A method for co-producing bio-aviation fuel from corncobs

Abstract

The present invention discloses a method for co-producing bio-aviation fuel from corncobs, which comprises the following steps: screening and pulverizing corncobs to control the particle size to be 10-15 mm; mixing the pulverized corncobs with furfural production wastewater containing acetic acid for hydrolysis reaction to generate a dilute furfural solution at 195-205 °C and 1.25-1.3 MPa; subjecting the solid residue after hydrolysis to alkali treatment to separate and obtain crude cellulose; subjecting the crude cellulose to acidolysis reaction by microwave heating in a solid acid catalyst and formic acid solution to generate a dilute levulinic acid solution; catalytically polymerizing the dilute furfural solution and the dilute levulinic acid solution under the action of a copper-based catalyst to generate a C10-C15 hydrocarbon mixture; generating a C10-C15 saturated hydrocarbon liquid mixture through oil-water separation and deoxygenation and hydrogenation reaction of a nickel-based catalyst; and finally through fractional distillation and activated carbon filtration; this method realizes the efficient co-production of furfural, cellulose and bio-aviation fuel from corncobs, and has the advantages of high raw material utilization rate, excellent catalytic efficiency, low energy consumption and environmental friendliness.

Description

Technical Field

[0001] The present invention relates to the technical field of biofuel preparation, and specifically to a method for co-producing bio-aviation fuel from corncobs. Background Art

[0002] Corncobs are agricultural and forestry biomass wastes, mainly composed of three major components: cellulose, hemicellulose, and lignin, and have rich renewable carbon resources. With the continuous growth of the global demand for sustainable energy, liquid fuels (such as bio-aviation fuel) based on biomass have received extensive attention due to their renewable and low-carbon emission characteristics.

[0003] Currently, the methods for preparing liquid fuels from lignocellulosic biomass mainly include processes such as hydrolysis, catalytic conversion, and hydrodeoxygenation. Among them, furfural is an important bio-based platform compound that can be generated by the hydrolysis of hemicellulose. However, the existing technologies have the following deficiencies in the process of preparing biofuels from corncobs. For example, Chinese Patent Authorization Publication No. CN117866673B discloses a method for preparing aviation fuel components from lignocellulosic biomass. The method for preparing furfural by a two-step process is as follows: First step: The corncobs are pre-treated by washing with water, generating a large amount of wastewater; Second step: After hydrolysis, additional filtration and stripping are required; Pentose dehydration to prepare furfural is carried out under the condition of an acid catalyst (sulfuric acid, acetic acid, or maleic acid), and a biphasic reaction system (such as water / dichloromethane or water / γ-valerolactone) is used for the reaction at 160 - 180 °C. The existing defects are as follows: First, the two-step method for preparing furfural pre-treats the raw materials by washing with water and filters and strips the hydrolysis solution, resulting in a large amount of wastewater and a low furfural conversion rate in the whole process; moreover, the equipment has high corrosion; Second, the one-pot method for producing cellulose results in low fiber purity and high impurity content in the hydrothermal cracking of cellulose; Third, the hydrocarbon components of the aviation fuel obtained by this process do not meet the calorific value and combustion standards of aviation fuel, and further deep processing is required in the follow-up; The existing technology relies on an additional acid catalyst (such as sulfuric acid), and the acid catalyst has high corrosiveness and is difficult to treat the waste liquid; The energy consumption is relatively high, such as the demand for high-temperature and high-pressure steam and the improper control of the excessive hydrogen gas flow rate during the hydrogenation process, increasing the cost.

[0004] Chinese Patent Application No. 202310157574.9 discloses the preparation of sustainable aviation fuel through a one-step solvent-free reaction using biomass-derived carbonyl compounds as intermediates. This patent only uses carbonyl compounds as intermediates and does not make full use of other biomass components (such as cellulose, lignin, etc.). It mainly relies on a one-step reaction, and the carbon chain growth is limited, making it difficult to prepare long-chain hydrocarbon fuels with more than C10-C15. Similarly, Chinese Patent Application No. 202310135285.9 provides a method for directly converting biomass to produce aviation liquid fuel. It directly generates liquid fuel through biomass pyrolysis, including pyrolysis, carbon chain growth, and condensation separation. The disadvantages and deficiencies are as follows: The pyrolysis process is unstable: During pyrolysis, it is easy to form coke and other uncontrollable by-products, resulting in unstable yields; Lack of catalytic control: It only relies on the high-temperature decomposition during the pyrolysis process and lacks precise catalyst control, affecting the fuel quality. During the pyrolysis process of this method, cellulose may undergo partial carbonization.

[0005] Chinese Patent Application No. 202010554841.2 discloses a high-performance aviation alternative fuel and its preparation method. Using a mixed solution or fermentation broth containing water, acetone, and optionally butanol and ethanol obtained from biomass fermentation as raw materials, after condensation reaction, trimerization condensation reaction, and hydrodeoxygenation reaction, high-performance aviation alternative fuel can be prepared. The existing defects are as follows: Limited raw material sources: The raw material is a fermentation broth, which is mainly applicable to sugar-based biomass and has insufficient direct utilization ability for agricultural and forestry waste; Complex reaction path: It involves multiple condensation and trimerization condensations, with many reaction steps and by-products, increasing the production complexity.

[0006] Chinese Patent Application No. 202280039111.6 discloses a method for bio-renewable light paraffin kerosene and sustainable aviation fuel. Under the conditions of producing a hydroisomerizer product containing a heavy hydroisomerizer fraction and LPK, hydroisomerize and hydrocrack the heavy hydrotreater fraction with a hydroisomerization catalyst. Multiple-step hydrogenation and isomerization reactions are used, involving various noble metal catalysts, resulting in higher production costs. The raw material is renewable light paraffins and does not involve the synthesis of bio-based platform compounds such as furfural or levulinic acid.

[0007] A method for co-producing bio-aviation fuel from corncobs is proposed to address the above problems. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the existing defects and provide a method for co-producing bio-aviation fuel from corncobs. By efficiently utilizing corncob resources, not only the conversion rates of furfural and cellulose are improved, but also high-calorie bio-aviation fuel can be co-produced, providing a more environmentally friendly and economical solution for biomass energy development. It solves the problems of low added value of furfural products and large fluctuations in the downstream market during the production of furfural from corncobs, and solves the problems of ineffective utilization and accumulation of furfural residues during the production of furfural, achieving the full utilization of corncobs. At the same time, it also provides a new production process and source channel for bio-aviation fuel, and can effectively solve the problems in the background technology.

[0009] To achieve the above object, the present invention provides the following technical solution: A method for co-producing bio-aviation fuel from corncobs, comprising the following steps:

[0010] Step 1: Screening and crushing of corncobs. Screen the corncobs to remove those with moisture content greater than 10%. Crush the screened corncobs and control the particle size to be 10-15 mm.

[0011] Step 2: Furfural production and hydrolysis reaction. Mix the crushed corncob particles with furfural production wastewater containing 3.5-4.5% acetic acid in a solid-liquid ratio of 5-8:1. Put the mixed raw materials into a hydrolysis reactor, and introduce primary steam or secondary steam to control the reaction temperature at 195-205 °C and the reaction pressure between 1.25-1.3 MPa. Continuously carry out the hydrolysis reaction to produce furfural. The volatilized furfural steam during the reaction is recovered by condensation to form a dilute solution containing 8-10% furfural.

[0012] Step 3: Washing of solid residue and separation of cellulose. The solid residue after the hydrolysis reaction is discharged and washed multiple times with primary water until the washing water is neutral. Add sodium hydroxide solution to the washed residue and heat it to 70-80 °C for 2-2.5 hours to effectively dissolve the cellulose in the alkaline solution. After the reaction, naturally cool it to room temperature and filter with a filter press to obtain crude cellulose.

[0013] Step 4: Acid hydrolysis of cellulose and formation of levulinic acid. Dissolve the crude cellulose in a 3-5% formic acid solution, carry out microwave pyrolysis reaction, then cool and filter the mixture, and then carry out filtration and water washing to obtain a dilute solution containing 6-9% levulinic acid.

[0014] Step 5: High-temperature catalytic polymerization. Mix the dilute furfural solution and the dilute levulinic acid solution, add a copper-based catalyst, and carry out a polymerization reaction at 260-280 °C to obtain a C10-C15 mixture.

[0015] Step 6: Oil-water separation and deoxygenation hydrogenation. The reaction solution in the reaction kettle is slowly cooled naturally. When the temperature drops to 50 - 60 °C, the reaction solution is transferred from the reaction kettle to the temporary storage tank. The reaction solution is stratified in the temporary storage tank. The upper layer is the aqueous solution, and the lower layer is the C10 - C15 mixture. The C10 - C15 mixture is transferred to the reaction kettle and a nickel-based catalyst is added simultaneously. Hydrogen is introduced, and the reaction kettle is heated to achieve the deoxygenation hydrogenation of the mixture.

[0016] Step 7: Rectification separation. The reaction mixture is subjected to atmospheric rectification separation to obtain a C10 - C15 hydrocarbon liquid mixture. Unsaturated hydrocarbons and oxygen-containing compounds are recycled. A copper-based catalyst is added to the C10 - C15 hydrocarbon mixture, and hydrogen is introduced simultaneously. The reaction kettle is further heated to convert the unsaturated carbon bonds of the hydrocarbons into saturated carbon bonds, turning the C10 - C15 hydrocarbon mixed liquid into a C10 - C15 saturated hydrocarbon liquid.

[0017] Step 8: Activated carbon filtration and purification. Activated carbon is added to the reaction mixture to filter the suspended matter of the hydrocarbons, facilitating the separation of saturated hydrocarbons and unsaturated hydrocarbons. At the same time, the activated carbon is centrifuged out, and the centrifuged liquid is distilled and separated to obtain a C10 - C15 saturated hydrocarbon liquid, which is the finished product of bio-aviation fuel.

[0018] Further, in Step 4, a solid acid catalyst is added to the formic acid solution to form a reaction solution. The ratio of formic acid to the solid acid catalyst is 50:1 to 100:1. After stirring evenly, crude cellulose is added, and the microwave heating temperature range is 120 - 150 °C; heating is carried out for 1.5 - 2 hours.

[0019] Further, the mass fraction of the sodium hydroxide solution is 30%, and the pH of the solution is adjusted to above 10.

[0020] Further, in Step 6, the hydrogen flow rate is 0.5 - 0.8 L / min, the reaction kettle is heated to 320 °C, and the pressure is controlled at 7 MPa.

[0021] Further, in Step 6, the hydrogen flow rate is increased to 1.0 - 1.5 L / min, the temperature is adjusted to 330 °C, and the pressure is maintained at 9 MPa.

[0022] Further, the copper-based catalyst is Cu / ZrO 2 or Cu-Ni.

[0023] Further, in Step 2, the steam temperature is 200 °C and the steam pressure is 1.3 MPa.

[0024] Further, the distillation adopts fractional distillation. In the first stage, the distillation temperature is controlled at 150 - 200 °C to separate low-boiling C10 hydrocarbons first. In the second stage, the temperature is increased to 200 - 250 °C to separate C11 - C15 hydrocarbons.

[0025] Further, the activated carbon used in Step 8 is modified activated carbon, the surface of which is treated by pickling or alkali washing. At the same time, the pore size distribution of the activated carbon is controlled such that the proportion of micropores of 0.5 - 2 nm is 50%; the proportion of mesopores of 2 - 50 nm is 40%; and the proportion of macropores greater than 50 nm is 10%.

[0026] Further, the acetic acid content in the dilute furfural solution is controlled at 3.8 - 4.2%.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. Through a reasonable process flow and catalyst system, the utilization rate of raw materials is effectively improved; in the production and hydrolysis reaction of furfural, the acetic acid component in the furfural production wastewater is used as an acidic catalyst, which not only reduces the demand for additional acidic catalysts but also reduces the wastewater discharge, achieving an environmental protection effect of energy conservation and emission reduction from the source. In addition, by controlling the crushing particle size of corncobs and reaction conditions, the conversion rate and recovery rate of furfural are further optimized.

[0029] 2. In the process of cellulose extraction, the present invention realizes the efficient separation of cellulose by using a sodium hydroxide solution with a specific concentration and controlling the temperature and reaction time; the crude cellulose has a high purity, which is conducive to the efficient production of levulinic acid in the subsequent process; at the same time, the introduction of solid acid catalysts such as SBA - 15 supported sulfonic acid or Amberlyst - 15 resin ensures the recyclability of the catalyst and the reaction stability during the acid hydrolysis of cellulose, further reducing catalyst loss and environmental pollution.

[0030] 3. In the catalytic polymerization and hydrodeoxygenation steps, the present invention effectively reduces the reaction temperature and hydrogen gas flow rate by using copper - based and nickel - based catalysts, while ensuring a high selectivity and yield of the target product; the improvement of hydrogen gas utilization efficiency not only reduces energy consumption but also reduces the waste of unreacted hydrogen gas; in addition, through the fractional distillation separation technology, hydrocarbons with different carbon chain lengths of C10 - C15 are effectively separated, improving the purity and calorific value of the bio - aviation fuel product.

[0031] 4. The new process for co - producing bio - aviation fuel from corncobs realizes the output of a multi - product chain from one end of the corncob, which is conducive to improving the added value of corncobs, the utilization rate of corncob components and economic value; the realization of the new process for co - producing bio - aviation fuel from corncobs reduces the production cost of bio - aviation fuel by 500 - 800 yuan compared with the production cost using waste oil as raw materials, effectively reducing the production cost of bio - aviation fuel and increasing the utilization rate and market share of bio - aviation fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic flow chart of the present invention; Detailed implementation mode

[0033] The present invention will be further elaborated below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Please refer to Figure 1 , the present invention provides a technical solution: a method for co-producing bio-aviation fuel from corncobs, including the following steps:

[0035] Step 1: Screening and pulverizing treatment of corncobs. Screen the corncobs, remove the corncobs with a moisture content greater than 10%, pulverize the screened corncobs, and control the particle size to be 10-15 mm; controlling the particle size of the corncob particles can avoid cellulose loss caused by excessive pulverization, ensure that the specific surface area of the corncob particles is large enough during hydrolysis, and provide more stable corncob particle quality for subsequent hydrolysis reactions;

[0036] The screened corncobs have a low moisture content and are suitable for subsequent processing; by accurately screening the moisture content and physical properties, while ensuring the quality of the raw materials, it reduces the interference of moisture in the subsequent process on the reaction effect.

[0037] Step 2: Furfural production and hydrolysis reaction. Mix the pulverized corncob particles with furfural production wastewater containing 3.5-4.5% acetic acid in a solid-liquid ratio of 5-8:1 evenly. The acetic acid component in the wastewater provides an acidic environment for the reaction, which helps hydrolysis conversion. The hydrolysis process decomposes lignocellulose and generates furfural as the target product. Put the mixed raw materials into a hydrolysis reactor, introduce primary steam or secondary steam, control the reaction temperature at 195-205 °C, and the reaction pressure between 1.25-1.3 MPa, and continuously carry out the hydrolysis reaction to generate furfural and other by-products. In terms of temperature, a two-stage temperature control system is adopted to optimize the steam use efficiency, reasonably adjust the reaction conditions, not only improve the conversion rate of furfural, but also reduce the corrosion of the equipment and enhance the sustainability of the process. The volatilized furfural steam in the reaction is recovered by condensation to form a dilute solution containing 8-10% furfural;

[0038] In this step 2, by introducing wastewater containing acetic acid as a solvent, it reduces the demand for acidic substances in the production process, not only saves costs, but also better utilizes wastewater resources to achieve closed-loop production. The reuse of wastewater greatly reduces the environmental pollution risk.

[0039] Step 3: Washing of solid residue and separation of cellulose. The solid residue after the hydrolysis reaction is discharged and washed multiple times with primary water until the washing water is neutral. Sodium hydroxide solution is added to the washed residue and heated to 70 - 80 °C for 2 - 2.5 hours to effectively dissolve cellulose in the alkaline solution. After the reaction, it is naturally cooled to room temperature, and the crude cellulose is obtained by filtration using a filter press;

[0040] During the alkali dissolution treatment, the present invention uses a sodium hydroxide solution under specific concentration and temperature conditions, maximizing the dissolution efficiency of cellulose, reducing the dissolution of non-cellulose substances, and maintaining the high purity of cellulose.

[0041] Step 4: Acid hydrolysis of cellulose and formation of levulinic acid. The crude cellulose is dissolved in a 3 - 5% formic acid solution and subjected to microwave pyrolysis reaction. Through microwave heating, a more uniform heating effect is provided. The radiant energy of the microwave enables cellulose to be rapidly hydrolyzed in an acidic environment and effectively improves the separation efficiency of levulinic acid. Then, the mixture is cooled and filtered, followed by filtration and water washing to obtain a dilute solution containing 6 - 9% levulinic acid;

[0042] Step 5: High-temperature catalytic polymerization. The dilute furfural solution and the dilute levulinic acid solution are mixed, a copper-based catalyst is added, and a polymerization reaction is carried out at 260 - 280 °C to obtain a C10 - C15 mixture. The application of the copper-based catalyst significantly reduces the reaction energy consumption and improves the selectivity of the target product;

[0043] Step 6: Oil-water separation and deoxygenation hydrogenation. The reaction solution in the reaction kettle is slowly cooled naturally. When it is cooled to 50 - 60 °C, the reaction solution is transferred from the reaction kettle to a temporary storage tank. The reaction solution is stratified in the temporary storage tank. The upper layer is an aqueous solution, and the lower layer is a C10 - C15 mixture. The C10 - C15 mixture is transferred to the reaction kettle and a nickel-based catalyst is added simultaneously. Hydrogen is introduced, and the reaction kettle is heated to achieve the deoxygenation hydrogenation of the mixture;

[0044] The efficient nickel-based catalyst combined with precise control of reaction conditions improves the hydrogenation efficiency and the quality of the target product; the use of high-pressure hydrogen reduces the oxygen content and increases the calorific value of hydrocarbons;

[0045] Step 7: Rectification separation. The reaction mixture is subjected to atmospheric rectification separation to obtain a C10 - C15 hydrocarbon liquid mixture. Unsaturated hydrocarbons and oxygen-containing compounds are recycled. A copper-based catalyst is added to the C10 - C15 hydrocarbon mixture, and hydrogen is introduced simultaneously. The reaction kettle is further heated to convert the unsaturated carbon bonds of hydrocarbons into saturated carbon bonds, converting the C10 - C15 hydrocarbon liquid mixture into a C10 - C15 saturated hydrocarbon liquid;

[0046] Step 8: Activated carbon filtration and purification. Add activated carbon to the reaction mixture to filter the hydrocarbon suspension, facilitating the separation of saturated hydrocarbons and unsaturated hydrocarbons. At the same time, centrifuge out the activated carbon and distill and separate the centrifuged liquid to obtain a C10-C15 saturated hydrocarbon liquid, which is the finished product of bio-aviation fuel.

[0047] In Step 4, add a solid acid catalyst to the formic acid solution to form a reaction solution. The ratio of formic acid to the solid acid catalyst is 50:1 to 100:1. After stirring evenly, add the crude cellulose. Use a sulfonic acid group solid acid as a co-catalyst. The sulfonic acid group solid acid is selected from SBA-15 supported sulfonic acid or Amberlyst-15 resin to stabilize the catalytic performance of the low-concentration acid, co-catalyze the hydrolysis of cellulose, improve the reaction efficiency, and at the same time the solid acid can be recycled. The microwave heating temperature range is 120 - 150 °C; if the temperature is too low, less than 120 °C, the cellulose decomposition rate will decrease significantly, and the reaction time will be extended to more than 4 hours, affecting the production capacity. If the temperature is too high, greater than 150 °C, the cellulose will be over-degraded, the generation of by-products such as furfural will increase, and at the same time the corrosion will be enhanced. Heat for 1.5 - 2 hours.

[0048] Table 1. Comparison table of formic acid concentration, temperature, catalyst content, and reaction time

[0049]

[0050] The mass fraction of the sodium hydroxide solution is 30%, and the pH of the solution is adjusted to above 10. Due to its strong alkalinity and high solubility, the sodium hydroxide solution can significantly improve the separation efficiency of the cellulose component in corn cobs.

[0051] In Step 6, the hydrogen flow rate is 0.5 - 0.8 L / min, the reaction kettle is heated to 320 °C, and the pressure is controlled at 7 MPa. If the hydrogen flow rate is too low, less than 0.5 L / min, the hydrogen source supply is insufficient, the reaction is incomplete, resulting in the residue of unsaturated hydrocarbons.

[0052] In Step 6, when the hydrogen flow rate is 1.0 - 1.5 L / min, the temperature is adjusted to 330 °C, and the pressure is maintained at 9 MPa. If the hydrogen flow rate is too high, greater than 1.5 L / min, it will cause hydrogen waste, directly discharge without fully participating in the reaction, and the gas-liquid phase mixing is not sufficient, which may lead to side reactions such as cracking.

[0053] The influence of the gas pressure inside the reactor on the reaction: at low pressure less than 5 MPa, the dissolution of hydrogen is insufficient, the reaction rate is slow, and there may be residues of unsaturated hydrocarbons, which is suitable for mild saturation treatment of shorter-chain hydrocarbons (such as C10-C12); at medium pressure of 5-7 MPa, it is suitable for the saturation reaction of most C10-C15 hydrocarbons, with moderate hydrogen solubility and a balance between reaction rate and selectivity; at high pressure greater than MPa, it is suitable for the reaction of longer-chain hydrocarbons such as C14-C15 and for reactions with a complete saturation requirement, and side reactions such as cracking or polymerization may be triggered.

[0054] The copper-based catalyst is Cu / ZrO 2 or Cu-Ni.

[0055] Introducing CeO 2 or La 2 O 3 as an additive is mainly to improve the anti-toxicity of the catalyst such as anti-sulfur, anti-chlorine, oxygen storage capacity, catalytic activity and stability; the following are the introduction methods and their optimization.

[0056] Introducing CeO 2 or La 2 O 3 The principle of introducing CeO 2 cerium oxide or La 2 O 3 lanthanum oxide uniformly distributed on the surface of the pre-prepared Cu / ZrO 2 catalyst to enhance the anti-toxicity, oxygen storage capacity and stability of the catalyst.

[0057] Preparation steps:

[0058] I. Prepare the Cu / ZrO 2 catalyst support by the co-precipitation method, mix Cu(NO 3 ) 2 and Zr(NO 3 ) 4 , co-precipitate to form Cu(OH) 2 and Zr(OH) 4 precipitates at pH 8-9, filter and wash, then dry at 105 °C for 12 hours and calcine at 500 °C for 4 hours;

[0059] II. Preparation of the CeO 2 / La 2 O 3 impregnation solution: prepare a Ce(NO 3 ) 3 or La(NO 3 ) 3 solution with a target loading of 5-10 wt%;

[0060] III. Impregnation process: Put the Cu / ZrO 2 catalyst into the impregnation solution and stir for 1 hour at room temperature to ensure uniform distribution of metal ions;

[0061] IV. Drying and calcination: Dry at 105°C for 12 hours and calcine at 500°C for 4 hours to completely decompose Ce(NO 3 ) 3 or La(NO 3 ) 3 to form CeO 2 or La 2 O 3 .

[0062] In step II, the steam temperature is 200°C and the steam pressure is 1.3 MPa to improve the furfural stripping efficiency.

[0063] The distillation is carried out in stages. In the first stage, control the distillation temperature at 150 - 200°C to separate low-boiling C10 hydrocarbons first. In the second stage, increase the temperature to 200 - 250°C to separate C11 - C15 hydrocarbons; Using staged distillation can avoid cross-contamination of different fractions and improve the separation accuracy.

[0064] The activated carbon used in step VIII is modified activated carbon, whose surface is treated by acid washing or alkali washing to further increase the adsorption sites. At the same time, the pore size distribution of the activated carbon is controlled as follows: micropores of 0.5 - 2 nm account for 50%; mesopores of 2 - 50 nm account for 40%; macropores larger than 50 nm account for 10%, so as to improve the adsorption capacity for impurities with different molecular weights, and realize solid-liquid separation by centrifugal separation and secondary filtration.

[0065] The acetic acid content of the dilute furfural solution is controlled at 3.8 - 4.2% to maintain the stability of the acid-catalyzed environment, thereby reducing the usage amount of additional acid catalyst and lowering the production cost. Example 1

[0066] A method for co-producing bio-aviation fuel from corncobs is provided, and the specific implementation steps are as follows:

[0067] Step 1: Screening and crushing of corncobs; Select 100 kg of corncob raw materials with a moisture content of less than 10%. Screen out the raw materials with excessive moisture, and use a crusher to crush the qualified corncobs to a particle size controlled within the range of 10 - 15 mm to ensure stability and reaction efficiency in the hydrolysis reaction;

[0068] Step 2: Furfural production and hydrolysis reaction; 100 kg of crushed corncob particles are mixed evenly with furfural production wastewater containing 3.8% acetic acid in a solid-liquid ratio of 6:1. The mixed raw materials are transferred to a hydrolysis reactor, and steam at 200 °C is introduced. The reaction pressure is controlled at 1.3 MPa, and the hydrolysis reaction is maintained for 60 minutes; the furfural vapor generated during the reaction is condensed and recovered by a condenser to obtain 80 L of a dilute solution with a furfural concentration of 9%;

[0069] Step 3: Washing of solid residue and separation of cellulose; After the solid residue after the hydrolysis reaction is discharged, it is washed multiple times with deionized water until the washing water is neutral. Subsequently, 30% sodium hydroxide solution is added to the solid residue at a liquid-solid ratio of 7:1, heated to 75 °C and stirred for 2.5 hours to fully dissolve the cellulose; after the reaction, it is naturally cooled to room temperature and filtered using a filter press to obtain 20 kg of crude cellulose;

[0070] Step 4: Acid hydrolysis of cellulose and formation of levulinic acid; 20 kg of the above-mentioned crude cellulose is dissolved in 3% formic acid solution, and Amberlyst-15 solid acid catalyst is added. The mass ratio of formic acid to solid acid is 50:1, and it is heated to 140 °C with microwave for 1.5 hours to complete cellulose hydrolysis, generating 50 L of a dilute levulinic acid solution with a levulinic acid content of 7%;

[0071] Step 5: High-temperature catalytic polymerization; 80 L of the furfural dilute solution obtained in Step 2 is mixed with 50 L of the levulinic acid dilute solution obtained in Step 4, and 10 g of Cu / ZrO 2 catalyst is added. It is heated to 270 °C in a reaction kettle, the reaction pressure is controlled at 5 MPa, and the reaction is carried out for 2 hours to generate 70 L of C10-C15 mixture;

[0072] Step 6: Oil-water separation and deoxygenation hydrogenation; After the reaction solution is naturally cooled to 60 °C, it is transferred to a storage tank for oil-water separation; the upper layer is the aqueous phase, and the lower layer is the C10-C15 mixture; 70 L of the C10-C15 mixture is transferred to a reaction kettle, 20 g of Ni-based catalyst is added, the hydrogen gas flow rate is 0.8 L / min, the reaction temperature is controlled at 320 °C, and the pressure is 7 MPa. The deoxygenation hydrogenation reaction is carried out for 2 hours to generate 60 L of a C10-C15 saturated hydrocarbon mixture;

[0073] Step 7: Rectification separation; The C10-C15 saturated hydrocarbon mixture is subjected to atmospheric pressure fractional rectification; in the first stage, the temperature is controlled at 150-200 °C to separate C10 hydrocarbons, and in the second stage, 200-250 °C to separate C11-C15 hydrocarbons, obtaining 55 L of the C10-C15 saturated hydrocarbon mixture;

[0074] Step 8: Activated carbon filtration and purification; Add 2 kg of modified activated carbon to the separated 55 L of C10-C15 hydrocarbon mixture, with acid washing + 50% of the micropore aperture being 0.5 - 2 nm, stir and filter to remove residual impurities; Centrifuge to discard the activated carbon, and perform rectification separation again to finally obtain 50 L of high-purity C10-C15 saturated hydrocarbon bio-aviation fuel product.

[0075] Through the efficient screening and treatment of corncobs, this example realizes the co-production of furfural, cellulose, and bio-aviation fuel; The furfural yield reaches 85%, the cellulose extraction rate is 90%, and the bio-aviation fuel yield is 80%. The product has high purity, and the catalyst can be recycled, effectively reducing production costs and improving resource utilization efficiency. Example 2

[0076] A method for co-producing bio-aviation fuel from corncobs is provided, and the specific implementation steps are as follows:

[0077] Step 1: Corncob screening and pulverization; Select 200 kg of corncob raw materials, use a screening device to remove corncobs with a moisture content greater than 10%, and use a high-speed pulverizer for pulverization. After pulverization, the particle size is controlled within the range of 8 - 12 mm to ensure the full progress of the hydrolysis reaction;

[0078] Step 2: Furfural production and hydrolysis reaction; Mix 200 kg of pulverized corncob particles with furfural production wastewater with an acetic acid content of 4% in a solid-liquid ratio of 7:1. The acetic acid in the wastewater serves as an acid catalyst to provide an acidic environment for the reaction;

[0079] Place the mixed raw materials in a continuous hydrolysis reactor, introduce primary steam, control the reaction temperature at 200 °C, maintain the pressure at 1.3 MPa, and the reaction time is 90 minutes. Hydrolyze to generate furfural vapor; The furfural vapor is recovered through a condensation device to obtain 150 L of a dilute solution with a furfural concentration of 10%;

[0080] Step 3: Washing of solid residue and cellulose separation; Drain the hydrolyzed solid residue, wash it three times with deionized water in a liquid-solid ratio of 6:1 until the pH of the washing water is close to neutral; Subsequently, add a 25% sodium hydroxide solution to the washed residue in a liquid-solid ratio of 8:1, raise the temperature of the reactor to 80 °C, and stir and react for 3 hours to promote the full dissolution of cellulose; After the reaction, naturally cool to room temperature and filter through a filter press to obtain 40 kg of crude cellulose with a purity of 96%;

[0081] Step 4: Acid hydrolysis of cellulose and formation of levulinic acid; Dissolve 40 kg of crude cellulose in 100 L of 4% formic acid solution, and add a sulfonic acid-based solid acid catalyst, Amberlyst-15. The mass ratio of formic acid to solid acid is 50:1. Heat with microwave to 145 °C and maintain the reaction for 2 hours to complete the acid hydrolysis reaction of cellulose, obtaining 120 L of a dilute levulinic acid solution with a levulinic acid concentration of 8%;

[0082] Step 5: High-temperature catalytic polymerization; Mix 150 L of the dilute furfural solution obtained in Step 2 with 120 L of the dilute levulinic acid solution obtained in Step 4, add 10 g of Cu / ZrO 2 -CeO 2 catalyst, heat to 275 °C in a reaction kettle, maintain the pressure at 5.5 MPa, and react for 2 hours to produce 110 L of a C10-C15 mixture;

[0083] Step 6: Oil-water separation and deoxygenation hydrogenation; After the reaction ends, let the reaction solution cool naturally to 50 °C, transfer it to a storage tank for oil-water separation; The upper aqueous solution is separated and recovered, and the lower C10-C15 mixture is transferred to a reaction kettle. Add 20 g of Ni-La 2 O 3 catalyst, introduce a hydrogen gas flow rate of 0.8 L / min, raise the temperature to 320 °C, maintain the pressure at 7 MPa, and carry out deoxygenation hydrogenation reaction for 2 hours to produce 100 L of a C10-C15 saturated hydrocarbon liquid mixture;

[0084] Step 7: Rectification separation; Carry out atmospheric rectification on the above C10-C15 saturated hydrocarbon liquid mixture:

[0085] First stage: Control the distillation temperature at 160 °C to separate C10 light hydrocarbons, obtaining 30 L;

[0086] Second stage: Raise the temperature to 230 °C to separate C11-C15 hydrocarbons, obtaining 70 L;

[0087] Step 8: Activated carbon filtration and purification; Add 2.5 kg of acid-washed modified activated carbon to the separated C10-C15 hydrocarbon mixture; Pore size distribution: micropores 0.5 - 2 nm account for 50%, mesopores 2 - 50 nm account for 40%. Stir and filter for 30 minutes, then centrifugally remove the activated carbon, and carry out secondary distillation rectification on the centrifuged liquid to obtain 98 L of high-purity C10-C15 saturated hydrocarbon liquid bio-aviation fuel product.

[0088] Example 2 effectively improves the utilization efficiency of corncob resources by further optimizing the hydrolysis reaction conditions, catalyst system and rectification separation process. Finally, the purity of bio-aviation fuel reaches 99.5%, showing significant advantages in terms of resource conservation, environmental friendliness and industrial feasibility, and is suitable for large-scale biomass fuel production.

[0089] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention has various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A method for producing bio-jet fuel by co-production of corncobs, characterized in that: The following steps are involved: Step 1: Screening and crushing of corn cobs. Screen the corn cobs, remove corn cobs with a moisture content greater than 10%, and crush the screened corn cobs to control the particle size to 10-15 mm. Step 2: Furfural production and hydrolysis reaction, crushed corn cob particles and furfural production wastewater, the wastewater contains 3.5-4.5% acetic acid, are mixed evenly at a solid-liquid ratio of 5-8:1, the mixed raw materials are placed in a hydrolysis reactor, primary steam or secondary steam is introduced, the reaction temperature is controlled at 195-205°C, the reaction pressure is between 1.25-1.3MPa, the hydrolysis reaction is continuously carried out to generate furfural, and the furfural vapor volatilized in the reaction is recovered by condensation to form a dilute solution containing 8-10% furfural; Step 3: Washing of solid residue and separation of cellulose. The solid residue after the hydrolysis reaction is discharged and washed multiple times with primary water until the washing water is neutral. Sodium hydroxide solution is added to the washed residue and heated to 70-80°C for 2-2.5 hours to effectively dissolve the cellulose in the alkaline solution. After the reaction is completed, the temperature is naturally lowered to room temperature and filtered using a filter press to obtain crude cellulose; Step 4: Acid hydrolysis of cellulose and generation of levulinic acid: dissolving crude cellulose in a 3-5% formic acid solution, subjecting the mixture to microwave pyrolysis, cooling and filtering the mixture, followed by filtering and washing to obtain a dilute solution containing 6-9% levulinic acid; Step 5: high temperature catalytic polymerization, mixing the dilute furfural solution with the dilute levulinic acid solution, adding a copper catalyst, and performing polymerization reaction at 260-280° C. to obtain a C10-C15 mixture; Step 6: Oil-water separation and deoxygenation and hydrogenation. The reaction liquid in the reactor is slowly cooled naturally. When the temperature drops to 50-60°C, the reaction liquid is moved from the reactor to a temporary storage tank. The reaction liquid is layered in the temporary storage tank. The upper layer is an aqueous solution and the lower layer is a C10-C15 mixture. The C10-C15 mixture is transferred to the reactor and a nickel catalyst is added. Hydrogen is introduced and the reactor is heated to achieve deoxygenation and hydrogenation of the mixture. Step 7: distillation separation, the reaction mixture is subjected to atmospheric distillation separation to obtain a C10-C15 hydrocarbon liquid mixture, and the unsaturated hydrocarbons and oxygen-containing compounds are recycled. A copper catalyst is added to the C10-C15 hydrocarbon mixture, and hydrogen is introduced at the same time. The reactor is heated continuously to convert the unsaturated carbon bonds of the hydrocarbons into saturated carbon bonds, and the C10-C15 hydrocarbon mixed liquid is converted into a C10-C15 saturated hydrocarbon liquid; Step 8: Activated carbon filtration and purification. Activated carbon is added to the reaction mixture to filter out the suspended hydrocarbons to facilitate the separation of saturated hydrocarbons and unsaturated hydrocarbons. The activated carbon is centrifuged and the effluent is distilled and separated to obtain C10-C15 saturated hydrocarbon liquid, which is the finished bio-jet fuel.

2. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: In step 4, a solid acid catalyst is added to a formic acid solution to form a reaction solution, the ratio of formic acid to the solid acid catalyst is 50:1 to 100:1, the crude cellulose is added after stirring evenly, and the microwave heating temperature range is 120-150° C.; heating is performed for 1.5-2 hours.

3. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: The mass fraction of sodium hydroxide solution is 30%, and the pH of the solution is adjusted to above 10.

4. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: In step 6, hydrogen is introduced at a flow rate of 0.5-0.8 L / min, the reactor is heated to 320° C., and the pressure is controlled at 7 MPa.

5. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: In step 6, the hydrogen flow rate is increased to 1.0-1.5 L / min, the temperature is adjusted to 330° C., and the pressure is maintained at 9 MPa.

6. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: The copper-based catalyst is Cu / ZrO2 or Cu-Ni.

7. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: In step 2, the steam temperature is 200° C. and the steam pressure is 1.3 MPa.

8. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: In step eight, distillation is performed by staged distillation. In the first stage, the distillation temperature is controlled at 150-200° C. to separate low-boiling C10 hydrocarbons first. In the second stage, the temperature is increased to 200-250° C. to separate C11-C15 hydrocarbons.

9. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: The activated carbon used in step eight is modified activated carbon, the surface of which is treated by acid washing or alkali washing. At the same time, the pore size distribution of the activated carbon is controlled as follows: micropores of 0.5-2nm account for 50%; mesopores of 2-50nm account for 40%; and macropores greater than 50nm account for 10%.

10. The method for producing bio-jet fuel from corncobs according to claim 1, characterized in that: The acetic acid content of the furfural dilute solution is controlled at 3.8-4.2%.

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