Method for co-producing biological aviation oil from corncobs

Abstract

The invention discloses a method for co-producing biological aviation oil from corncobs, which comprises the following steps: screening and crushing the corncobs, and controlling the particle size to be 10-15mm; the method comprises the following steps: mixing crushed corncobs with furfural production wastewater containing acetic acid, and carrying out hydrolysis reaction to generate a furfural dilute solution at 195-205 DEG C and 1.25-1.3 MPa; carrying out alkali treatment on the hydrolyzed solid residues, and separating to obtain a cellulose crude product; carrying out microwave heating on the cellulose crude product in a solid acid catalyst and a formic acid solution to carry out acidolysis reaction to generate a levulinic acid dilute solution; the method comprises the following steps: carrying out catalytic polymerization on a dilute furfural solution and a 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 a deoxidation hydrogenation reaction of a nickel-based catalyst; and finally carrying out segmented rectification and activated carbon filtration. The method realizes efficient co-production of furfural, cellulose and biological aviation oil in the corncob, and has the advantages of high raw material utilization rate, excellent catalytic efficiency, low energy consumption, environmental friendliness and the like.

Description

Technical Field

[0001] The invention relates to the technical field of biofuel preparation, in particular to a method for producing bio-aviation fuel by co-production with corncobs. Background Art

[0002] Corncob is a kind of agricultural and forestry biomass waste, mainly composed of cellulose, hemicellulose and lignin, and has rich renewable carbon resources. As the global demand for sustainable energy continues to grow, liquid fuels (such as bio-jet fuel) based on biomass have attracted widespread attention due to their renewability and low carbon emission characteristics.

[0003] At present, the methods for preparing liquid fuels from lignocellulosic biomass mainly include processes such as hydrolysis, catalytic conversion and hydrogenation deoxygenation. Among them, furfural is an important bio-based platform compound that can be produced by hydrolysis of hemicellulose. However, the prior art has the following deficiencies in the process of preparing biofuels from corn cobs. For example, Chinese Patent Authorization Announcement No. CN117866673B discloses a method for preparing aviation fuel components from lignocellulosic biomass, which uses a two-step method to prepare furfural. The first step is to pre-treat the corn cobs by washing them with water to produce a large amount of wastewater; the second step is to require additional filtration and stripping after hydrolysis; pentose is dehydrated to prepare furfural under acid catalyst conditions (sulfuric acid, acetic acid or maleic acid), and a two-phase reaction system (such as water / dichloromethane or water / γ-valerolactone) is used to react at 160-180°C; the defect is that one 1. The two-step method for producing furfural involves washing the raw materials for pretreatment, filtering and stripping the hydrolyzate. The entire process produces a large amount of wastewater and has a low furfural conversion rate; and the equipment is highly corrosive. 2. The one-pot production of cellulose results in low fiber purity, and the cellulose hydrothermal cracking impurity content is high. 3. The process produces aviation fuel hydrocarbon components, which do not meet the calorific value and combustion standards of aviation fuel and require further deep processing. Existing technologies rely on additional acid catalysts (such as sulfuric acid), which are highly corrosive and difficult to treat waste liquids. Energy consumption is high, such as the demand for high-temperature and high-pressure steam and improper control of excessive hydrogen flow rates during hydrogenation, which increases costs.

[0004] Chinese Patent Application No. 202310157574.9 discloses the preparation of sustainable aviation fuel by 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 above C10-C15. Similarly, Chinese Patent Application No. 202310135285.9 provides a method for directly converting biomass to produce aviation liquid fuel, which directly generates liquid fuel by pyrolysis of biomass, including pyrolysis, carbon chain growth and condensation separation. The disadvantages and shortcomings are that the pyrolysis process is unstable: coke and other uncontrollable by-products are easily formed during the pyrolysis process, resulting in unstable yields; lack of catalytic control: it only relies on high-temperature decomposition of the pyrolysis process, lacks precise catalyst control, and affects the fuel quality. In this method, cellulose may be partially carbonized during the pyrolysis process.

[0005] Chinese patent application No. 202010554841.2 discloses a high-performance alternative aviation fuel and a method for preparing the same; the method uses a mixed liquid or fermentation liquid containing water, acetone, and optional butanol and ethanol obtained by biomass fermentation as a raw material, and after condensation reaction, trimerization condensation reaction and hydrogenation deoxygenation reaction, a high-performance alternative aviation fuel can be prepared. The defects are that the source of raw materials is limited: the raw material is fermentation liquid, which is mainly suitable for sugar biomass, and the direct utilization capacity of agricultural and forestry waste is insufficient; the reaction path is complex: it involves multiple condensation and trimerization condensation, with more reaction steps and more by-products, which increases the complexity of production.

[0006] Chinese patent application No. 202280039111.6 discloses a method for bio-renewable light paraffin kerosene and sustainable aviation fuel, in which a heavy hydroprocessor fraction is hydroisomerized and hydrocracking is carried out using a hydroisomerization catalyst under the condition of producing a hydroisomerizer product comprising a heavy hydroisomerizer fraction and LPK. Multi-step hydrogenation and isomerization reactions are used, involving multiple precious metal catalysts, and the production cost is relatively high. The raw materials are renewable light paraffins, and the synthesis of bio-based platform compounds such as furfural or levulinic acid is not involved.

[0007] In view of the above problems, a method for producing bio-jet fuel by co-production of corn cobs is proposed. 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-jet fuel with corn cobs. Through the efficient utilization of corn cob resources, not only the conversion rate of furfural and cellulose is improved, but also high-calorific value bio-jet fuel can be co-produced, providing a more environmentally friendly and economical solution for biomass energy development, solving the problems of low added value of furfural products and large fluctuations in the downstream market in the existing process of producing furfural from corn cobs, solving the problem of ineffective utilization and accumulation of furfural residues in the process of furfural production, achieving full utilization of corn cobs, and also providing a new production process and source channel for bio-jet fuel, which 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 producing bio-jet fuel by co-production of corn cobs, comprising the following steps: 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.

[0010] Furthermore, 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, 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.

[0011] Furthermore, the mass fraction of the sodium hydroxide solution is 30%, and the pH value of the solution is adjusted to above 10.

[0012] Furthermore, in step six, 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.

[0013] Furthermore, in step six, 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.

[0014] Furthermore, the copper-based catalyst is Cu / ZrO2 or Cu-Ni.

[0015] Furthermore, in step 2, the steam temperature is 200° C. and the steam pressure is 1.3 MPa.

[0016] Furthermore, the distillation adopts 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.

[0017] Furthermore, the activated carbon used in step eight is modified activated carbon, the surface of which is treated by acid washing or alkali washing, and 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%.

[0018] Furthermore, the acetic acid content of the furfural dilute solution is controlled at 3.8-4.2%.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. Through a reasonable process flow and catalyst system, the utilization rate of raw materials is effectively improved; in the production and hydrolysis of furfural, the acetic acid component in the furfural production wastewater is used as an acid catalyst, which not only reduces the demand for additional acid catalysts, but also reduces the amount of wastewater discharged, achieving the environmental protection effect of energy saving and emission reduction from the source. In addition, by controlling the crushing particle size of corn cobs and reaction conditions, the conversion rate and recovery rate of furfural are further optimized.

[0020] 2. In the process of cellulose extraction, the present invention realizes efficient separation of cellulose by adopting a sodium hydroxide solution of a specific concentration and controlling the temperature and reaction time; the crude cellulose has high purity, which is conducive to the efficient generation of subsequent levulinic acid; at the same time, the introduction of solid acid catalysts, such as SBA-15 loaded sulfonic acid or Amberlyst-15 resin, ensures the catalyst recyclability and reaction stability during the cellulose acidolysis process, and further reduces catalyst loss and environmental pollution.

[0021] 3. In the catalytic polymerization and hydrodeoxygenation steps, the present invention effectively reduces the reaction temperature and hydrogen flow rate by using copper and nickel catalysts, while ensuring a high selectivity and yield of the target product; the improvement in hydrogen utilization efficiency not only reduces energy consumption, but also reduces the waste of unreacted hydrogen; in addition, through the segmented distillation separation technology, hydrocarbons with different carbon chain lengths of C10-C15 are effectively distinguished, thereby improving the purity and calorific value of bio-jet fuel products.

[0022] 4. The development of a new process for the co-production of bio-jet fuel from corn cobs has achieved the output of a one-end and multiple-end product chain of corn cobs, which is beneficial to increasing the added value of corn cobs, improving the utilization rate of corn cob components and the economic value; the realization of the development of a new process for the co-production of bio-jet fuel from corn cobs has reduced the production cost of bio-jet fuel by 500-800 yuan compared with the production cost of using waste oils as raw materials, effectively reducing the production cost of bio-jet fuel, reducing the dependence of bio-jet fuel on government subsidies, and increasing the utilization rate and market share of bio-jet fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the process of the present invention; DETAILED DESCRIPTION

[0024] The present invention is further described 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.

[0025] See also Figure 1 The present invention provides a technical solution: a method for producing bio-jet fuel by co-production of corn cobs, comprising the following steps: Step 1: Screening and crushing of corn cobs. Screen the corn cobs, remove corn cobs with a moisture content greater than 10%, crush the screened corn cobs, and control the particle size to 10-15 mm. Control the size of the corn cob particles to avoid cellulose loss caused by excessive crushing, ensure that the specific surface area of ​​the corn cob particles is large enough during hydrolysis, and provide a more stable corn cob particle quality for the subsequent hydrolysis reaction; The screened corn cobs have a lower moisture content and are suitable for subsequent processing; by accurately screening the moisture content and physical properties, the quality of the raw materials is ensured while reducing the interference of moisture in subsequent processes on the reaction effect.

[0026] Step 2: Furfural production and hydrolysis reaction. The crushed corn cob particles and furfural production wastewater, which contains 3.5-4.5% acetic acid, are mixed evenly at a solid-liquid ratio of 5-8:1. The acetic acid component in the wastewater provides an acidic environment for the reaction, which is conducive to hydrolysis and conversion. The hydrolysis process realizes the decomposition of lignocellulose and generates furfural as the target product. The mixed raw materials are placed in a hydrolysis reactor, and primary steam or secondary steam is introduced to control the reaction temperature at 195-205°C and the reaction pressure at 1.25-1.3MPa. The hydrolysis reaction is continued to generate furfural and other by-products. In terms of temperature, a two-level temperature control system is used to optimize the use efficiency of steam and reasonably adjust the reaction conditions, which not only improves the conversion rate of furfural, but also reduces the corrosiveness of the equipment and improves the sustainability of the process. The furfural vapor volatilized in the reaction is recovered by condensation to form a dilute solution containing 8-10% furfural. In step 2, by introducing wastewater containing acetic acid as a solvent, the demand for acidic substances in the production process is reduced, which not only saves costs but also makes better use of wastewater resources to achieve closed-loop production. The reuse of wastewater greatly reduces the risk of environmental pollution.

[0027] 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; In the alkaline dissolution treatment process, the present invention adopts a sodium hydroxide solution with specific concentration and temperature conditions, which maximizes the dissolution efficiency of cellulose, reduces the dissolution of non-cellulose substances, and maintains the high purity of cellulose.

[0028] Step 4: Acid hydrolysis of cellulose and generation of levulinic acid. The crude cellulose is dissolved in a 3-5% formic acid solution and subjected to microwave pyrolysis reaction. Microwave heating provides a more uniform heating effect. The radiation of microwaves can rapidly hydrolyze cellulose in an acidic environment and effectively improve the separation efficiency of levulinic acid. The mixed solution is then cooled and filtered, and then filtered and washed 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. The use of the copper catalyst significantly reduces the reaction energy consumption and improves the selectivity of the target product; 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. High-efficiency nickel-based catalysts combined with precise control of reaction conditions improve hydrogenation efficiency and target product quality; the use of high-pressure hydrogen reduces oxygen content and increases the calorific value of hydrocarbons; 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.

[0029] 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, and the crude cellulose is added after stirring evenly, and a sulfonic acid solid acid is used as a synergistic catalyst. The sulfonic acid solid acid uses SBA-15 loaded sulfonic acid or Amberlyst-15 resin to stabilize the catalytic performance of low-concentration acid, synergistically catalyze the hydrolysis of cellulose, and improve the reaction efficiency. At the same time, the solid acid can be recycled and reused. The microwave heating temperature range is 120-150°C; if the temperature is too low, less than 120°C, the cellulose decomposition rate is significantly reduced, and the reaction time is extended to more than 4 hours, affecting the production capacity. If the temperature is too high, greater than 150°C, the cellulose is excessively degraded, the generation of by-products such as furfural increases, and the corrosiveness is increased. The heating is 1.5-2 hours.

[0030] Table 1. Comparison of formic acid concentration, temperature, catalyst content and reaction time

[0031] The mass fraction of 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 components in corn cobs.

[0032] In step six, 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. If the hydrogen flow rate is too low, less than 0.5 L / min, the hydrogen source supply is insufficient, the reaction is incomplete, and unsaturated hydrocarbons remain.

[0033] In step six, 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. An excessively high hydrogen flow rate of more than 1.5 L / min results in hydrogen waste, which is directly discharged without fully participating in the reaction. Insufficient mixing of the gas and liquid phases may lead to side reactions, such as cracking.

[0034] The effect of the gas pressure inside the reactor on the reaction. When the low pressure is less than 5 MPa, the hydrogen is not sufficiently dissolved, the reaction rate is slow, and there may be residual unsaturated hydrocarbons. It is suitable for mild saturation treatment of shorter-chain hydrocarbons (such as C10-C12). The medium pressure is 5-7 MPa, which is suitable for most C10-C15 hydrocarbon saturation reactions. The hydrogen solubility is moderate, and the reaction rate and selectivity are balanced. The high pressure is greater than MPa, which is suitable for reactions with longer-chain hydrocarbons such as C14-C15 and full saturation requirements, and may induce side reactions such as cracking or polymerization.

[0035] The copper-based catalyst is Cu / ZrO2 or Cu-Ni.

[0036] The introduction of CeO2 or La2O3 as an additive in copper-based catalysts is mainly to improve the catalyst's anti-toxicity such as sulfur resistance, chlorine resistance, oxygen storage capacity, catalytic activity and stability; the following is the introduction method and its optimization.

[0037] The principle of introducing CeO2 or La2O3 into copper-based catalysts: CeO2 cerium oxide or La2O3 lanthanum oxide is evenly distributed on the surface of the pre-prepared Cu / ZrO2 catalyst by impregnation method to improve the catalyst's anti-toxicity, oxygen storage capacity and stability.

[0038] Preparation steps: 1. Prepare the Cu / ZrO2 catalyst support by coprecipitation method: mix Cu(NO3)2 and Zr(NO3)4, coprecipitate at pH 8-9 to form Cu(OH)2 and Zr(OH)4 precipitates, filter and wash, dry at 105℃ for 12 hours, and calcine at 500℃ for 4 hours; 2. Preparation of CeO2 / La2O3 impregnation solution: Prepare Ce(NO3)3 or La(NO3)3 solution with a target loading of 5-10 wt%; 3. Impregnation process: Place the Cu / ZrO2 catalyst into the impregnation solution and stir for 1 hour at room temperature to ensure uniform distribution of metal ions; 4. Drying and calcination: Dry at 105℃ for 12 hours and calcine at 500℃ for 4 hours to completely decompose Ce(NO3)3 or La(NO3)3 to form CeO2 or La2O3.

[0039] In step 2, the steam temperature is 200° C. and the steam pressure is 1.3 MPa to improve the furfural stripping efficiency.

[0040] The distillation adopts segmented distillation. In the first stage, the distillation temperature is controlled at 150-200℃ to separate the low-boiling point C10 hydrocarbons first. In the second stage, the temperature is increased to 200-250℃ to separate the C11-C15 hydrocarbons. The segmented distillation can avoid cross-contamination of different fractions and improve the separation accuracy.

[0041] The activated carbon used in step eight is modified activated carbon, whose surface is treated with acid 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 0.5-2nm account for 50%; mesopores of 2-50nm account for 40%; and macropores greater than 50nm account for 10%, thereby improving the adsorption capacity for impurities of different molecular weights, and achieving solid-liquid separation through centrifugal rejection and secondary filtration.

[0042] The acetic acid content of the furfural dilute solution is controlled at 3.8-4.2% to maintain the stability of the acid catalytic environment, thereby reducing the use of additional acid catalysts and reducing production costs. Example 1

[0043] A method for producing bio-jet fuel by co-production of corn cobs is provided, and the specific implementation steps are as follows: Step 1: corn cob screening and crushing: 100 kg of corn cob raw materials with a moisture content of less than 10% are selected, raw materials with excessive moisture are removed by screening, and qualified corn cobs are crushed by a crusher until the particle size is controlled within the range of 10-15 mm to ensure the stability and reaction efficiency of the hydrolysis reaction; Step 2: Furfural production and hydrolysis reaction: 100kg of crushed corn cob particles and furfural production wastewater containing 3.8% acetic acid are mixed evenly at a solid-liquid ratio of 6:1. The mixed raw materials are transferred to the hydrolysis reactor, and steam at 200°C is introduced. The reaction pressure is controlled to be 1.3MPa, and the hydrolysis reaction is maintained for 60 minutes; the furfural vapor generated during the reaction is condensed and recovered through a condenser to obtain 80L of a dilute solution with a furfural concentration of 9%; Step 3: Washing of solid residue and separation of cellulose; After the solid residue after the hydrolysis reaction is discharged, it is washed several times with deionized water until the washing water is neutral. Subsequently, 30% sodium hydroxide solution is added to the solid residue, with a liquid-to-solid ratio of 7:1, heated to 75°C and stirred for 2.5 hours to fully dissolve the cellulose; after the reaction is completed, it is naturally cooled to room temperature and filtered using a filter press to obtain 20 kg of crude cellulose; Step 4: Acid hydrolysis of cellulose and generation of levulinic acid: 20 kg of the above crude cellulose was dissolved in a 3% formic acid solution, and an Amberlyst-15 solid acid catalyst was added, with a mass ratio of formic acid to solid acid of 50:1. The mixture was heated to 140°C using a microwave for 1.5 hours to complete the hydrolysis of the cellulose and generate 50 L of a dilute levulinic acid solution with a levulinic acid content of 7%. Step 5: high temperature catalytic polymerization; 80L of the dilute furfural solution obtained in step 2 was mixed with 50L of the dilute levulinic acid solution obtained in step 4, 10g of Cu / ZrO2 catalyst was added, and the mixture was heated to 270°C in a reactor, the reaction pressure was controlled at 5MPa, and the reaction was carried out for 2 hours to generate 70L of a C10-C15 mixture; Step 6: Oil-water separation and deoxygenation and hydrogenation; after the reaction liquid is naturally cooled to 60°C, it is moved into a temporary storage tank for oil-water separation; the upper layer is the water phase, and the lower layer is the C10-C15 mixture; 70L of the C10-C15 mixture is transferred to the reactor, 20g of Ni-based catalyst is added, and hydrogen is introduced at a flow rate of 0.8L / min. The reaction temperature is controlled at 320°C and the pressure is 7MPa. The deoxygenation and hydrogenation reaction is carried out for 2 hours to generate 60L of C10-C15 saturated hydrocarbon mixture; Step 7: distillation separation; the C10-C15 saturated hydrocarbon mixture is subjected to atmospheric pressure staged distillation; the temperature is controlled at 150-200°C in the first stage to separate C10 hydrocarbons, and 200-250°C in the second stage to separate C11-C15 hydrocarbons, to obtain 55L of C10-C15 saturated hydrocarbon mixture; Step 8: Activated carbon filtration and purification; add 2kg of modified activated carbon to 55L of separated C10-C15 hydrocarbon mixture, with acid washing + micropore size 0.5-2nm accounting for 50%, and stir and filter to remove residual impurities; remove the activated carbon by centrifugation, and separate it again by distillation, and finally obtain 50L of high-purity C10-C15 saturated hydrocarbon bio-jet fuel product.

[0044] This embodiment achieves the co-production of furfural, cellulose and bio-jet fuel through efficient screening and processing of corn cobs; the furfural yield reaches 85%, the cellulose extraction rate is 90%, the bio-jet fuel yield is 80%, the product purity is high, and the catalyst can be recycled, which effectively reduces production costs and improves resource utilization. Example 2

[0045] A method for producing bio-jet fuel by co-production of corn cobs is provided, and the specific implementation steps are as follows: Step 1: corn cob screening and crushing: 200 kg corn cob raw materials are selected, corn cobs with a moisture content greater than 10% are removed through a screening device, and then crushed using a high-speed crusher. The particle size after crushing is controlled within the range of 8-12 mm to ensure that the hydrolysis reaction is fully carried out; Step 2: Furfural production and hydrolysis reaction: 200 kg of crushed corn cob particles and furfural production wastewater with an acetic acid content of 4% are mixed evenly at 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. The mixed raw materials are placed in a continuous hydrolysis reactor, primary steam is introduced, the reaction temperature is controlled at 200°C, the pressure is maintained at 1.3MPa, the reaction time is 90 minutes, and the furfural steam is hydrolyzed to generate furfural steam; the furfural steam is recovered through a condensing device to obtain 150L of a dilute solution containing 10% furfural; Step 3: washing the solid residue and separating it from the cellulose; the solid residue after hydrolysis was discharged and washed three times with deionized water at a liquid-to-solid ratio of 6:1 until the pH of the washing water was close to neutral; then, 25% sodium hydroxide solution was added to the washed residue at a liquid-to-solid ratio of 8:1, the temperature of the reactor was raised to 80°C, and the reaction was stirred for 3 hours to promote the full dissolution of the cellulose; after the reaction was completed, the reaction mixture was naturally cooled to room temperature and filtered through a filter press to obtain 40 kg of crude cellulose with a purity of 96%; Step 4: Acid hydrolysis of cellulose and generation of levulinic acid: 40 kg of crude cellulose was dissolved in 100 L of 4% formic acid solution, and a sulfonic acid solid acid catalyst, Amberlyst-15, was added, and the mass ratio of formic acid to solid acid was 50:1. The mixture was heated to 145°C by microwave and the reaction was maintained for 2 hours to complete the acid hydrolysis of cellulose and obtain 120 L of a dilute levulinic acid solution with a levulinic acid concentration of 8%. Step 5: high temperature catalytic polymerization; 150L of the dilute furfural solution obtained in step 2 was mixed with 120L of the dilute levulinic acid solution obtained in step 4, 10g of Cu / ZrO2-CeO2 catalyst was added, and the mixture was heated to 275°C in a reactor, the pressure was maintained at 5.5MPa, and the reaction time was 2 hours to generate 110L of a C10-C15 mixture; Step 6: Oil-water separation and deoxygenation and hydrogenation; after the reaction is completed, the reaction liquid is naturally cooled to 50°C and transferred to a temporary storage tank for oil-water separation; the upper aqueous solution is separated and recovered, and the lower C10-C15 mixture is transferred to a reactor, 20g Ni-La2O3 catalyst is added, hydrogen is introduced at a flow rate of 0.8L / min, the temperature is raised to 320°C, the pressure is maintained at 7MPa, and the deoxygenation and hydrogenation reaction is carried out for 2 hours to generate 100L of C10-C15 saturated hydrocarbon liquid mixture; Step 7: Distillation separation: subjecting the C10-C15 saturated hydrocarbon liquid mixture to atmospheric distillation: Stage 1: Control the distillation temperature at 160°C to separate C10 light hydrocarbons and obtain 30L; The second stage: the temperature was raised to 230 °C to separate the C11-C15 hydrocarbons and obtain 70L; Step 8: Activated carbon filtration and purification; add 2.5kg of acid-washed modified activated carbon to the separated C10-C15 hydrocarbon mixture; pore size distribution: micropores 0.5-2nm account for 50%, mesopores 2-50nm account for 40%, stir and filter for 30 minutes, then centrifuge to remove the activated carbon, and perform secondary distillation on the removed liquid to obtain 98L of high-purity C10-C15 saturated hydrocarbon liquid bio-aviation fuel product.

[0046] Example 2 effectively improves the utilization efficiency of corn cob resources by further optimizing the hydrolysis reaction conditions, catalyst system and distillation separation process. The final purity of bio-jet fuel reaches 99.5%. It has significant advantages in resource conservation, environmental friendliness and industrial feasibility, and is suitable for large-scale biomass fuel production.

[0047] The basic principles, main features and advantages of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may also be subject to various changes and improvements, which all fall within the scope of the present invention to be protected.

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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