High-calorific-value stable combustion bio-blended fuel and preparation method thereof

Abstract

The present application relates to the technical field of biofuel preparation, and discloses a high-calorific-value stable-combustion bio-blended fuel and a preparation method thereof, which comprises polar ester components, straight-chain alkane components, branched-chain alkane components and halogenated alkane components in a proportion by weight. The preparation method adopts a step-by-step temperature control feeding combined with a stage speed regulation shearing process, heats and melts high-carbon straight-chain alkane to form a liquid-phase matrix, adds isomeric alkane at a high temperature and improves the double-layer stirring speed for mechanical shearing and dispersion, slowly drops the halogenated alkane components and mixes the polar ester components after constant temperature and cooling. Through the synergistic cooperation of multiple categories of hydrocarbons and oxygen-containing compounds, the branched-chain structure steric hindrance is used to interfere with the formation of macromolecular wax crystal network, and the halogenated component is dissociated to control the chain reaction rate. The present application takes into account the high-calorific-value output and stable combustion, suppresses the cylinder knock, improves the low-temperature flow performance of the fuel, and generates a homogeneous transparent liquid.

Description

Technical Field

[0001] This invention relates to the field of biofuel preparation technology, specifically to a high-calorific-value, stable-combustion bio-blended fuel and its preparation method. Background Technology

[0002] The consumption of traditional fossil fuels leads to environmental problems, making the search for renewable alternatives a key research focus. Bio-based fuels are widely available, have low carbon emissions, and are widely used in internal combustion engine power systems. Internal combustion engines dominate long-distance transportation and heavy machinery, placing high demands on fuel energy density and combustion stability.

[0003] Existing bio-based fuels generally suffer from low volumetric calorific value, resulting in insufficient engine power output. To improve calorific value, the proportion of straight-chain alkanes is usually increased. Straight-chain alkanes have a low hydrocarbon mass ratio and release a high amount of heat during combustion, which can compensate for the deficiency in basic calorific value by increasing their proportion. However, straight-chain macromolecules lack branching structures, have a single carbon-carbon bond activation energy, a short ignition delay, and a fast combustion chain reaction rate. This can easily cause excessively high instantaneous pressure rise in the cylinder, leading to knocking and affecting the smooth operation and lifespan of the engine. At the same time, high content of straight-chain macromolecular hydrocarbons is prone to regular arrangement and formation of a dense wax crystal network at low temperatures. The crystallization of macromolecules directly leads to an increase in fuel pour point, resulting in poor low-temperature fluidity. During storage and transportation in cold winter regions, fuel viscosity is prone to a sharp increase. Increased viscosity hinders fuel transmission in the pumping system, leading to poor fuel supply or even engine stalling.

[0004] Furthermore, to comprehensively regulate physicochemical properties, it is usually necessary to blend various additives with different structures into the fuel system. Adding polar esters can improve oxygen supply and lubrication performance; however, there is significant interfacial tension between polar molecules and the non-polar hydrocarbon skeleton, resulting in poor compatibility. Different types of components have different boiling points and mutual solubilities. Conventional simple stirring and mixing processes, relying on a single rotation speed at room temperature, cannot completely break down intermolecular agglomerates, easily leading to micro-phase separation. After prolonged settling, differences in physical density cause liquid phase stratification in the unevenly mixed system, with increased concentration of heavy components at the bottom and aggregation of light components at the surface. This also disrupts the overall consistency of fuel performance, leading to coking of the fuel injectors and carbon deposits inside the combustion chamber. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-calorific-value, stable-combustion bio-blended fuel and its preparation method, solving the problems of low volumetric calorific value, violent combustion process that easily leads to detonation, poor fluidity due to macromolecular crystallization at low temperatures, and poor compatibility of multiple substances resulting in liquid phase stratification in existing bio-based fuels.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a high-calorific-value, stable-combustion bio-blended fuel, employing the following technical solution: A high-calorific-value, stable-combustion bio-blended fuel, comprising the following components in parts by weight: The polar ester components include 6.00–7.62 parts of methyl palmitate, 0.38–0.52 parts of methyl octadecanoate-9,12-dienoate, and 0.74–1.02 parts of methyl cis-11-octadecenoate. The straight-chain alkane components include 2.90–3.30 parts of tetradecane, 2.80–3.10 parts of n-pentadecane, and 18.25–18.65 parts of n-nonadecane; The branched-chain alkane components include 0.14–0.20 parts of 2-methylundecane, 0.12–0.18 parts of 3-methylundecane, 0.36–0.50 parts of 3,6-dimethyldecane, 0.33–0.47 parts of 3,7-dimethyldecane, 0.56–0.74 parts of 3,8-dimethylundecane, 0.57–0.79 parts of 3,8-dimethyldecane, 7.80–8.20 parts of 10-methyleicosane, 3.25–3.55 parts of 2,5-dimethyldodecane, 3.10–3.60 parts of 5-methyltridecane, and 3.59–4.01 parts of 4-methyltridecane. 3-Methyl-5-propylnonane 0.95–1.35 parts, 3-methyl-tetradecane 7.89–8.61 parts, 6-methylundecane 1.69–2.21 parts, 2,5-dimethyldecane 3.87–4.53 parts, 2,2,4,4,6,8,8-heptamethylnonane 2.56–3.14 parts, 5-methyl-tetradecane 5.50–6.20 parts, 7-methylheptadecane 1.70–2.00 parts, 4-methyltetradecane 3.74–4.16 parts, 2,5-dimethyltetrazane 5.14–5.46 parts, 2-methyltetradecane 3.00–3.40 parts; The haloalkane component includes 6.96 to 7.44 parts of 2-bromododecane.

[0007] By adopting the above technical solution, a mixed system is constructed from multiple types of hydrocarbons and oxygen-containing compounds. Straight-chain alkanes, due to their low carbon-to-hydrogen mass ratio, release more heat during combustion, which is beneficial to increasing the basic calorific value of the system and improving the ignition delay period. The branched structure of isomers easily breaks the regular arrangement between chains, increasing the free space of molecules and thus interfering with the formation of wax crystal networks in straight-chain alkanes at low temperatures. This can reduce the fuel pour point and cold filter plugging point to a certain extent while maintaining the carbon content. During the combustion stage, due to steric hindrance, the activation energy for carbon bond breaking of branched molecules differs from that of straight-chain molecules, resulting in a relatively slower chain reaction rate and suppressing the tendency for cylinder knocking. The oxygen-containing properties introduced by the polar groups of esters help improve the local oxygen supply environment, promote the oxidation reaction of hydrocarbons, and reduce the generation of soot caused by oxygen deficiency. The polar groups also easily adhere to the metal surface to form a boundary lubrication film, which compensates for the insufficient lubricity of the pure hydrocarbon system. The bromine atom at the end of 2-bromododecane dissociates in the early stage of heating to generate bromine free radicals, which combine with the highly active free radicals generated by combustion. By consuming the chain carrier, they control the chain reaction proliferation rate, making the heat release relatively uniform and reducing the probability of the formation of local high-temperature zones.

[0008] Preferably, the bio-blended fuel is in a completely transparent, homogeneous liquid state without any molecular aggregates.

[0009] By employing the above technical solutions, relying on intermolecular solvent effects and van der Waals forces, polar esters, nonpolar alkanes, and haloalkanes are fused within the system, making microscopic phase separation less likely. The continuous boiling point distribution and different solubility levels interfere with the crystallization tendency of high-melting-point components, ensuring relatively consistent physicochemical properties of the fuel during storage and pumping, thus helping to prevent injector coking and fluctuations in operating conditions.

[0010] Preferably, the 2-bromododecane in the component is obtained by the following preparation method: 2-Dodecyl alcohol and a 48 wt% aqueous solution of hydrobromic acid were added to a reactor equipped with a stirrer, thermometer and reflux condenser. Stirring was started to ensure that the materials in the reactor were fully and evenly mixed. The molar ratio of 2-dodecyl alcohol to pure hydrobromic acid was controlled to be 1:1.1 to 1:1.5. Keep the material in the reactor under constant stirring, and slowly add concentrated sulfuric acid with a mass fraction of 98 wt% into the reactor using a constant pressure dropping funnel. The mass of the concentrated sulfuric acid added is 20 to 30 wt% of the mass of the 2-dodecyl alcohol. During the dropping process, control the temperature in the reactor to be maintained at 20 to 30°C. After the concentrated sulfuric acid is added, the external cooling system is removed, and the reactor is heated by a heating mantle to raise the temperature of the material system inside the reactor to 95-115°C for constant temperature reflux reaction for 3-5 hours. After the reflux reaction is completed, the heating is stopped and the material inside the reactor is allowed to cool down naturally to room temperature. Deionized water is added to the mixture for dilution, and an appropriate amount of n-hexane is added as the extraction solvent. The mixture is stirred and extracted for 10-20 minutes. The mixture is then transferred to a separatory funnel and allowed to stand for separation. The lower aqueous phase waste liquid is discharged, and the upper organic phase is retained. Add a 5 wt% sodium bicarbonate aqueous solution to the organic phase and wash until neutral. After separating the aqueous phase, add anhydrous magnesium sulfate to dry the neutral organic phase. After standing for 2-3 hours, filter to remove the desiccant to obtain a crude mixture containing the n-hexane. The crude product mixture is transferred to a vacuum distillation apparatus to distill off the n-hexane at atmospheric pressure and a lower temperature. The system pressure is then controlled at 10 mmHg, the temperature is increased, and the middle fraction corresponding to the boiling point range is collected.

[0011] By adopting the above technical solution, the 2-dodecyl alcohol hydroxyl group is protonated under acidic conditions to form an easily leaving group. The temperature control of 20 to 30°C reduces local high-temperature points and limits the premature elimination of secondary alcohols to form double-bonded substances. When the temperature is raised and refluxed, bromide ions launch a nucleophilic attack on the protonated alcohol molecule and release water molecules. Sulfuric acid absorbs water, causing the reaction equilibrium to shift towards the formation of haloalkanes. The reactants are washed with water and extracted with n-hexane to separate residual acid. After neutralization with sodium bicarbonate, anhydrous magnesium sulfate is used for dehydration and vacuum distillation to separate the low-boiling-point solvent and high-boiling-point residue. This extraction process reduces the risk of inorganic acid residues corroding subsequent blending and metal pipelines.

[0012] Preferably, when adding deionized water to the mixture for dilution, the volume of deionized water added is 0.5 to 1.5 times the total volume of the reaction solution.

[0013] By adopting the above technical solution, adding an appropriate amount of deionized water to dilute the residual acid solution reduces the viscosity of the aqueous phase and widens the physical density difference between the two phases, which facilitates sedimentation and stratification. A reasonable water volume range can inhibit the carbonization reaction initiated by the acid solution on the extractant, while avoiding excessive waste liquid treatment.

[0014] Secondly, the present invention provides a method for preparing a high-calorific-value, stable-combustion bio-blended fuel, employing the following technical solution: A method for preparing a high-calorific-value, stable-combustion bio-blended fuel includes the following steps: Accurately measured n-nonadecane, n-pentadecane, and tetradecane are fed into a stainless steel reactor equipped with a heating jacket, a double-layer combined stirring paddle, an air-to-air nitrogen protection system, and a condensation reflux device. The reactor jacket heating is turned on, and high-purity nitrogen is continuously introduced into the reactor to replace the air inside. The stirring system is started to continuously perform pre-stirring and mixing. While maintaining stirring and gas phase protection inside the reactor, the metered amounts of 10-methyleicosane, 2,5-dimethyldodecane, 5-methyltridecane, 4-methyl-tridecane, 3-methyl-5-propylnonane, 3-methyl-tetradecane, 5-methyl-tetradecane, 7-methylheptadecane, 4-methyltetradecane, 2,5-dimethyltridecane, and 2-methyltetradecane are slowly added batch by batch into the stainless steel reactor. After the feeding is completed, the heating jacket is adjusted to raise and maintain the temperature of the material system inside the reactor. Under the condition that the temperature of the material inside the reactor is kept stable, metered amounts of 2-methylundecane, 3-methylundecane, 3,6-dimethyldecane, 3,7-dimethyldecane, 3,8-dimethyl-undecane, 3,8-dimethyldecane, 6-methylundecane, 2,5-dimethyldecane, and 2,2,4,4,6,8,8-heptamethylnonane are added to the reactor in batches. After the addition is completed, the speed of the main agitator is increased to perform strong shear dispersion and maintain a stable high-speed homogeneous state. Turn on the cooling water circulation in the jacket of the stainless steel reactor to lower and stabilize the temperature of the material system inside the reactor. While maintaining steady stirring, slowly add 2-bromododecane dropwise into the stainless steel reactor, controlling the feeding rate. Continue to maintain a constant temperature for the materials inside the reactor. Add measured amounts of methyl palmitate, methyl octadecanoate-9,12-dienoate, and methyl cis-11-octadecenoate into the reactor while stirring. Then stop heating, start circulating cooling, and discharge the material after it has naturally cooled to the discharge temperature. After precision filtration, the finished bio-blended fuel is obtained.

[0015] By employing the above technical solution, heating causes high-melting-point, high-carbon, straight-chain alkanes to undergo a phase transition, forming a liquid matrix. Simultaneously, nitrogen is introduced to remove oxygen and prevent oxidation of non-polar hydrocarbons. Adding medium- to long-chain isoalkanes to the heated system enhances the thermal kinetic energy of the isomeric molecules, promoting their penetration into the straight-chain molecular network and blocking crystallization pathways through side-chain steric hindrance. With the addition of short-chain and multi-side-chain branched alkanes, the hydrodynamic shear stress applied by the double-layered combined stirring paddle causes microscopic interweaving of chain segments of different molecular weights, reducing molecular aggregates within the system. To control volatilization, haloalkanes are slowly added dropwise after the system is cooled, followed by the mixing of polar esters while maintaining this low temperature. The solvent effect reduces intermolecular interfacial tension, promoting the miscibility of oxygen-containing substances with the hydrocarbon matrix.

[0016] Preferably, when the jacket heating of the reactor is turned on, the temperature of the material system inside the reactor is 62-68°C; when the stirring system is started to continuously perform pre-stirring and mixing, the speed of the stirrer is 450-550 rpm, and the mixing and homogenization time is 18-22 min.

[0017] By adopting the above technical solution, the initial heating range of 62 to 68°C is slightly higher than the melting point of the straight-chain components, which facilitates the liquefaction of solid materials; combined with a specific rotation speed and homogenization time, it helps the temperature field distribution inside the liquid phase to become more uniform and reduces local condensation.

[0018] Preferably, during the process of raising and maintaining the temperature of the material system inside the reactor, the maintained temperature of the material system inside the reactor is 68–72°C.

[0019] By adopting the above technical solution, the temperature is slightly increased to 68 to 72°C, which not only improves the diffusion coefficient of heterogeneous components, but also helps to prevent the imbalance caused by the gasification of light components.

[0020] Preferably, in the process of increasing the speed of the main stirrer for strong shear dispersion, the speed of the main stirrer is 1800-2200 rpm.

[0021] By adopting the above technical solution, high-speed operation of 1800 to 2200 rpm can generate turbulence, and mechanical shear force acts on the mixture, which helps to break up agglomerates and promote refinement and mutual solubility.

[0022] Preferably, in the process of lowering and stabilizing the temperature of the material system inside the reactor, the temperature of the material system inside the reactor is stabilized at 58–62°C.

[0023] By adopting the above technical solution, the operating temperature is lowered to 58 to 62°C. This condition keeps the fluid at a low viscosity and reduces the saturated vapor pressure of the halogenated components to control volatilization during feeding.

[0024] Preferably, while maintaining a constant temperature for the material inside the vessel, the material temperature is 58–62°C; and when the material is discharged after naturally cooling to the discharge temperature, the discharge temperature is 20–25°C.

[0025] By adopting the above technical solution, maintaining a temperature of 58 to 62°C facilitates the penetration of oxygen-containing polar molecules into the alkane framework. Setting the discharge temperature in the range of 20 to 25°C reduces the risk of oxidation and discoloration of the material upon contact with air, while also minimizing heat loss during canning.

[0026] This invention provides a high-calorific-value, stable-combustion bio-blended fuel and its preparation method. It has the following beneficial effects: 1. This invention combines straight-chain alkanes, branched alkanes, polar esters, and haloalkanes. It utilizes the low C-H ratio of straight-chain alkanes to increase the overall calorific value, combines the activation energy difference caused by steric hindrance of branched alkanes to moderate the chain reaction rate, and introduces 2-bromododecane to dissociate bromine free radicals in the early stage of heating to consume the chain carrier, thereby controlling the chain reaction proliferation rate. Thus, it balances high calorific value output with stable combustion and suppresses the tendency of cylinder knock.

[0027] 2. This invention adds a variety of medium- and long-chain isomers with methyl side chains to the basic carbon skeleton, using the branched structure to disrupt the regular arrangement of molecules and increase the free space between molecules, thus preventing straight-chain alkanes from forming a tight wax crystal network at low temperatures. This reduces the pour point and cold filter plugging point while maintaining the total carbon content of the fuel, thereby improving the flow properties of the fuel at low temperatures.

[0028] 3. This invention employs a step-by-step temperature-controlled feeding process combined with staged speed-regulated shearing to heat and melt straight-chain alkanes to form a liquid matrix. Isoalkanes are added in a heated environment, and the hydrodynamic shear stress of a double-layer combined stirring paddle is used to cause different chain segments to interweave microscopically to eliminate molecular aggregates. Halogenated alkanes and polar esters are added dropwise under a cooling and isothermal state. The interfacial tension is reduced by the intermolecular solvent effect, resulting in a homogeneous and transparent liquid fuel without phase separation. Attached Figure Description

[0029] Figure 1 This is a graph showing the change in sediment content over thermal aging time according to the present invention. Figure 2 This is a characteristic curve of the distillation range of the present invention; Figure 3 This is a comparison diagram of the volumetric lower heating value and kinematic viscosity of the present invention; Figure 4 This is a graph showing the apparent heat release rate of the present invention as a function of crankshaft angle. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing 2-bromododecane, including the following steps: Step 1: Add 2-dodecyl alcohol and a 48wt% aqueous solution of hydrobromic acid to a reactor equipped with a stirrer, thermometer and reflux condenser. The molar ratio of 2-dodecyl alcohol to pure hydrobromic acid is controlled at 1:1.1. Turn on the stirrer and set the stirring speed to 150 rpm to ensure that the materials in the reactor are fully mixed. Step 2: Keep the material in the reactor under constant stirring. Use a constant pressure dropping funnel to slowly add concentrated sulfuric acid with a mass fraction of 98 wt% into the reactor. The mass of the concentrated sulfuric acid added is 20 wt% of the mass of 2-dodecyl alcohol. During the dropping process, strictly control the temperature inside the reactor by using an external ice-water bath to keep it at 20°C to prevent the secondary alcohol from overheating locally under strong acid and causing the elimination and dehydration side reaction. Step 3: After the concentrated sulfuric acid is added, the external cooling system is removed and the heating mantle is used to heat the reactor to raise the temperature of the material system inside the reactor to 95°C. At this temperature, a constant temperature reflux reaction is carried out for 3 hours. During this process, 2-dodecyl alcohol and hydrobromic acid undergo a nucleophilic substitution reaction under the catalysis and water absorption of sulfuric acid to generate 2-bromododecane. Step 4: After the reflux reaction is complete, stop heating and allow the material in the reactor to cool down to room temperature naturally. Add deionized water with a volume of 0.5 times the total volume of the reaction solution to dilute the mixture. Then add an appropriate amount of n-hexane as the extraction solvent and stir for 10 minutes. Transfer the mixture to a separatory funnel and let it stand to separate into layers. Discard the lower aqueous phase waste liquid and retain the upper organic phase. Step 5: Add 5 wt% sodium bicarbonate aqueous solution to the organic phase and wash until neutral. After separating the aqueous phase, add anhydrous magnesium sulfate to dry the neutral organic phase. After standing for 2 hours, filter to remove the desiccant and obtain a crude mixture containing n-hexane. Step 6: Transfer the above mixture to a vacuum distillation apparatus. First, distill off the n-hexane used as the extractant at atmospheric pressure and a lower temperature. Then, control the absolute pressure of the system to 10 mmHg, raise the temperature, and collect the middle fraction in the corresponding boiling point range to obtain purified 2-bromododecane liquid. The purity of the liquid is above 98.0 wt% as determined by gas chromatography.

[0032] Preparation Example 2: This preparation example provides a method for preparing 2-bromododecane, including the following steps: Step 1: Add 2-dodecyl alcohol and a 48wt% aqueous solution of hydrobromic acid to a reactor equipped with a stirrer, thermometer and reflux condenser. The molar ratio of 2-dodecyl alcohol to pure hydrobromic acid is controlled at 1:1.3. Turn on the stirrer and set the stirring speed to 200 rpm to ensure that the materials in the reactor are fully and evenly mixed. Step 2: Keep the material in the reactor under constant stirring. Use a constant pressure dropping funnel to slowly add concentrated sulfuric acid with a mass fraction of 98 wt% into the reactor. The mass of the concentrated sulfuric acid added is 25 wt% of the mass of 2-dodecyl alcohol. During the dropping process, strictly control the temperature inside the reactor through an external cold water bath to keep it at 25°C to prevent the secondary alcohol from overheating locally under strong acid and causing the elimination and dehydration side reaction. Step 3: After the concentrated sulfuric acid is added, the external cooling system is removed and the heating mantle is used to heat the reactor to raise the temperature of the material system inside the reactor to 105°C. At this temperature, a constant temperature reflux reaction is carried out for 4 hours. During this process, 2-dodecyl alcohol and hydrobromic acid undergo a nucleophilic substitution reaction under the catalysis and water absorption of sulfuric acid to generate 2-bromododecane. Step 4: After the reflux reaction is complete, stop heating and allow the material in the reactor to cool down to room temperature naturally. Add an equal volume of deionized water to the mixture for dilution, then add an appropriate amount of n-hexane as the extraction solvent and stir for 15 minutes. Transfer the mixture to a separatory funnel and let it stand to separate into layers. Discard the lower aqueous phase waste liquid and retain the upper organic phase. Step 5: Add 5 wt% sodium bicarbonate aqueous solution to the organic phase and wash until neutral. After separating the aqueous phase, add anhydrous magnesium sulfate to dry the neutral organic phase. After standing for 2 hours, filter to remove the desiccant and obtain a crude mixture containing n-hexane. Step 6: Transfer the above mixture to a vacuum distillation apparatus. First, distill off the n-hexane used as the extractant at atmospheric pressure and a lower temperature. Then, control the absolute pressure of the system to 10 mmHg, raise the temperature, and collect the middle fraction in the corresponding boiling point range to obtain purified 2-bromododecane liquid. The purity of the liquid is above 98.5 wt% as determined by gas chromatography.

[0033] Preparation Example 3: This preparation example provides a method for preparing 2-bromododecane, including the following steps: Step 1: Add 2-dodecyl alcohol and a 48wt% aqueous solution of hydrobromic acid to a reactor equipped with a stirrer, thermometer and reflux condenser. The molar ratio of 2-dodecyl alcohol to pure hydrobromic acid is controlled at 1:1.5. Turn on the stirrer and set the stirring speed to 250 rpm to ensure that the materials in the reactor are fully mixed. Step 2: Keep the material in the reactor under constant stirring. Use a constant pressure dropping funnel to slowly add concentrated sulfuric acid with a mass fraction of 98 wt% into the reactor. The mass of the concentrated sulfuric acid added is 30 wt% of the mass of 2-dodecyl alcohol. During the dropping process, strictly control the temperature inside the reactor through an external water bath to keep it at 30°C to prevent the secondary alcohol from undergoing premature elimination and dehydration side reactions under strong acid and excessively high temperature. Step 3: After the concentrated sulfuric acid is added, the external cooling system is removed and the heating mantle is used to heat the reactor to raise the temperature of the material system inside the reactor to 115°C. At this temperature, a constant temperature reflux reaction is carried out for 5 hours. During this process, 2-dodecyl alcohol and hydrobromic acid undergo a nucleophilic substitution reaction under the strong catalysis and water absorption of sulfuric acid to generate 2-bromododecane. Step 4: After the reflux reaction is complete, stop heating and allow the material in the reactor to cool down to room temperature naturally. Add deionized water with a volume of 1.5 times the total volume of the reaction solution to dilute the mixture. Then add an appropriate amount of n-hexane as the extraction solvent and stir for 20 minutes. Transfer the mixture to a separatory funnel and let it stand to separate into layers. Discard the lower aqueous phase waste liquid and retain the upper organic phase. Step 5: Add a 5 wt% sodium bicarbonate aqueous solution to the organic phase and wash until neutral. After separating the aqueous phase, add anhydrous magnesium sulfate to dry the neutral organic phase. After standing for 3 hours, filter to remove the desiccant and obtain a crude mixture containing n-hexane and a small amount of olefin byproducts. Step Six: Transfer the above mixture to a precision vacuum distillation apparatus. First, distill off n-hexane as the extractant at atmospheric pressure and a lower temperature. Then, control the absolute pressure of the system at 10 mmHg and slowly increase the temperature. First, collect and discard the fore fraction to remove trace amounts of dodecene impurities generated by the side reaction. Finally, collect the middle fraction corresponding to the boiling point range to obtain purified 2-bromododecane liquid. Gas chromatography analysis shows that its purity reaches over 99.0 wt%.

[0034] Examples 1-3: Example 1

[0035] This embodiment provides a bio-blended fuel and its preparation method, wherein the raw materials are weighed according to the following mass proportions: Methyl palmitate 6.00 parts, methyl octadecanoate-9,12-dienoate 0.38 parts, methyl cis-11-octadecenoate 0.74 parts, 2-methylundecane 0.14 parts, 3-methylundecane 0.12 parts, 3,6-dimethyldecane 0.36 parts, 3,7-dimethyldecane 0.33 parts, 3,8-dimethyl-undecane 0.56 parts, 3,8-dimethyldecane 0.57 parts, 10-methyleicosane 7.80 parts, 2,5-dimethyldodecane 3.25 parts, 5-methyltridecane 3.10 parts, 4-methyl-tridecane 3.59 parts. 6.96 parts of 2-bromododecane, 0.95 parts of 3-methyl-5-propylnonane, 7.89 parts of 3-methyltetradecane, 18.25 parts of n-nonadecane, 1.69 parts of 6-methylundecane, 3.87 parts of 2,5-dimethyldecane, 2.56 parts of 2,2,4,4,6,8,8-heptamethylnonane, 5.50 parts of 5-methyltetradecane, 1.70 parts of 7-methylheptadecane, 3.74 parts of 4-methyltetradecane, 5.14 parts of 2,5-dimethyltridecane, 3.00 parts of 2-methyltetradecane, 2.80 parts of n-pentadecane, and 2.90 parts of tetradecane.

[0036] The method for preparing this bio-blended fuel includes the following steps: Step 1: Accurately measure n-nonadecane, n-pentadecane, and tetradecane and feed them into a stainless steel reactor equipped with a heating jacket, a double-layer combined stirring paddle, a gas-connected nitrogen protection system, and a condensation reflux device; turn on the reactor jacket heating and control the temperature of the material system inside the reactor to 62°C, while continuously introducing high-purity nitrogen into the reactor to replace the air inside; start the stirring system and adjust the stirring speed to 450 rpm, continuously pre-stirring and mixing for 18 minutes to ensure that the high-carbon straight-chain alkanes are completely melted and form a homogeneous phase; Step 2: Maintaining the stirring state and gas phase protection in the reactor as described above, slowly add the measured amounts of 10-methyleicosane, 2,5-dimethyldodecane, 5-methyltridecane, 4-methyl-tridecane, 3-methyl-5-propylnonane, 3-methyl-tetradecane, 5-methyl-tetradecane, 7-methylheptadecane, 4-methyltetradecane, 2,5-dimethyltridecane, and 2-methyltetradecane into the stainless steel reactor in batches. After the addition is completed, adjust the heating jacket to raise and maintain the temperature of the material system in the reactor at 68°C, promoting the thermal diffusion of medium and long chain isomers in the matrix. Step 3: Under the condition that the temperature of the material in the reactor is stably maintained at 68℃, add the metered 2-methylundecane, 3-methylundecane, 3,6-dimethyldecane, 3,7-dimethyldecane, 3,8-dimethyldecane, 6-methylundecane, 2,5-dimethyldecane, 3,8-dimethyl-undecane, and 2,2,4,4,6,8,8-heptamethylnonane batch by batch; after the addition is completed, increase the speed of the main stirrer and control the speed to 1800 rpm for strong shear dispersion, maintain the high-speed homogeneous state stably until the system is transformed into a completely transparent homogeneous liquid without molecular aggregates; Step 4: Turn on the cooling circulating water of the stainless steel reactor jacket to lower and stabilize the temperature of the material system inside the reactor at 58°C; while maintaining steady stirring, slowly add 2-bromododecane prepared by the method of Preparation Example 1 into the reactor, controlling the feeding rate to avoid material volatilization caused by excessively high local concentration; Step 5: Continue to maintain the material temperature in the reactor at a constant 58°C. Add the measured amounts of methyl palmitate, methyl octadecanoate-9,12-dienoate, and methyl cis-11-octadecenoate into the reactor. Keep stirring until the polar esters and non-polar alkanes become completely miscible through a multi-stage solvent effect. Then stop heating, start circulating cooling, and discharge the material after it naturally cools to 20°C. After precision filtration, the finished bio-blended fuel is obtained. Example 2

[0037] This embodiment provides a bio-blended fuel and its preparation method, wherein the raw materials are weighed according to the following mass proportions: Methyl palmitate 6.81 parts, methyl octadecanoate-9,12-dienoate 0.45 parts, methyl cis-11-octadecenoate 0.88 parts, 2-methylundecane 0.17 parts, 3-methylundecane 0.15 parts, 3,6-dimethyldecane 0.43 parts, 3,7-dimethyldecane 0.40 parts, 3,8-dimethyl-undecane 0.65 parts, 3,8-dimethyldecane 0.68 parts, 10-methyleicosane 8.00 parts, 2,5-dimethyldodecane 3.40 parts, 5-methyltridecane 3.35 parts, 4-methyl-tridecane 3.80 parts. 7.20 parts of 2-bromododecane, 1.15 parts of 3-methyl-5-propylnonane, 8.25 parts of 3-methyltetradecane, 18.45 parts of n-nonadecane, 1.95 parts of 6-methylundecane, 4.20 parts of 2,5-dimethyldecane, 2.85 parts of 2,2,4,4,6,8,8-heptamethylnonane, 5.85 parts of 5-methyltetradecane, 1.85 parts of 7-methylheptadecane, 3.95 parts of 4-methyltetradecane, 5.30 parts of 2,5-dimethyltridecane, 3.20 parts of 2-methyltetradecane, 2.95 parts of n-pentadecane, and 3.10 parts of tetradecane.

[0038] The method for preparing this bio-blended fuel includes the following steps: Step 1: Accurately measure n-nonadecane, n-pentadecane, and tetradecane and feed them into a stainless steel reactor equipped with a heating jacket, a double-layer combined stirring paddle, a gas-connected nitrogen protection system, and a condensation reflux device; turn on the reactor jacket heating and control the temperature of the material system inside the reactor to 65°C, while continuously introducing high-purity nitrogen into the reactor to replace the air inside; start the stirring system and adjust the stirring speed to 500 rpm, continuously pre-stirring and mixing for 20 minutes to ensure that the high-carbon straight-chain alkanes are completely melted and form a homogeneous phase; Step 2: Maintaining the stirring state and gas phase protection in the reactor as described above, slowly add the measured amounts of 10-methyleicosane, 2,5-dimethyldodecane, 5-methyltridecane, 4-methyl-tridecane, 3-methyl-5-propylnonane, 3-methyl-tetradecane, 5-methyl-tetradecane, 7-methylheptadecane, 4-methyltetradecane, 2,5-dimethyltridecane, and 2-methyltetradecane to the stainless steel reactor in batches. After the addition is completed, adjust the heating jacket to raise and maintain the temperature of the material system in the reactor at 70°C, promoting the thermal diffusion of medium- and long-chain isomers in the matrix. Step 3: Under the condition that the temperature of the material in the reactor is stably maintained at 70℃, add the metered 2-methylundecane, 3-methylundecane, 3,6-dimethyldecane, 3,7-dimethyldecane, 3,8-dimethyldecane, 6-methylundecane, 2,5-dimethyldecane, 3,8-dimethyl-undecane, and 2,2,4,4,6,8,8-heptamethylnonane batch by batch; after the addition is completed, increase the speed of the main stirrer and control the speed to 2000 rpm for strong shear dispersion, maintain the high-speed homogeneous state stably until the system is transformed into a completely transparent homogeneous liquid without molecular aggregates; Step 4: Turn on the cooling circulating water of the stainless steel reactor jacket to lower and stabilize the temperature of the material system inside the reactor at 60°C; while maintaining steady stirring, slowly add 2-bromododecane prepared by the method of Preparation Example 2 into the reactor, controlling the feeding rate to avoid material volatilization caused by excessively high local concentration; Step 5: Continue to maintain the material temperature in the reactor at a constant 60°C. Add the measured amounts of methyl palmitate, methyl octadecanoate-9,12-dienoate, and methyl cis-11-octadecenoate into the reactor. Keep stirring until the polar esters and non-polar alkanes become completely miscible through a multi-stage solvent effect. Then stop heating, start circulating cooling, and discharge the material after it naturally cools to 20°C. After precision filtration, the finished bio-blended fuel is obtained. Example 3

[0039] This embodiment provides a bio-blended fuel and its preparation method, wherein the raw materials are weighed according to the following mass proportions: Methyl palmitate 7.62 parts, methyl octadecanoate-9,12-dienoate 0.52 parts, methyl cis-11-octadecenoate 1.02 parts, 2-methylundecane 0.20 parts, 3-methylundecane 0.18 parts, 3,6-dimethyldecane 0.50 parts, 3,7-dimethyldecane 0.47 parts, 3,8-dimethyl-undecane 0.74 parts, 3,8-dimethyldecane 0.79 parts, 10-methyleicosane 8.20 parts, 2,5-dimethyldodecane 3.55 parts, 5-methyltridecane 3.60 parts, 4-methyl-tridecane 4.01 parts. 7.44 parts of 2-bromododecane, 1.35 parts of 3-methyl-5-propylnonane, 8.61 parts of 3-methyltetradecane, 18.65 parts of n-nonadecane, 2.21 parts of 6-methylundecane, 4.53 parts of 2,5-dimethyldecane, 3.14 parts of 2,2,4,4,6,8,8-heptamethylnonane, 6.20 parts of 5-methyltetradecane, 2.00 parts of 7-methylheptadecane, 4.16 parts of 4-methyltetradecane, 5.46 parts of 2,5-dimethyltridecane, 3.40 parts of 2-methyltetradecane, 3.10 parts of n-pentadecane, and 3.30 parts of tetradecane.

[0040] The method for preparing this bio-blended fuel includes the following steps: Step 1: Accurately measure n-nonadecane, n-pentadecane, and tetradecane and feed them into a stainless steel reactor equipped with a heating jacket, a double-layer combined stirring paddle, a nitrogen protection system with gas connection, and a reflux condenser; turn on the reactor jacket heating and control the temperature of the material system inside the reactor to 68°C, while continuously introducing high-purity nitrogen into the reactor to replace the air inside; start the stirring system and adjust the stirring speed to 550 rpm, continuously pre-stirring and mixing for 22 minutes to ensure that the high-carbon straight-chain alkanes are completely melted and form a homogeneous phase; Step 2: Maintaining the stirring state and gas phase protection in the reactor as described above, slowly add the measured amounts of 10-methyleicosane, 2,5-dimethyldodecane, 5-methyltridecane, 4-methyl-tridecane, 3-methyl-5-propylnonane, 3-methyl-tetradecane, 5-methyl-tetradecane, 7-methylheptadecane, 4-methyltetradecane, 2,5-dimethyltridecane, and 2-methyltetradecane to the stainless steel reactor in batches. After the addition is completed, adjust the heating jacket to raise and maintain the temperature of the material system in the reactor at 72°C, promoting the thermal diffusion of medium- and long-chain isomers in the matrix. Step 3: Under the condition that the temperature of the material in the reactor is stably maintained at 72℃, add the metered 2-methylundecane, 3-methylundecane, 3,6-dimethyldecane, 3,7-dimethyldecane, 3,8-dimethyldecane, 6-methylundecane, 2,5-dimethyldecane, 3,8-dimethyl-undecane, and 2,2,4,4,6,8,8-heptamethylnonane batch by batch; after the addition is completed, increase the speed of the main stirrer and control the speed to 2200 rpm for strong shear dispersion, maintain the high-speed homogeneous state stably until the system is transformed into a completely transparent homogeneous liquid without molecular aggregates; Step 4: Turn on the cooling circulating water of the stainless steel reactor jacket to lower and stabilize the temperature of the material system inside the reactor at 62°C; while maintaining steady stirring, slowly add 2-bromododecane prepared by the method of Preparation Example 3 into the reactor, controlling the feeding rate to avoid material volatilization caused by excessively high local concentration; Step 5: Continue to maintain the material temperature in the reactor at a constant temperature of 62℃, and add the measured methyl palmitate, methyl octadecanoate-9,12-dienoate, and methyl cis-11-octadecenoate into the reactor; keep stirring until the polar esters and non-polar alkanes are completely miscible through multi-stage solvent effects; then stop heating, start circulating cooling, and discharge the material after it naturally drops to 25℃. After precision filtration, the finished bio-blended fuel is obtained.

[0041] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that the high volumetric calorific value unit (2-bromododecane) is missing in the formulation, and the missing 7.20 parts by mass are replaced by tetradecane in equal amounts. All other raw material components, proportions and preparation methods are the same.

[0042] Comparative Example 2: Compared with Example 2, the difference is that the high-carbon straight-chain alkane skeleton (n-nonadecane, n-pentadecane, tetradecane) is missing in the formulation, and the missing total of 24.50 parts by mass is replaced by an equal amount of isomeric alkane components (taking 2-methyltetradecane as an example). All other raw material components, proportions and preparation methods are the same.

[0043] Comparative Example 3: Compared to Example 2, the difference lies in the removal of all isomeric alkane components (2-methylundecane, 3-methylundecane, 3,6-dimethyldecane, 3,7-dimethyldecane, 3,8-dimethyl-undecane, 3,8-dimethyldecane, 6-methylundecane, 2,5-dimethyldecane) used to connect the intermediate distillation range, resulting in the disruption of the continuous distillation range gradient group. The missing 8.63 parts by mass are replaced by tetradecane in equal amounts. All other raw material components, proportions, and preparation methods are the same.

[0044] Comparative Example 4: Compared with Example 2, the difference is that the functional special additive component (2,2,4,4,6,8,8-heptamethylnonane) was removed from the formulation, and the missing 2.85 parts by mass were replaced by tetradecane in equal amounts. All other raw material components, proportions and preparation methods are the same.

[0045] Comparative Example 5: Compared with Example 2, the difference is that the overall compound raw material system of the present invention, which consists of various polar / nonpolar alkanes, esters and special functional components, is completely replaced with an equal mass of existing commercial commodities (commercially available ordinary fatty acid methyl ester biodiesel), while all other performance test conditions are the same.

[0046] Test Examples 1-4: Test Example 1: Characterization Test of Component Miscibility and Chemical Inertness This test example is used to evaluate the homogeneous stability of the bio-blended fuels prepared in each embodiment at the macroscopic level, and to examine whether side reactions occur in each component under compounding and long-term storage conditions at the microscopic molecular scale, thereby examining the actual effect of the physical compounding scheme of the present invention.

[0047] Take 500 mL of each of the finished fuel samples prepared in Examples 1, 2, 3 and Comparative Example 5, and put them into borosilicate glass bottles with polytetrafluoroethylene sealing gaskets as test objects.

[0048] Each group of samples was placed in an ultrasonic cleaner and ultrasonically treated for 15 minutes at 25°C and 40 kHz to eliminate any tiny air bubbles that might remain inside the fluid.

[0049] Quantitatively extract 50 mL from each sample, determine the initial flash point using an automatic micro-closed-cup flash point analyzer, and allow it to stand at room temperature (20-25℃). Measure the initial light transmittance at 600 nm using a spectrophotometer to establish an initial homogeneous reference.

[0050] The remaining fuel samples were divided into three portions and placed in a -10°C low-temperature constant temperature storage box, a 25°C room temperature dark incubator, and a 60°C high-temperature accelerated thermal aging oven for long-term storage. On the 7th, 15th, 30th, 60th and 90th days of storage, their macroscopic phase was observed regularly, and physical inhomogeneities such as turbidity, layering, emulsification or precipitation of crystals were recorded.

[0051] For samples subjected to accelerated thermal aging in a 60℃ high-temperature oven, quantitative sampling was conducted at 72h, 144h, and 288h of aging, and the sediment content (mg / 100mL) was used to characterize the thermal aging stability of the system.

[0052] Samples from each group were extracted after 288 hours of aging and analyzed using a Fourier transform infrared spectroscopy (FTIR) instrument at 4000-400 cm⁻¹. -1 A full-spectrum scan was performed across the wavenumber range to compare changes in characteristic absorption peaks before and after aging, with a focus on monitoring the 560 cm⁻¹ peak. -1 The nearby C-Br bond stretching vibration peak and 1640 cm⁻¹ -1 Does the characteristic peak of the nearby C=C double bond undergo a significant change in intensity or shift in position?

[0053] Simultaneously, samples before and after aging were injected into a gas chromatograph-mass spectrometer (GC-MS), with a split ratio of 50:1. The initial column temperature was set to 50℃ and held for 2 min, then increased to 300℃ at a rate of 10℃ / min and held for 10 min. The relative change rate of peak area of ​​each alkane and ester component in the total ion chromatogram (TIC) was compared semi-quantitatively to check for the presence of new impurity peaks such as dodecene isomers generated due to the elimination reaction of 2-bromododecane.

[0054] It should be noted that in this test example, phase stability observation continued for 90 days; the sediment / filter residue content test at 60℃ was used as a short-cycle accelerated thermal aging evaluation, with a test cycle of 288 hours. These two tests were used to evaluate long-term storage compatibility and high-temperature thermal aging stability, respectively.

[0055] Table 1. Changes in sediment / filter residue content during accelerated thermal aging test at 60℃ Example 1 0.11 0.14 0.18 0.23 Example 2 0.07 0.09 0.13 0.16 Example 3 0.14 0.17 0.22 0.29 Comparative Example 5 0.38 0.94 1.82 3.47 Figure 1 This is a fitting trend graph showing the change of sediment / filter residue content over time during accelerated thermal aging at 60℃ in Examples 1-3 and Comparative Example 5 of the present invention. The scatter points in the graph represent actual sampled test data, and the smooth curves connecting the scatter points are growth trend fitting lines based on the test data. From bottom to top, each curve corresponds to Example 2, Example 1, Example 3, and Comparative Example 5, which serves as a control group for conventional fatty acid methyl ester biodiesel. The slope and extension trend of the curves reflect the sediment formation and evolution of each sample under high-temperature conditions.

[0056] Conclusion: Based on Table 1 and Figure 1Based on the data evolution trend, the bio-blended fuel system provided in this embodiment of the invention exhibits good physical compatibility and chemical stability under accelerated thermal aging conditions at 60℃. After 288 hours of continuous testing in a thermal aging environment at 60℃, Example 2, using a specific formulation, showed a slight increase in sediment / filter residue content from the initial 0.07 mg / 100 mL to 0.16 mg / 100 mL, while maintaining a macroscopically transparent and homogeneous phase without obvious turbidity, stratification, emulsification, or crystal precipitation. In contrast, the conventional fatty acid methyl ester biodiesel (Comparative Example 5), used as a control, showed a significant increase in sediment / filter residue content to 3.47 mg / 100 mL within the same test period, a substantial increase compared to the examples. This suggests that single ester components are relatively prone to oxidative polymerization and condensation deposition under long-term heating conditions.

[0057] The aforementioned performance differences are presumably related to the solvent effect and the interaction mechanism between the components in the compound system. Polar long-chain fatty acid methyl esters (such as methyl palmitate, methyl octadecanoate-9,12-dienoate, etc.) contain some unsaturated double bonds, posing a certain risk of thermal oxidation at high temperatures. The high-carbon straight-chain alkanes introduced in this scheme (such as n-nonadecane, n-pentadecane, and tetradecane, etc.) can form a nonpolar alkane matrix in the system, which to some extent increases the average intermolecular distance between unsaturated ester molecules, thereby reducing their effective collision frequency and the probability of polymerization.

[0058] Analysis of the special additive component 2-bromododecane showed that the FTIR and GC-MS full-spectrum data did not change significantly before and after high-temperature aging. The characteristic peaks attributed to the C-Br bond in Example 2 did not show significant attenuation or shift, and no new characteristic peaks attributed to the dodecene isomer were detected in the system. This indicates that the haloalkane component did not undergo significant elimination reactions under the current compounding system and test temperature, exhibiting a certain degree of thermal aging stability. Its stability is presumably related to its long-chain nonpolar structure and the solvation environment formed by the surrounding continuous alkane phase, which can reduce its effective contact with potentially reactive substances to a certain extent. Furthermore, the addition of 2,2,4,4,6,8,8-heptamethylnonane, as a multi-branched isoalkane, will delay the contact reaction between localized primary free radicals and other reactive intermediates through steric hindrance and dilution effects, thereby helping to maintain the phase and compositional stability of the entire compounding system. In summary, the bio-blended fuel provided by this invention is not merely a simple mechanical blending of the components, but rather a relatively stable physical compound system formed through compatibility matching, solvation effect, and interaction between the components.

[0059] Test Example 2: Continuous Vaporization Relay and Simulated Distillation Range Characteristics Test This test example is used to evaluate the volatility characteristics and distillation range distribution of each sample during the heated evaporation process, to examine the distillation continuity of the multi-component compound system, and to verify the vaporization performance of the formulation under heated conditions.

[0060] 10 mL each of the bio-blended fuels prepared in Examples 1, 2, and 3, as well as Comparative Example 3 (conventional fatty acid methyl ester biodiesel without the addition of multi-level straight-chain alkanes) and Comparative Example 4 (a simple blend of low-carbon alcohol components and fatty acid methyl esters with only mechanical blending) were used as test subjects.

[0061] Referring to the standard test method of SH / T 0558-2016 "Determination of Boiling Range Distribution of Petroleum Fractions by Gas Chromatography", the above-mentioned fuel samples were diluted with carbon disulfide solvent at a mass ratio of 1:10 and then placed into automatic sample bottles for testing.

[0062] A gas chromatograph equipped with a flame ionization detector (FID) and a non-polar cross-linked silicone capillary column was used to determine the simulated distillation range. The injection port temperature was set to 320℃, the detector temperature to 350℃, the carrier gas to be high-purity helium, and the column flow rate to be controlled at a constant linear velocity.

[0063] The column was programmed to run at 35°C for 1 min initially, then linearly heated to 350°C at a rate of 15°C / min, and held at the final temperature for 15 min to promote the complete elution of heavy components.

[0064] Before sample testing, a correction mixture of n-alkanes consisting of C5 to C40 was injected to establish a correlation curve between retention time and boiling point.

[0065] 1 μL of each sample dilution was injected sequentially for chromatographic acquisition, and the FID chromatographic response signal and elution time of each sample were recorded. The cumulative mass fraction of the effluent was calculated by the slice integration method, and the equivalent boiling point data corresponding to the recovery rates of 5%, 10%, 30%, 50%, 70%, 90%, and 95% were derived.

[0066] Table 2. Gas Chromatography Simulated Distillation Range Distribution Data Example 1 162.3 185.1 234.6 268.4 301.2 335.7 348.1 Example 2 158.9 182.4 231.1 264.8 298.5 332.1 345.6 Example 3 165.7 188.2 237.9 272.5 305.8 339.4 352.0 Comparative Example 3 315.2 322.8 330.5 335.6 340.1 348.9 355.2 Comparative Example 4 82.4 85.1 110.2 312.4 320.7 335.6 342.3 Figure 2 These are simulated distillation range characteristic curves of Examples 1-3 and Comparative Examples 3 and 4 of the present invention. The solid lines, dashed lines, and dotted lines containing circular, square, and triangular markings correspond to Examples 1, 2, and 3 of the present invention, respectively; the short dotted lines containing diamond markings and concentrated in the high-temperature region correspond to Example 3; the solid lines containing star markings and exhibiting obvious step changes correspond to Example 4. Each curve shows the trend of fuel boiling point temperature change with increasing volatile recovery rate.

[0067] Conclusion: Based on the data in Table 2, there are certain differences in the boiling point distribution range between the example group and the comparative example group. In Comparative Example 3, the 5% to 95% distillation temperature is concentrated in the range of 315.2℃ to 355.2℃, with the components mainly distributed in the high-temperature range. This concentrated and heavy distillation range characteristic may have a certain impact on the low-temperature atomization and cold start process of fuel in the engine. Although Comparative Example 4 added low-boiling-point substances, when its recovery rate increased from 30% to 50%, the boiling point increased from 110.2℃ to 312.4℃, a large temperature range, indicating a lack of intermediate distillates between the low-boiling-point and high-boiling-point fractions. In actual heated volatilization processes, such mixed systems exhibit a trend of segmented volatilization of light and heavy components, which can adversely affect the continuity of fuel evaporation.

[0068] In contrast, the distillation range data of Examples 1, 2, and 3 of this invention show a relatively wide temperature distribution range, with good continuity between the boiling ranges of each fraction. Taking Example 2 as an example, its 5% distillation temperature is 158.9°C, providing a relatively volatile front-end component for the system, which helps improve the ignition lead process under low-temperature conditions. The subsequent 30%, 50%, and 70% recovery boiling points are distributed at 231.1°C, 264.8°C, and 298.5°C, respectively, with the final 95% distillation temperature reaching 345.6°C. The temperature change is relatively uniform throughout the process, with no obvious temperature stagnation or large jumps observed.

[0069] The above data results indicate that the compound system of this scheme exhibits good vaporization continuity. The low-to-medium boiling point components, such as tetradecane and pentadecane, preferentially volatilize in the initial heating stage. The addition of n-nonadecane and the multi-branched 2,2,4,4,6,8,8-heptamethylnonane, utilizing the differences in carbon chain length and branching structure, complements the mid-range distillation and increases the overlap of boiling points among the components within the system. Test results also show that 2-bromododecane maintains good compatibility with other components during volatilization, without causing significant distillation range deviations or breaks. Long-chain fatty acid methyl esters mainly volatilize gradually in the higher temperature range. By compounding straight-chain and branched alkanes with different carbon numbers, this system constructs a relatively gentle distillation range distribution gradient, which can, to some extent, improve the problem of excessive concentration of fractions in traditional biofuels, enabling them to exhibit relatively uniform and continuous evaporation characteristics under heating conditions.

[0070] Test Example 3: Comparison Test of Fuel Physicochemical Properties and Volumetric Calorific Value Enhancement This test case is used to evaluate the conventional physicochemical properties of each sample as a power fuel, and focuses on the synergistic effect of the multi-component compound system on the lower heating value of the fuel volume, so as to evaluate its energy density and hydrodynamic characteristics in practical applications.

[0071] The bio-blended fuels prepared in Examples 1, 2, and 3, as well as Comparative Examples 3 and 4, were selected as test subjects for routine physicochemical properties and calorific value determination.

[0072] According to GB / T 1884-2000 "Laboratory Determination of Density of Crude Oil and Liquid Petroleum Products (Density Meter Method)", the liquid density of each sample was determined in a constant temperature water bath at 20℃, which served as the basis for subsequent volumetric calorific value conversion.

[0073] According to GB / T 265-1988 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products", a Pintosh kinematic viscometer with an inner diameter that meets the technical requirements was selected, and the kinematic viscosity of each sample was measured in a constant temperature bath at 40℃ to evaluate the flow characteristics of fuel during transportation and injection.

[0074] For samples with a flash point higher than 40℃, the flash point temperature of the sample was determined using an automatic closed-cup flash point apparatus in accordance with GB / T 261-2021 "Determination of Flash Point - Binsky-Martin Closed-Cup Cup Method". For low flash point samples such as Comparative Example 4, the closed-cup flash point method suitable for low flash point liquids was used to evaluate the storage and transportation safety of the compounded components.

[0075] According to GB / T 384-2025 "Determination of Calorific Value of Hydrocarbon Fuels - Oxygen Bomb Calorimeter Method", the mass calorific value of each fuel sample was determined using an oxygen bomb calorimeter, and the lower mass calorific value was calculated according to the standard method.

[0076] By combining the liquid density data measured at 20℃, the volumetric lower heating value of each fuel sample was quantitatively calculated by multiplying the mass lower heating value by the liquid density.

[0077] Table 3. Results of Fuel Physicochemical Properties and Calorific Value Measurement Example 1 0.834 2.86 68.5 42.23 35.22 Example 2 0.831 2.74 63.5 42.45 35.28 Example 3 0.839 2.95 71.0 42.02 35.25 Comparative Example 3 0.882 4.31 172.0 37.56 33.13 Comparative Example 4 0.812 2.12 24.5 36.12 29.33 Figure 3 This is a comparison chart of volumetric lower heating value and kinematic viscosity for Examples 1-3 and Comparative Examples 3 and 4 of the present invention. In the chart, the left vertical axis corresponds to the volumetric lower heating value, the right vertical axis corresponds to the kinematic viscosity at 40°C, and the horizontal axis represents different fuel samples. The left and right vertical axes correspond to different physical quantities and do not indicate that they share the same numerical scale. The solid black line containing circular markers shows the distribution trend of the volumetric lower heating value of each sample, while the dashed gray line containing equilateral triangle markers shows the distribution of the kinematic viscosity of each sample.

[0078] Conclusion: According to the data in Table 3, the test results of the embodiment group and the comparative example group of this invention showed different performance in conventional physicochemical indicators and calorific value. Comparative Example 3, as a conventional fatty acid methyl ester biodiesel without alkane blending, mainly consists of long-chain unsaturated or saturated fatty acid esters, although it showed a value of 0.882 g / cm³.3 Its liquid density is [not specified], but due to its lower mass calorific value of 37.56 MJ / kg, the volumetric lower calorific value is limited to 33.13 MJ / L. Simultaneously, its kinematic viscosity at 40℃ is 4.31 mm². 2 / s. In fuel injection systems, higher kinematic viscosity can negatively impact the atomized droplet size and uniformity of fuel spray. Comparative Example 4, while physically blending lower-carbon alcohols reduced the system viscosity to some extent, resulted in a decrease in both the mass calorific value and volumetric calorific value of the fuel due to the lower energy density of the lower-carbon alcohols. The lower volumetric calorific value dropped to 29.33 MJ / L, and the measured closed-cup flash point was 24.5℃. This result indicates that while simply using physical blending of lighter components can alter viscosity characteristics, it can negatively affect the overall energy density and flash point safety of the fuel.

[0079] In contrast, Examples 1, 2, and 3 of this invention, by introducing multi-level straight-chain alkanes and branched-chain alkanes with specific structures, exhibit a synergistic adjustment trend in various physicochemical properties of the fuel. Taking Example 2 as an example, the liquid density of the sample was maintained at 0.831 g / cm³. 3 Due to the inclusion of high-calorific-value aliphatic hydrocarbon components, its lower mass calorific value reaches 42.45 MJ / kg, which, after conversion, is 35.28 MJ / L, showing a certain degree of improvement compared to Comparative Examples 3 and 4. This result indicates that through reasonable component blending design, fuels can still maintain or improve energy output per unit volume during the process of becoming lighter and less viscous, thus helping to improve the energy carrying capacity of fuels within a limited volume.

[0080] From the perspective of fluid transport and safety indicators, the kinematic viscosity of the example group was stably distributed at 2.74 mm. 2 / s to 2.95mm 2 Between 0.5°C and 0.5°C, this range is close to the kinematic viscosity level of common diesel fuels, providing suitable flow resistance for high-pressure injection systems and contributing to the stability of the atomization process. Furthermore, based on the patterns observed in Test Examples 1 and 2, hydrocarbon components such as tetradecane, pentadecane, and n-nonadecane exhibit good miscibility and compatibility with long-chain fatty acid methyl esters. The closed-cup flash point test results show that the flash points of the example group remain within the range of 63.5°C to 71.0°C, meeting the basic flash point safety requirements for common automotive diesel fuels.

[0081] The test data above show that the blending system improves the constraint between high viscosity and low calorific value of traditional biofuels to a certain extent by adjusting the carbon number distribution of straight-chain alkanes and branched alkanes, so that the blended fuel can balance volumetric calorific value performance and fluid transport characteristics while maintaining a macroscopic homogeneous state.

[0082] Test Example 4: Bench Engine Internal Combustion Dynamics, Rough Combustion, and Knocking Tendency Test This test case is used to evaluate the internal combustion dynamics performance, rough combustion and knocking tendency of various fuel samples on a single-cylinder direct injection diesel engine bench, and to examine the combustion heat release law and pressure rise rate characteristics of multi-component compound systems in actual power plants.

[0083] The bio-blended fuels prepared in Examples 1, 2, and 3, as well as Comparative Examples 3 and 4, were placed in the engine fuel supply system as test subjects.

[0084] A single-cylinder bench diesel engine equipped with a high-pressure common rail system was selected, connected to an electric dynamometer and bench control system, and the engine was adjusted to run stably at a fixed speed of 1800 rpm and a constant load of 50%, while maintaining the coolant outlet temperature at 80±2℃ and the engine oil temperature at 85±3℃.

[0085] A cylinder pressure sensor is installed on the cylinder head of the diesel engine, connected to a charge amplifier and a high-speed data acquisition card, to collect the cylinder pressure signal in real time. The sampling resolution is set to 0.1°C / A.

[0086] Switch the fuel supply system and introduce the above-mentioned fuel samples respectively. Under the conditions of common rail pressure of 120MPa and injection advance angle fixed at 8°A before top dead center, continuously collect cylinder pressure data for at least 100 cycles and perform indicator diagram averaging to calculate the ignition delay period, maximum cylinder pressure and maximum pressure rise rate under 50% load conditions.

[0087] Combustion analysis software was used to calculate the maximum cylinder pressure, maximum pressure rise rate, and ignition delay period (crankshaft angle span from the start of fuel injection to when the accumulated heat release reaches 10% of the total heat release) of each fuel sample during the combustion process based on the average cylinder pressure data.

[0088] The engine load was changed to 100% full load, and the abnormal and rough combustion or knocking phenomenon of each fuel sample was monitored under high load conditions. At least 500 combustion cycles were continuously collected under full load conditions, and the peak value of the maximum apparent heat release rate and the knocking cycle rate of each sample under full load conditions were recorded. The knocking cycle rate was determined by combining the abnormal pressure oscillation amplitude and the maximum pressure rise rate threshold in the cylinder pressure signal.

[0089] Table 4. Results of Engine Bench Combustion Dynamics and Knocking Tendency Measurements Example 1 6.4 7.38 0.46 84.6 0 Example 2 6.1 7.45 0.43 81.2 0 Example 3 6.7 7.31 0.49 86.4 0 Comparative Example 3 7.6 7.62 0.56 78.9 0.5 Comparative Example 4 9.8 8.35 0.84 108.7 4.2 Figure 4This is a graph showing the evolution of the apparent heat release rate as a function of crankshaft angle in a bench engine under full-load conditions for Examples 1-3 and Comparative Examples 3 and 4 of the present invention. The horizontal axis represents the crankshaft angle relative to top dead center, and the vertical axis represents the calculated apparent heat release rate. This graph complements the scalar data from the test examples, aiming to present the dynamic process of fuel combustion. The thick black solid line branch corresponds to the trend of Example 2, while the other curves with different gray levels and line types correspond to the heat release trajectories of Examples 1, 3, and Comparative Examples 3 and 4, respectively, to visually demonstrate the differences in energy release rates between the premixed combustion period and the main combustion period for different fuel systems.

[0090] Conclusion: According to the data in Table 4, the test results of the embodiment group and the comparative example group of this invention show different test results in terms of engine bench combustion dynamics parameters and tendency for rough combustion or knocking. The test results of comparative example 4 show that its ignition delay period is extended to 9.8℃A. Combined with the distribution characteristics of the separation between low-boiling point and high-boiling point components in the previous distillation range test, this phenomenon is related to the preferential vaporization of light alcohol components and the relatively low cetane number of low carbon alcohols. A longer ignition delay period usually leads to the accumulation of more combustible mixture in the combustion chamber before ignition, thus forming a more intense premixed combustion heat release in the early stage of ignition. Test data show that the peak value of the maximum apparent heat release rate of comparative example 4 reaches 108.7 J / ℃A, while the maximum cylinder pressure rises to 8.35 MPa. Correspondingly, the maximum pressure rise rate of this sample is 0.84 MPa / ℃A, which indicates that it has a significant tendency for rough combustion under test conditions. The knocking cycle rate recorded by bench testing was 4.2%. Under long-term operating conditions, this combustion state will have a certain adverse effect on the mechanical load of the engine piston and connecting rod mechanism. Comparative Example 3, as an unblended conventional fatty acid methyl ester, is affected by its high kinematic viscosity, which limits fuel atomization and air-fuel mixing processes, resulting in a measured ignition delay of 7.6 °C A. Although this sample did not exhibit obvious knocking, its heat release process showed a certain lag, with a maximum cylinder pressure of 7.62 MPa.

[0091] In contrast, the embodiments of this invention, through the blending of multi-level straight-chain alkanes with branched-chain alkanes of specific structures, formed a system characteristic with a relatively continuous distillation range distribution. Test results show that this characteristic helps improve the evaporation and mixing process of fuel and gas in bench combustion tests. Taking Example 2 as an example, its ignition delay period is 6.1 °C A. This result suggests that the low- and medium-boiling-point components in the blended system vaporize earlier at the end of the compression stroke and participate in the ignition stage, which to some extent helps reduce the probability of fuel accumulation during the premixing stage. Subsequent exothermic data show that the peak value of the maximum apparent heat release rate in Example 2 is controlled at 81.2 J / °C A, combined with... Figure 4Based on the heat release trajectory, it is speculated that high-carbon straight-chain alkanes and high-calorific-value branched alkanes participate in the combustion heat release during the main combustion period in a relatively continuous manner. Cylinder pressure monitoring results show that the maximum cylinder pressure in Example 2 is 7.45 MPa, and the maximum pressure rise rate is 0.43 MPa / ℃A, reflecting that the cylinder pressure increases relatively smoothly with the crankshaft angle.

[0092] In the full-load knocking tendency test, Examples 1, 2, and 3 all achieved a 0% knocking cycle rate throughout the entire test cycle. This set of test data indicates that by adjusting the structure of the compounded alkane components, the overlap of boiling point distributions within the system is improved, which promotes a more continuous volatilization and combustion exothermic process, thus exhibiting a suppressive effect on abnormally rapid premixed combustion and pressure oscillations in the experiment. Combined with the aforementioned physicochemical indicators, the relatively suitable kinematic viscosity and gentle distillation range gradient are expected to help reduce the risk of component flashing or localized accumulation in the cylinder of the blended fuel.

[0093] In summary, the bench test data confirms that the compound system of the present invention can release heat in the premixed combustion stage relatively smoothly while maintaining the set volumetric calorific value, thereby reducing the maximum pressure rise rate and mechanical load during the operation of a single-cylinder diesel engine. This has certain technical reference value for improving the stability and safety of engine operation under high load conditions.

Claims

1. A high-calorific-value, stable-combustion bio-blended fuel, characterized in that, It contains the following components by weight: Polar ester components: 7.12–9.16 parts; The straight-chain alkane component is 23.95–25.05 parts; Branched-chain alkane components: 55.86–63.30 parts; The haloalkane component is 6.96 to 7.44 parts.

2. The high-calorific-value, stable-combustion bio-blended fuel according to claim 1, characterized in that, The polar ester component is selected from at least one of methyl palmitate, methyl octadec-9,12-dienoate and methyl cis-11-octadecenoate; The straight-chain alkane component is selected from at least one of tetradecane, n-pentadecanane, and n-nonadecanane; The branched alkane component is selected from at least one of 2-methylundecane, 3-methylundecane, 3,6-dimethyldecane, 3,7-dimethyldecane, 3,8-dimethyl-undecane, 3,8-dimethyldecane, 10-methyleicosane, 2,5-dimethyldodecane, 5-methyltridecane, 4-methyl-tridecane, 3-methyl-5-propylnonane, 3-methyl-tetradecane, 6-methylundecane, 2,5-dimethyldecane, 2,2,4,4,6,8,8-heptamethylnonane, 5-methyl-tetradecane, 7-methylheptadecane, 4-methyltetradecane, 2,5-dimethyltridecane, and 2-methyltetradecane. The haloalkane component includes 2-bromododecane.

3. The high-calorific-value, stable-combustion bio-blended fuel according to claim 2, characterized in that, The following components are contained in parts by weight: Polar ester components: methyl palmitate 6.00-7.62 parts, methyl octadecanoate-9,12-dienoate 0.38-0.52 parts, methyl cis-11-octadecenoate 0.74-1.02 parts; Straight-chain alkane components: tetradecane 2.90–3.30 parts, n-pentadecane 2.80–3.10 parts, n-nonadecane 18.25–18.65 parts; Branched alkane components: 2-methylundecane 0.14–0.20 parts, 3-methylundecane 0.12–0.18 parts, 3,6-dimethyldecane 0.36–0.50 parts, 3,7-dimethyldecane 0.33–0.47 parts, 3,8-dimethyl-undecane 0.56–0.74 parts, 3,8-dimethyldecane 0.57–0.79 parts, 10-methyleicosane 7.80–8.20 parts, 2,5-dimethyldodecane 3.25–3.55 parts, 5-methyltridecane 3.10–3.60 parts, 4-methyl-tridecane 3.59–4.01 parts. 3-Methyl-5-propylnonane 0.95–1.35 parts, 3-methyl-tetradecane 7.89–8.61 parts, 6-methylundecane 1.69–2.21 parts, 2,5-dimethyldecane 3.87–4.53 parts, 2,2,4,4,6,8,8-heptamethylnonane 2.56–3.14 parts, 5-methyl-tetradecane 5.50–6.20 parts, 7-methylheptadecane 1.70–2.00 parts, 4-methyltetradecane 3.74–4.16 parts, 2,5-dimethyltetrazane 5.14–5.46 parts, 2-methyltetradecane 3.00–3.40 parts; Halogenated alkane component: 6.96–7.44 parts of 2-bromododecane.

4. The high-calorific-value, stable-combustion bio-blended fuel according to claim 1, characterized in that, It is a homogeneous liquid that is completely transparent and contains no molecular aggregates.

5. A method for preparing a high-calorific-value, stable-combustion bio-blended fuel according to any one of claims 1-4, characterized in that, Includes the following steps: Accurately measured straight-chain alkane components are fed into a stainless steel reactor equipped with a heating jacket, a double-layer combined stirring paddle, an air-to-air nitrogen protection system, and a condensation reflux device. The reactor jacket heating is turned on, and the temperature of the material system inside the reactor is controlled at 62-68°C. At the same time, high-purity nitrogen is continuously introduced into the reactor to replace the air inside the reactor. The stirring system is started to continuously perform pre-stirring and mixing to ensure that the high-carbon straight-chain alkane is completely melted and forms a homogeneous phase. While maintaining the stirring state and gas phase protection in the reactor, the metered branched alkane components are slowly added to the stainless steel reactor in batches. After the feeding is completed, the heating jacket is adjusted to raise and maintain the temperature of the material system in the reactor, thereby promoting the thermal diffusion of medium and long chain isomers in the matrix. Under the condition that the temperature of the material in the reactor is kept stable, the remaining metered branched alkane components are added to the reactor in batches. After the addition is completed, the speed of the main stirrer is increased to carry out strong shear dispersion. The high-speed homogeneous state is maintained stably until the system is transformed into a completely transparent homogeneous liquid without molecular aggregates. Turn on the cooling water circulation of the stainless steel reactor jacket to lower and stabilize the temperature of the material system inside the reactor at 58-62℃. While maintaining steady stirring, slowly add the metered haloalkane components dropwise into the reactor, controlling the feeding rate to avoid material volatilization caused by excessively high local concentrations. The material temperature inside the reactor is maintained at a constant temperature of 58-62℃. The metered polar ester components are added to the reactor and stirred until the polar esters and non-polar alkanes are completely miscible through a multi-stage solvent effect. Then, heating is stopped, and circulating cooling is started. After the material naturally drops to the discharge temperature, it is discharged and then filtered through a precision filter to obtain the finished bio-blended fuel.

6. The preparation method according to claim 5, characterized in that, During the pre-mixing process, the speed of the stirrer is adjusted to 450-550 rpm, and the mixing and homogenization time is 18-22 min.

7. The preparation method according to claim 5, characterized in that, The temperature at which the material system inside the reactor is raised and maintained is 68–72°C.

8. The preparation method according to claim 5, characterized in that, During the high-intensity shear dispersion, the rotation speed is controlled to 1800-2200 rpm; during the discharge process after the material naturally cools down to the discharge temperature, the discharge temperature is 20-25℃.

9. The preparation method according to claim 5, characterized in that, The haloalkane component includes 2-bromododecane, and the 2-bromododecane is prepared by the following steps: Add 2-dodecyl alcohol and a 48 wt% aqueous solution of hydrobromic acid to a reactor equipped with a stirrer, thermometer and reflux condenser. Turn on the stirrer and set the stirring speed to 150-250 rpm to ensure that the materials in the reactor are fully mixed. The molar ratio of 2-dodecyl alcohol to pure hydrobromic acid is controlled to be 1:1.1 to 1:1.

5. Keep the material in the reactor under constant stirring. Use a constant pressure dropping funnel to slowly add concentrated sulfuric acid with a mass fraction of 98 wt% into the reactor. The mass of concentrated sulfuric acid added is 20-30 wt% of the mass of 2-dodecyl alcohol. During the dropping process, strictly control the temperature inside the reactor through an external water bath to keep it at 20-30℃. After the addition is complete, the external cooling system is removed and the heating jacket is used to heat the reactor to raise the temperature of the material system inside the reactor to 95-115°C. At this temperature, a constant temperature reflux reaction is carried out for 3-5 hours. After the reflux reaction is complete, stop heating and allow the material in the reactor to cool down to room temperature naturally. Add 0.5 to 1.5 times the total volume of the reaction solution of deionized water to dilute the mixture. Then add an appropriate amount of n-hexane as the extraction solvent and stir for 10 to 20 minutes. Transfer the mixture to a separatory funnel and let it stand to separate into layers. Discard the lower aqueous phase waste liquid and retain the upper organic phase. Add a 5 wt% sodium bicarbonate aqueous solution to the organic phase and wash until neutral. After separating the aqueous phase, add anhydrous magnesium sulfate to dry the neutral organic phase. After standing for 2-3 hours, filter to remove the desiccant to obtain a crude mixture containing n-hexane. The crude product mixture was transferred to a vacuum distillation apparatus. Hexane, used as an extractant, was first distilled off at atmospheric pressure and a lower temperature. Then, the absolute pressure of the system was controlled at 10 mmHg, the temperature was increased, and the middle fraction corresponding to the boiling point range was collected.

10. The preparation method according to claim 9, characterized in that, During the process of heating and collecting the intermediate fractions in the corresponding boiling point range, the temperature is increased slowly. The fore fraction is collected and removed first to eliminate trace amounts of dodecene impurities generated by the side reaction. Finally, the intermediate fractions in the corresponding boiling point range are collected to obtain purified 2-bromododecane liquid. The purity of the liquid is above 98.0 wt% as determined by gas chromatography.

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