Coal-based power fuel for piston engines, method for its production and use

Abstract

The present application provides a coal-based power fuel suitable for a piston engine, a preparation method and application thereof. The coal-based power fuel comprises, in terms of percentage by weight, 10-99wt% coal direct liquefaction oil and 1-90wt% coal indirect liquefaction oil; wherein the coal direct liquefaction oil is obtained by coal direct liquefaction reaction, hydrofining reaction, hydrocracking reaction and cutting of coal in oil coal slurry and hydrogen in sequence; the coal direct liquefaction oil is distillate oil with distillation range T1 min -T1 max , T1 min is 140-180 DEG C, and T1 max is 220-280 DEG C; the coal indirect liquefaction oil is obtained by cutting of coal indirect liquefaction diesel; the coal indirect liquefaction oil is distillate oil with distillation range T2 min -T2 max , T2 min is 140-160 DEG C, and T2 max is 220-280 DEG C.

Description

Technical Field

[0001] This invention relates to the field of coal liquefaction for fuel production technology, and more specifically, to a coal-based power fuel suitable for piston engines, its preparation method, and its application. Background Technology

[0002] Piston engines have gained widespread application in the field of unmanned aerial vehicles (UAVs) due to their significant advantages such as small size, light weight, high power-to-weight ratio, and simple structure and operation. Among them, spark-ignition piston engines have become the mainstream power unit for UAVs due to their high thermal efficiency and power-to-weight ratio. As technology accelerates the substitution of labor, the functions and application scenarios of UAVs continue to expand, gradually upgrading from simple short-duration, short-distance flight missions to complex operations such as cargo transportation and patrol monitoring. The requirements for payload capacity and cruise duration have also increased significantly, placing higher demands on the performance standards of fuels for UAVs.

[0003] Currently, gasoline and aviation kerosene are the main engine fuels used for drones. Gasoline, as a fuel for drones, has a core drawback: its low energy density directly limits the drone's range, making it difficult to meet the needs of heavy-load, long-distance operations. Furthermore, gasoline's extremely low flash point poses significant safety hazards during transportation, storage, and refueling, further restricting its application in medium and large-sized drones. Compared to gasoline, its primary advantage is its higher energy density, which effectively extends the drone's flight time and increases payload capacity within the limited fuel tank volume. Meanwhile, aviation kerosene has low volatility and a high flash point, exhibiting outstanding safety performance. However, due to its higher density, its kinematic viscosity also increases, leading to increased difficulty in fuel atomization and ultimately causing poor engine starting performance, posing a challenge to its adaptability in low-temperature environments.

[0004] The low energy density of existing gasoline fuel directly limits the payload capacity of drones and shortens their cruising range, making it unable to meet the needs of complex operational scenarios such as cargo transportation and long-distance patrol and monitoring. At the same time, its extremely low flash point makes it prone to volatilization and the formation of flammable and explosive vapors during transportation, storage and on-site refueling, posing significant safety hazards such as leakage, fire and explosion, which seriously restricts its large-scale application in medium and large-sized drones.

[0005] While existing aviation kerosene (No. 3 jet fuel) has a higher energy density, which can extend the range and increase the load under the premise of limited fuel tank volume, when a higher density jet fuel is selected to further optimize the range performance, its kinematic viscosity will increase simultaneously (especially the viscosity increase is more obvious in low temperature environment). This results in larger atomized particle size and poorer atomization uniformity of the fuel in the engine fuel injection system, which not only affects the combustion efficiency, but also causes difficulty in engine cold start and a reduced start success rate.

[0006] The existing fuels are all general-purpose products and have not been optimized for the characteristics of drone engines, such as small size, high speed, frequent start-stop, and large fluctuations in operating conditions. As a result, key indicators such as fuel energy release efficiency, atomization adaptability, and safety performance cannot be accurately matched with the engine's operating characteristics, which in turn restricts the improvement of the overall operational performance of drones.

[0007] In summary, it is of great significance to research and develop a special fuel for UAVs that combines high energy density, suitable kinematic viscosity, high safety performance, and good low-temperature fluidity. This can solve the shortcomings of gasoline in terms of poor range and low safety, overcome the problems of difficult atomization of high-density aviation kerosene and poor low-temperature start-up, and achieve efficient compatibility with UAV spark-ignition piston engines, meeting the comprehensive requirements for range, load, safety, and environmental adaptability in complex operating scenarios. Summary of the Invention

[0008] The main objective of this invention is to provide a coal-based power fuel suitable for piston engines, its preparation method, and its application, in order to solve the problem that existing coal-based power fuels are difficult to simultaneously possess high energy density, suitable kinematic viscosity, high safety performance, and good low-temperature fluidity, which makes them unable to be efficiently adapted to UAVs and restricts the improvement of UAV range, payload capacity, safety, and stability.

[0009] To achieve the above objectives, the present invention provides a coal-based power fuel suitable for piston engines. By weight percentage, the coal-based power fuel comprises: 10–99 wt% direct coal liquefaction oil and 1–90 wt% indirect coal liquefaction oil; wherein the direct coal liquefaction oil is obtained sequentially by reacting coal and hydrogen in a coal-oil slurry through a direct coal liquefaction reaction, a hydrorefining reaction, a hydrocracking reaction, and a cutting process; the direct coal liquefaction oil has a distillation range of T1. min ~T1 max Distillate oil between, T1 min The temperature ranges from 140 to 180℃, and T1 is... max The temperature range is 220–280℃; coal-to-liquid oil is obtained by cutting coal-to-liquid diesel oil; the distillation range of coal-to-liquid oil is T2. min ~T2 max Distillate oil between, T2 min The temperature is 140–160℃, T2 max The temperature ranges from 220 to 280℃.

[0010] Furthermore, direct coal liquefaction oil includes C8 to C6 oil. 15 Cycloalkanes, C9-C 16 Straight-chain alkanes, C9-C 15 Aromatic hydrocarbons; coal-to-liquids oil includes C8-C64 hydrocarbons. 15 Cycloalkanes, C9-C 16 Straight-chain alkanes, C9-C15 Aromatic hydrocarbons; preferably, the weight percentage of aromatic hydrocarbons in coal-based power fuel is ≤5wt%.

[0011] Further, by weight percentage, the coal-based power fuel includes: 50-99 wt% direct coal liquefaction oil and 1-50 wt% indirect coal liquefaction oil; preferably, the coal-oil slurry includes starting solvent oil and coal, wherein the starting solvent oil is selected from the hydrogenated fractionation product of decrystalline anthracene oil and wash oil as raw materials; more preferably, it is the hydrogenated fractionation product of decrystalline anthracene oil and wash oil as raw materials in a mass ratio of 1:1.

[0012] To achieve the above objectives, another aspect of the present invention provides a method for preparing the coal-based power fuel suitable for piston engines provided in this application. The method includes: step S1, reacting coal in a coal-oil slurry with hydrogen via direct coal liquefaction to obtain direct coal liquefaction products; step S2, performing a first cut on the direct coal liquefaction products to obtain light distillate oil and heavy distillate oil; the light distillate oil is a fraction with a temperature less than or equal to the first cut temperature, and the heavy distillate oil is a fraction with a temperature greater than the first cut temperature, wherein the first cut temperature is 300–320°C. Step S3: The light distillate oil undergoes a hydrorefining reaction, resulting in refined light oil and refined heavy oil after a second cut. The refined light oil is the fraction with a temperature less than or equal to the second cut temperature, and the refined heavy oil is the fraction with a temperature greater than the second cut temperature, which is 180–220°C. Step S4: The refined heavy oil undergoes a hydrocracking reaction to obtain hydrocracking products. Step S5: The hydrocracking products are mixed with the refined light oil to obtain a mixture. Step S6: The mixture undergoes a third cut to obtain direct coal liquefaction oil. The direct coal liquefaction oil has a distillation range of T1. min ~T1 max Distillate oil between, T1 min The temperature ranges from 140 to 180℃, and T1 is... max The temperature is 220–280℃; in step S7, the coal-to-liquid diesel is subjected to a fourth cut to obtain coal-to-liquid oil; the coal-to-liquid oil has a distillation range of T2. min ~T2 max Distillate oil between, T2 min The temperature is 140–160℃, T2 max The temperature is 220–280℃; in step S8, the direct coal liquefaction oil and the indirect coal liquefaction oil are mixed to obtain coal-based power fuel.

[0013] Furthermore, the method for preparing coal-based power fuel suitable for piston engines further includes: hydrogenating the heavy distillate oil obtained in step S2 to obtain recovered solvent oil, and returning the recovered solvent oil to step S1; preferably, step S1 includes: mixing coal and solvent oil to obtain coal-oil slurry; reacting the coal-oil slurry with hydrogen to undergo direct coal liquefaction to obtain direct coal liquefaction products; preferably, cracked heavy oil is also obtained in step S6, and the cracked heavy oil is returned to step S4; the cracked heavy oil has a distillation range > T1. max The fraction; preferably, in step S7, T2 min The temperature is 140–160℃, T2 max The temperature ranges from 230 to 250℃.

[0014] Furthermore, the hydrorefining reaction is carried out at a temperature of 330–390 °C, a pressure of 6.0–19.0 ​​MPa, and a volume hourly space velocity of 0.5–3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (500-1500):1; and / or, the catalyst used in the hydrorefining reaction is a supported hydrorefining catalyst, comprising a first support and a first active metal oxide; the first support is selected from amorphous alumina or aluminum silicate, and the metal element in the first active metal oxide is selected from one or more of Group VIB and / or Group VIII; preferably, the metal element in the first active metal oxide is selected from non-noble metals of Group VIB, and the weight percentage of the first active metal oxide in the supported hydrorefining catalyst is 0.5-30 wt%; or, the metal element in the first active metal oxide is selected from one or more of Group VIII, and the weight percentage of the first active metal oxide in the supported hydrorefining catalyst is 1-10 wt%; preferably, the metal element in the first active metal oxide is selected from one or more of Mo, W, Co, and Ni.

[0015] Furthermore, the hydrorefining reaction is carried out at a temperature of 340–380 °C, a pressure of 10.0–15.0 MPa, and a volume hourly space velocity of 1.0–2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (800-1000):1.

[0016] Furthermore, the hydrocracking reaction is carried out at a temperature of 330–400 °C, a pressure of 8.0–19.0 ​​MPa, and a volume hourly space velocity of 1.0–4.0 h⁻¹. -1The hydrogen-to-oil volume ratio is (500–1500):1; and / or, the catalyst used in the hydrocracking reaction is a supported hydrocracking catalyst, comprising a second support and a second active metal oxide; the second support is selected from molecular sieves or alumina, and the metal element in the second active metal oxide is selected from one or more of Group VIB and Group VIII; preferably, the second support is a molecular sieve, and the weight percentage of the molecular sieve is 10–40 wt%; the molecular sieve is selected from one or more of USY-type, β-type, and SAPO-type; preferably, the metal element in the second active metal oxide is selected from one or more of Group VIB, and the weight percentage of the second active metal oxide in the supported hydrocracking catalyst is 0.5–30 wt%; or, the metal element in the second active metal oxide is selected from one or more of Group VIII, and the weight percentage of the second active metal oxide in the supported hydrocracking catalyst is 1–5 wt%; preferably, the metal element in the second active metal oxide is selected from one or more of Mo, W, Co, and Ni.

[0017] Furthermore, the hydrocracking reaction is carried out at a temperature of 350–380 °C, a pressure of 10.0–15.0 MPa, and a volume hourly space velocity of 2.0–3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (800-1000):1.

[0018] Another aspect of the present invention provides an application of the coal-based power fuel for piston engines provided in this application in the field of unmanned aerial vehicles (UAVs).

[0019] By applying the technical solution of this invention, the coal-based power fuel provided in this application, with direct coal liquefaction oil as its main component, can increase the calorific value generated per unit volume. When applied to the field of unmanned aerial vehicles (UAVs), it can release more energy than traditional fuels under the premise of the same oil phase volume, thereby improving the UAV's range and payload capacity, meeting the complex operational needs of long-distance patrol and monitoring, cross-regional cargo transportation, and significantly expanding the UAV's operational radius and application boundaries. Moreover, compared with traditional aviation kerosene, under the same density conditions, the coal-based power fuel with the specific distillation range and composition provided in this application can achieve a lower kinematic viscosity. The low viscosity characteristic can optimize the fuel atomization effect, allowing for more complete combustion and improving combustion efficiency. Under the same kinematic viscosity conditions, the coal-based power fuel provided in this application has a higher energy density, thereby improving the fuel's energy output efficiency.

[0020] Furthermore, the coal-based power fuel with the specific distillation range and composition provided in this application possesses a low freezing point, enabling it to operate stably in extremely cold environments. It ensures continuous and reliable fuel supply without the need for additional anti-gelling agents, completely resolving core issues such as incomplete combustion and easy solidification / clogging of fuel lines in low-temperature environments caused by the high viscosity of aviation kerosene of the same density. This significantly improves the fuel's adaptability and safety under extreme operating conditions. Moreover, the flash point of the coal-based power fuel provided in this application is significantly higher than that of gasoline (≥40℃), exhibiting extremely low volatility during transportation, storage, and refueling. It is unlikely to form flammable and explosive vapors, effectively avoiding safety hazards such as leaks, fires, and explosions, and meeting the safety management requirements for large-scale applications of medium and large-sized UAVs. Simultaneously, the inherent high thermal stability of direct coal liquefaction oil prevents the fuel from undergoing thermal decomposition and producing carbon deposits or gum under high engine speed and high load conditions, further enhancing safety and stability, reducing the incidence of UAV operation accidents, and providing core safety assurance for large-scale promotion. Furthermore, compared to other ratios, limiting the content of direct coal liquefaction oil and indirect coal liquefaction oil in coal-based power fuel to the above-mentioned range can also improve the smoke point and combustion efficiency of coal-based power fuel.

[0021] The coal direct liquefaction oil described in this application is obtained by sequentially reacting coal and hydrogen in a coal-oil slurry through a coal direct liquefaction reaction, a hydrorefining reaction, a hydrocracking reaction, and a cutting process. The coal direct liquefaction oil produced by the segmented hydrorefining method exhibits excellent yield, and the coal-based power fuel containing it can effectively balance the two mutually restrictive performance requirements of high energy density and low kinematic viscosity, as well as high flash point and low freezing point. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 A schematic diagram of the structure of the coal-based power fuel preparation system for piston engines provided in this application is shown.

[0024] The above figures include the following reference numerals:

[0025] 10. Coal direct liquefaction reactor; 11. Coal-oil slurry inlet; 20. First cutting device; 30. Hydrorefining reactor; 40. Second cutting device; 50. Hydrocracking reactor; 51. Refined heavy oil inlet; 60. First mixing device; 70. Third cutting device; 71. Cracking heavy oil outlet; 80. Fourth cutting device; 90. Second mixing device; 100. Hydrorefining reactor; 101. Recovered solvent oil outlet. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0027] As described in the background section, existing coal-based power fuels suffer from difficulties in simultaneously achieving high energy density, suitable kinematic viscosity, high safety performance, and good low-temperature fluidity. This results in inefficient adaptation to drones, hindering improvements in drone range, payload capacity, safety, and stability. To address these technical problems, the first aspect of this application provides a coal-based power fuel suitable for piston engines. By weight percentage, the coal-based power fuel comprises: 10–99 wt% direct coal liquefaction oil and 1–90 wt% indirect coal liquefaction oil. The direct coal liquefaction oil is obtained sequentially from coal and hydrogen in a coal-oil slurry through direct coal liquefaction, hydrorefining, hydrocracking, and cutting. The direct coal liquefaction oil has a distillation range of T1. min ~T1 max Distillate oil between, T1 min The temperature ranges from 140 to 180℃, and T1 is... max The temperature range is 220–280℃; coal-to-liquid oil is obtained by cutting coal-to-liquid diesel oil; the distillation range of coal-to-liquid oil is T2. min ~T2 max Distillate oil between, T2 min The temperature is 140–160℃, T2 max The temperature ranges from 220 to 280℃.

[0028] The coal-based power fuel provided in this application uses direct coal liquefaction oil as its main component, which can increase the calorific value generated per unit volume. When applied to the field of UAVs, it can release more energy than traditional fuels under the premise of the same oil phase volume, thereby improving the UAV's range and payload capacity, meeting the complex operational needs of long-distance patrol and monitoring, cross-regional cargo transportation, and significantly expanding the UAV's operating radius and application boundaries. Moreover, compared with traditional aviation kerosene, under the same density conditions, the coal-based power fuel with the specific distillation range and composition provided in this application can achieve a lower kinematic viscosity. The low viscosity characteristic can optimize the fuel atomization effect, allowing for more complete combustion and improving combustion efficiency. Under the same kinematic viscosity conditions, the coal-based power fuel provided in this application has a higher energy density, thereby improving the fuel's energy output efficiency.

[0029] Furthermore, the coal-based power fuel with the specific distillation range and composition provided in this application possesses a low freezing point, enabling it to operate stably in extremely cold environments. It ensures continuous and reliable fuel supply without the need for additional anti-gelling agents, completely resolving core issues such as incomplete combustion and easy solidification / clogging of fuel lines in low-temperature environments caused by the high viscosity of aviation kerosene of the same density. This significantly improves the fuel's adaptability and safety under extreme operating conditions. Moreover, the flash point of the coal-based power fuel provided in this application is significantly higher than that of gasoline (≥40℃), exhibiting extremely low volatility during transportation, storage, and refueling. It is unlikely to form flammable and explosive vapors, effectively avoiding safety hazards such as leaks, fires, and explosions, and meeting the safety management requirements for large-scale applications of medium and large-sized UAVs. Simultaneously, the inherent high thermal stability of direct coal liquefaction oil prevents the fuel from undergoing thermal decomposition and producing carbon deposits or gum under high engine speed and high load conditions, further enhancing safety and stability, reducing the incidence of UAV operation accidents, and providing core safety assurance for large-scale promotion. Furthermore, compared to other ratios, limiting the content of direct coal liquefaction oil and indirect coal liquefaction oil in coal-based power fuel to the above-mentioned range can also improve the smoke point and combustion efficiency of coal-based power fuel.

[0030] The coal direct liquefaction oil described in this application is obtained by sequentially reacting coal and hydrogen in a coal-oil slurry through a coal direct liquefaction reaction, a hydrorefining reaction, a hydrocracking reaction, and a cutting process. The coal direct liquefaction oil produced by the segmented hydrorefining method exhibits excellent yield, and the coal-based power fuel containing it can effectively balance the two mutually restrictive performance requirements of high energy density and low kinematic viscosity, as well as high flash point and low freezing point.

[0031] In a preferred embodiment, the direct coal liquefaction oil comprises C8 to C96. 15 Cycloalkanes, C9-C 16 Straight-chain alkanes and C9-C6 15 Aromatic hydrocarbons; coal-to-liquids oil includes C8-C64 hydrocarbons. 15 Cycloalkanes, C9-C 16 Straight-chain alkanes and C9-C6 15 Aromatic hydrocarbons. The use of coal direct liquefaction oil and coal indirect liquefaction oil with the above-mentioned specific components is beneficial for improving the energy density of coal-based power fuels, reducing kinematic viscosity, increasing flash point, and lowering freezing point, thereby improving the range, payload capacity, safety, and stability of UAVs.

[0032] To improve the cleanliness of coal-based fuel combustion, reduce particulate matter and harmful pollutant emissions, decrease engine carbon deposits and nozzle coking, enhance storage oxidation stability, ensure fuel system material compatibility, and extend the service life of power equipment, in a preferred embodiment, the weight percentage of aromatics in the coal-based fuel is ≤5 wt%. Preferably, the weight percentage of aromatics in the coal-based fuel is ≤4 wt%, ≤3 wt%, or ≤2 wt%.

[0033] In a preferred embodiment, the coal-based power fuel, by weight percentage, comprises 50–99 wt% direct coal liquefaction oil and 1–50 wt% indirect coal liquefaction oil. Compared to other ranges, limiting the content of direct and indirect coal liquefaction oil in the coal-based power fuel to the above range is beneficial for increasing the energy density of the coal-based power fuel, reducing kinematic viscosity, increasing the flash point and reducing the freezing point, and also for increasing the smoke point and combustion efficiency of the coal-based power fuel, thereby improving the range, payload capacity, safety, and stability of the UAV.

[0034] To improve the efficiency of direct coal liquefaction, preferably, the coal-oil slurry includes starting solvent oil and coal, wherein the starting solvent oil includes, but is not limited to, the hydrogenated fractionation product of decrystalline anthracene oil and wash oil as raw materials; more preferably, the hydrogenated fractionation product of decrystalline anthracene oil and wash oil as raw materials in a mass ratio of 1:1.

[0035] The second aspect of this application provides a method for preparing the coal-based power fuel suitable for piston engines as described above. The method includes: step S1, reacting coal in a coal-oil slurry with hydrogen via direct coal liquefaction to obtain direct coal liquefaction products; step S2, performing a first cut on the direct coal liquefaction products to obtain light distillate oil and heavy distillate oil; the light distillate oil is a fraction with a temperature less than or equal to the first cut temperature, and the heavy distillate oil is a fraction with a temperature greater than the first cut temperature, wherein the first cut temperature is 300–320°C; step S3... Light distillate oil undergoes hydrorefining reaction, and after a second cut, refined light oil and refined heavy oil are obtained; the refined light oil is the fraction with a temperature less than or equal to the second cut temperature, and the refined heavy oil is the fraction with a temperature greater than the second cut temperature, which is 180–220°C; in step S4, the refined heavy oil undergoes hydrocracking reaction to obtain hydrocracking products; in step S5, the hydrocracking products are mixed with the refined light oil to obtain a mixture; in step S6, the mixture is subjected to a third cut to obtain direct coal liquefaction oil; the direct coal liquefaction oil has a distillation range of T1. min ~T1 max Distillate oil between, T1 min The temperature ranges from 140 to 180℃, and T1 is... max The temperature is 220–280℃; in step S7, the coal-to-liquid diesel is subjected to a fourth cut to obtain coal-to-liquid oil; the coal-to-liquid oil has a distillation range of T2. min ~T2 max Distillate oil between, T2 min The temperature is 140–160℃, T2 max The temperature is 220–280℃; in step S8, the direct coal liquefaction oil and the indirect coal liquefaction oil are mixed to obtain coal-based power fuel.

[0036] This application uses steps S1 to S6 of the above preparation method to prepare direct coal liquefaction oil, and then mixes it with the indirect coal liquefaction oil obtained in step S7 to obtain the desired coal-based power fuel suitable for piston engines.

[0037] In step S2, compared to other ranges, limiting the temperature of the first cut within the above range can effectively separate light distillate oil, which is convenient for subsequent hydrorefining reaction, reduces the hydrorefining load, and also reduces the loss of light distillate oil and increases the yield.

[0038] In step S3, the light distillate oil undergoes a hydrorefining reaction, which removes heteroatoms such as sulfur, nitrogen, and oxygen and converts aromatics into saturated hydrocarbons. After a second cutting process, refined light oil and refined heavy oil are obtained. The refined light oil has reached the target reaction fraction, with reduced density, viscosity, and pour point, thus requiring no further hydrocracking. However, the refined heavy oil contains more heavy components, and its low-temperature flow properties do not meet the target reaction fraction. It also still contains a small amount of aromatics. Therefore, the refined heavy oil needs to undergo a hydrocracking reaction (step S4) to convert the aromatics into saturated hydrocarbons, achieving macromolecular cracking and upgrading, thereby converting it into the target reaction fraction.

[0039] The coal-based power fuel prepared in this application, with direct coal liquefaction oil as its main component, can increase the calorific value generated per unit volume. When applied to the field of unmanned aerial vehicles (UAVs), it can release more energy than traditional fuels under the premise of the same oil phase volume, thereby improving the UAV's range and payload capacity, meeting the complex operational needs of long-distance patrol and monitoring, cross-regional cargo transportation, and significantly expanding the UAV's operational radius and application boundaries. Moreover, compared with traditional aviation kerosene, under the same density conditions, the coal-based power fuel with the specific distillation range and composition prepared in this application can achieve a lower kinematic viscosity. The low viscosity characteristic can optimize the fuel atomization effect, allowing for more complete combustion and improving combustion efficiency. Under the same kinematic viscosity conditions, the coal-based power fuel prepared in this application has a higher energy density, thereby improving the fuel's energy output efficiency.

[0040] Furthermore, the coal-based power fuel with the specific distillation range and composition obtained in this application possesses a low freezing point, enabling it to operate stably in extremely cold environments. It ensures continuous and reliable fuel supply without the need for additional anti-condensing agents, completely solving the core problems faced by aviation kerosene of the same density due to its high viscosity, such as incomplete combustion and easy solidification and blockage of fuel lines at low temperatures. This significantly improves the fuel's adaptability and safety under extreme operating conditions. Moreover, the flash point of the coal-based power fuel obtained in this application is significantly higher than that of gasoline (≥40℃), exhibiting extremely low volatility during transportation, storage, and refueling. It is unlikely to form flammable and explosive vapors, effectively avoiding safety hazards such as leakage, fire, and explosion, and meeting the safety management requirements for large-scale applications of medium and large-sized UAVs. Simultaneously, the inherent high thermal stability of direct coal liquefaction oil prevents the fuel from thermally decomposing and producing carbon deposits or gum under high engine speed and high load conditions, further enhancing its safety and stability, reducing the incidence of UAV operation accidents, and providing core safety assurance for large-scale promotion. Furthermore, compared to other ratios, limiting the content of direct coal liquefaction oil and indirect coal liquefaction oil in coal-based power fuel to the above-mentioned range can also improve the smoke point and combustion efficiency of coal-based power fuel.

[0041] In a preferred embodiment, the above-mentioned method for preparing coal-based power fuel suitable for piston engines further includes: hydrogenating the heavy distillate oil obtained in step S2 to obtain recovered solvent oil, and returning the recovered solvent oil to step S1. This method is beneficial for improving the utilization rate of heavy distillate oil and for the preparation of coal-oil slurry.

[0042] The direct coal liquefaction reaction described in this application is well known in the art and can be referred to Chinese patent application CN200410070249.6. In a preferred embodiment, step S1 includes: mixing coal with solvent oil to obtain an oil-coal slurry; and reacting the oil-coal slurry with hydrogen to obtain the direct coal liquefaction product. Using the above method for the direct coal liquefaction reaction is beneficial for improving the product yield.

[0043] In a preferred embodiment, cracked heavy oil is also obtained in step S6, and the cracked heavy oil is returned to step S4; the cracked heavy oil has a distillation range > T1. max The fraction of cracked heavy oil is relatively heavy, has high viscosity, and poor low-temperature fluidity. In order to improve the utilization rate of cracked heavy oil, it is mixed with refined heavy oil and then subjected to hydrocracking reaction to obtain the target fraction product.

[0044] To further improve the smoke point and combustion efficiency of coal-based power fuels, preferably, in step S7, T2 min The temperature is 140–160℃, T2 max The temperature ranges from 230 to 250℃.

[0045] In a preferred embodiment, the hydrorefining reaction is carried out at a temperature of 330–390°C, a pressure of 6.0–19.0 ​​MPa, and a volume hourly space velocity of 0.5–3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (500–1500):1. The process parameters in the hydrorefining reaction include, but are not limited to, the above ranges. Limiting them within these ranges is beneficial for improving the removal rate of sulfur, nitrogen, oxygen, and other heteroatoms in light distillate oils, and for increasing the efficiency of converting aromatics to saturated hydrocarbons in light distillate oils. Specifically, the reaction temperature of the hydrorefining reaction can be 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, or any two of the above values; the reaction pressure of the hydrorefining reaction can be 6.0 MPa, 7.0 MPa, 8.0 MPa, 9.0 MPa, 10.0 MPa, 11.0 MPa, 12.0 MPa, 13.0 MPa, 14.0 MPa, 15.0 MPa, 16.0 MPa, 17.0 MPa, 18.0 MPa, 19.0 MPa, or any two of the above values; the volume hourly space velocity can be 0.5 h⁻¹. -1 1.0h -1 1.5h -1 2.0h -1 2.5h -1 3.0h -1 Or any range between any two of the above values; the hydrogen-to-oil volume ratio can be 500:1, 600:1, 700:1, 800:1, 850:1, 900:1, 950:1, 1000:1, 1100:1, 1200:1, 1300:1, 1400:1, 1500:1 or any range between any two of the above values.

[0046] In a preferred embodiment, the hydrorefining reaction is carried out at a temperature of 340–380°C, a pressure of 10.0–15.0 MPa, and a volume hourly space velocity of 1.0–2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (800-1000):1. The process parameters in the hydrorefining reaction include, but are not limited to, the above range. Limiting them to this range helps to further improve the removal rate of sulfur, nitrogen, oxygen, and other heteroatoms in light distillate oils, further improve the efficiency of converting aromatics into saturated hydrocarbons, and thus reduce the aromatic content in the product.

[0047] In a preferred embodiment, the catalyst used in the hydrorefining reaction is a supported hydrorefining catalyst, comprising a first support and a first active metal oxide; the first support includes, but is not limited to, amorphous alumina or aluminum silicate, and the metal element in the first active metal oxide includes, but is not limited to, one or more elements from Group VIB and / or Group VIII. Using the aforementioned types of first supports and first active metal oxides is beneficial for improving the efficiency of the hydrorefining reaction; it also helps to increase the removal rate of heteroatoms from light distillate oils and the yield of aromatics converted to saturated hydrocarbons in light distillate oils.

[0048] To further improve the efficiency of hydrorefining reactions and increase the removal rate of heteroatoms and the yield of aromatics converted to saturated hydrocarbons in light distillate oils, in a preferred embodiment, the metal element in the first active metal oxide includes, but is not limited to, non-noble metals of Group VIB, and the weight percentage of the first active metal oxide in the supported hydrorefining catalyst is 0.5–30 wt%; or, the metal element in the first active metal oxide includes, but is not limited to, one or more of Group VIII, and the weight percentage of the first active metal oxide in the supported hydrorefining catalyst is 1–10 wt%. The weight percentage of the first active metal oxide refers to the mass percentage of the first active metal oxide in the catalyst used in the hydrorefining reaction.

[0049] In order to further improve the efficiency of hydrorefining reaction, increase the removal rate of heteroatoms in light distillate oil and the yield of aromatics converted into saturated hydrocarbons, in a preferred embodiment, the metal element in the first active metal oxide includes, but is not limited to, one or more of Mo, W, Co and Ni.

[0050] In a preferred embodiment, the hydrocracking reaction is carried out at a temperature of 330–400°C, a pressure of 8.0–19.0 ​​MPa, and a volume hourly space velocity of 1.0–4.0 h⁻¹. -1The hydrogen-to-oil volume ratio is (500–1500):1. The process parameters for hydrocracking include, but are not limited to, the above range. Limiting them within this range facilitates further cracking of large molecules in the refined heavy oil into smaller molecules, allowing some residual aromatic components to be further converted into saturated hydrocarbons, thereby improving the low-temperature fluidity of the subsequently produced coal-based power fuel. Specifically, the reaction temperature for hydrocracking can be 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, or any two of the above values; the reaction pressure for hydrocracking can be 8.0 MPa, 9.0 MPa, 10.0 MPa, 11.0 MPa, 12.0 MPa, 13.0 MPa, 14.0 MPa, 15.0 MPa, 16.0 MPa, 17.0 MPa, 18.0 MPa, 19.0 MPa, or any two of the above values; and the volume hourly space velocity (VHSV) can be 1.0 h⁻¹. -1 1.5h -1 2.0h -1 2.5h -1 3.0h -1 3.5h -1 4.0h -1 The hydrogen-to-oil volume ratio can be 500:1, 600:1, 700:1, 800:1, 850:1, 900:1, 950:1, 1000:1, 1100:1, 1200:1, 1300:1, 1400:1, 1500:1, or any two of the above values.

[0051] In a preferred embodiment, the hydrocracking reaction is carried out at a temperature of 350–380°C, a pressure of 10.0–15.0 MPa, and a volume hourly space velocity (VHSV) of 2.0–3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (800-1000):1. The process parameters for hydrocracking include, but are not limited to, the above range. Limiting them to the above range is beneficial to improving the conversion efficiency of large molecules in refined heavy oil into small molecules, allowing some of the remaining aromatic components to be further converted into saturated hydrocarbons, thereby improving the low-temperature fluidity of the subsequently produced coal-based power fuel.

[0052] In order to improve the efficiency of cracking large molecules into small molecules in refined heavy oil, and at the same time to improve the efficiency of converting aromatics into saturated hydrocarbons, in a preferred embodiment, the catalyst used in the hydrocracking reaction is a supported hydrocracking catalyst, including a second support and a second active metal oxide; the second support includes, but is not limited to, molecular sieves or alumina, and the metal element in the second active metal oxide includes, but is not limited to, one or more of Group VIB and Group VIII.

[0053] To improve the efficiency of cracking large molecules into smaller molecules in refined heavy oil, and simultaneously to improve the efficiency of converting aromatics into saturated hydrocarbons, in a preferred embodiment, the second support is a molecular sieve, and the weight percentage of the molecular sieve is 10–40 wt%; the molecular sieve includes, but is not limited to, one or more of USY-type, β-type, and SAPO-type. Here, the weight percentage of the molecular sieve refers to the mass proportion of the molecular sieve in the catalyst used in the hydrocracking reaction.

[0054] To further improve the efficiency of large-molecule cracking into smaller molecules in refined heavy oil, and to further improve the efficiency of aromatic hydrocarbon conversion into saturated hydrocarbons, in a preferred embodiment, the metal element in the second active metal oxide includes, but is not limited to, one or more elements from Group VIB, and the second active metal oxide accounts for 0.5–30 wt% of the weight of the supported hydrocracking catalyst; or, the metal element in the second active metal oxide includes, but is not limited to, one or more elements from Group VIII, and the second active metal oxide accounts for 1–5 wt% of the weight of the supported hydrocracking catalyst. The weight percentage of the second active metal oxide refers to the mass percentage of the second active metal oxide in the catalyst used in the hydrocracking reaction.

[0055] To further improve the efficiency of cracking large molecules into smaller molecules in refined heavy oil, and to further improve the efficiency of converting aromatics into saturated hydrocarbons, preferably, the metal element in the second active metal oxide includes, but is not limited to, one or more of Mo, W, Co and Ni.

[0056] A third aspect of this application also provides a preparation system for the aforementioned coal-based power fuel suitable for piston engines, such as... Figure 1As shown, the preparation system includes: a coal direct liquefaction reactor 10, a first cutting device 20, a hydrorefining reactor 30, a second cutting device 40, a hydrocracking reactor 50, a first mixing device 60, a third cutting device 70, a fourth cutting device 80, and a second mixing device 90. The coal direct liquefaction reactor 10 is used to directly liquefy coal and hydrogen in a coal-oil slurry to obtain coal direct liquefaction products; the coal direct liquefaction reactor 10 is provided with a coal-oil slurry inlet 11, a hydrogen inlet, and a coal direct liquefaction product outlet; the first cutting device 20 is used to perform a first cutting of the coal direct liquefaction product to obtain light distillate oil and heavy distillate oil; the first cutting device 20 is provided with a coal direct liquefaction product inlet, a light distillate oil outlet, and a heavy distillate oil outlet, with the coal direct liquefaction product inlet and the coal direct liquefaction product outlet connected; the hydrorefining reactor 30... The device is used for hydrorefining light distillate oil to obtain hydrorefined products. The hydrorefining reactor 30 is equipped with a hydrogen inlet, a light distillate oil inlet, and a hydrorefined product outlet; the light distillate oil inlet and outlet are connected. A second cutting device 40 is used to perform a second cutting of the hydrorefined products to obtain refined light oil and refined heavy oil; the second cutting device 40 is equipped with a hydrorefined product inlet, a refined light oil outlet, and a refined heavy oil outlet; the hydrorefined product inlet and outlet are connected. A hydrocracking reactor 50 is used for further hydrocracking of the refined light oil and heavy oil. Heavy oil is subjected to hydrocracking to obtain hydrocracking products; the hydrocracking reactor 50 is equipped with a refined heavy oil inlet 51 and a hydrocracking product outlet; the refined heavy oil inlet 51 is connected to the refined light oil outlet; a first mixing device 60 is used to mix the hydrocracking products with the refined light oil to obtain a mixture; the first mixing device 60 is equipped with a hydrocracking product inlet, a refined light oil inlet, and a mixture outlet; the hydrocracking product inlet is connected to the hydrocracking product outlet; the refined light oil inlet is connected to the refined light oil outlet; a third cutting device 70 is used to perform a third cutting of the mixture. The process involves cutting coal to obtain direct coal liquefaction oil; a third cutting device 70 is equipped with a mixture inlet and a direct coal liquefaction oil outlet; the mixture inlet and the mixture outlet are connected; a fourth cutting device 80 is used to perform a fourth cutting of indirect coal liquefaction diesel to obtain indirect coal liquefaction oil; the fourth cutting device 80 is equipped with an indirect coal liquefaction diesel inlet and an indirect coal liquefaction oil outlet; a second mixing device 90 is used to mix direct coal liquefaction oil and indirect coal liquefaction oil to obtain coal-based power fuel; the second mixing device 90 is equipped with a direct coal liquefaction oil inlet, an indirect coal liquefaction oil inlet, and a coal-based power fuel outlet.

[0057] The aforementioned preparation system can produce the coal-based power fuel with the specific distillation range and composition provided in this application. The coal-based power fuel provided in this application possesses advantages such as high energy density, suitable kinematic viscosity, high safety performance, and good low-temperature fluidity. Its application in the field of unmanned aerial vehicles (UAVs) can improve the endurance and payload capacity of UAVs, meeting the needs of complex operations such as long-distance patrol and monitoring, and cross-regional cargo transportation, significantly expanding the operational radius and application boundaries of UAVs. Simultaneously, it can significantly improve the adaptability and safety of the fuel under extreme operating conditions, enhance operational safety and stability, reduce the incidence of UAV operational accidents, and provide core safety guarantees for large-scale promotion.

[0058] In a preferred embodiment, such as Figure 1 As shown, the preparation system provided in this application further includes: a hydrogenation reactor 100, used for hydrogenating heavy distillate oil to obtain recovered solvent oil; the hydrogenation reactor 100 is provided with a heavy distillate oil inlet and a recovered solvent oil outlet 101; wherein, the heavy distillate oil inlet and the heavy distillate oil outlet are connected; the recovered solvent oil outlet 101 is connected to the coal-oil slurry inlet 11. Using the above method can obtain recovered solvent oil, which is beneficial to improving the utilization rate of heavy distillate oil, reducing preparation costs, and also facilitates the preparation of coal-oil slurry, making subsequent direct coal liquefaction reactions easier.

[0059] In a preferred embodiment, such as Figure 1 As shown, the third cutting device 70 is also equipped with a cracked heavy oil outlet 71, which is connected to the refined heavy oil inlet 51. Cracking heavy oil has a relatively heavy fraction, high viscosity, and poor low-temperature fluidity. To improve the utilization rate of cracked heavy oil, it is mixed with refined heavy oil and then fed into the hydrocracking reactor 50 for hydrocracking reaction, which can yield the target fraction product.

[0060] In a preferred embodiment, the hydrorefining reactor 30 is internally packed with a catalyst, including but not limited to a supported hydrorefining catalyst, comprising a first support and a first active metal oxide; the first support includes but is not limited to amorphous alumina or aluminum silicate, and the first active metal oxide includes but is not limited to one or more metals from Group VIB and / or Group VIII. Using the aforementioned types of first supports and first active metal oxides is beneficial for improving the efficiency of the hydrorefining reaction; it also helps to increase the removal rate of heteroatoms from light distillate oils and the yield of aromatics converted to saturated hydrocarbons in light distillate oils.

[0061] In a preferred embodiment, the hydrocracking reactor 50 is internally packed with a catalyst, including but not limited to supported hydrocracking catalysts, comprising a second support and a second active metal oxide; the second support includes but is not limited to molecular sieves or alumina, and the second active metal oxide includes but is not limited to one or more metals from Group VIB and Group VIII. Using the aforementioned types of second supports and second active metal oxides is beneficial for improving the efficiency of cracking large molecules into smaller molecules in refined heavy oil, and also for improving the efficiency of converting aromatics into saturated hydrocarbons.

[0062] The fourth aspect of this application also provides an application of the coal-based power fuel provided above for piston engines in the field of unmanned aerial vehicles (UAVs). The coal-based power fuel provided above possesses the advantages of high energy density, suitable kinematic viscosity, high safety performance, and good low-temperature fluidity. Its application in the UAV field can improve the UAV's range and payload capacity, meeting the needs of complex operations such as long-distance patrol and monitoring, and cross-regional cargo transportation, significantly expanding the UAV's operating radius and application boundaries. Simultaneously, it can also significantly improve the fuel's adaptability and safety under extreme operating conditions, enhancing operational safety and stability, reducing the incidence of UAV operational accidents, and providing core safety guarantees for large-scale promotion.

[0063] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0064] It should be noted that in this application, "catalyst loading amount" refers to the percentage of the catalyst volume to the internal volume of the device.

[0065] Example 1

[0066] A method for preparing a coal-based power fuel suitable for piston engines, employing methods such as... Figure 1 The preparation system shown is used for preparation, and the specific steps include:

[0067] (1) Coal and starting solvent oil are mixed to obtain coal-oil slurry. The coal-oil slurry and hydrogen are introduced into the coal direct liquefaction reactor 10 so that the coal in the coal-oil slurry and hydrogen can undergo a direct coal liquefaction reaction to obtain the coal direct liquefaction product. The starting solvent oil is a hydrogenated fractionation product of decrystalline anthracene oil and wash oil with a mass ratio of 1:1.

[0068] (2) The coal direct liquefaction product obtained in step (1) is first cut using the first cutting device 20 to obtain light distillate oil (fraction ≤280℃) and heavy distillate oil (fraction >280℃).

[0069] The heavy distillate oil is hydrogenated using a hydrogenation reactor 100 to obtain recovered solvent oil; the recovered solvent oil is then returned to the coal direct liquefaction reactor 10.

[0070] (3) The light distillate oil obtained in step (2) is subjected to a hydrorefining reaction in hydrorefining reactor 30 to obtain hydrorefining reaction product; wherein the reaction temperature of the hydrorefining reaction is 360℃, the reaction pressure is 12.0MPa, and the volume hourly space velocity is 1.5h. -1 The hydrogen-to-oil volume ratio is 800:1; the hydrorefining reactor 30 is filled with a supported hydrorefining catalyst, including a first support Al2O3 and first active metal oxides NiO and MoO3, wherein the NiO content is 4wt%, the MoO3 content is 20wt%, and the loading amount is 88 vol%.

[0071] The hydrorefining reaction product is further cut using a second cutting device 40 to obtain refined light oil (fraction ≤180℃) and refined heavy oil (fraction >180℃).

[0072] (4) The refined heavy oil was subjected to hydrocracking reaction in a hydrocracking reactor 50 to obtain hydrocracking products; wherein the reaction temperature of the hydrocracking reaction was 370℃, the reaction pressure was 15.0MPa, and the volume hourly space velocity was 2.0h. -1 The hydrogen-to-oil volume ratio is 1000:1; the hydrocracking reactor 50 is loaded with a supported hydrocracking catalyst, including a second support USY-type molecular sieve and Al2O3 (mass ratio of the two is 3:7), and second active metal oxides NiO and WO3, wherein the NiO content is 3.5wt%, the WO3 content is 25wt%, and the loading amount is 75vol%.

[0073] (5) The hydrocracking reaction product obtained in step (4) is mixed with the refined light oil obtained in step (3) in the first mixing device 60 to obtain a mixture.

[0074] (6) The mixture obtained in step (5) is cut by the third cutting device 70 to obtain a fraction (coal direct liquefaction oil) and cracked heavy oil with a distillation range of 145-220℃; the cracked heavy oil is returned to the hydrocracking reactor 50 for hydrocracking reaction.

[0075] (7) The fourth cutting device 80 is used to perform the fourth cutting of coal-to-liquid diesel oil to obtain a fraction with a distillation range of 150-250℃, which is coal-to-liquid oil.

[0076] (8) The direct coal liquefaction oil obtained in step (6) and the indirect coal liquefaction oil obtained in step (7) are mixed using a second mixing device 90, with a weight ratio of 90:10, to obtain coal-based power fuel.

[0077] By weight percentage, this coal-based power fuel comprises 90 wt% direct coal liquefaction oil and 10 wt% indirect coal liquefaction oil. The aromatics content in this coal-based power fuel is 2.0 wt%.

[0078] Examples 2 to 6

[0079] The difference from Example 1 is that the reaction process conditions were changed, as detailed in Table 1.

[0080] Table 1

[0081]

[0082] Example 7

[0083] The difference from Example 5 is that the weight ratio of direct coal liquefaction oil to indirect coal liquefaction oil is 99:1, that is, the coal-based power fuel includes 99 wt% direct coal liquefaction oil and 1 wt% indirect coal liquefaction oil. The remaining steps are the same as in Example 5.

[0084] Example 8

[0085] The difference from Example 5 is that the weight ratio of direct coal liquefaction oil to indirect coal liquefaction oil is 50:50, that is, the coal-based power fuel includes 50 wt% direct coal liquefaction oil and 50 wt% indirect coal liquefaction oil. The remaining steps are the same as in Example 5.

[0086] Comparative Example 1

[0087] It uses commercially available petroleum-based gasoline. Its density is low (below 0.775 g / cm³). 3 It has a low energy density (volume calorific value) and a low flash point.

[0088] Comparative Example 2

[0089] It uses petroleum-based No. 3 jet fuel. It has a high content of sulfur, nitrogen, and aromatics.

[0090] Comparative Example 3

[0091] The difference from Example 5 is that the weight ratio of direct coal liquefaction oil to indirect coal liquefaction oil is 5:95, meaning the coal-based power fuel comprises 5 wt% direct coal liquefaction oil and 95 wt% indirect coal liquefaction oil. The remaining steps are the same as in Example 5. Its density is low (below 0.775 g / cm³). 3 It has a lower energy density (volume calorific value) and slightly higher viscosity.

[0092] Performance tests were conducted on the oils used in all embodiments and comparative examples, including:

[0093] (1) Density testing shall be conducted in accordance with GB / T 1884-2000 and GB / T 1885-1998;

[0094] (2) The sulfur content was tested according to SH / T 0689-2000;

[0095] (3) Nitrogen content was tested according to NB / SH / T 0704-2010;

[0096] (4) Kinematic viscosity testing shall be conducted in accordance with GB / T 265-1988;

[0097] (5) The freezing point shall be tested in accordance with SH / T 0770-2005;

[0098] (6) The flash point was tested according to the GB / T 261-2021 method;

[0099] (7) The volumetric calorific value was tested according to GB / T 384-2025;

[0100] (8) The smoke point shall be tested according to the GB / T 382-2025 method;

[0101] (9) The hydrocarbon composition of the distillate was tested according to NB / SH / T 0606-2019;

[0102] (10) The content of gum was tested according to the GB / T 8019-2025 method;

[0103] (11) Thermal stability shall be tested in accordance with GB / T 9169-2023;

[0104] (12) The spray particle size was tested according to GB / T 19077-2024.

[0105] The test results are shown in Tables 2 and 3.

[0106] Table 2

[0107]

[0108] Table 3

[0109]

[0110] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0111] The coal-based power fuel provided in this application uses direct coal liquefaction oil as its main component, which can increase the calorific value generated per unit volume. When applied to the field of UAVs, it can release more energy than traditional fuels under the premise of the same oil phase volume, thereby improving the UAV's range and payload capacity, meeting the complex operational needs of long-distance patrol and monitoring, cross-regional cargo transportation, and significantly expanding the UAV's operating radius and application boundaries. Moreover, compared with traditional aviation kerosene, under the same density conditions, the coal-based power fuel with the specific distillation range and composition provided in this application can achieve a lower kinematic viscosity. The low viscosity characteristic can optimize the fuel atomization effect, allowing for more complete combustion and improving combustion efficiency. Under the same kinematic viscosity conditions, the coal-based power fuel provided in this application has a higher energy density, thereby improving the fuel's energy output efficiency.

[0112] Furthermore, the coal-based power fuel with the specific distillation range and composition provided in this application possesses a low freezing point, enabling it to operate stably in extremely cold environments. It ensures continuous and reliable fuel supply without the need for additional anti-gelling agents, completely resolving core issues such as incomplete combustion and easy solidification / clogging of fuel lines in low-temperature environments caused by the high viscosity of aviation kerosene of the same density. This significantly improves the fuel's adaptability and safety under extreme operating conditions. Moreover, the flash point of the coal-based power fuel provided in this application is significantly higher than that of gasoline (≥40℃), exhibiting extremely low volatility during transportation, storage, and refueling. It is unlikely to form flammable and explosive vapors, effectively avoiding safety hazards such as leaks, fires, and explosions, and meeting the safety management requirements for large-scale applications of medium and large-sized UAVs. Simultaneously, the inherent high thermal stability of direct coal liquefaction oil prevents the fuel from undergoing thermal decomposition and producing carbon deposits or gum under high engine speed and high load conditions, further enhancing safety and stability, reducing the incidence of UAV operation accidents, and providing core safety assurance for large-scale promotion. Furthermore, compared to other ratios, limiting the content of direct coal liquefaction oil and indirect coal liquefaction oil in coal-based power fuel to the above-mentioned range can also improve the smoke point and combustion efficiency of coal-based power fuel.

[0113] The coal direct liquefaction oil described in this application is obtained by sequentially reacting coal and hydrogen in a coal-oil slurry through a coal direct liquefaction reaction, a hydrorefining reaction, a hydrocracking reaction, and a cutting process. The coal direct liquefaction oil produced by the segmented hydrorefining method exhibits excellent yield, and the coal-based power fuel containing it can effectively balance the two mutually restrictive performance requirements of high energy density and low kinematic viscosity, as well as high flash point and low freezing point.

[0114] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A coal-based power fuel suitable for piston engines, characterized in that, The coal-based power fuel, by weight percentage, comprises: 10-99 wt% direct coal liquefaction oil and 1-90 wt% indirect coal liquefaction oil; The coal direct liquefaction oil is obtained by sequentially reacting coal and hydrogen in a coal-oil slurry through a coal direct liquefaction reaction, a hydrorefining reaction, a hydrocracking reaction, and a cutting process; the coal direct liquefaction oil has a distillation range of T1. min ~T1 max Distillate oil between, T1 min The temperature ranges from 140 to 180℃, and T1 is... max The temperature ranges from 220 to 280℃. The coal-to-liquids oil is obtained by cutting coal-to-liquids diesel oil; the coal-to-liquids oil has a distillation range of T2. min ~T2 max Distillate oil between, T2 min The temperature is 140–160℃, T2 max The temperature ranges from 220 to 280℃.

2. The coal-based power fuel suitable for piston engines according to claim 1, characterized in that, The coal direct liquefaction oil includes C8 to C9. 15 Cycloalkanes, C9-C 16 Straight-chain alkanes and C9-C6 15 Aromatic hydrocarbons; the coal-to-liquid oil includes C8 to C94 hydrocarbons. 15 Cycloalkanes, C9-C 16 Straight-chain alkanes and C9-C6 15 Aromatic hydrocarbons; Preferably, the weight percentage of aromatics in the coal-based power fuel is ≤5wt%.

3. The coal-based power fuel suitable for piston engines according to claim 1 or 2, characterized in that, By weight percentage, the coal-based power fuel comprises: 50-99 wt% of direct coal liquefaction oil and 1-50 wt% of indirect coal liquefaction oil; Preferably, the oil-coal slurry comprises starting solvent oil and coal, wherein the starting solvent oil is selected from the hydrogenation fractionation product of decrystalline anthracene oil and wash oil as raw materials; more preferably, it is the hydrogenation fractionation product of decrystalline anthracene oil and wash oil as raw materials in a mass ratio of 1:

1.

4. A method for preparing a coal-based power fuel suitable for a piston engine according to any one of claims 1 to 3, characterized in that, The preparation method includes: Step S1 involves reacting coal in the coal-oil slurry with hydrogen to undergo a direct coal liquefaction reaction, yielding direct coal liquefaction products. Step S2: The direct coal liquefaction product is first cut to obtain light distillate oil and heavy distillate oil; the light distillate oil is a fraction with a temperature less than or equal to the first cutting temperature, and the heavy distillate oil is a fraction with a temperature greater than the first cutting temperature, wherein the temperature of the first cutting temperature is 300-320℃. Step S3: The light distillate oil is subjected to a hydrorefining reaction, and after a second cut, refined light oil and refined heavy oil are obtained; the refined light oil is a fraction with a temperature less than or equal to the second cut temperature, and the refined heavy oil is a fraction with a temperature greater than the second cut temperature, wherein the temperature of the second cut is 180-220°C. Step S4: The refined heavy oil is subjected to hydrocracking to obtain hydrocracking products; Step S5: Mix the hydrocracking product with the refined light oil to obtain a mixture. Step S6: Perform a third cut on the mixture to obtain direct coal liquefaction oil; the direct coal liquefaction oil has a distillation range of T1. min ~T1 max Distillate oil between, T1 min The temperature ranges from 140 to 180℃, and T1 is... max The temperature ranges from 220 to 280℃. Step S7: Perform a fourth cut on the coal-to-liquid diesel to obtain coal-to-liquid oil; the coal-to-liquid oil has a distillation range of T2. min ~T2 max Distillate oil between, T2 min The temperature is 140–160℃, T2 max The temperature ranges from 220 to 280℃. Step S8: Mix the direct coal liquefaction oil with the indirect coal liquefaction oil to obtain the coal-based power fuel.

5. The method for preparing coal-based power fuel suitable for piston engines according to claim 4, characterized in that, The preparation method further includes: hydrogenating the heavy distillate oil obtained in step S2 to obtain a recovered solvent oil, and returning the recovered solvent oil to step S1; Preferably, step S1 includes: mixing the coal with solvent oil to obtain coal-oil slurry; and reacting the coal-oil slurry with hydrogen to perform a direct coal liquefaction reaction to obtain the direct coal liquefaction product. Preferably, in step S6, cracked heavy oil is also obtained, and the cracked heavy oil is returned to step S4; the cracked heavy oil has a distillation range > T1. max The fraction; Preferably, in step S7, T2 min The temperature is 140–160°C, and the T2 temperature is... max The temperature ranges from 230 to 250℃.

6. The method for preparing coal-based power fuel suitable for piston engines according to claim 4, characterized in that, The hydrogenation refining reaction is carried out at a temperature of 330–390 °C, a pressure of 6.0–19.0 ​​MPa, and a volume hourly space velocity of 0.5–3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (500–1500):1; and / or, The catalyst used in the hydrorefining reaction is a supported hydrorefining catalyst, comprising a first support and a first active metal oxide; the first support is selected from amorphous alumina or aluminum silicate, and the metal element in the first active metal oxide is selected from one or more of Group VIB and / or Group VIII. Preferably, the metal element in the first active metal oxide is selected from non-noble metals in Group VIB, and the first active metal oxide accounts for 0.5 to 30 wt% of the weight of the supported hydrorefining catalyst; or, the metal element in the first active metal oxide is selected from one or more in Group VIII, and the first active metal oxide accounts for 1 to 10 wt% of the weight of the supported hydrorefining catalyst; preferably, the metal element in the first active metal oxide is selected from one or more of Mo, W, Co, and Ni.

7. The method for preparing coal-based power fuel suitable for piston engines according to claim 6, characterized in that, The hydrogenation refining reaction is carried out at a temperature of 340–380 °C, a pressure of 10.0–15.0 MPa, and a volume hourly space velocity of 1.0–2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (800-1000):

1.

8. The method for preparing coal-based power fuel suitable for piston engines according to claim 4, characterized in that, The hydrocracking reaction is carried out at a temperature of 330–400 °C, a pressure of 8.0–19.0 ​​MPa, and a volume hourly space velocity of 1.0–4.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (500–1500):1; and / or, The catalyst used in the hydrocracking reaction is a supported hydrocracking catalyst, comprising a second support and a second active metal oxide; the second support is selected from molecular sieves or alumina, and the metal element in the second active metal oxide is selected from one or more of Group VIB and Group VIII. Preferably, the second support is a molecular sieve, and the molecular sieve has a weight percentage of 10-40 wt%; the molecular sieve is selected from one or more of the USY-type, β-type, and SAPO-type; preferably, the metal element in the second active metal oxide is selected from one or more of Group VIB, and the second active metal oxide accounts for 0.5-30 wt% of the weight of the supported hydrocracking catalyst; or, the metal element in the second active metal oxide is selected from one or more of Group VIII, and the second active metal oxide accounts for 1-5 wt% of the weight of the supported hydrocracking catalyst; preferably, the metal element in the second active metal oxide is selected from one or more of Mo, W, Co, and Ni.

9. The method for preparing coal-based power fuel suitable for piston engines according to claim 8, characterized in that, The hydrocracking reaction is carried out at a temperature of 350–380 °C, a pressure of 10.0–15.0 MPa, and a volume hourly space velocity of 2.0–3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is (800-1000):

1.

10. The application of any one of claims 1 to 3 of a coal-based power fuel suitable for piston engines in the field of unmanned aerial vehicles (UAVs).

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