 8. GC results showed a C15 yield of 93%, and no C8 / C9 byproducts were detected. Although the yield remained high, the increased amount of the noble metal Pd in ​​the catalyst made it less cost-effective than in Example 22.

[0078] The degradation results of the waste PC plastics in Examples 8-23 above are summarized in the table below:

[0079] 8 [Pd / γ-Al2O3] - 0.03 / 0 200 6 80 9 9 Pt / gamma-Al203 - 0.03 / 0 200 6 11 12 10 <![CDATA[Ni / γ-Al2O3]]> - 0.03 / 0 200 6 0 0 11 <![CDATA[Pd / Nb2O5]]> - 0.03 / 0 200 6 0 0 12 <![CDATA[Pd / SiO2]]> - 0.03 / 0 200 6 0 0 13 Pd / C - 0.03 / 0 200 6 8 21 14 Pd / MgO - 0.03 / 0 200 6 0 0 15 <![CDATA[Pd / γ-Al2O3+H3[P(Mo3O 10 )4]]]> 1:1 0.03+0.03 200 6 92 7 16 <![CDATA[Pd / γ-Al2O3+H3PW 12 THE 40 ]]> 1:1 0.03+0.03 200 6 12 28 17 <![CDATA[Pd / γ-Al2O3+H4SiW 12 THE 40 ]]> 1:1 0.03+0.03 200 6 11 21 18 <![CDATA[Pd / γ-Al2O3+H3[P(Mo3O 10 )4]]]> 1:1 0.01+0.01 200 6 0 0 19 <![CDATA[Pd / γ-Al2O3+H3[P(Mo3O 10 )4]]]> 1:2 0.01+0.02 200 6 69 6 20 <![CDATA[Pd / γ-Al2O3+H3[P(Mo3O 10 )4]]]> 1:3 0.01+0.03 200 6 22 0 21 <![CDATA[Pd / γ-Al2O3+H3[P(Mo3O 10 )4]]]> 1:1 0.015+0.015 200 6 80 7 22 <![CDATA[Pd / γ-Al2O3+H3[P(Mo3O 10 )4]]]> 2:1 0.02+0.01 200 6 95 0 23 <![CDATA[Pd / γ-Al2O3+H3[P(Mo3O 10 )4]]]> 5:1 0.025+0.005 200 6 93 0

[0080] A clear conclusion can be drawn from the data in the table above:

[0081] (1) The decisive role of the catalytic system: When using metal-supported catalysts alone, only Pd / γ-Al2O3 showed good activity (80% C15 yield), while other Pd-based catalysts or Pt and Ni catalysts had very low or even no activity (Examples 8-14). This fully demonstrates that the matching of metal type and support is crucial, and the combination of Pd and γ-Al2O3 is the optimal choice for this invention.

[0082] (2) Synergistic effect of solid superacids: When Pd / γ-Al2O3 was used in combination with phosphomolybdic acid (Example 15), the C15 yield was significantly increased from 80% to 92%, which confirmed that solid superacids effectively catalyzed the breaking of ester bonds in PC plastics and provided the necessary reaction intermediate for subsequent hydrogenation. However, the synergistic effect of phosphotungstic acid and silicotungstic acid was far less than that of phosphomolybdic acid (Examples 16-17), indicating that the type of acid has a significant impact.

[0083] (3) Screening of the optimal ratio: Through comparison of Examples 15 and 19-23, it was found that the mass ratio of Pd / γ-Al2O3 to phosphomolybdic acid and the total amount both affect the reaction results. When the ratio of the two is unbalanced (e.g., 1:3, Example 20) or the total amount is insufficient (e.g., 0.02g total amount, Example 18), a high yield cannot be obtained. The optimal conditions are a mass ratio of 2:1 and a total catalyst amount of 0.03g (corresponding to 30 wt% of plastic), under which the C15 yield can reach 95% and there are no cracking byproducts (Example 22).

[0084] III. Product Performance Testing

[0085] The physicochemical properties of the high-density aviation fuel product obtained in Example 22 (whose main component is propane-2,2-dimethyldicyclohexane) were tested, and the results are as follows:

[0086] Density (20℃) g / mL 0.931 ~0.80 GB / T 1884 Volumetric heat of combustion MJ / L 40.4 ~34.7 GB / T 384 Mass heat of combustion MJ / kg 43.4 ~43.0 GB / T 384 Freezing point ℃ -35.5 < -47 GB / T 2430

[0087] As shown in the table above, the aviation fuel prepared by this invention has extremely high density (0.931 g / mL) and volumetric heat of combustion (40.4 MJ / L), significantly superior to traditional petroleum-based RP-3 aviation fuel. Its gravimetric heat of combustion is also at a high level. Simultaneously, its freezing point is below -35°C, meeting the basic low-temperature performance requirements for aviation fuel. This high-density characteristic allows it to provide longer range or greater payload within the same fuel tank volume, making it particularly suitable for aerospace applications with stringent requirements for fuel energy density, such as UAVs, missiles, and high-performance aircraft.

[0088] In summary, this invention successfully developed a novel one-pot degradation method for producing high-density aviation fuel from waste PC plastic. This method utilizes a bifunctional catalytic system composed of a specific Pd / γ-Al₂O₃ catalyst and a solid superacid, phosphomolybdic acid, to achieve a direct, efficient, and highly selective conversion from waste polymers to high-value clean fuel under mild hydrogen pressure and temperature. This method is simple, low-cost, and produces high-performance products, providing a highly promising technical solution for addressing waste plastic pollution and developing a circular economy.

[0089] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing high-density aviation fuel by degrading waste PC plastic, characterized in that, Includes the following steps: In a hydrogen atmosphere, waste PC plastic, metal-supported catalyst and solid superacid additive are mixed in a reaction solvent and subjected to a one-pot catalytic reaction in a high-pressure reactor. After the reaction is completed, the mixture is separated to obtain high-density aviation fuel.

2. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 1, characterized in that, The metal-supported catalyst is an X / Y type supported catalyst, wherein the active component X is selected from one or more of Pd, Ni, and Pt; the support Y is selected from one or more of γ-Al2O3, Nb2O5, C, SiO2, and MgO; and the solid superacid additive is selected from one or more of phosphomolybdic acid, phosphotungstic acid, and silicotungstic acid.

3. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 2, characterized in that, In the metal-supported catalyst X / Y, the mass ratio of active component X to support Y is (0.01-0.1):1, preferably 0.05:

1.

4. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 1, characterized in that, The metal-supported catalyst X / Y is prepared by an equal-volume impregnation method, including the following steps: (a) Pretreatment of the carrier: The carrier Y is calcined in a muffle furnace at 80-550℃ for 2-4 hours to obtain the pretreated carrier Y; (b) Impregnation: Prepare a soluble salt solution of active component X, and add the pretreated carrier Y to the soluble salt solution at a mass ratio of active component X to carrier Y of (0.01-0.1):1, and impregnate with equal volume by stirring at 60°C for 4-8 hours. (c) Drying and calcination: After impregnation, dry at 80-160℃ and calcinate at 200-500℃ for 2-8 hours to obtain the metal-supported catalyst precursor; (d) Reduction activation: The catalyst precursor is placed in a tube furnace and activated at a hydrogen pressure of 0.1-2.0 MPa and a hydrogen space velocity of 100-5000 h⁻¹. -1 The metal-supported catalyst X / Y was activated at a reduction temperature of 200-550℃ for 3-8 h to obtain the activated catalyst.

5. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 1, characterized in that, The mass ratio of the metal-supported catalyst to the solid superacid additive is (0.5-2):1, preferably (1-2):1, and more preferably 2:

1.

6. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 1, characterized in that, The catalytic reaction is carried out at a temperature of 160-220℃, a hydrogen pressure of 1-5 MPa, and a reaction time of 6-12 h.

7. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 1, characterized in that, The mass ratio of the waste PC plastic, the metal-supported catalyst, and the solid superacid additive is 1:(0.1-0.5):(0.05-0.25), preferably 1:0.3:0.

15.

8. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 1, characterized in that, The main component of the high-density aviation fuel is propane-2,2-dimethyldicyclohexane, with a content of not less than 90 wt%; the high-density aviation fuel has a density greater than 0.90 g / mL, a heat of combustion greater than 40 MJ / kg, and a freezing point lower than -35℃.

9. The method for preparing high-density aviation fuel by degrading waste PC plastic according to claim 1, characterized in that, The reaction solvent is cyclohexane, and its amount is 20-100 times the mass of waste PC plastic.