Carbon-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to a carbon-based catalyst and a preparation method and application thereof, the preparation method comprises the following steps: washing coal-based activated carbon with deionized water for later use, pouring hydrogen peroxide with the mass concentration of 10%-20% into the coal-based activated carbon, sealing and impregnating the coal-based activated carbon, washing the impregnated coal-based activated carbon with deionized water, and drying to obtain the carbon-based catalyst. The method is simple, low in cost, green and pollution-free. The prepared catalyst is good in aviation fuel selectivity, high in conversion rate and not prone to inactivation, and can be widely applied to existing oil refining and chemical equipment and production processes. The prepared aviation fuel is excellent in component proportion and superior in quality. In addition, the waste plastics can be efficiently converted into gasoline or diesel oil only by changing the catalytic temperature, and the method has the remarkable advantage that the target product is controllable, so that the industrial production efficiency is greatly improved. The method can effectively realize high-valued reutilization of solid waste resources, alleviates the problem of environmental pollution, and has a good industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a carbon-based catalyst and a preparation method and application thereof. Background Art

[0002] Through catalytic pyrolysis technology, waste plastics can be converted into energy products such as high-value transportation fuels, which can achieve efficient recycling and reuse of waste plastics and solve the problem of plastic pollution.

[0003] Catalysts are the key to improving reaction efficiency and optimizing product distribution during catalytic pyrolysis reactions. Commonly used catalysts include molecular sieves, bifunctional metals, and activated carbons. Molecular sieve catalysts have the advantages of high specific surface area and porosity. Currently, in the available literature, the highest aviation fuel yield obtained by catalyzing molecular sieve catalysts is 80.8wt.% (Energy Conversion and Management 299(2024), 117825), but the selectivity is only 73.1%, and the catalyst has poor stability and is easily deactivated. Bifunctional metal catalysts have the advantages of good stability, strong activity, and high selectivity. Currently, in the available literature, the highest aviation fuel selectivity obtained by catalyzing bifunctional metal catalysts is 80.27% (FuelProcessing Technology 230(2022), 107205), but the liquid oil yield is only 48.71%, and the proportion of aromatics reaches 53.46%, which does not meet the aviation fuel standards. It also has the disadvantages of high cost and complex preparation methods.

[0004] Activated carbon catalysts have become a research hotspot in recent years due to their unique advantages such as low cost and long catalyst life. Currently, in the available literature, the selectivity of liquid aviation fuel prepared from biomass-based activated carbon can reach up to 93.13% (Industrial & Engineering Chemistry Research 59.39 (2020): 17451-17461), but alkanes only account for 39.11%, and the quality is far below the aviation fuel standard; therefore, it is urgent to develop new and efficient catalyst preparation methods and apply them to the field of waste plastic pyrolysis to increase the yield and quality of liquid fuel, and at the same time promote the commercialization of plastic waste resource utilization. Summary of the invention

[0005] The purpose of the present invention is to provide a carbon-based catalyst and a preparation method and application thereof in order to solve the above problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] The invention provides a method for preparing a carbon-based catalyst. Coal-based activated carbon is washed with deionized water and then kept aside. Hydrogen peroxide with a mass concentration of 10% to 20% is poured into the coal-based activated carbon to seal and impregnate it. The impregnated coal-based activated carbon is washed with deionized water and then dried to obtain a carbon-based catalyst.

[0008] As a further optimization scheme of the present invention, the particle size of the coal-based activated carbon is 420-590 μm; the amount of hydrogen peroxide with a mass concentration of 10%-20% for impregnating the coal-based activated carbon is 30 mL / g; the impregnation time is 24 hours; treatment with hydrogen peroxide of different concentrations has a significant effect on the structure of the coal-based activated carbon, that is, when the concentration is low, the coal-based activated carbon will produce new small holes to increase the attachment rate of the active groups, and at a higher concentration, hydrogen peroxide corrodes the small holes by oxidizing the surface of the carbon material to form activated carbon with mainly large holes and richer active groups; by controlling the impregnation ratio and time, the coal-based activated carbon can be fully and evenly oxidized and modified by hydrogen peroxide;

[0009] The drying temperature is 105°C and the drying time is 24h; by controlling the drying temperature and time, it is ensured that all the moisture in the modified activated carbon is removed.

[0010] The present invention also provides a carbon-based catalyst, which is prepared by the above-mentioned method for preparing a carbon-based catalyst.

[0011] The present invention also provides an application of the carbon-based catalyst in preparing liquid fuel by catalytic pyrolysis of plastics.

[0012] As a further optimization scheme of the present invention, the plastic is at least one of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET); the liquid fuel includes gasoline C5~C12, aviation fuel C8~C16, and diesel C10~C23.

[0013] As a further optimization solution of the present invention, the liquid fuel is aviation fuel C8-C16.

[0014] The present invention also provides a method for preparing liquid fuel by catalytic pyrolysis of plastic using the above-mentioned carbon-based catalyst, comprising the following steps:

[0015] (1) using an ex situ catalytic pyrolysis method to pyrolyze the plastic, and using an inert gas as a carrier gas to carry the plastic pyrolysis gas into a reactor containing the carbon-based catalyst for a catalytic pyrolysis reaction to obtain a gaseous pyrolysis product;

[0016] (2) The gaseous pyrolysis products are passed through a condensing device containing dichloromethane and methanol, condensed, and collected to obtain liquid fuel.

[0017] It should be noted that although plastics can be cracked into gaseous products in a short time by rapidly increasing the temperature, the two processes of thermal cracking and catalytic reaction can be separated by ex situ catalytic pyrolysis, which facilitates the activation of the catalyst and the control of the catalytic temperature, thereby improving the selectivity of liquid products (such as diesel, aviation fuel, gasoline).

[0018] As a further optimization scheme of the present invention, the plastic is at least one of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET);

[0019] The particle size of the plastic is 1 to 100 mm;

[0020] The mass ratio of the plastic to the carbon-based catalyst is 1:2 to 2:1.

[0021] As the mass of plastic raw materials increases, the oil yield gradually increases, but the quality of the oil product will decrease; when the raw materials increase to a certain mass, wax will be produced; therefore, the mass ratio of plastic to catalyst can be adjusted within the above range to improve the quality of liquid oil.

[0022] As a further optimization scheme of the present invention, in step (1), the pyrolysis temperature is 450°C to 600°C; the pyrolysis reaction time is 25 minutes;

[0023] Different temperatures have a significant effect on the formation of products. At lower temperatures, liquid products (such as oils) and solid products (such as waxes) are more likely to form. At lower temperatures, polymer chains break to form larger hydrocarbons, while at higher temperatures, gaseous products such as H 2 , CH 4 , C 2 H 2 etc.; the temperature and time of pyrolysis can be controlled within the above range to obtain a pyrolysis product that is beneficial to the subsequent reaction;

[0024] In step (1), the inert gas is nitrogen, and the flow rate of the nitrogen is 55 to 85 mL / min;

[0025] Different flow rates also have a significant effect on the distribution of products. At higher flow rates, the plastic pyrolysis products quickly pass through the catalyst to form medium- and long-chain hydrocarbons, thereby improving the selectivity of diesel and aviation fuel, while at lower flow rates, they tend to form aromatics and short-chain alkanes, thereby improving the selectivity of gasoline. The inert gas flow rate can be controlled within the above range to obtain highly selective liquid aviation fuel;

[0026] In step (1), the catalytic temperature is 450°C to 600°C, and the catalytic reaction time is 25 minutes;

[0027] The catalytic temperature mainly affects the distribution and selectivity of the products. The products after the first stage of pyrolysis will be further cracked and reformed under the action of the catalyst. At lower catalytic temperatures, the products tend to form long-chain alkanes, thereby improving the selectivity of diesel and aviation fuel; while at higher catalytic temperatures, the products tend to generate low-quality hydrocarbons, thereby improving the selectivity of gasoline. The catalytic temperature and time can be controlled within the above range to effectively obtain highly selective liquid fuel.

[0028] As a further optimization scheme of the present invention, in step (2), the condensation temperature is -15°C to 0°C, and the volume ratio of dichloromethane to methanol is 1:1.

[0029] The beneficial effects of the present invention are:

[0030] 1) The present invention uses hydrogen peroxide as an activating agent and coal-based activated carbon as a modified material, and prepares a coal-based activated carbon catalyst by an impregnation method. The whole process is simple, non-toxic, harmless, green and pollution-free, and has low raw material cost and high industrial application value;

[0031] 2) The carbon-based catalyst prepared by the present invention has good selectivity for aviation fuel C8-C16, high conversion rate, high activity, excellent stability, and is not easy to deactivate; and the obtained aviation fuel has excellent component ratio and high quality, and can be widely used in existing oil refining and chemical equipment and production processes;

[0032] 3) The carbon-based catalyst prepared by the present invention can also efficiently convert waste plastics into gasoline C5-C12 or diesel C10-C23 by simply changing the catalytic temperature, which has the significant advantage of controllable target products, thereby greatly improving industrial production efficiency;

[0033] 4) In the aviation fuel prepared by the present invention, the selectivity of aviation fuel C8-C16 in the liquid product is not less than 93%, wherein the mass proportions of alkanes and aromatics are 78.36% and 20.93%, respectively, which meet the component ratio standard of aviation fuel; at the same time, the mass ratio of liquid products in the total gas-liquid-solid products is not less than 90%, showing a higher liquid yield and better quality.

[0034] 5) The present invention uses waste plastic as raw material to prepare liquid fuel. This technology not only alleviates the problem of increasing shortage of fossil fuels, but also reduces environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1The present invention is a flow chart of preparing a carbon-based catalyst and using the carbon-based catalyst to catalytically pyrolyze plastics to prepare liquid fuel.

[0036] Figure 2 It is an experimental diagram showing the effects of different mass ratios of the carbon-based catalyst and raw material (plastic) of the present invention on the selectivity of aviation fuel.

[0037] Figure 3 It is an experimental diagram showing the influence of different mass ratios of the carbon-based catalyst and raw materials of the present invention on the selectivity of each component in aviation fuel.

[0038] Figure 4 The graph is an experimental diagram showing the effects of the carbon-based catalyst and raw materials of the present invention on the selectivity of aviation fuel and the selectivity of each component in aviation fuel through catalytic reactions at different catalytic temperatures.

[0039] Figure 5 This is an experimental diagram showing the effects of the carbon-based catalyst and raw materials of the present invention on the selectivity of different liquid fuels under catalytic reactions at different catalytic temperatures.

[0040] Figure 6 This is an experimental diagram showing the effect of the carbon-based catalyst of the present invention on the selectivity of various components in aviation fuel after continuous use for 1 to 10 times. DETAILED DESCRIPTION

[0041] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0042] 1. Materials

[0043] 1. Plastics: low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET). The following tests use low-density polyethylene LDPE with a particle size of 1 to 100 mm.

[0044] 2. Coal-based activated carbon: particle size is 420-590μm.

[0045] Unless otherwise specified, the methods used in this application are conventional methods known to those skilled in the art, and the reagents and other materials used are commercially available products unless otherwise specified.

[0046] 2. Methods

[0047] 2.1. Method for preparing liquid fuel by catalytic pyrolysis of plastic using carbon-based catalyst (e.g. Figure 1), the steps are as follows:

[0048] (1) Preparation of carbon-based catalyst: Weigh 1 g of coal-based activated carbon into a container, pour in 30 mL of 0% to 20% hydrogen peroxide, seal the container and let it stand at room temperature for 24 hours; then, pour out the excess liquid, wash with deionized water 2 to 3 times, and dry in a constant temperature drying oven at 105° C. for 24 hours to obtain (0% to 20%) O-AC catalyst for use;

[0049] (2) Place 100 mg of LDPE particles in a pyrolysis system, set the pyrolysis temperature to 450°C to 600°C, the pyrolysis time to 25 min, use nitrogen as the carrier gas, and the nitrogen flow rate to 55 to 85 mL / min;

[0050] (3) Weigh a carbon-based catalyst in a mass ratio of 1:1 to the plastic and place it in the catalytic system. Set the temperature of the catalytic section to 450°C to 600°C. Activate for 20 minutes to remove impurities such as moisture and stabilize its performance. Open the high-temperature valve and raise the pyrolysis furnace. Nitrogen carries the pyrolysis product formed in step (2) into the catalytic section. React for 25 minutes to obtain a mixed product.

[0051] (4) The mixed product obtained in step (3) is passed through a three-stage cold trap filled with dichloromethane and methanol (v / v=1), the temperature of the cold trap is -15°C to 0°C (-15°C is used in the experiment of the present invention), and the condensable components are condensed and collected as pyrolysis oil, and the non-condensable components are combustible gases (H 2 and CH 4 etc.), which can then circulate heat for the pyrolysis system.

[0052] 2.2 Single Factor Experiment

[0053] 2.2.1. Based on the method in step 2.1, the effect of thermal cracking temperature on the selectivity of liquid fuel was detected. The adjustment of thermal cracking temperature and the control of other factors are shown in Table 1:

[0054] Table 1 Single factor experimental conditions (thermal cracking temperature)

[0055]

[0056] The liquid fuel prepared in the above test groups 1-4 was subjected to GC-MS testing, and the product distribution results of the liquid fuel are shown in Table 2:

[0057] Table 2 Product distribution statistics of liquid fuel of test groups 1-4

[0058]

[0059] Note: Oil yield = oil mass / plastic mass*100%; gasoline range yield = gasoline mass / oil mass*100%; aviation fuel range yield = aviation fuel mass / oil mass*100%; diesel range yield = diesel mass / oil mass*100%.

[0060] Experimental conclusion: From the data of the above test groups 1 to 4, it can be seen that when the mass ratio of plastic to catalyst is fixed at 1:1, the catalytic temperature (500°C) and nitrogen flow rate (65mL / min) remain unchanged. By changing the thermal cracking temperature (450-600°C), significant differences in oil yield can be observed; too low thermal cracking temperature will lead to insufficient pyrolysis of LDPE, while too high pyrolysis temperature will increase the generation of gas and coke. Therefore, the liquid oil yield first increases and then decreases with the increase of pyrolysis temperature.

[0061] 2.2.2. Based on the method of step 2.1 and test group 1, the nitrogen flow rate was adjusted, and the effect of the nitrogen flow rate on the selectivity of liquid fuel was detected. The adjustment of the thermal cracking temperature and the control of other factors were specifically shown in Table 3:

[0062] Table 3 Single factor experimental conditions (nitrogen flow rate)

[0063]

[0064] The liquid fuel prepared in the above test groups 1, 5-7 was subjected to GC-MS detection, and the product distribution results of the liquid fuel are shown in Table 4:

[0065] Table 4 Product distribution statistics of liquid fuels in test groups 1, 5-7

[0066]

[0067] Note: Oil yield = oil mass / plastic mass*100%; gasoline range yield = gasoline mass / oil mass*100%; aviation fuel range yield = aviation fuel mass / oil mass*100%; diesel range yield = diesel mass / oil mass*100%.

[0068] Experimental conclusion: From the data of the above test groups 1, 5-7, it can be concluded that when the ratio of raw materials to catalysts is fixed at 1:1, the pyrolysis temperature and the catalytic temperature are kept unchanged at 500°C, and only the nitrogen flow rate is changed (ranging from 55 to 85 mL / min), it can be observed that there are significant differences in the oil yield and the selectivity for gasoline, aviation fuel and diesel; with the increase of the nitrogen flow rate, the residence time of the plastic pyrolysis gas on the catalyst is shortened, resulting in insufficient contact between the pyrolysis gas and the catalyst. This phenomenon weakens the catalyst's ability to break CC bonds and CH bonds, and tends to form alkanes greater than C16. Therefore, the selectivity for gasoline and aviation fuel decreases, while the selectivity for diesel gradually increases.

[0069] 2.2.3. Based on the method in step 2.1 and test group 1, only the mass ratio of plastic to catalyst was adjusted, and the effect of the mass ratio of plastic to catalyst on the selectivity of liquid fuel and the selectivity of each component in aviation fuel was detected. The adjustment of thermal cracking temperature and the control of other factors are shown in Table 5:

[0070] Table 5 Single factor experimental conditions (mass ratio of plastic to catalyst)

[0071]

[0072]

[0073] The liquid fuel prepared in the above test groups 1, 8, and 9 was tested by GC-MS. The product distribution results of the liquid fuel are as follows: Figure 2-3 As shown in Table 6:

[0074] Table 6 Product distribution statistics of liquid fuels in test groups 1, 8 and 9

[0075]

[0076] Note: Oil yield = oil mass / plastic mass*100%; gasoline range yield = gasoline mass / oil mass*100%; aviation fuel range yield = aviation fuel mass / oil mass*100%; diesel range yield = diesel mass / oil mass*100%.

[0077] Experimental conclusion: Based on the data of the above test groups 1, 8, and 9 and Figure 2-3It can be concluded that under the same conditions of pyrolysis temperature (500℃), catalytic temperature (500℃) and nitrogen flow rate (65mL / min), as the mass ratio of plastic to catalyst (15% O-AC) increases from 1:2 to 2:1, the oil yield gradually increases; however, due to the limited active sites of the catalyst, when the ratio continues to increase, the catalytic effect gradually decreases, resulting in an increase in long-chain alkanes greater than C16 in the product; the selectivity of aviation fuel and gasoline is reduced, while the selectivity of diesel is improved.

[0078] 2.2.4. Based on the method in step 2.1 and test group 1, only the concentration of hydrogen peroxide was adjusted, and the effect of the concentration of hydrogen peroxide on the selectivity of liquid fuel was tested. The adjustment of the thermal cracking temperature and the control of other factors are shown in Table 7:

[0079] Table 7 Single factor experimental conditions (hydrogen peroxide concentration)

[0080]

[0081] Note: “-” indicates that coal-based activated carbon that has not been modified with hydrogen peroxide is used as the catalyst, that is, commercially available coal-based activated carbon.

[0082] The liquid fuel prepared in the above test groups 1, 5-7 was subjected to GC-MS detection, and the product distribution results of the liquid fuel are shown in Table 8:

[0083] Table 8 Product distribution statistics of test groups 1, 10-12 liquid fuel

[0084]

[0085] Note: Oil yield = oil mass / plastic mass*100%; gasoline range yield = gasoline mass / oil mass*100%; aviation fuel range yield = aviation fuel mass / oil mass*100%; diesel range yield = diesel mass / oil mass*100%.

[0086] Experimental conclusion: From the data of the above test groups 1, 10-12, it can be concluded that when the ratio of raw material to catalyst is fixed at 1:1, under the same pyrolysis temperature (500℃), catalytic temperature (500℃) and nitrogen flow rate (65mL / min), with the increase of hydrogen peroxide concentration, the selectivity of gasoline and aviation fuel gradually increases, while the selectivity of diesel decreases; because hydrogen peroxide treatment can increase the pores of activated carbon and increase the content of weakly acidic groups, thereby promoting the breakage of CC bonds and CH bonds, and converting long-chain molecules in pyrolysis gas into short-chain alkanes and aromatics; however, if the acidity is too strong or the pores are too small, the small molecule chains will be further broken to generate gaseous products, such as H 2 and CH 4 Etc., so the liquid oil yield shows a trend of first increasing and then decreasing;

[0087] Compared with the unmodified commercially available coal-based activated carbon, the coal-based activated carbon catalyst modified with 15% hydrogen peroxide showed significant advantages in the catalytic oil production process of plastic pyrolysis gas: the oil yield was as high as 90.9% and no wax was generated; the aviation fuel selectivity was increased by 10.51%.

[0088] 2.2.5. Based on the method of step 2.1 and test group 1, only the catalytic reaction temperature was adjusted, and the effect of the catalytic reaction temperature on the selectivity of liquid fuel and the selectivity of each component in aviation fuel was detected. The adjustment of the thermal cracking temperature and the control of other factors are shown in Table 9:

[0089] Table 9 Single factor experimental conditions (catalytic reaction temperature)

[0090]

[0091] The liquid fuel prepared in the above test groups 1, 13-15 was subjected to GC-MS testing. The product distribution results of the liquid fuel are as follows: Figure 4-5 As shown in Table 10:

[0092] Table 10 Product distribution statistics of test groups 1, 10-12 liquid fuel

[0093]

[0094] Note: Oil yield = oil mass / plastic mass*100%; gasoline range yield = gasoline mass / oil mass*100%; aviation fuel range yield = aviation fuel mass / oil mass*100%; diesel range yield = diesel mass / oil mass*100%.

[0095] Experimental conclusion: Based on the data of the above test groups 1, 13 to 15 and Figure 4-5It can be concluded that when the ratio of raw materials to catalyst (15% O-AC) is fixed at 1:1, the pyrolysis temperature (500℃) and nitrogen flow rate (65mL / min) are kept unchanged, and only the catalyst temperature (450-600℃) is changed, it can be observed that there are significant differences in the oil yield and the selectivity for gasoline, aviation kerosene and diesel; with the increase of catalytic temperature, the selectivity of alkanes gradually decreases, while the selectivity of aromatics gradually increases. Under high temperature conditions, the catalyst has an enhanced ability to break CC bonds and CH bonds, and is more inclined to form low-quality hydrocarbons, thereby improving the selectivity for gasoline and aviation kerosene, but reducing the selectivity for diesel; in addition, at different catalytic temperatures, the modified catalyst can prepare a variety of high-value fuels, for example: at 450℃, the selectivity for diesel reaches 84.89%, at 500℃, the selectivity for aviation fuel reaches 93.75%, of which alkanes account for 78.36%; at 600℃, the selectivity for gasoline reaches 92.29%. The modified catalyst not only improves the quality of oil products, but also can efficiently prepare a variety of fuels.

[0096] 2.3 Carbon-based catalyst stability test

[0097] Experimental Group 16: The only difference from Experimental Group 1 is that in step (2), the injection is continued 1-10 times, 100 mg / time LDPE particles, that is, the carbon-based catalyst is recycled 1-10 times.

[0098] Based on the data of the above test group 1 and Figure 6 It can be concluded that under the same pyrolysis temperature (500℃), catalytic temperature (500℃) and nitrogen flow rate (65mL / min), 100mg of plastic is injected each time, and the injection is continuous for 1-10 times; as the number of injections increases, the selectivity for aviation fuel gradually decreases, but the change is slow; the coal-based activated carbon catalyst modified with 15% hydrogen peroxide has a better pore structure, richer active groups and moderate acidity, showing high selectivity and good catalytic activity and stability, and can break the long-chain macromolecules in the pyrolysis gas to generate C8~C16 alkanes and a small amount of aromatics, and is not easily deactivated by carbon deposition; the experimental results show that without any treatment, the catalyst still maintains good catalytic activity after 10 consecutive cycles. Therefore, the catalyst has excellent stability and catalytic performance.

[0099] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing a carbon-based catalyst, characterized in that: The coal-based activated carbon is washed with deionized water and set aside. Hydrogen peroxide with a mass concentration of 10% to 20% is poured into the coal-based activated carbon to seal and impregnate it. The impregnated coal-based activated carbon is washed with deionized water and then dried to obtain a carbon-based catalyst.

2. The method for preparing a carbon-based catalyst according to claim 1, characterized in that: The particle size of the coal-based activated carbon is 420-590 μm; the amount of hydrogen peroxide with a mass concentration of 10%-20% used for impregnating the coal-based activated carbon is 30 mL / g.

3. A carbon-based catalyst, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 2.

4. Use of the carbon-based catalyst as claimed in claim 3 in the preparation of liquid fuel by catalytic pyrolysis of plastics.

5. The use according to claim 4, characterized in that: The plastic is at least one of low-density polyethylene, high-density polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyethylene terephthalate; the liquid fuel includes gasoline C5-C12, aviation fuel C8-C16, and diesel C10-C23.

6. The use according to claim 5, characterized in that: The liquid fuel is aviation fuel C8-C16.

7. A method for preparing liquid fuel by catalytic pyrolysis of plastic using the carbon-based catalyst as claimed in claim 3, characterized in that: The following steps are involved: (1) using an ex situ catalytic pyrolysis method to pyrolyze the plastic, and using an inert gas as a carrier gas to carry the plastic pyrolysis gas into a reactor containing the carbon-based catalyst for a catalytic pyrolysis reaction to obtain a gaseous pyrolysis product; (2) The gaseous pyrolysis products are passed through a condensing device containing dichloromethane and methanol, condensed, and collected to obtain liquid fuel.

8. The method according to claim 7, characterized in that: The plastic is at least one of low-density polyethylene, high-density polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyethylene terephthalate; the particle size of the plastic is 1 to 100 mm; and the mass ratio of the plastic to the carbon-based catalyst is 1:2 to 2:

1.

9. The method according to claim 7, characterized in that: In step (1), the pyrolysis temperature is 450°C to 600°C, and the pyrolysis reaction time is 25 minutes; the inert gas is nitrogen, and the flow rate of the nitrogen is 55 to 85 mL / min; the catalytic temperature is 450°C to 600°C, and the catalytic reaction time is 25 minutes.

10. The method according to claim 7, characterized in that: In step (2), the condensation temperature is -15°C to 0°C, and the volume ratio of dichloromethane to methanol is 1:1.

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