Biofuel and preparation method thereof

Abstract

The present application discloses a biofuel and a preparation method thereof, and relates to the field of bioenergy technology. A method for preparing biofuel comprises the following steps: drying and crushing the biomass raw material, using an acetone system as a reaction medium, adding an ionic liquid catalyst, heating to carry out a liquefaction reaction, and obtaining a liquefied product; centrifuging and washing the liquefied product, and then performing rotary evaporation to obtain a biofuel precursor; adding a hydrogen donor, a zero-valent metal, a hydrogenation catalyst, and water to the biofuel precursor, heating and stirring in a closed environment, and performing a hydrogenation deoxygenation reaction to obtain a reaction product; filtering and rotary evaporating the reaction product to obtain biofuel. The present application realizes the conversion from biomass to biofuel, and the oxygen content of the prepared biofuel is greatly reduced, and the calorific value is significantly improved, which provides a possibility for replacing some non-renewable energy sources.

Description

Technical Field

[0001] The present application relates to the field of bioenergy technology, and in particular to a biofuel and a preparation method thereof. Background Art

[0002] Biofuel is a renewable, biodegradable, clean energy source. The development and application of biofuel can reduce people's dependence on fossil energy. Biomass resources refer to all organic matter formed directly or indirectly through photosynthesis by green plants, including plants, animals, microorganisms, and their excretions and metabolites. They have the advantages of being renewable, low-polluting, widely distributed, carbon neutral, and low in sulfur and nitrogen. Converting biomass into liquid products through chemical methods to produce biofuels that can be used as a substitute for petroleum diesel will help promote energy substitution, reduce environmental pressures, and control urban air pollution. However, the process of converting biomass into liquid products is generally inefficient, and the liquid products have a high oxygen content, resulting in a low calorific value, which limits the application of biofuels. Summary of the Invention

[0003] The main purpose of this application is to provide a biofuel and a preparation method thereof, aiming to solve the technical problem that the biofuel obtained by biomass conversion has a high oxygen content.

[0004] To achieve the above objectives, the present application proposes a method for preparing biofuel, comprising the following steps:

[0005] After the biomass raw material is dried and crushed, an acetone system is used as a reaction medium, an ionic liquid catalyst is added, and heating is performed to carry out a liquefaction reaction to obtain a liquefied product;

[0006] The liquefied product is centrifuged and washed, and then subjected to rotary evaporation to obtain a biofuel precursor;

[0007] adding a hydrogen donor, a zero-valent metal, a hydrogenation catalyst, and water to the biofuel precursor, heating and stirring in a closed environment to perform a hydrodeoxygenation reaction to obtain a reaction product;

[0008] The reaction product is filtered and rotary evaporated to obtain biofuel.

[0009] Optionally, the step of drying and crushing the biomass raw material includes:

[0010] The biomass raw material is dried at 95° C.-110° C. for 4 h-8 h, the moisture content of the dried biomass raw material is controlled between 2 wt%-4 wt%, and then the biomass raw material is crushed to a particle size of 80 μm-100 μm.

[0011] Optionally, in the step of using an acetone system as a reaction medium and adding an ionic liquid catalyst, the acetone system comprises acetone and hydrochloric acid; wherein the mass ratio of acetone to hydrochloric acid is 100:(3-4);

[0012] The ionic liquid catalyst is 1-ethyl-3-methylimidazolium chloride.

[0013] Optionally, the step of heating to perform a liquefaction reaction to obtain a liquefied product comprises:

[0014] A homogeneous reactor was used for the liquefaction reaction. The reaction was heated to 140-150°C at a heating rate of 1.2-1.6°C / min under closed conditions, and then kept warm for 4-5 hours while stirring at a speed of 10-15 r / min. After the reaction was completed, the reaction was cooled to room temperature to obtain a liquefied product.

[0015] Optionally, the step of centrifuging and washing the liquefied product and then performing rotary evaporation to obtain a biofuel precursor comprises:

[0016] The liquefied product is centrifuged multiple times to obtain a filtrate and a solid residue, and the solid residue is washed multiple times with acetone. The washing liquid is collected and rotary evaporated together with the filtrate at 25° C.-32° C. to obtain a biofuel precursor.

[0017] Optionally, in the step of adding a hydrogen donor, a zero-valent metal, a hydrogenation catalyst and water to the biofuel precursor, the hydrogen donor is sodium borohydride;

[0018] The zero-valent metal is at least one of zinc, aluminum, and iron;

[0019] The hydrogenation catalyst comprises an active metal component and a zirconium diboride whisker-molecular sieve composite carrier, wherein the active metal component comprises Ni, Cu, Co, W and Mo.

[0020] Optionally, the loading amount of the active metal component in the hydrogenation catalyst is 15%-25%; wherein the molar ratio of Ni / Co is 1:1, the molar ratio of Cu / (Ni+Co) is (0.4-0.8):1, and the molar ratio of W / Mo is 1:1;

[0021] The mass ratio of the zirconium diboride whisker to the molecular sieve in the zirconium diboride whisker-molecular sieve composite carrier is 1:(1-1.5).

[0022] Optionally, the step of preparing the hydrogenation catalyst comprises:

[0023] The molecular sieve and the zirconium diboride whisker are ball-milled for 10-15 hours, dried at 70-80° C. for 8-12 hours, and then calcined at 500-600° C. for 2-4 hours to obtain a zirconium diboride whisker-molecular sieve composite carrier;

[0024] dissolving a soluble salt of the active metal component in water to obtain an active component solution;

[0025] The zirconium diboride whisker-molecular sieve composite carrier is immersed in the active component solution, stirred and mixed, and then allowed to stand for 6 hours to 10 hours. Then, it is dried at 100° C. to 120° C. for 8 hours to 12 hours, and then calcined at 400° C. to 500° C. for 2 hours to 4 hours to obtain the hydrogenation catalyst.

[0026] Optionally, the step of heating and stirring in a closed environment to perform a hydrodeoxygenation reaction to obtain a reaction product comprises:

[0027] After hydrogen is introduced for purging, the mixture is heated to 240°C-400°C in a closed reactor at a heating rate of 3°C / min-4°C / min, kept warm for 0.5h-1h, and stirred at a speed of 160r / min-200r / min to carry out a hydrodeoxygenation reaction. After the reaction is completed, the mixture is water-cooled to room temperature within 8min-12min to obtain a reaction product.

[0028] The present application also proposes a biofuel obtained by the above-mentioned biofuel preparation method.

[0029] This application has at least the following beneficial effects:

[0030] The present application first liquefies the biomass feedstock, using an acetone-ionic liquid catalyst as the liquefaction system. The ionic liquid catalyst can convert the cellulose, hemicellulose, and lignin in the biomass into low-molecular-weight intermediates. These intermediates can further react and transform in the acetone solvent to form furan-based biofuel precursors. At the same time, the acetone itself also undergoes a condensation reaction, so that the liquefied products mainly include furfural-acetone, 5-hydroxymethylfurfural-acetone, acetone-acetone, etc., which together constitute the effective components of the biofuel precursor, reduce the generation of by-products and the processing steps, and improve the reaction efficiency and the yield of the liquefied product.

[0031] The present application further performs a hydrodeoxygenation treatment on the biofuel precursor to reduce the oxygen content and increase the calorific value. A stable, efficient, and environmentally friendly hydrogen supply system is provided by a hydrogen donor, a zero-valent metal, and a hydrogenation catalyst. The zero-valent metal can react with water to produce in-situ hydrogen, thereby avoiding the problem of insufficient hydrogen supply from the hydrogen donor and ensuring hydrogen supply. At the same time, the metal oxide generated by the zero-valent metal also has a catalytic effect, thereby producing a synergistic acceleration effect with the hydrogenation catalyst, further promoting the deoxygenation reaction of the biofuel precursor and increasing the yield of the biofuel. The hydrodeoxygenation efficiency is significantly higher than that of commonly used externally added gaseous hydrogen, the reaction conditions are also milder, and the hydrocarbon compound content in the biofuel is significantly increased, the oxygen-containing compound content is significantly reduced, and the calorific value is significantly increased.

[0032] The carbon chain length distribution of the biofuel in this application is mainly C5-C18, while diesel is a mixture of various hydrocarbons. The liquefied product of this application meets the carbon chain length requirements of diesel oil, and after hydrodeoxygenation treatment, the oxygen content is greatly reduced, and the calorific value is significantly improved, which has the potential to replace some non-renewable energy sources (such as diesel). BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0034] Figure 1 This is a flow chart of the method for preparing biofuel described in the examples of this application.

[0035] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] In view of the technical problems existing in the prior art, the embodiments of the present application provide a method for preparing biofuel, such as Figure 1 As shown, the following steps are included:

[0038] S10, drying and crushing the biomass raw material, using an acetone system as a reaction medium, adding an ionic liquid catalyst, heating to perform a liquefaction reaction, and obtaining a liquefied product.

[0039] In a specific implementation process, the step of drying and crushing the biomass raw material includes:

[0040] The biomass raw material is dried at 95° C.-110° C. for 4 h-8 h, the moisture content of the dried biomass raw material is controlled between 2 wt%-4 wt%, and then the biomass raw material is crushed to a particle size of 80 μm-100 μm.

[0041] The biomass raw materials used in this application are crop straw, herbaceous plants, woody plants or any mixture thereof, which are rich in cellulose, hemicellulose and lignin. After catalytic degradation, cellulose, hemicellulose and lignin can be degraded into liquid intermediates with high or low molecular mass and reactive activity (i.e., biofuel precursors), which are then used to prepare biofuel.

[0042] Specifically, the acetone system includes acetone and hydrochloric acid; wherein the mass ratio of acetone to hydrochloric acid is 100:(3-4).

[0043] This application uses acetone as the liquefaction solvent and adds an appropriate amount of hydrochloric acid to provide protons for the reaction. During the catalytic liquefaction process, the glycosidic bonds of cellulose and hemicellulose in the biomass raw material are first broken to form monosaccharide structures such as glucose and xylose. The monosaccharide structures are unstable and continue to hydrolyze to form furfural and 5-hydroxymethylfurfural with furan rings and their derivatives, which then undergo aldol condensation reactions with acetone to form furan-based biofuel precursors. At the same time, the reaction solvent acetone itself also undergoes condensation reactions to jointly constitute the biofuel precursor components, thereby improving the yield of the liquefied product and reducing the generation of by-products.

[0044] The ionic liquid catalyst used in this application is 1-ethyl-3-methylimidazolium chloride, and the mass ratio of biomass raw material to 1-ethyl-3-methylimidazolium chloride is 5: (1-3). Since components such as cellulose, hemicellulose and lignin in biomass are usually difficult to dissolve directly, the solubility of these components can be increased by using ionic liquid catalysis, providing a better reaction matrix for the liquefaction reaction. 1-ethyl-3-methylimidazolium chloride can effectively promote the pyrolysis and cracking of biomass in the catalytic liquefaction reaction. During the high-temperature liquefaction process, biomass may experience some undesirable side reactions (such as excessive cracking, coke formation, etc.). 1-ethyl-3-methylimidazolium chloride as a catalyst can adjust the reaction environment and reduce the incidence of these side reactions.

[0045] In a specific implementation process, the step of heating to carry out liquefaction reaction to obtain a liquefied product includes:

[0046] A homogeneous reactor was used for the liquefaction reaction. The reaction was heated to 140-150°C at a heating rate of 1.2-1.6°C / min under closed conditions, and then kept warm for 4-5 hours while stirring at a speed of 10-15 r / min. After the reaction was completed, the reaction was cooled to room temperature to obtain a liquefied product.

[0047] The present application adopts acetone-ionic liquid catalyst as liquefaction system. The polarity and solubility characteristics of acetone can help improve the interaction between biomass and 1-ethyl-3-methylimidazolium chloride catalyst and provide a good solvent environment for 1-ethyl-3-methylimidazolium chloride. 1-ethyl-3-methylimidazolium chloride can convert cellulose, hemicellulose and lignin in biomass into low molecular weight intermediates. These intermediates can further react and transform in acetone solvent to form different liquid products. The combination of acetone and 1-ethyl-3-methylimidazolium chloride catalyst helps to reduce the reaction Temperature, and improve the thermal stability of the reaction, so that the reaction can proceed under relatively mild conditions, improve the reaction efficiency, inhibit the formation of certain by-products, and improve the yield and quality of the liquefied product. The liquefied product obtained after catalytic liquefaction mainly includes furfural-acetone, 5-hydroxymethylfurfural-acetone, acetone-acetone, etc., with a carbon chain length distribution mainly of C5-C18 and a relative molecular weight of mostly less than 300. Diesel is a mixture of various hydrocarbons. The liquefied product of the present application meets the carbon chain length requirements of diesel oil, and at the same time reduces the generation and treatment steps of by-products, thereby improving the reaction efficiency and the yield of the liquefied product.

[0048] S20, centrifuging and washing the liquefied product, and then performing rotary evaporation to obtain a biofuel precursor.

[0049] In a specific implementation process, the liquefied product is centrifuged multiple times to obtain a filtrate and a solid residue, and the solid residue is washed multiple times with acetone. The washing liquid is collected and rotary evaporated together with the filtrate at 25° C.-32° C. to obtain a biofuel precursor.

[0050] S30, adding a hydrogen donor, a zero-valent metal, a hydrogenation catalyst and water to the biofuel precursor, heating and stirring in a closed environment to perform a hydrogenation deoxygenation reaction to obtain a reaction product.

[0051] In the specific implementation process, hydrogen is first introduced to purge the reactor, and then the reactor is sealed and heated to 240°C-400°C at a heating rate of 3°C / min-4°C / min, and kept warm for 0.5h-1h. At the same time, stirring is maintained at a speed of 160r / min-200r / min to carry out hydrodeoxygenation reaction. After the reaction is completed, it is water-cooled to room temperature within 8min-12min to obtain a reaction product.

[0052] Specifically, the hydrogen donor is sodium borohydride. Because sodium borohydride molecules contain a high hydrogen content (approximately 10.6%), they can provide a large number of hydrogen atoms, enabling them to effectively participate in the hydrodeoxygenation reaction of oxygen-containing functional groups in the liquefied product, reducing the formation of oxides and improving deoxygenation efficiency. Compared with other hydrogen sources, sodium borohydride does not require high-pressure hydrogen equipment, can release hydrogen under relatively mild conditions, and is relatively low in cost.

[0053] The zero-valent metal described in this application is at least one of zinc, aluminum, and iron. The zero-valent metal can react with water to produce in-situ hydrogen, thereby avoiding the potential hydrogen shortage problem associated with sodium borohydride. The resulting metal oxide also acts as a catalyst, synergistically accelerating the deoxygenation reaction of the biofuel precursor with the hydrogenation catalyst. This significantly increases the hydrocarbon content of the biofuel, significantly reduces the oxygen-containing compound content, and significantly improves the calorific value.

[0054] The hydrogenation catalyst described in the present application includes an active metal component and a zirconium diboride whisker-molecular sieve composite carrier, wherein the active metal component includes Ni, Cu, Co, W and Mo.

[0055] The loading amount of the active metal component in the hydrogenation catalyst is 15%-25%; wherein the molar ratio of Ni / Co is 1:1, the molar ratio of Cu / (Ni+Co) is (0.4-0.8):1, and the molar ratio of W / Mo is 1:1.

[0056] Specifically, the preparation steps of the hydrogenation catalyst include:

[0057] The molecular sieve and zirconium diboride whiskers are ball-milled for 10-15 hours, dried at 70-80°C for 8-12 hours, and calcined at 500-600°C for 2-4 hours to obtain a zirconium diboride whisker-molecular sieve composite carrier;

[0058] dissolving a soluble salt of the active metal component in water to obtain an active component solution;

[0059] The zirconium diboride whisker-molecular sieve composite carrier is immersed in the active component solution, stirred and mixed, and then allowed to stand for 6 hours to 10 hours. Then, it is dried at 100° C. to 120° C. for 8 hours to 12 hours, and then calcined at 400° C. to 500° C. for 2 hours to 4 hours to obtain the hydrogenation catalyst.

[0060] The hydrogenation catalyst of the present application uses Ni, Cu, Co, W, and Mo as the main active ingredients. Ni can effectively promote the reaction of oxides (such as phenols, aldehydes, and acids) with hydrogen, thereby reducing the oxygen content in the biofuel precursor. Cu has good electronic conductivity, which can enhance the electron transfer performance of the catalyst and improve the reaction efficiency. Co has very high catalytic activity for oxygen atoms on aromatic rings and can increase the heat resistance of the catalyst. W can provide strong acidity and metal surface catalytic activity, helping to improve the selectivity and hydrogenation capacity of the reaction in the hydrodeoxygenation reaction and increase the yield of biofuel. Mo has good activity at high temperatures, which can enhance the stability and activity of the catalyst, promote the hydrodeoxygenation reaction of phenols and aldehydes, and alleviate the problem of catalyst poisoning. The combined use of Ni, Cu, Co, W, and Mo greatly improves the efficiency of the hydrodeoxygenation reaction and reduces the oxygen content of biofuel.

[0061] Specifically, the mass ratio of zirconium diboride whiskers to molecular sieves in the zirconium diboride whisker-molecular sieve composite carrier is 1:(1-1.5).

[0062] The molecular sieve is one of Y-type molecular sieve, β-type molecular sieve, ZSM-5 molecular sieve, SAPO molecular sieve, and MCM-41 molecular sieve, preferably Y-type molecular sieve, with a SiO2 / Al2O3 molar ratio of 18-30 and a pore volume of 0.25 cm 3 / g-0.40cm 3 / g, with a specific surface area of 800m 2 / g-1000m 2 / g, and the relative crystallinity is 90%-120%.

[0063] The present application uses zirconium diboride whisker composite molecular sieve as a hydrogenation catalyst carrier. The crystal structure of zirconium diboride whiskers has high mechanical strength and thermal stability. After being composited with molecular sieve, it can provide a support structure with a high specific surface area, so that the metal active components can be evenly distributed and maintain good stability. Due to the special structure of zirconium diboride whiskers, they can help regulate the size and distribution of the molecular sieve pores, effectively limiting the penetration of large molecular reactants. In the hydrodeoxygenation reaction, this pore structure helps to selectively remove oxygen elements and avoid unnecessary side reactions. Since byproducts may poison the catalyst surface and reduce catalytic activity, the zirconium diboride whisker-molecular sieve composite carrier helps to reduce catalyst deactivation and extend the service life of the catalyst through its excellent stability and anti-poisoning ability. At the same time, zirconium diboride also has a strong hydrogen adsorption capacity, so that the composite carrier can effectively adsorb hydrogen, improve the utilization efficiency of hydrogen in the reaction, further improve the efficiency of the reaction, and thus increase the yield of biofuel.

[0064] S40, filtering and rotary evaporating the reaction product to obtain biofuel.

[0065] In a specific implementation process, the reaction product is vacuum filtered through a solvent filter to separate the solid and liquid, and then the filtrate is rotary evaporated at 34° C. to remove volatile organic compounds such as acetone.

[0066] The embodiments of the present application further provide a biofuel obtained by the above-mentioned biofuel preparation method.

[0067] The above technical solutions of the present application are described in detail below with reference to specific embodiments.

[0068] Example 1

[0069] A method for preparing biofuel comprises the following steps:

[0070] 100 g of biomass raw material was dried at 100° C. for 6 h, the moisture content was controlled to 3 wt %, and then ground to a particle size of 90 μm. 1000 g of acetone and 35 g of hydrochloric acid were mixed, and 30 g of 1-ethyl-3-methylimidazolium chloride was added. The mixture was added together with the ground biomass raw material into a homogeneous reactor for liquefaction reaction. The mixture was heated to 145° C. at a heating rate of 1.4° C. / min under closed conditions, and then kept warm for 4.5 h while stirring at a speed of 12 rpm. After the reaction was completed, the mixture was cooled to room temperature to obtain a liquefied product.

[0071] The liquefied product is centrifuged multiple times to obtain a filtrate and a solid residue, and the solid residue is washed multiple times with acetone, and the washing liquid is collected and rotary evaporated together with the filtrate at 29° C. to obtain a biofuel precursor;

[0072] By mechanical ball milling, 10 g of zirconium diboride whiskers and 12 g of molecular sieve were ball milled for 12 h, dried at 75 ° C for 10 h, and calcined at 550 ° C for 3 h to obtain a zirconium diboride whisker-molecular sieve composite carrier;

[0073] Combine Ni(NO3)2·6H2O 2g, Cu(NO3)2 2.4g, Co(NO3)2·6H2O 2g, W(CH3COO) 61.4g, (NH4)6Mo7O 24 Dissolve 0.2 g of 4H2O in 100 mL of water to obtain an active ingredient solution;

[0074] The zirconium diboride whisker-molecular sieve composite support was immersed in the active component solution, stirred and mixed, and then allowed to stand for 8 hours. The mixture was then dried at 110°C for 10 hours and calcined at 450°C for 3 hours to obtain a hydrogenation catalyst.

[0075] After hydrogen was introduced into the reactor for purging, 10 g of biofuel precursor, 4 g of sodium borohydride, 2 g of iron, 10 g of hydrogenation catalyst and 150 mL of water were added to the reactor and sealed. The reactor was heated to 300° C. at a heating rate of 3.5° C. / min and kept warm for 0.7 h while stirring at a speed of 180 r / min to carry out a hydrodeoxygenation reaction. After the reaction was completed, the reactor was cooled to room temperature within 10 min to obtain a reaction product.

[0076] The reaction product was vacuum filtered and then rotary evaporated at 34° C. to obtain biofuel.

[0077] Example 2

[0078] A method for preparing biofuel comprises the following steps:

[0079] 100 g of biomass raw material was dried at 95° C. for 8 h, the moisture content of the dried biomass raw material was controlled at 2 wt %, and then the mixture was pulverized to a particle size of 80 μm. 1000 g of acetone and 30 g of hydrochloric acid were mixed, and 30 g of 1-ethyl-3-methylimidazolium chloride was added. The mixture was added together with the pulverized biomass raw material into a homogeneous reactor for liquefaction reaction. The mixture was heated to 140° C. at a heating rate of 1.2° C. / min under closed conditions, and then kept warm for 5 h while stirring at a speed of 10 r / min. After the reaction was completed, the mixture was cooled to room temperature to obtain a liquefied product.

[0080] The liquefied product is centrifuged multiple times to obtain a filtrate and a solid residue, and the solid residue is washed multiple times with acetone, and the washing liquid is collected and rotary evaporated together with the filtrate at 25° C. to obtain a biofuel precursor;

[0081] By mechanical ball milling, 10 g of zirconium diboride whiskers and 10 g of molecular sieve were ball milled for 10 h, dried at 70° C. for 12 h, and calcined at 500° C. for 4 h to obtain a zirconium diboride whisker-molecular sieve composite carrier;

[0082] Combine Ni(NO3)2·6H2O 2g, Cu(NO3)2 1.6g, Co(NO3)2·6H2O 2g, W(CH3COO) 61.4g, (NH4)6Mo7O 24 Dissolve 0.2 g of 4H2O in 100 mL of water to obtain an active ingredient solution;

[0083] The zirconium diboride whisker-molecular sieve composite support was immersed in the active component solution, stirred and mixed, and then allowed to stand for 6 hours, and then dried at 100°C for 12 hours, and calcined at 400°C for 4 hours to obtain a hydrogenation catalyst;

[0084] After hydrogen was introduced into the reactor for purging, 10 g of biofuel precursor, 4 g of sodium borohydride, 2 g of zinc, 8 g of hydrogenation catalyst and 150 mL of water were added to the reactor and sealed. The reactor was then heated to 250° C. at a heating rate of 3° C. / min and kept warm for 1 hour while stirring at a speed of 160 r / min to carry out a hydrodeoxygenation reaction. After the reaction was completed, the reactor was cooled to room temperature within 8 minutes to obtain a reaction product.

[0085] The reaction product was vacuum filtered and then rotary evaporated at 34° C. to obtain biofuel.

[0086] Example 3

[0087] A method for preparing biofuel comprises the following steps:

[0088] 100 g of biomass raw material was dried at 110° C. for 4 h, the moisture content of the dried biomass raw material was controlled at 4 wt %, and then the raw material was crushed to a particle size of 100 μm. 1000 g of acetone and 40 g of hydrochloric acid were mixed, and 30 g of 1-ethyl-3-methylimidazolium chloride was added. The mixture was added together with the crushed biomass raw material into a homogeneous reactor for liquefaction reaction. The mixture was heated to 150° C. at a heating rate of 1.6° C. / min under closed conditions, and then kept warm for 4 h while stirring at a speed of 15 rpm. After the reaction was completed, the mixture was cooled to room temperature to obtain a liquefied product.

[0089] The liquefied product is centrifuged multiple times to obtain a filtrate and a solid residue, and the solid residue is washed multiple times with acetone. The washing liquid is collected and rotary evaporated together with the filtrate at 32° C. to obtain a biofuel precursor;

[0090] By mechanical ball milling, 10 g of zirconium diboride whiskers and 15 g of molecular sieve were ball milled for 15 h, dried at 80 ° C for 8 h, and calcined at 600 ° C for 2 h to obtain a zirconium diboride whisker-molecular sieve composite carrier;

[0091] Combine Ni(NO3)2·6H2O 3g, Cu(NO3)2 3.6g, Co(NO3)2·6H2O 3g, W(CH3COO) 62.1g, (NH4)6Mo7O 24 Dissolve 0.3 g of 4H2O in 100 mL of water to obtain an active ingredient solution;

[0092] The zirconium diboride whisker-molecular sieve composite support was impregnated in the active component solution, stirred and mixed, and then allowed to stand for 10 hours, then dried at 120°C for 8 hours, and calcined at 500°C for 2 hours to obtain a hydrogenation catalyst;

[0093] After hydrogen was introduced into the reactor for purging, 12 g of biofuel precursor, 4 g of sodium borohydride, 1 g of aluminum, 1 g of iron, 10 g of hydrogenation catalyst and 150 mL of water were added to the reactor and sealed. The reactor was sealed and heated to 350° C. at a heating rate of 4° C. / min, kept warm for 0.5 h, while maintaining stirring at a speed of 200 r / min to carry out hydrodeoxygenation reaction. After the reaction was completed, the reactor was cooled to room temperature within 12 minutes to obtain a reaction product.

[0094] The reaction product was vacuum filtered and then rotary evaporated at 34° C. to obtain biofuel.

[0095] Experimental example

[0096] The biofuel prepared in the examples of this application was tested for its C, H, O, and S content, and its calorific value was also tested. A conventional diesel sample was used as a control. The C, H, and O content was tested according to the GB / T19143-2017 standard, while the S content was tested according to the ASTM5453-2016 standard. The test results are shown in Table 1 below. The calorific value was tested using a bomb calorimeter in accordance with the ASTM D4809 standard. The test results are shown in Table 2 below.

[0097] Table 1

[0098] Group C (m%) H (m%) O(m%) S (mg / L) Example 1 82.1 16.9 1.7 2.2 Example 2 81.8 16.4 1.8 2.9 Example 3 81.6 16.7 1.7 2.0 Diesel samples 85.1 14.1 0.9 14.6

[0099] As can be seen from Table 1, since the carbon chain length distribution of the biofuel of the present application is mainly C5-C18, which basically meets the carbon chain length used in diesel oil, the proportion of C element is only slightly lower than that of the diesel sample. Moreover, after hydrodeoxygenation, the proportion of H element in the biofuel of the present application is very close to that of the diesel sample, and the proportion of O element is only slightly higher than that of the diesel sample. However, the S element in the biofuel of the present application is much lower than that of the diesel sample. The presence of sulfides in diesel not only causes corrosion of equipment and aging of the bellows, but also increases the formation of carbon deposits during use, and also generates atmospheric pollutants during combustion. The S element content in the biofuel of the present application is extremely low, indicating that it is more environmentally friendly.

[0100] Table 2

[0101] Group Calorific value (MJ / kg) Example 1 39.37 Example 2 38.70 Example 3 38.88 Diesel samples 43

[0102] As can be seen from Table 2, the calorific value of the biofuel of the present application is slightly lower than that of the diesel sample, mainly because its oxygen content is higher. The calorific value is affected to a certain extent by the oxygen content. However, it can basically meet the calorific value requirements for automotive diesel use (the calorific value range of automotive diesel is roughly between 38.7MJ / kg and 40.5MJ / kg), indicating that the biofuel of the present application has the potential to be used as diesel.

[0103] The above are merely optional embodiments of the present application and do not limit the patent scope of the present application. All equivalent structural transformations made using the contents of the present application specification and drawings under the inventive concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for preparing biofuel, characterized in that: The following steps are involved: After the biomass raw material is dried and crushed, an acetone system is used as a reaction medium, an ionic liquid catalyst is added, and heating is performed to carry out a liquefaction reaction to obtain a liquefied product; the acetone system comprises acetone and hydrochloric acid; wherein the mass ratio of acetone to hydrochloric acid is 100:(3-4); the ionic liquid catalyst is 1-ethyl-3-methylimidazolium chloride; The liquefied product is centrifuged and washed, and then subjected to rotary evaporation to obtain a biofuel precursor; A hydrogen donor, a zero-valent metal, a hydrogenation catalyst, and water are added to the biofuel precursor, and the mixture is heated and stirred in a closed environment to perform a hydrodeoxygenation reaction to obtain a reaction product; the hydrogen donor is sodium borohydride; the zero-valent metal is at least one of zinc, aluminum, and iron; and the hydrogenation catalyst comprises an active metal component and a zirconium diboride whisker-molecular sieve composite carrier, wherein the active metal component comprises Ni, Cu, Co, W, and Mo; The reaction product is filtered and rotary evaporated to obtain biofuel.

2. The method for preparing biofuel according to claim 1, characterized in that: The step of drying and crushing the biomass raw material comprises: The biomass raw material is dried at 95° C.-110° C. for 4 h-8 h, the moisture content of the dried biomass raw material is controlled between 2 wt%-4 wt%, and then the biomass raw material is crushed to a particle size of 80 μm-100 μm.

3. The method for preparing biofuel according to claim 1, wherein: The step of heating to carry out liquefaction reaction to obtain a liquefied product comprises: A homogeneous reactor was used for the liquefaction reaction. The reaction was heated to 140-150°C at a heating rate of 1.2-1.6°C / min under closed conditions, and then kept warm for 4-5 hours while stirring at a speed of 10-15 r / min. After the reaction was completed, the reaction was cooled to room temperature to obtain a liquefied product.

4. The method for preparing biofuel according to claim 1, characterized in that: The step of centrifuging and washing the liquefied product and then performing rotary evaporation to obtain a biofuel precursor comprises: The liquefied product is centrifuged multiple times to obtain a filtrate and a solid residue, and the solid residue is washed multiple times with acetone. The washing liquid is collected and rotary evaporated together with the filtrate at 25° C.-32° C. to obtain a biofuel precursor.

5. The method for preparing biofuel according to claim 4, characterized in that: The loading amount of the active metal component in the hydrogenation catalyst is 15%-25%; wherein the molar ratio of Ni / Co is 1:1, the molar ratio of Cu / (Ni+Co) is (0.4-0.8):1, and the molar ratio of W / Mo is 1:1; The mass ratio of the zirconium diboride whisker to the molecular sieve in the zirconium diboride whisker-molecular sieve composite carrier is 1:(1-1.5).

6. The method for preparing biofuel according to claim 5, characterized in that: The preparation step of the hydrogenation catalyst comprises: The molecular sieve and the zirconium diboride whisker are ball-milled for 10-15 hours, dried at 70-80° C. for 8-12 hours, and then calcined at 500-600° C. for 2-4 hours to obtain a zirconium diboride whisker-molecular sieve composite carrier; dissolving a soluble salt of the active metal component in water to obtain an active component solution; The zirconium diboride whisker-molecular sieve composite carrier is immersed in the active component solution, stirred and mixed, and then allowed to stand for 6 hours to 10 hours. Then, it is dried at 100° C. to 120° C. for 8 hours to 12 hours, and then calcined at 400° C. to 500° C. for 2 hours to 4 hours to obtain the hydrogenation catalyst.

7. The method for preparing biofuel according to claim 1, characterized in that: The step of heating and stirring in a closed environment to perform a hydrodeoxygenation reaction to obtain a reaction product comprises: After hydrogen is introduced for purging, the mixture is heated to 240°C-400°C in a closed reactor at a heating rate of 3°C / min-4°C / min, kept warm for 0.5h-1h, and stirred at a speed of 160r / min-200r / min to carry out a hydrodeoxygenation reaction. After the reaction is completed, the mixture is water-cooled to room temperature within 8min-12min to obtain a reaction product.

8. A biofuel, characterized in that: Obtained by the biofuel preparation method according to any one of claims 1 to 7.

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