Method for improving heat absorption performance of hydrocarbon fuel

Abstract

The invention relates to a method for improving the endothermic performance of hydrocarbon fuel, in particular to application of fullerene as a hydrocarbon fuel endothermic reaction accelerant. Aiming at the problems of poor thermal cracking and catalytic cracking selectivity and serious carbon deposit of the hydrocarbon fuel, the invention adopts fullerene as a hydrocarbon fuel endothermic cracking accelerator, and utilizes the special cage structure and superstrong electron-obtaining ability of fullerene to effectively initiate rapid generation of alkyl radicals, so as to improve the thermal cracking efficiency of the hydrocarbon fuel. Therefore, the cracking reaction performance of the hydrocarbon fuel is improved, and the heat absorption capacity of the hydrocarbon fuel in the cracking process is improved. Meanwhile, due to the fact that the fullerene has high density and heat value, the density and heat value of the fuel can be effectively improved by adding the fullerene. Therefore, the application mode provided by the invention has a good application prospect in a hydrocarbon fuel endothermic cracking reaction.

Description

Technical Field

[0001] The invention relates to a method for improving the heat absorption performance of hydrocarbon fuels, in particular to the application of fullerene as a hydrocarbon fuel endothermic reaction promoter, and belongs to the field of aircraft thermal protection. Background Art

[0002] With the development of aviation technology, high-speed aircraft technology with speeds exceeding Mach 5 has become a hot topic in international research. During high-speed flight, the nose, leading edge of the wing and engine of the aircraft will be subjected to very high heat loads. Using heat-absorbing hydrocarbon fuels to actively cool high heat flux parts is an effective way to solve this problem.

[0003] The heat absorption capacity of hydrocarbon fuels mainly comes from temperature rise, phase change and chemical reaction heat absorption. Chemical reaction heat absorption is mainly provided by two endothermic reactions: cracking and reforming. The cracking reaction of the fuel is often accompanied by the formation of coking and carbon deposits, which inhibits the heat absorption performance and even causes blockage of channels, nozzles and other parts. In order to enable the aircraft to reach a higher flight speed and ensure flight safety, it is necessary to improve the heat absorption capacity (heat sink) of the fuel during the endothermic cracking process and reduce the generation of carbon deposits. Adding additives to the fuel or using catalysts in the fuel path becomes a necessary means. This requires the additives or catalysts to have high reaction activity, endothermic reaction selectivity and carbon deposit inhibition performance, which places high demands on the additives or catalysts.

[0004] According to the mechanism of the thermal cracking reaction of hydrocarbon fuels, the initiation step in the thermal cracking process of hydrocarbon fuels is the rate-determining step of the whole reaction. The generation of free radicals will promote the premature occurrence of chain cracking reactions, thus facilitating the improvement of the cracking rate and conversion rate. Oil-soluble initiators can be well dissolved in hydrocarbon fuels to form a homogeneous solution, effectively overcoming the disadvantages such as deactivation and regeneration existing in the application of heterogeneous catalysts. Wickham et al. [Journal of Propulsion and Power, 24, 55–63] compared the initiation effects of azo and peroxide initiators on the model fuel n-heptane. The research shows that these initiators have good promoting effects on cracking when the addition amount is 2 wt%, and the product distribution is not significantly affected. Guo Yongsheng et al. [Energy, 2006, 31, 2773–2790] studied the initiation effect of triethylamine on n-heptane. The results show that amine initiators also have good initiation effects and can improve the endothermic capacity of fuels by increasing the cracking degree. Liu Guozhu et al. [Energy Fuels, 2009, 23, 1, 356–365] investigated the effects of three commonly used initiators in the supercritical cracking process of n-dodecane. From the investigation results of the addition amount, as the addition amount increases to 2 wt%, the cracking conversion rate increases significantly. It should be noted that the addition amount of small molecule initiators basically needs to reach 2 wt% or higher when they play an obvious cracking promoting role. This is because the initiation temperature of small molecule initiators is relatively low, and the free radicals generated at this temperature are not sufficient to initiate the cleavage of hydrocarbon fuels.

[0005] Due to the special cage-like structure, super strong electron-withdrawing ability and other special physical and chemical properties of fullerenes, they have good application prospects in many fields such as light, electricity, magnetism, and catalysis. In recent years, as a functional additive for energetic materials, fullerenes have played an important role in improving the combustion performance and thermal safety of energetic materials. Fullerenes and their derivatives show great application potential in the field of energetic materials. However, there is no report on the research of fullerenes as promoters for the endothermic cracking of hydrocarbon fuels.

[0006] As a promoter for the endothermic reaction of hydrocarbon fuels, due to the special cage-like structure and super strong electron-withdrawing ability of fullerenes, they can effectively promote the generation of free radicals in hydrocarbon fuels, thus accelerating the initiation process and promoting the progress of the endothermic cracking reaction, and reducing the cracking reaction temperature.

[0007] Based on the above research status, the present invention provides a method for improving the endothermic performance of hydrocarbon fuels, especially the application of fullerenes as promoters for the endothermic reaction of hydrocarbon fuels. As a promoter for the endothermic reaction of hydrocarbon fuels, due to its special cage-like structure and super strong electron-withdrawing ability, fullerenes can effectively promote the generation of free radicals in hydrocarbon fuels, thus accelerating the initiation process and promoting the progress of the endothermic cracking reaction, and reducing the cracking reaction temperature. Summary of the Invention

[0008] Aiming at the problems of low cracking efficiency, high cracking temperature, poor reaction selectivity and serious carbon deposition in the thermal cracking process of pure hydrocarbon fuels, the present invention provides a method for improving the endothermic performance of hydrocarbon fuels, especially the application of fullerenes as promoters for endothermic reactions of hydrocarbon fuels. This method can effectively improve the endothermic capacity of hydrocarbon fuels, and has the advantages of high endothermic reaction activity, strong endothermic performance, good controllability, and less coking and carbon deposition.

[0009] To achieve the above object, the technical solution of the present invention is as follows:

[0010] A method for improving the endothermic performance of hydrocarbon fuels provided by the present invention, especially the application of fullerenes as promoters for endothermic reactions of hydrocarbon fuels.

[0011] A method for improving the endothermic performance of hydrocarbon fuels provided by the present invention, especially the application of fullerenes as promoters for endothermic reactions of hydrocarbon fuels, wherein the fullerenes include one or more combinations of C20, C60, C70, C76, and C80.

[0012] A method for improving the endothermic performance of hydrocarbon fuels provided by the present invention, especially the application of fullerenes as promoters for endothermic reactions of hydrocarbon fuels, wherein the fullerenes include alkylated fullerenes, and the alkyl group is an alkane, cycloalkane, or aromatic hydrocarbon with 4 to 15 carbon atoms.

[0013] A method for improving the endothermic performance of hydrocarbon fuels provided by the present invention, especially the application of fullerenes as promoters for endothermic reactions of hydrocarbon fuels, wherein the addition amount of the fullerenes is 0.1 - 5 wt% of the hydrocarbon fuel, preferably 0.2 - 4 wt%, and more preferably 0.5 - 3 wt%.

[0014] A method for improving the endothermic performance of hydrocarbon fuels provided by the present invention, especially the application of fullerenes as promoters for endothermic reactions of hydrocarbon fuels. Before the endothermic reaction, an appropriate amount of fullerenes can be added to the hydrocarbon fuel. The hydrocarbon fuel is one or more combinations of the following three types of substances: (a) industrial kerosene fraction; (b) commercial kerosene products such as RP-3, etc.; (c) hydrocarbons with 6 to 20 carbon atoms, including straight-chain alkanes, branched-chain alkanes, cycloalkanes, straight-chain alkenes, branched-chain alkenes, cycloalkenes, aromatic hydrocarbons, and their mixtures.

[0015] A method for improving the endothermic performance of hydrocarbon fuels, especially the application of fullerenes as promoters for the endothermic reaction of hydrocarbon fuels. The flow rate of the mixture of fullerenes and hydrocarbon fuels is 0.1 - 5 g / s, preferably 0.3 - 4 g / s, more preferably 0.5 - 4 g / s; the pressure of the endothermic reaction system is 0.1 - 10 MPa, preferably 0.1 - 8 MPa, more preferably 0.1 - 6 MPa; the temperature of the material at the reactor outlet is 400 - 900 °C, preferably 450 - 880 °C, more preferably 500 - 850 °C.

[0016] The technical solution of the present invention uses fullerenes as promoters for the endothermic cracking of hydrocarbon fuels. Utilizing the special cage-like structure and strong electron-withdrawing ability of fullerenes, it can effectively initiate the rapid generation of alkyl radicals, thereby improving the cracking reaction performance of hydrocarbon fuels and enhancing the endothermic capacity during the cracking process of hydrocarbon fuels. At the same time, due to the relatively high density and calorific value of fullerenes, the addition of fullerenes can effectively increase the density and calorific value of the fuel. Therefore, the application method provided by the present invention has good application prospects in the endothermic cracking reaction of hydrocarbon fuels.

[0017] The advantages of the present invention are as follows: (1) Fullerenes can be well dissolved in hydrocarbon fuels and do not form layers in the fuel, which is beneficial to the design of the heat exchange system; (2) Fullerenes have relatively high calorific value and density, and the addition of fullerenes can increase the density and calorific value of the fuel; (3) The special structure and electron-withdrawing ability of fullerenes can promote the generation of alkyl radicals, promote the cracking reaction, and reduce the cracking reaction temperature. Brief Description of the Drawings

[0018] Figure 1 It is a schematic flow diagram of the fuel cracking reaction evaluation device.

[0019] In the figure: 1 - high-pressure gas, 2 - pressure reducing valve, 3 - mass flowmeter, 4 - fuel storage tank, 5 - high-pressure constant flow pump, 6 - insulator, 7 - reactor, 8 - DC power supply, 9 - condenser, 10 - large-aperture filter, 11, 11’ - small-aperture filters, 12 - back pressure valve, 13 - gas-liquid separator, 14 - tail gas mass flowmeter, 15 - gas product collector, 16 - liquid product collector; T - temperature measurement point, P - pressure measurement point, v - spot welding thermocouple.

[0020] Figure 2 It is a comparison chart of the heat sink test results of Example 1, Example 2, and the comparative example.

[0021] Figure 3 It is a comparison chart of the gas production rate results of Example 1, Example 2, and Comparative Example 1.

[0022] Figure 4 It is a comparison chart of the heat sink test results of Example 3 and Example 4.

[0023] Figure 5 It is a comparison chart of the heat sink test results of Example 5, Example 6, and Example 7. Detailed implementation manners

[0024] The present invention provides a method for improving the endothermic performance of hydrocarbon fuels, especially the application of fullerenes as promoters for endothermic reactions of hydrocarbon fuels. The main implementation manners are as follows:

[0025] The process of the reaction evaluation device used in the present invention is as Figure 1 shown. The mixture of fullerenes and hydrocarbon fuels is continuously passed through the reactor at a required flow rate by using a metering pump or an external pressure. The reactor is generally a metal tube with an inner diameter of 1-4 mm, a wall thickness of 0.2-2.0 mm, and a length of 50-5000 mm. The wall material of the tube is a heat-resistant metal (including alloys, such as: GH3128).

[0026] Heating electrodes are arranged at both ends of the reactor and are in good contact with the outer wall of the reactor. During the experiment, the reactor is electrified, and the heat required for the reaction is quickly provided through the wall current heating effect. A temperature measuring device is arranged behind the reactor to measure the temperature of the outlet material (oil temperature). A condenser is arranged behind the temperature measuring device to quickly cool the material after the reaction. A back pressure device is arranged behind the condenser to maintain the pressure required for the reaction. Since part of the material is vaporized due to the reaction in the reactor, a gas-liquid separation device is arranged at an appropriate position to separate the gas-liquid two phases and measure and analyze them separately.

[0027] The endothermic capacity of the hydrocarbon fuel at different outlet oil temperatures is obtained by calculating the difference between the heating electric power consumed in this process and the natural heat dissipation power. The reaction performance (gas production rate, product selectivity, etc.) at this oil temperature is obtained by quantitative analysis of the collected gas-liquid products.

[0028] The following examples will further illustrate the present invention, but do not limit the present invention accordingly.

[0029] Example 1: Taking No. 3 jet fuel as the hydrocarbon fuel, adding 2 wt% of fullerene C60 to it as an endothermic reaction promoter. Using a GH3128 tube with an inner diameter of 2 mm, a wall thickness of 0.5 mm, and a length of 800 mm as the reactor, and using a metering pump to pass the No. 3 jet fuel added with fullerene C60 through the reactor at a feed flow rate of 1 g / s, and maintaining the system pressure at 3.5 MPa. Passing an electric current through the reactor wall to provide the heat required for fuel endotherm, controlling an appropriate heating power to obtain a stable outlet oil temperature, taking samples of the gas-liquid products for measurement, and increasing the heating power after obtaining sufficient process data to conduct the next temperature point test. When the system pressure shows a sharp rise or large fluctuations, it indicates that more coke has formed in the system, and the experiment is stopped. Finally, calculate the fuel heat sink, pyrolysis gas production rate, product selectivity and other performances corresponding to different outlet oil temperatures according to the heating power, heat dissipation power, gas-liquid product quantity and composition analysis results, and the reaction performance data are listed in Figure 2 、 Figure 3 and Table 1.

[0030] Comparative example: Repeating Example 1, but directly using this type of kerosene as the feedstock (without adding fullerene C60 to it), and the reaction performance data are listed in Figure 2 、 Figure 3 and Table 1.

[0031] Example 2: Repeating Example 1, with the process and conditions the same as those in Example 1, the difference being that the addition amount of fullerene C60 is 3 wt% of the fuel, and the reaction performance data are listed in Figure 2 、 Figure 3 .

[0032] Example 3: Repeating Example 1, with the process and conditions the same as those in Example 1, the difference being that the addition amount of fullerene C60 is 0.1 wt% of the fuel, the fuel feed flow rate is 0.1 g / s, and the reaction pressure is 0.1 MPa, and the reaction performance data are listed in Figure 4 .

[0033] Example 4: Repeating Example 1, with the process and conditions the same as those in Example 1, the difference being that the addition amount of fullerene C60 is 5 wt% of the fuel, the feed space velocity is 5 g / s, and the reaction pressure is 10 MPa, and the reaction performance data are listed in Figure 4 .

[0034] Example 5: Repeating Example 1, with the process and conditions the same as those in Example 1, the difference being that using fullerene C70 as the endothermic reaction promoter, and the reaction performance data are also listed in Figure 5 .

[0035] Example 6: Repeat Example 1 with the same process and conditions as in Example 1, except that fullerene C80 is used as the endothermic reaction promoter, and its reaction performance data are also listed in Figure 5 .

[0036] Example 7: Repeat Example 1 with the same process and conditions as in Example 1, except that fullerene C60 alkylated with cyclopentane is used as the endothermic reaction promoter, and its reaction performance data are also listed in Figure 5 .

[0037] From Figure 2 , Figure 3 it can be seen that, compared with using no additives (Comparative Example 1), when using fullerenes as the cracking promoter for hydrocarbon fuels, the cracking performance of the fuel has changed significantly. From Figure 2 it can be seen that when fullerene C60 is not added, the heat sink curve of No. 3 jet fuel is at the bottom of the three lines, and its endothermic performance is the worst at the same temperature. The measured highest outlet temperature is 771 °C, and the highest heat sink is only 4.0 MJ / kg. When the content of fullerene C60 is 2 wt%, the fuel heat sink curve is at the top of the three lines, and its endothermic performance is the best at the same temperature. The measured highest outlet temperature is 802 °C, and the highest heat sink reaches 4.5 MJ / kg. When the content of fullerene C60 is further increased to 3 wt%, the endothermic performance of the fuel decreases compared with that when the content of fullerene C60 is 2 wt%, but it is still higher than that of No. 3 jet fuel without adding fullerene C60. The measured highest outlet temperature is 837 °C, and the highest heat sink still reaches 4.5 MJ / kg.

[0038] Figure 3 is the gas production rate (i.e., cracking efficiency) corresponding to different outlet oil temperatures in the fuel cracking experiment. The gas production rate under different fullerene C60 contents has a good corresponding relationship with the change trend of the fuel heat sink. As the temperature increases, the gas production rate of the fuel increases significantly, and the heat sink also increases accordingly. When the fuel outlet temperature is lower than 700 °C, the gas production rate with 2 wt% fullerene C60 content is slightly higher than that with 3 wt% fullerene C60 content; when the temperature is higher than 750 °C, the gas production rate with 3 wt% fullerene C60 content increases rapidly, and the gas production rate reaches 76.9 wt% at 850 °C, and the gas production rate is significantly higher than that of No. 3 jet fuel and that with 2 wt% fullerene C60 content.

[0039] From Figure 4It can be seen that when the addition amount of fullerene C60 is 0.1% wt, there is no obvious promotion effect on the endothermic performance of No. 3 jet fuel. At a feed flow rate of 0.1 g / s, the experiment only ran to 655 °C. When the addition amount of fullerene C60 is 5% wt, the promotion effect on the endothermic performance of No. 3 jet fuel is obvious. At a feed flow rate of 5 g / s, the experiment ran to 900 °C, and the heat sink reached 4.6 MJ / kg.

[0040] It can be seen from Figure 5 that when 2% wt of fullerene C70, fullerene C80, and cyclopentane-alkylated fullerene C60 are respectively added to No. 3 jet fuel, the calorific value of the fuel is significantly increased, and the operating temperature is significantly increased.

[0041] Based on Figures 2 to 5 the reaction results, it can be known that the fullerene additive plays an obvious role in improving the endothermic ability of the fuel, improving the reaction selectivity, inhibiting carbon deposition, and increasing the fuel use temperature. The method for improving the endothermic performance of hydrocarbon fuels provided by the present invention mainly has the following advantages: (1) Fullerene can be well dissolved in hydrocarbon fuels and does not stratify in the fuel, which is beneficial to the design of the heat exchange system; (2) Fullerene has a high calorific value and density, and the addition of fullerene can increase the density and calorific value of the fuel; (3) The special structure and electron-withdrawing ability of fullerene can promote the generation of alkyl free radicals, promote the cracking reaction, and reduce the cracking reaction temperature.

[0042] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes can be made to the present invention. Any modifications, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for improving the endothermic performance of hydrocarbon fuels, characterized in that: Fullerenes are added to hydrocarbon fuels as promoters for endothermic reactions of hydrocarbon fuels.

2. The method according to claim 1, characterized in that: The fullerenes include one or more combinations of C20, C60, C70, C76, and C80 fullerenes.

3. The method according to claim 1 or 2, characterized in that: The fullerenes include alkylated fullerenes, and the alkyl group is one or more of alkanes with 4 to 15 carbon atoms, cycloalkanes with 4 to 15 carbon atoms, and aromatic hydrocarbons with 6 to 15 carbon atoms.

4. The method according to claim 1, characterized in that: The addition amount of fullerenes is 0.1-5 wt% of the hydrocarbon fuel, preferably 0.2-4 wt%, and more preferably 0.5-3 wt%.

5. The method according to claim 1, characterized in that: The hydrocarbon fuel is one or more combinations of the following three types of substances: (a) industrial kerosene fractions; (b) commercial kerosene products such as RP-3; (c) hydrocarbons with 6 to 20 carbon atoms, including one or more of straight-chain alkanes, branched-chain alkanes, cycloalkanes, straight-chain alkenes, branched-chain alkenes, cycloalkenes, aromatic hydrocarbons, and their mixtures.

6. The method according to claim 1, characterized in that: During the reaction process, the feed flow rate of the mixture of fullerenes and hydrocarbon fuel is 0.1-5 g / s, the system pressure is 0.1-10 MPa, and the temperature of the reactor outlet material is 400-900 °C.

7. The method according to claim 6, characterized in that: The reactor is a metal tube with an inner diameter of 1-4 mm, a wall thickness of 0.2-2.0 mm, and a length of 50-5000 mm. The wall material of the tube is heat-resistant metal (including alloys, such as: GH3128).

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