Biomass long-chain oxygen-containing additive for improving solubility of methanol in diesel oil, and preparation method and application thereof

Abstract

This invention relates to a biomass long-chain oxygenated additive for improving the solubility of methanol in diesel fuel, its preparation method, and its application. Biomass undergoes directional pyrolysis on a Fe-Ce composite metal oxide catalyst. The pyrolysis products are dried, condensed, and filtered to collect the liquid-phase crude bio-oil. The entire pyrolysis process is carried out under inert gas protection. The resulting liquid-phase product is added to a thermoelectric coupling reactor, where long-chain oxygenated polyols are prepared through electrochemical polymerization and thermochemical hydrogenation. After the reaction, the solid catalyst and the liquid-phase alcohol mixture are separated by filtration. The mixture solution after the thermoelectric reaction is then separated and purified using a rotary evaporator to obtain the pure biomass long-chain oxygenated additive. Compared with existing technologies, this invention can effectively improve the solubility of methanol in diesel fuel, achieve different proportions of methanol and diesel fuel miscibility, and simultaneously improve the thermal efficiency of methanol-diesel fuel.

Description

Technical Field

[0001] This invention belongs to the field of biomass-based diesel fuel additives, specifically relating to a method for preparing and applying a long-chain oxygenated biomass additive that improves the solubility of methanol in diesel fuel. Background Technology

[0002] The global tension over fossil fuels has spurred the rapid development of renewable energy. Renewable energy fuels, represented by biomass, are widely used as alternative fuels to alleviate fossil fuel shortages and global environmental problems. Due to the economic viability and sustainable application of alcohols, methanol can be blended with diesel as an alternative fuel, thereby reducing fossil fuel consumption during diesel production. In practical applications, directly adding a methanol-diesel mixture to the cylinder is more in line with industrial needs than adding methanol and diesel separately for co-firing. Pre-mixed methanol-diesel fuel does not require modification of the fuel injection system from single-nozzle to dual-nozzle, and the micro-explosion phenomenon caused by the difference in boiling points of the mixed fuels can improve combustion and increase combustion efficiency.

[0003] However, the differences in polarity and intermolecular forces between methanol and diesel make them immiscible. Typically, a certain amount of surfactant or co-solvent is added when blending methanol and diesel fuels to improve the solubility of methanol in diesel, thereby preparing a stable blended fuel and preventing fuel phase separation. Currently, most additives are alcohols, ethers, and esters, but hydroxyl groups are superior to carbonyl groups in their solubilizing properties. The crude bio-oil obtained from biomass pyrolysis mostly consists of unsaturated oxygen-containing alcohols, ethers, and aldehydes. Through catalytic hydrogenation polymerization, long-chain oxygen-containing polyols can be obtained. Unlike light alcohols, long-chain polyols, after hydrogenation, maintain similar physicochemical properties to diesel fuel, reducing the impact of additives on methanol-diesel fuel.

[0004] Patent CN102459518A discloses a self-sustaining method for producing high-quality liquid fuel from biomass. In this method, biomass is hydropyrolyzed in a reaction vessel containing molecular hydrogen and a deoxygenation catalyst to produce a partially deoxygenated hydropyrolysis liquid. This liquid is then hydrogenated using a hydroconversion catalyst to produce a substantially completely deoxygenated hydrocarbon liquid and a gas mixture containing CO and light hydrocarbon gases (C1-C3). This gas mixture is reformed in a steam reformer to produce reformed molecular hydrogen, which is then introduced into the reaction vessel used for hydropyrolyzing the biomass. The deoxygenated hydrocarbon liquid product is further separated to produce diesel fuel, gasoline, or a mixture of gasoline and diesel fuel. However, this invention uses a thermocatalytic method for hydrodeoxygenation, requiring high-temperature and high-pressure reaction conditions, and necessitates a large amount of hydrogen during the reaction.

[0005] Patent CN107033977A discloses a mutual solvent for methanol-diesel and its preparation method. The methanol-diesel mutual solvent of this invention consists of castor oil polyether and castor oil polyether ester. The lipophilic groups are mainly alicyclic, aromatic, and propylene oxide; the hydrophilic groups are mainly hydroxyl and ethylene oxide, which can connect to more hydroxyl groups in methanol. The methanol-diesel prepared with this additive has stable quality, a clear and transparent appearance, is not cloudy or layered, has a long storage time, and can be mixed with national standard diesel in any proportion without emulsification. However, the preparation method of this mutual solvent is complex, requiring the addition of key organic compounds multiple times at various temperatures, and demanding high reaction control.

[0006] Patent CN115029165A discloses a methanol-diesel microemulsion dispersant, its preparation method, and its application. This invention uses a solid superacid catalyst to catalyze the preparation of ester dispersants. The prepared ester dispersant is mainly a mixture of pentaerythritol monooleate and dioleate. Pentaerythritol monooleate and dioleate, due to their polyhydroxyl and long carbon chain structures, are typical amphiphilic molecules, exhibiting both hydrophilic and lipophilic properties. Compared to fatty acid methyl esters and ethyl esters, their structures are more suitable as dispersants for methanol-diesel microemulsion fuels. However, in the formulation of this compound dispersant, C6-C10 fatty alcohols need to be added for further action, meaning the prepared ester dispersant cannot be used as a standalone co-solvent to improve the miscibility of methanol-diesel.

[0007] Patent CN114891543A discloses a formulation and method for synthesizing methanol diesel. The formulation comprises light coal tar, methanol, aviation kerosene, kerosene, ethyl acetate, ferrocene, isobutanol, propylene glycol, dimethyl carbonate, and propylene glycol methyl ether. It involves two main steps: mixing denatured methanol with aviation kerosene and kerosene; and mixing ethyl acetate and dimethyl carbonate with light coal tar. Finally, methanol diesel fuel is prepared under the catalysis of ferrocene. While this invention uses inexpensive and readily available raw materials, has a simple process, and achieves a product yield as high as 99.9%, the improvement in methanol solubility relies on mixing with light alcohols and ethers. The flash points of light alcohols and ethers are far lower than those required for diesel fuel, and their blending ratio affects the flash point of the methanol diesel.

[0008] Currently, the key solubilizing substances in methanol-diesel additives are generally alcohols, ethers, and esters. Additives with alcohols as the main solubilizer typically have a carbon chain length of less than 6, which, when mixed, reduces the combustion performance of diesel fuel. Therefore, kerosene needs to be added to improve the overall properties of the methanol fuel. Additives with ethers or esters as the main solubilizers often have complex preparation processes and require the addition of alcohol to enhance their solubilizing ability. Most currently disclosed inventions synthesize methanol-diesel additives from specific components and are mostly compound additives, lacking preparation processes from the source of components to synthesize multifunctional diesel additives and simplify methanol-diesel fuel formulations. Additives prepared from biomass mostly require stringent reaction conditions, lacking preparation processes for additives reacting at medium to low temperatures. Furthermore, thermocatalytic hydrogenation cannot increase the carbon chain length, limiting its application to biomass pyrolysis products.

[0009] Patent CN201911351924.5 discloses a biomass-based long-chain alcohol ether oxygen-containing additive, its preparation method, and its application. The additive raw material is agricultural and forestry waste, with the general chemical formula R-(OC). 1-3 ) n -R-OH. The preparation method includes the following steps: Step 1, drying and pretreating the biomass feedstock, then rapidly pyrolyzing it under an inert atmosphere to obtain pyrolysis products containing water, gas, aqueous bio-oil, and oil-phase bio-oil. The aqueous bio-oil is separated and catalytically hydrogenated to obtain a polyol; Step 2, catalytically dehydrating the polyol obtained in Step 1 under an alkaline catalyst system to obtain epoxides; Step 3, reacting the epoxides obtained in Step 2 with methanol through a molecular sieve catalyst, separating and removing the solid catalyst to obtain a long-chain alcohol ether oxygen-containing additive. The application is the use of the additive in liquid fuels. This technology can be miscible with diesel in any proportion, but it cannot directionally generate alcohol precursors in biomass pyrolysis, and the thermocatalytic hydrogenation and epoxide preparation processes require high pressure and temperature. Summary of the Invention

[0010] The purpose of this invention is to overcome the defects of the prior art by providing a biomass long-chain oxygenated additive that improves the solubility of methanol in diesel, its preparation method and application. The invention synthesizes long-chain oxygenated polyols from inexpensive biomass under relatively mild conditions as methanol co-solvents, thereby improving the miscibility of methanol and diesel, allowing methanol to be mixed with diesel in any proportion, and thus improving the combustion performance of methanol diesel fuel.

[0011] The objective of this invention can be achieved through the following technical solution: a method for preparing a biomass long-chain oxygenated additive to improve the solubility of methanol in diesel fuel, the method comprising the following steps:

[0012] 1) Biomass is directionally pyrolyzed on Fe-Ce composite metal oxide catalyst. The pyrolysis products are dried, condensed, and filtered to collect the crude bio-oil in liquid phase. The entire pyrolysis process is carried out under inert gas protection.

[0013] 2) The liquid product obtained in step 1) is added to a thermoelectric coupling reactor, and long-chain oxygen-containing polyols are prepared by electrochemical polymerization and thermochemical hydrogenation. After the reaction, the solid catalyst and the liquid alcohol mixture are separated by filtration.

[0014] 3) The mixture solution after thermoelectric reaction is separated and purified by rotary evaporator to obtain pure biomass long-chain oxygenated additive, which can be used as diesel additive.

[0015] Further, in step 1), pine or redwood is selected as the biomass raw material for forestry. Before pyrolysis, it needs to be dried and weighed at 100-110℃ until the quality is stable.

[0016] The Fe-Ce composite metal oxide catalyst was synthesized by a co-precipitation method: soluble iron and cerium salts with a Fe / Ce molar ratio of 1:1 were dissolved in deionized water to obtain a mixed metal salt solution. The pH was adjusted to 7.5–8.5, and the temperature was controlled at 65–75℃. After aging and filtration, the precipitate was repeatedly washed with deionized water until neutral, dried at 55–65℃, calcined at 450–550℃ for 4–6 hours, and then pulverized to obtain the Fe-Ce composite metal oxide catalyst.

[0017] Further, step 1) of biomass pyrolysis specifically involves: placing the biomass raw material and the Fe-Ce composite metal oxide catalyst in the reaction tube of the pyrolysis furnace; purging the reaction tube of the pyrolysis furnace with inert gas at a rate of 0.1–0.5 L / h at room temperature to remove air and prevent air from oxidizing the pyrolysis products; then continuously supplying inert gas to the reaction tube at a rate of 0.1–0.5 L / h and heating; stopping the supply of inert gas when the center temperature of the reaction tube reaches 280–300 °C; then raising the temperature to 600–650 °C at a rate of 20–25 °C / min, holding for 10 min, and then stopping the heating; and finally collecting the liquid phase product after drying and condensation.

[0018] Further, in step 1), the mass ratio of the Fe-Ce composite metal oxide catalyst to the biomass feedstock is 0.2 to 0.3:1; the inert gas is nitrogen.

[0019] Further, the thermoelectric coupling reactor described in step 2) is equipped with a thermochemical catalyst and an electrochemical catalyst, and connected to a hydrogen source. The liquid phase product obtained in step 1) is subjected to thermoelectric catalytic hydrogenation polymerization in the thermoelectric coupling reactor for quality improvement, converting the unsaturated and complex pyrolysis liquid phase product into a long-chain oxygen-containing polyol. During the hydrogenation polymerization process, hydrogen gas is introduced at a pressure of 0.1–1 MPa at a rate of 50–100 mL / min. Simultaneously, the pyrolysis liquid phase product in the reactor and the built-in electrodes form an electrolytic cell, maintaining an electrolysis voltage of 1.3–1.5 V. The reaction temperature is controlled at 150–200 °C, and the reaction time is 2–3 h. A uniform stirring speed of 25–40 r / min is maintained throughout the reaction.

[0020] Furthermore, the thermochemical catalyst is a commercial zeolite catalyst, and the electrochemical catalyst is a commercial copper foam. The catalyst is cleaned with deionized water and dried under vacuum at 50-60°C before use.

[0021] The amount of zeolite catalyst added is 4 to 6% of the total mass of the liquid phase product.

[0022] Further, the distillation conditions of the rotary evaporator in step 3) are: under pressure of 0.01 to 0.02 MPa, at 50 to 65 °C, and under reduced pressure for 20 to 40 minutes.

[0023] The present invention also provides a biomass long-chain oxygenated additive for improving the solubility of methanol in diesel fuel, prepared by any of the above methods.

[0024] The present invention also provides an application of a biomass long-chain oxygenated additive, wherein the biomass long-chain oxygenated additive is added to a methanol-diesel mixture system and stirred at a constant speed of 1000-1500 r / min for 30-40 min to obtain methanol-diesel fuel.

[0025] Furthermore, the amount of the biomass long-chain oxygenated additive added is 20-25% of the total mass of the methanol-diesel mixture system, which improves the solubility of methanol in diesel by 90-100% and ensures that the volume ratio of methanol is 15-90%.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] (1) Existing methanol and diesel cosolvents often have complex formulations and require the interaction of multiple organic alcohol esters to achieve the effect of cosolvent. This invention utilizes the diversity of products after biomass pyrolysis and condensation to prepare long-chain oxygen-containing polyol ethers as methanol cosolvents in one step. They can be directly mixed with methanol and diesel to exert the effect of cosolvent, effectively improving the miscibility of methanol and diesel.

[0028] (2) Compared with the negative impact of traditional light alcohol additives on the physicochemical properties of diesel, the structure and properties of long-chain oxygenated fuels are similar to those of diesel components, which can ensure that the blended methanol diesel fuel has the required physicochemical values ​​when no other components are added.

[0029] (3) Biomass long-chain oxygen-containing additives are prepared through a process of pyrolysis → hydrogenation polymerization → purification. The process is simple and energy-efficient. The carbonyl content in the pyrolysis products is increased by utilizing the directional selection function of a self-made pyrolysis catalyst. Thermoelectric coupling catalysis enables the polymerization to lengthen the carbon chain and the hydrogenation to produce alcohols, thereby increasing the yield of long-chain oxygen-containing polyols in multiple ways. Finally, the difference in boiling points between molecules in the hydrogenated mixture is used to separate small molecules from large molecules, ensuring the purity of the long-chain oxygen-containing additive product.

[0030] (4) The thermo-electric coupling reaction promotes each other. The hydrogen produced by electropolymerization can be used as a hydrogen source for thermocatalysis, reducing the amount of hydrogen supplied from the outside. The temperature of thermocatalysis can also promote the efficiency of electrochemical polymerization.

[0031] (5) Using biomass to prepare polyols as additives for methanol diesel fuel is a low-cost and readily available approach, with low overall process costs and low difficulty in industrialization. In addition to promoting the solubility of methanol in diesel, long-chain oxygen-containing polyols can also be used as biomass fuels to mix with methanol diesel, thereby improving the combustion performance of the blended fuel. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the preparation process of the biomass long-chain oxygen-containing additive of the present invention.

[0033] Figure 2 This invention relates to the solubility characteristics of a biomass long-chain oxygenated additive—methanol—diesel at different blending ratios.

[0034] Figure reference numerals: 1 Nitrogen cylinder; 2 Nitrogen flow meter; 3 Pyrolysis furnace; 4 Switch; 5 Temperature control panel; 6 Condensation device; 7 Collection bottle; 8 Tail gas treatment device; 9 Hydrogen cylinder; 10 Hydrogen flow meter; 11 Thermoelectric coupling reactor; 12 Stirring device; 13 Temperature controller; 14 DC power supply; 15 Rotary evaporator; 16 Collection bottle; 17 Collection bottle. Detailed Implementation

[0035] To enable those skilled in the art to understand the technical solution of the present invention more clearly, the present invention will be described in detail below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0036] This invention utilizes the liquid-phase products from the directional pyrolysis of biomass to prepare long-chain oxygen-containing additives via catalytic hydrogenation. Specifically, the process involves: directional pyrolysis of biomass → hydrogenation polymerization of the liquid-phase products → product purification. The preparation process consists of steps including directional pyrolysis of biomass raw materials under the catalysis of a self-made Fe-Ce composite metal oxide catalyst, hydrogenation polymerization of the pyrolysis liquid-phase products in a thermoelectric coupling reactor, and purification and refining of the reaction products using a rotary evaporator. All raw materials used in this invention, except for the self-made Fe-Ce composite metal oxide catalyst, are conventional commercially available materials in the field. The self-made Fe-Ce composite metal oxide catalyst used in the following examples is synthesized via a co-precipitation method, specifically: Fe(NO3)3·9H2O and Ce(NO3)3·6H2O are dissolved in deionized water at a Fe / Ce molar ratio of 1 to obtain a mixed metal salt solution. The metal salt solution is mixed with 3M ammonia water to adjust the pH to 8±0.1, and the temperature is controlled at 70±1℃. After aging and filtration, the precipitate was repeatedly washed with deionized water until neutral, and then dried at 60°C for 12 hours. After drying, it was calcined at 500°C for 5 hours, and then pulverized to obtain the Fe-Ce composite metal oxide catalyst.

[0037] like Figure 1 As shown, the preparation method of the biomass long-chain oxygenated additive for improving methanol solubility in diesel fuel according to the present invention includes the following steps:

[0038] Step 1: Select pine or redwood as the forestry biomass raw material. Before pyrolysis, the biomass raw material needs to be dried and weighed at 100–110℃ until its quality stabilizes. Place the biomass raw material and Fe-Ce composite metal oxide catalyst in a quartz tube within the pyrolysis furnace 3 (the mass ratio of Fe-Ce composite metal oxide catalyst to biomass raw material is 0.2–0.3:1). Open the valve of nitrogen cylinder 1 and control the nitrogen purging rate at 0.1–0.5 L / h using nitrogen flow meter 2. After purging for 0.5–1 h, continue purging with nitrogen at the same rate. Simultaneously, turn on switch 4 and set the heating program using temperature control panel 5 to begin pyrolysis. When the center temperature of the quartz tube reaches 280–300℃, stop the nitrogen supply. Then, increase the temperature at 20–25℃ / min to 600–650℃, maintain this temperature for 10 min, and then stop heating. After pyrolysis, the gas passes through the condenser 6, the liquid phase products are collected by the collection bottle 7, and other non-condensable gases are treated by the tail gas treatment device 8 before being discharged into the atmosphere.

[0039] Step two: The liquid phase product from collection bottle 7 in step one is added to thermoelectric coupling reactor 11. Thermoelectric coupling reactor 11 contains a zeolite catalyst (i.e., hydrogenation catalyst) and two electrodes (i.e., electropolymerization catalyst - copper foam). Thermoelectric coupling reactor 11 is connected to hydrogen cylinder 9 via a gas pipeline, and a hydrogen flow meter 10 is installed on the gas pipeline. Thermoelectric coupling reactor 11 is equipped with a stirring device 12 and a temperature controller 13, and is connected to a DC power supply 14. The valve of hydrogen cylinder 9 is opened, and the hydrogen flow rate is controlled by the hydrogen flow meter 10. The temperature control program of the temperature controller 13, the rotation speed of the stirring device 12, and the output voltage of the DC power supply 14 are set to begin the upgrading of the pyrolysis liquid phase product. During the hydrogenation polymerization process, hydrogen is introduced at a rate of 50–100 mL / min, and the pressure is controlled at 0.1–1 MPa. Simultaneously, the pyrolysis liquid phase product in the reactor and the built-in electrodes form an electrolytic cell, maintaining the electrolysis voltage at 1.3–1.5 V. The reaction temperature was controlled at 150–200℃, and the reaction time was 2–3 hours. A uniform stirring speed of 25–40 r / min was maintained during the reaction. The catalyst needed to be washed with deionized water and dried under vacuum at 50–60℃ before use. The amount of zeolite catalyst added was related to the total amount of liquid-phase products, with a mass fraction of 4–6%. After the reaction, the liquid-phase products and zeolite catalyst were separated by filtration.

[0040] Step 3: The liquid product obtained after hydrogenation contains not only long-chain oxygen-containing polyols but also small-molecule short-chain hydrocarbons and alcohols. Based on the different boiling points of these molecules, the mixture solution in the thermoelectric coupling reactor is separated and purified using a rotary evaporator to obtain pure biomass-based long-chain oxygen-containing polyols as diesel additives. Specifically: the solution after the reaction in step 2 is added to rotary evaporator 15 for purification. The distillation temperature is set between 50 and 65°C, the distillation time is 20 to 40 minutes, and the distillation pressure is 0.01 to 0.02 MPa. Light alcohols and ethers with low boiling points are collected in collection bottle 16, and the remaining long-chain oxygen-containing polyols are collected in collection bottle 17. The biomass long-chain oxygen-containing polyol process of this invention is simple and can utilize the long-chain oxygen-containing organic matter after the pyrolysis of biomass macromolecules as a methanol co-solvent. By adding 30% by volume of long-chain oxygen-containing polyols to a methanol-diesel mixture, methanol can be mixed with diesel in any proportion.

[0041] Example 1

[0042] Step 1: Purchase redwood biomass pellets as the biomass raw material for this embodiment, with a calorific value of 4200–4600 kcal / kg. Place the biomass raw material in an oven and dry it at 105°C, weighing it every 3 hours until the mass of the redwood biomass pellets no longer changes, for a total drying time of 30 hours. Mix the dried biomass with the Fe-Ce composite metal catalyst and add it to the quartz tube of pyrolysis furnace 3, with a Fe-Ce composite metal catalyst to biomass mass ratio of 0.25:1. Before the reaction, the pyrolysis furnace needs to be continuously purged with nitrogen at a rate of 0.2 L / h for 0.5 h at room temperature to remove all air and prevent air from oxidizing the pyrolysis products. After purging, nitrogen purging should continue at the same rate. Simultaneously, the pyrolysis furnace switch 4 should be turned on, and the heating program should be set via the temperature control panel 5. When the center temperature of the quartz tube reaches 280°C, the nitrogen supply should be stopped. The temperature should then be increased to 600°C at a rate of 20°C / min and held at 600°C for 10 min before heating is stopped. After pyrolysis, the product is dried, and the liquid phase is collected by condensation.

[0043] Step two involves adding the liquid-phase product obtained in step one to thermoelectric coupling reactor 11. The unsaturated and complex pyrolysis liquid-phase product is converted into a long-chain oxygen-containing polyol through thermoelectric catalytic hydrogenation polymerization. During hydrogenation polymerization, hydrogen gas is introduced at a pressure of 0.5 MPa at a rate of 60 mL / min. Simultaneously, the pyrolysis liquid-phase product in the reactor and the built-in electrodes form an electrolytic cell, maintaining an electrolysis voltage of 1.4 V. The reaction temperature is controlled at 150℃, and the reaction time is 3 hours. The reaction is maintained with a uniform stirring speed of 25 r / min. The catalyst for the hydrogenation reaction is the commercial zeolite catalyst HZSM-5, and the electropolymerization catalyst is copper foam. The catalysts are washed with deionized water and dried under vacuum at 60℃ before use. The amount of zeolite catalyst added is related to the total amount of liquid-phase product, with a mass fraction of 5%. After the reaction, the liquid-phase product and zeolite catalyst are separated by filtration.

[0044] Step three: The liquid product obtained after hydrogenation contains not only long-chain oxygen-containing polyols but also small-molecule short-chain hydrocarbons and alcohols. Based on the different boiling points of these molecules, the mixture solution in the thermoelectric coupling reactor is separated and purified using a rotary evaporator 15 to obtain pure biomass-based long-chain oxygen-containing polyols for use as diesel additives. The reaction solution needs to be distilled under reduced pressure in a rotary evaporator at 0.01 MPa, with the distillation temperature set at 60℃ and the distillation time at 40 min to remove low-boiling-point small-molecule organic matter while retaining the main components of the high-molecular-weight long-chain oxygen-containing additive, namely the polyol mixture.

[0045] The remaining product after distillation is the long-chain oxygen-containing additive of the present invention. The yield of the long-chain oxygen-containing additive is about 35%, and after rotary evaporation, the purity exceeds 95%.

[0046] This additive can be applied to methanol-diesel mixtures of varying proportions. After addition, it needs to be stirred at a constant speed of 1000 r / min for 30 min to ensure thorough mixing of methanol, diesel, and the long-chain oxygenated additive. The additive of this invention is added at 30% of the total volume, which can improve the solubility of methanol in diesel by 99%, ensuring that methanol and diesel are miscible in any proportion.

[0047] Example 2

[0048] Step 1: Purchase pine biomass pellets as the biomass feedstock for this example. The calorific value is between 4300 and 4500 kcal / kg. Dry the biomass in an oven at 105°C, weighing it every 3 hours until the mass of the pine biomass pellets no longer changes. The total drying time is 30 hours. Mix the biomass feedstock with a self-made Fe-Ce composite metal catalyst and add it to the quartz tube of pyrolysis furnace 3. The catalyst-to-biomass feedstock mass ratio is 0.25. Before the reaction, the quartz tube inside the pyrolysis furnace needs to be continuously purged with nitrogen at a rate of 0.2 L / h at room temperature for 0.5 hours to remove air and prevent oxidation of the pyrolysis products. After purging, continue purging with nitrogen at the same rate. Simultaneously, turn on the pyrolysis furnace switch 4 and set the heating program of the pyrolysis furnace through the temperature control panel 5. When the center temperature of the quartz tube reaches 280°C, stop the nitrogen supply. Then, increase the temperature to 600°C at a rate of 20°C / min, hold at 600°C for 10 minutes, and then stop heating. After pyrolysis, the product is dried and condensed to collect the liquid phase product.

[0049] Step two involves adding the liquid-phase product obtained in step one to thermoelectric coupling reactor 11. The unsaturated and complex pyrolysis liquid-phase product is converted into a long-chain oxygen-containing polyol through thermoelectric catalytic hydrogenation polymerization. During hydrogenation polymerization, hydrogen gas is introduced at a pressure of 0.5 MPa at a rate of 60 mL / min. Simultaneously, the pyrolysis liquid-phase product in the reactor and the built-in electrodes form an electrolytic cell, maintaining an electrolysis voltage of 1.4 V. The reaction temperature is controlled at 150℃, and the reaction time is 3 hours. The reaction is maintained with a uniform stirring speed of 25 r / min. The catalyst for the hydrogenation reaction is the commercial zeolite catalyst HZSM-5, and the electropolymerization catalyst is copper foam. The catalysts are washed with deionized water and dried under vacuum at 60℃ before use. The amount of zeolite catalyst added is related to the total amount of liquid-phase product, with a mass fraction of 5%. After the reaction, the liquid-phase product and zeolite catalyst are separated by filtration.

[0050] Step three: The liquid product obtained after hydrogenation contains not only long-chain oxygen-containing polyols but also small-molecule short-chain hydrocarbons and alcohols. Based on the different boiling points of these molecules, the mixture solution in the thermoelectric coupling reactor is separated and purified using a rotary evaporator 15 to obtain pure biomass-based long-chain oxygen-containing polyols for use as diesel additives. The reaction solution needs to be distilled under reduced pressure in a rotary evaporator at 0.01 MPa, with the distillation temperature set at 60℃ and the distillation time at 40 min to remove low-boiling-point small-molecule organic matter while retaining the main components of the high-molecular-weight long-chain oxygen-containing additive, namely the polyol mixture.

[0051] The remaining product after distillation is the long-chain oxygenated additive of this invention. This additive can be applied to methanol-diesel mixtures of different proportions. After addition, it needs to be stirred at a constant speed of 1000 r / min for 30 min to ensure thorough mixing of methanol, diesel, and the long-chain oxygenated additive. The additive of this invention is added at 30% of the total amount, which can improve the solubility of methanol in diesel by 99%, ensuring that methanol and diesel are miscible in any proportion.

[0052] Comparative Example

[0053] Using the biomass-based long-chain alcohol ether oxygen-containing additive prepared in Example 1 of patent CN201911351924.5 as a comparative example, the performance of the additive obtained in the examples of this invention is compared as follows:

[0054] Comparative Example 60-65 260 ppm 350ppm Example 1 64-68 200ppm 340ppm Example 2 67-70 190ppm 320ppm

[0055] As can be seen from the table above, compared with the comparative example, the biomass long-chain oxygenated additives prepared in Examples 1 and 2 of this invention have higher cetane numbers and lower CO and NO emissions. This better ensures that when mixed with diesel, the combustion performance of the blended fuel can be improved and the emission of air pollutants can be reduced.

[0056] The long-chain oxygen-containing polyol additives prepared in Examples 1-2 were mixed with methanol-diesel solutions of different proportions to test the solubility of the additives of the present invention. Specific steps included: adding long-chain oxygen-containing polyols and diesel fuels of different volume ratios to test tubes to prepare fuel mixtures, with a total mixture volume of 10 mL. The mouths of the test tubes containing the mixtures were sealed with thermoplastic film to prevent reagent evaporation and adsorption of water from the air. The test tubes were then vortexed on a mixer for 1 minute. Finally, these test tubes were placed at an ambient temperature of 15°C for 24 hours, and the layering within the test tubes was observed.

[0057] Test results as follows Figure 2 As shown. Figure 2The mixed fuel is a solution of the long-chain oxygen-containing polyol additive of this invention, methanol, and diesel. In Example 1, the additive prepared requires a volume percentage of 0.4 to achieve any mixing ratio of methanol and diesel, i.e., a maximum methanol volume percentage of 0.6; at a volume percentage of 0.3, the maximum methanol volume percentage in the mixed solution is 0.2, i.e., a methanol / diesel ratio of 2 / 5. In Example 2, the additive prepared requires a volume percentage of 0.3 to achieve any mixing ratio of methanol and diesel, i.e., a maximum methanol volume percentage of 0.7 in the mixed solution. This also indicates that pine wood is more suitable for preparing the long-chain oxygen-containing polyol of this invention as a methanol co-solvent in diesel.

[0058] The foregoing has shown and described the basic process, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a biomass long-chain oxygenated additive to improve the solubility of methanol in diesel fuel, characterized in that, The method includes the following steps: 1) Directional pyrolysis of biomass on a Fe-Ce composite metal oxide catalyst. The specific steps of biomass pyrolysis are as follows: Before the reaction, the reaction tube in the pyrolysis furnace is purged with inert gas at a rate of 0.1~0.5 L / h at room temperature to remove all air; then, inert gas is supplied to the reaction tube at a rate of 0.1~0.5 L / h and heated. When the temperature at the center of the reaction tube reaches 280~300 ℃, the supply of inert gas is stopped. Then, the temperature is increased to 600~650 ℃ at a rate of 20~25 ℃ / min. The pyrolysis products are dried, condensed, and filtered before the liquid phase products are collected. The entire pyrolysis process is carried out under inert gas protection. The Fe / Ce molar ratio of the Fe-Ce composite metal oxide catalyst is 1:

1. 2) The liquid product obtained in step 1) is added to a thermoelectric coupling reactor to prepare a long-chain oxygen-containing polyol through electrochemical polymerization and thermochemical hydrogenation. After the reaction, the solid catalyst and the liquid alcohol mixture are separated by filtration. The thermoelectric coupling reactor is equipped with a thermochemical catalyst and an electrochemical catalyst and is connected to a hydrogen source. The reaction conditions are as follows: water vapor is introduced at a pressure of 0.1~1MPa at a rate of 50~100 mL / min, the voltage applied during the reaction is 1.3~1.5 V, the reaction temperature is 100~150 ℃, and the reaction time is maintained at 2~3 h. 3) The liquid alcohol mixture after the thermoelectric reaction is separated and purified by a rotary evaporator to obtain pure biomass long-chain oxygenated additive.

2. The method for preparing a biomass long-chain oxygenated additive to improve the solubility of methanol in diesel oil according to claim 1, characterized in that, Step 1) Pre-treat the biomass at 100~110℃ before pyrolysis.

3. The method for preparing a biomass long-chain oxygenated additive to improve the solubility of methanol in diesel oil according to claim 1, characterized in that, Step 1) The mass ratio of Fe-Ce composite metal oxide catalyst to biomass feedstock is 0.2~0.3:1; The inert gas mentioned is nitrogen.

4. The method for preparing a biomass long-chain oxygenated additive to improve the solubility of methanol in diesel oil according to claim 1, characterized in that, The thermochemical catalyst is a commercial zeolite catalyst, and the electrochemical catalyst is a commercial copper foam. The catalysts are cleaned with deionized water and dried under vacuum at 50~60 ℃ before use. The amount of zeolite catalyst added is 4-6% of the total mass of the liquid phase product.

5. The method for preparing a biomass long-chain oxygenated additive to improve the solubility of methanol in diesel oil according to claim 1, characterized in that, The distillation conditions of the rotary evaporator in step 3) are: at a pressure of 0.01~0.02 MPa, at 50~65 °C, and under reduced pressure for 20~40 min.

6. A biomass long-chain oxygenated additive for improving the solubility of methanol in diesel fuel, prepared by any one of claims 1 to 5.

7. An application of the biomass long-chain oxygenated additive as described in claim 6, characterized in that, The biomass long-chain oxygenated additive is added to the methanol-diesel mixture and stirred at a constant speed of 1000~1500 r / min for 30~40 min to obtain methanol-diesel fuel.

8. The application of the biomass long-chain oxygenated additive according to claim 7, characterized in that, The amount of the biomass long-chain oxygenated additive added is 20-25% of the total mass of the methanol-diesel mixture system, which improves the solubility of methanol in diesel by 90-100% and ensures that the volume ratio of methanol is 15-90%.

Images