Biomass-based liquid fuel oil preparation method

Abstract

The invention belongs to the technical field of biomass fuel oil, and particularly relates to a biomass-based liquid fuel oil preparation method which comprises the following steps: mechanical pulverization, enzymolysis reaction, catalytic pyrolysis, hydrogenation upgrading, solid-liquid separation and distillation refining. Crop straw is used as a raw material and is mixed with a compound enzyme preparation, so that macromolecules such as cellulose are degraded into micromolecular saccharides; carrying out catalytic pyrolysis, and converting the product into pyrolytic oil by accurately controlling the reaction conditions under the action of a catalyst; in the preparation process, the catalyst can reduce the pyrolysis temperature, inhibit the generation of nitrogen oxides and improve the oxidation resistance stability of the fuel oil, the compound enzyme preparation is mild in reaction and low in energy consumption, and all the steps synergistically optimize the physicochemical properties of the fuel oil, so that the prepared biomass-based liquid fuel oil has a high calorific value and high combustion efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass fuel, and in particular relates to a method for preparing liquid fuel based on biomass. Background Art

[0002] As the main energy source, traditional fossil fuels not only face the problem of gradually decreasing reserves during use, but also emit a large amount of greenhouse gases and pollutants during combustion, which poses a serious threat to the ecological environment. Therefore, the development of clean and renewable alternative energy sources has become a top priority. Biomass energy, as an abundant renewable energy source, has the advantages of wide sources and carbon neutrality, and has received widespread attention. Among them, straw is one of the main wastes of agricultural production and has a huge output. However, most of the current straw treatment methods are still mainly direct incineration or random discarding, which not only causes a waste of resources, but also causes serious environmental pollution problems, such as air pollution and soil quality decline.

[0003] In the research field of preparing liquid fuel from biomass, a variety of technologies have been proposed and explored. For example, biomass is converted into combustible fuels through processes such as pyrolysis and gasification. However, these existing technologies have many defects when processing straw. On the one hand, the structure of straw is complex and contains a large amount of cellulose, hemicellulose and lignin, which makes it difficult to react during the conversion process and requires higher reaction conditions, such as high temperature and high pressure, which not only increases energy consumption and equipment costs, but also reduces conversion efficiency. On the other hand, the existing technology is not effective in improving the quality of liquid fuel. The prepared fuel often has problems such as low calorific value, poor stability, and high impurity content, which is difficult to meet the needs of practical applications. In summary, the development of an efficient, low-cost preparation method that can convert straw into high-quality liquid fuel is of great practical significance for solving the energy crisis, realizing the resource utilization of straw, and protecting the environment. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing liquid fuel based on biomass. The fuel prepared by the method for preparing liquid fuel based on biomass of the present invention has high calorific value and high combustion efficiency, can fully release energy, and provide stable power output for the engine; in the catalytic pyrolysis process, sepiolite serves as a carrier of cerium oxide, and highly disperses cerium oxide particles to fully expose its active sites, accelerate oxygen storage and release, accelerate the oxidation reaction of hydrocarbons in the fuel, and reduce the activation energy of the combustion reaction, thereby reducing the temperature of the pyrolysis process and improving the combustion efficiency; in the combustion process of the fuel, the catalyst continues to play a role, accurately adjusting the oxygen concentration and reaction temperature in the combustion area, on the one hand, effectively inhibiting the generation of thermal nitrogen oxides; on the other hand, the catalyst enhances the catalytic conversion of nitrogen-containing compounds in the fuel, prompting them to be converted into harmless nitrogen before or during combustion. The use of composite enzyme preparations to carry out enzymatic hydrolysis under mild conditions can specifically degrade macromolecular substances such as cellulose in straw. The reaction conditions are mild, energy consumption is low, equipment requirements are low, and it is environmentally friendly. Hydrogen is introduced into the hydrogenation and quality improvement process to reduce the oxygen content of the liquid product under specific pressure, temperature and catalyst, thereby improving the calorific value and stability of the fuel.

[0005] The present invention provides a method for preparing a biomass-based liquid fuel, wherein the biomass-based liquid fuel is prepared from the following raw materials in parts by weight: 80-100 parts of straw, 6-10 parts of a catalyst, 5-8 parts of a composite enzyme preparation, 0.05-0.01 parts of BHA (butylated hydroxyanisole), and 0.5-1 parts of SDS (sodium dodecyl sulfate); The composite enzyme preparation is a mixed enzyme of cellulase, hemicellulase and xylanase in a mass ratio of 3:2:1; The straw is crop straw, including corn, wheat and rice straw; The biomass-based liquid fuel preparation method specifically comprises the following steps: S1, mechanical crushing of straw, selecting dry straw, using a crusher to mechanically crush the straw into 0.5-2 mm, placing the crushed straw in a forced air drying oven at 110 °C for 4-6 h to obtain crushed straw; S2, enzymatic hydrolysis reaction, the crushed straw is mixed with the composite enzyme preparation, and SDS is added at the same time. The pH is controlled to be maintained at 4.5-5.5 in a constant temperature water bath at 45-55 ℃, and stirred for 12 h to degrade the macromolecular substances such as cellulose in the straw into small molecular sugars to obtain a mixture; S3, catalytic pyrolysis, filtering the mixture to obtain a solid residue, transferring the solid residue to a pyrolysis reaction device, adding 5-7 parts of a catalyst, and heating at N 2In the atmosphere, the temperature is raised to 350-450 °C at a heating rate of 10 °C, and pyrolysis is carried out at this temperature for 30-60 min to produce pyrolysis oil; S4, hydrogenation and upgrading, the obtained pyrolysis oil is transferred to a high-pressure reactor, hydrogen is introduced to keep the pressure in the high-pressure reactor at 1-3 MPa, BHA and 1-3 parts of catalyst are added, and stirred at 200-300 °C for 1-3 h to obtain a reaction product. The oxygen content in the liquid product is reduced by hydrogenation reaction, and the calorific value and stability of the fuel are improved; S5, solid-liquid separation, filtering the reaction product, using a filter membrane with a pore size of 0.2-0.5 µm to separate solid impurities, obtaining a liquid portion, and centrifuging the liquid portion for 15 min to obtain a clarified crude liquid fuel; S6, distillation and refining, distilling and refining the crude liquid fuel, first collecting the light fraction with a boiling point of 60-200 °C, then raising the temperature to 200-350 °C, collecting the heavy fraction with a boiling point in this range, and the light fraction and the heavy fraction together constitute the biomass-based liquid fuel.

[0006] The catalyst is prepared from the following raw materials in weight ratio: sepiolite: Ce(NO 3 ) 3 6H 2 O:Ni(NO 3 ) 2 6H 2 O:PEG (polyethylene glycol) = 12:1-4:1-2:1; The preparation method of the catalyst specifically comprises the following steps: A1, weigh Ce(NO 3 ) 3 6H 2 O and Ni (NO 3 ) 2 6H 2 O is dissolved in deionized water to form a mixed salt solution with a concentration of 0.1-0.5 mol / L; A2, add sepiolite to the mixed salt solution, stir magnetically, slowly add ammonia water, control the pH at 8-10, then slowly add PEG, stir for 2 h, and obtain a mixture; A3, washing the mixture with deionized water and centrifuging, then placing it in a vacuum drying oven and drying it at 80 °C for 12-24 h to obtain a precursor powder; A4, placing the precursor powder in a muffle furnace for calcination, raising the temperature to 400-600 °C at a heating rate of 2-5 °C / min, and calcining at this temperature for 2-4 h to obtain a catalyst.

[0007] Compared with the prior art, the present invention has the following beneficial effects: The fuel prepared by the biomass-based liquid fuel preparation method of the present invention has high calorific value and high combustion efficiency, can fully release energy, and provide stable power output for the engine; in the catalytic pyrolysis process, the added catalyst greatly promotes the full decomposition and conversion of straw, reduces the carbon smoke, tar and other pollutants generated by incomplete combustion from the source, and the subsequent hydrogenation and distillation refining steps specifically remove the sulfur-containing and nitrogen-containing compounds in the fuel, so that when the biomass liquid fuel is burned, the emission of pollutants such as sulfur dioxide and nitrogen oxides is greatly reduced; in the catalytic pyrolysis process, sepiolite is used as a carrier of cerium oxide, and the cerium oxide particles are highly dispersed to fully expose its active sites, accelerate oxygen storage and release, accelerate the oxidation reaction of hydrocarbons in the fuel, and reduce the activation energy of the combustion reaction, thereby reducing the temperature of the pyrolysis process, making the combustion reaction easier to carry out, and improving the combustion efficiency; in the fuel combustion process, the catalyst continues to play a role, accurately adjusts the oxygen concentration and reaction temperature in the combustion area, on the one hand, effectively inhibits the generation of thermal nitrogen oxides; on the other hand, the catalyst enhances the catalytic conversion effect of the nitrogen-containing compounds in the fuel, prompting them to be converted into harmless nitrogen before or during combustion. The catalyst added in the present invention has a good antioxidant effect. On the one hand, it can inhibit the oxidation reaction of fuel oil during storage and use, and prevent the fuel oil from deteriorating due to oxidation. On the other hand, the catalyst can adsorb impurities and free radicals in the fuel oil, reduce their initiation and promotion of the oxidation reaction of the fuel oil, improve the antioxidant stability of the fuel oil, and extend the storage period of the fuel oil. The composite enzyme preparation is used to carry out enzymatic hydrolysis under mild conditions, which can specifically degrade macromolecular substances such as cellulose in straw. The reaction conditions are mild, the energy consumption is low, the equipment requirements are low, and it is environmentally friendly; the catalytic pyrolysis accurately controls the heating rate, pyrolysis temperature and time, and cooperates with the catalyst to efficiently convert the enzymatic hydrolysis product into pyrolysis oil, thereby improving the yield and selectivity of the target product; hydrogen is introduced into the hydrogenation and quality improvement link to reduce the oxygen content of the liquid product, improve the calorific value and stability of the fuel oil, improve the combustion performance, and make the biomass liquid fuel oil more suitable for existing combustion equipment. Through the biomass-based liquid fuel preparation method of the present invention, the viscosity, acid value, and ash content of the fuel oil are reduced, the liquefaction yield is improved, the heavy oil component is reduced, the fuel oil has better fluidity, reduced corrosiveness, and improved cleanliness, and is more convenient for storage, transportation, and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A flow chart of the preparation of biomass-based liquid fuel prepared for the present invention; Figure 2 SEM image of the catalyst added to the biomass-based liquid fuel prepared by the present invention; Figure 3 The cyclic stability diagram of the catalyst used in Example 2 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0009] In order to make the technical solution of the present invention better understood by the technical personnel in the field, and to make the above-mentioned features, purposes and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with the embodiments. The embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0010] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0011] In the following examples, unless otherwise specified, conventional methods are used; the materials used in the following examples, unless otherwise specified, are all new materials purchased from the market.

[0012] according to Figure 1 The preparation flow chart of biomass-based liquid fuel of the present invention is shown in the following specific embodiments: Example 1: This example provides a method for preparing a biomass-based liquid fuel, wherein the biomass-based liquid fuel is prepared from the following raw materials in parts by weight: 80 parts of straw, 6 parts of catalyst, 5 parts of complex enzyme preparation, 0.05 parts of BHA, and 0.5 parts of SDS; The composite enzyme preparation is a mixed enzyme of cellulase, hemicellulase and xylanase in a mass ratio of 3:2:1; the straw is crop straw, including corn, wheat and rice straw; The biomass-based liquid fuel preparation method specifically comprises the following steps: S1, mechanical crushing, 80 portions of dry straw were selected, and the straw was mechanically crushed into 0.5 mm using a crusher. The crushed straw was placed in a forced air drying oven at 110 °C for 4 h to obtain crushed straw; S2, enzymatic hydrolysis reaction, the crushed straw was mixed with 5 parts of compound enzyme preparation, and 0.5 parts of SDS was added at the same time, and the reaction was carried out at a constant temperature water bath at 45 °C, pH was maintained at 4.5, and the reaction speed was 150 rpm for 12 h to degrade the macromolecular substances such as cellulose in the straw into small molecular sugars to obtain a mixture; S3, catalytic pyrolysis, filtering the mixture to obtain a solid residue, transferring the solid residue to a pyrolysis reaction device, adding 5 parts of a catalyst, and heating at N 2 Under the atmosphere, the temperature was raised to 350 °C at a heating rate of 10 °C, and pyrolysis was carried out at this temperature for 30 min to produce pyrolysis oil; S4, hydrogenation and upgrading, the obtained pyrolysis oil is transferred to a high-pressure reactor, hydrogen is introduced to keep the pressure in the high-pressure reactor at 1 MPa, 0.05 parts of BHA and 1 part of catalyst are added, and the reaction is stirred at 200 °C and 300 rpm for 1 h to obtain a reaction product; S5, solid-liquid separation, filtering the reaction product, using a filter membrane with a pore size of 0.2 µm to separate solid impurities, obtaining a liquid portion, centrifuging the liquid portion at a speed of 5000 rpm for 15 min, and obtaining a clarified crude liquid fuel; S6, distillation and refining, distill and refine the crude liquid fuel, first collect the light fraction with a boiling point of 60°C, then increase the temperature to 200°C, and collect the heavy fraction with a boiling point in this range. The light fraction and the heavy fraction together constitute the biomass-based liquid fuel.

[0013] The catalyst is prepared from the following raw materials in weight ratio: sepiolite: Ce(NO 3 ) 3 6H 2 O:Ni(NO 3 ) 2 6H 2 O:PEG=12:1:1:1; The preparation method of the catalyst specifically comprises the following steps: A1, weigh Ce(NO 3 ) 3 6H 2 O and Ni (NO 3 ) 2 6H 2 O was dissolved in deionized water to form a mixed salt solution with a concentration of 0.1 mol / L; A2, add sepiolite to the mixed salt solution, stir magnetically, slowly add ammonia water, control the pH to 8, then slowly add PEG, stir at 300 rpm for 2 h to obtain a mixture; A3, the mixture was washed with deionized water and centrifuged three times, and then placed in a vacuum drying oven and dried at 80 °C for 12 h to obtain a precursor powder; A4, the precursor powder is placed in a muffle furnace for calcination, the temperature is increased to 400°C at a heating rate of 2°C / min, and calcined at this temperature for 2 h to obtain a catalyst.

[0014] Example 2: This example provides a method for preparing a biomass-based liquid fuel, wherein the biomass-based liquid fuel is prepared from the following raw materials in parts by weight: 90 parts of straw, 8 parts of catalyst, 6 parts of complex enzyme preparation, 0.08 parts of BHA, and 0.8 parts of SDS; The composite enzyme preparation is a mixed enzyme of cellulase, hemicellulase and xylanase in a mass ratio of 3:2:1; the straw is crop straw, including corn, wheat and rice straw; The biomass-based liquid fuel preparation method specifically comprises the following steps: S1, mechanical crushing, 90 portions of dry straw were selected, and the straw was mechanically crushed to 1 mm using a crusher. The crushed straw was placed in a forced air drying oven at 110 °C for 5 h to obtain crushed straw; S2, enzymatic hydrolysis reaction, the crushed straw was mixed with 6 parts of compound enzyme preparation, and 0.8 parts of SDS was added at the same time, and the reaction was carried out at 200 rpm for 12 h in a constant temperature water bath at 55 °C, with the pH maintained at 5, to degrade the macromolecular substances such as cellulose in the straw into small molecular sugars to obtain a mixture; S3, catalytic pyrolysis, filtering the mixture to obtain a solid residue, transferring the solid residue to a pyrolysis reaction device, adding 6 parts of catalyst, 2 Under the atmosphere, the temperature was raised to 450 °C at a heating rate of 10 °C, and pyrolysis was carried out at this temperature for 60 min to produce pyrolysis oil; S4, hydrogenation and upgrading, the obtained pyrolysis oil is transferred to a high-pressure reactor, hydrogen is introduced to keep the pressure in the high-pressure reactor at 2 MPa, 0.08 parts of BHA and 2 parts of catalyst are added, and the reaction is stirred at 300 °C and 300 rpm for 2 h to obtain a reaction product; S5, solid-liquid separation, filtering the reaction product, using a filter membrane with a pore size of 0.3 µm to separate solid impurities, obtaining a liquid portion, centrifuging the liquid portion at 6000 rpm for 15 min, and obtaining a clarified crude liquid fuel; S6, distillation and refining, distill and refine the crude liquid fuel, first collect the light fraction with a boiling point of 120°C, then increase the temperature to 320°C, and collect the heavy fraction with a boiling point in this range. The light fraction and the heavy fraction together constitute the biomass-based liquid fuel.

[0015] The catalyst is prepared from the following raw materials in weight ratio: sepiolite: Ce(NO 3 ) 3 6H 2 O:Ni(NO 3 ) 2 6H 2 O:PEG=12:3:2:1; The preparation method of the catalyst specifically comprises the following steps: A1, weigh Ce(NO 3 ) 3 6H 2O and Ni (NO 3 ) 2 6H 2 O was dissolved in deionized water to form a mixed salt solution with a concentration of 0.3 mol / L; A2, add sepiolite to the mixed salt solution, stir magnetically, slowly add ammonia water, control the pH to 10, then slowly add PEG, stir at 300 rpm for 2 h to obtain a mixture; A3, the mixture was washed with deionized water and centrifuged three times, and then placed in a vacuum drying oven and dried at 80 °C for 20 h to obtain a precursor powder; A4, the precursor powder is placed in a muffle furnace for calcination, the temperature is increased to 500°C at a heating rate of 3°C / min, and calcined at this temperature for 4 h to obtain a catalyst.

[0016] Example 3: This example provides a method for preparing a biomass-based liquid fuel, wherein the biomass-based liquid fuel is prepared from the following raw materials in parts by weight: 100 parts of straw, 10 parts of catalyst, 8 parts of complex enzyme preparation, 0.01 parts of BHA, and 1 part of SDS; The composite enzyme preparation is a mixed enzyme of cellulase, hemicellulase and xylanase in a mass ratio of 3:2:1; the straw is crop straw, including corn, wheat and rice straw; The biomass-based liquid fuel preparation method specifically comprises the following steps: S1, mechanical crushing, select 100 portions of dry straw, use a crusher to mechanically crush the straw to 2 mm, and place the crushed straw in a forced air drying oven at 110 °C for 6 h to obtain crushed straw; S2, enzymatic hydrolysis reaction, the crushed straw was mixed with 8 parts of compound enzyme preparation, and 1 part of SDS was added at the same time, and the reaction was carried out at 200 rpm for 12 h in a constant temperature water bath at 55 °C, with the pH maintained at 5.5, so that the macromolecular substances such as cellulose in the straw were degraded into small molecular sugars to obtain a mixture; S3, catalytic pyrolysis, filtering the mixture to obtain a solid residue, transferring the solid residue to a pyrolysis reaction device, adding 7 parts of catalyst, 2 Under the atmosphere, the temperature was raised to 450 °C at a heating rate of 10 °C, and pyrolysis was carried out at this temperature for 60 min to produce pyrolysis oil; S4, hydrogenation and upgrading, the obtained pyrolysis oil is transferred to a high-pressure reactor, hydrogen is introduced to keep the pressure in the high-pressure reactor at 3 MPa, 0.01 parts of BHA and 3 parts of catalyst are added, and the reaction is stirred at 300 °C and 300 rpm for 3 h to obtain a reaction product; S5, solid-liquid separation, filtering the reaction product, using a filter membrane with a pore size of 0.5 µm to separate solid impurities, obtaining a liquid portion, centrifuging the liquid portion at 8000 rpm for 15 min, and obtaining a clarified crude liquid fuel; S6, distillation and refining, distill and refine the crude liquid fuel, first collect the light fraction with a boiling point of 200°C, then increase the temperature to 350°C, collect the heavy fraction with a boiling point in this range, and the light fraction and the heavy fraction together constitute the biomass-based liquid fuel.

[0017] The catalyst is prepared from the following raw materials in weight ratio: sepiolite: Ce(NO 3 ) 3 6H 2 O:Ni(NO 3 ) 2 6H 2 O:PEG=12:4:2:1; The preparation method of the catalyst specifically comprises the following steps: A1, weigh Ce(NO 3 ) 3 6H 2 O and Ni (NO 3 ) 2 6H 2 O was dissolved in deionized water to form a mixed salt solution with a concentration of 0.5 mol / L; A2, add sepiolite to the mixed salt solution, stir magnetically, slowly add ammonia water, control the pH to 10, then slowly add PEG, stir at 300 rpm for 2 h to obtain a mixture; A3, the mixture was washed with deionized water and centrifuged three times, and then placed in a vacuum drying oven and dried at 80 °C for 24 h to obtain a precursor powder; A4, the precursor powder is placed in a muffle furnace for calcination, the temperature is increased to 600°C at a heating rate of 5°C / min, and calcined at this temperature for 4 h to obtain a catalyst.

[0018] The difference between Comparative Example 1 and Example 2 is that a single catalyst, cerium oxide, is used, and the rest is exactly the same as Example 2.

[0019] The difference between Comparative Example 2 and Example 2 is that the enzymatic hydrolysis step is eliminated, and the rest is exactly the same as Example 2.

[0020] The difference between Comparative Example 3 and Example 2 is that the hydrogenation upgrading step is eliminated, and the rest is exactly the same as Example 2.

[0021] Experimental Example 1: The liquefaction rate is calculated as follows: Y% = (M0 -M 1 ) / M 0 ×100%, where Y represents the liquefaction yield, %; M 1 Represents the mass of the residue in the liquefied product, g; M 0 The mass of straw used in the liquefaction process, g, is recorded in Table 1.

[0022] Determination of viscosity: Place the liquefied product in the drum of the NDJ-4 rotary viscometer, and place the drum in a constant temperature oscillating water bath with humidity controlled at 40°C. Select an appropriate rotor to measure the dynamic viscosity of the product, and record the viscosity in Table 1.

[0023] Determination of acid value: Take 0.15-0.2 g of the liquefied product, dissolve it in 25 mL of dioxane aqueous solution (dioxane: water = 4:1 V / V), and titrate to the equilibrium point using a calibrated 0.09 mol / L sodium hydroxide solution.

[0024] Determination of ash content: Using the incineration method, the biomass liquid fuel is heated to 775°C under aerobic conditions and burned. The remaining residue is the ash content, which is recorded in Table 1.

[0025] Determination of heavy oil components: Weigh 1.0-1.5g of the liquefied product into a constant weight weighing bottle, put it into a 105°C oven to dry until the product has a constant weight, take it out, cool it to room temperature and weigh it. The heavy oil component results are recorded in Table 1.

[0026] Table 1

[0027] Experimental Example 2: The calorific value of the biomass-based liquid fuel prepared by the present invention was tested using an oxygen bomb calorimeter. The biomass-based liquid fuel prepared by Examples 1-3 and Comparative Examples 1-3 of the present invention was used as a sample. First, benzoic acid was used to calibrate the heat capacity of the instrument. Then, the sample was injected into a combustion dish with a syringe, and the mass of the sample was weighed. The combustion dish was placed in an oxygen bomb, connected to an ignition wire, filled with 2-3 MPa of oxygen, and then placed in the inner cylinder of the calorimeter. A certain amount of water was added, and the calorimeter was started to record the water temperature. The calorimeter was ignited and burned. After the water temperature stabilized, the temperature change was recorded. The calorific value was calculated based on the heat capacity and the temperature change. The average value of 5 experiments was taken and compared with traditional fossil fuels. The recorded calorific value results are shown in Table 2.

[0028] Experimental Example 3: The combustion efficiency of the biomass-based liquid fuel prepared by the present invention was tested. The biomass-based liquid fuel prepared by Examples 1-3 and Comparative Examples 1-3 of the present invention was used as a sample. First, an experimental device including a combustion furnace, a fuel and oxygen supply system, and a product analysis system was built; the sample was loaded into the oil storage tank, the combustion furnace was started and heated to the set value, the fuel and oxygen supply system was turned on, and the flow rate was adjusted to fully burn the fuel. The concentration of the combustion products was monitored with a gas analyzer, and the fuel and oxygen consumption rates were recorded. The combustion efficiency was calculated by calculating the fuel and oxygen consumption rates and combining the product concentration. The combustion efficiency values ​​were recorded in Table 2, and the data were analyzed and the combustion process was improved in a targeted manner.

[0029] Table 2

[0030] From the results in Table 1, it can be seen that the liquid fuel prepared by the biomass-based liquid fuel preparation method of the present invention has good fluidity, can be efficiently atomized and burned in the equipment, and the acidic substances and impurities in the fuel are effectively controlled, which not only reduces corrosion to the equipment, but also reduces carbon deposits and wear. At the same time, the proportion of light components in the fuel is relatively high, which improves the quality, so that it exhibits excellent performance in terms of combustion efficiency, equipment adaptation and environmental protection.

[0031] As can be seen from Table 2, the calorific value of the biomass-based liquid fuel prepared in Examples 1-3 of the present invention is significantly higher than that of Comparative Examples 1-3, indicating that the catalyst catalytic pyrolysis and hydrogenation upgrading steps added in the preparation process effectively remove impurities with high oxygen content in the reaction process, increase the carbon and hydrogen content in the liquid fuel, and improve the calorific value; as for the combustion efficiency, the embodiment reached 91.21%, indicating that the catalyst used and the optimized preparation process enable the liquid fuel to be in more sufficient contact with oxygen during combustion, thereby achieving efficient combustion.

[0032] Figure 2 This is a SEM image of the catalyst prepared by the present invention. The SEM image shows a disordered and porous microstructure. The fibers of sepiolite create a large number of active sites and pores, which accelerate the generation and transfer of active oxygen, thereby accelerating the catalytic pyrolysis reaction. In addition, the macroscopic structure of sepiolite does not change significantly due to the addition of cerium oxide. Figure 3 The stability of the catalyst used in the present invention is shown in that the biomass fuel oil yield is still higher than 80% after the catalyst is recycled four times, which shows good stability compared with the single catalyst cerium oxide.

[0033] In summary, the present invention is based on the biomass-based liquid fuel preparation method to prepare liquid fuel with good performance, using crop straw as raw material, with composite enzyme preparation, specific catalyst, and multi-step collaborative treatment, successfully solving multiple problems in the preparation and use of biomass fuel. In the preparation stage, the composite enzyme preparation starts straw conversion under mild conditions, and the catalytic pyrolysis link is precisely regulated, which improves the generation efficiency and selectivity of the product; the catalyst used, with the help of the synergy of sepiolite and cerium oxide active ingredients, not only reduces the pyrolysis temperature, but also plays multiple functions in the combustion process, and improves the quality of fuel in all directions; the obtained fuel has high calorific value and high combustion efficiency, can provide stable energy for the engine, greatly reduce the emission of pollutants such as carbon smoke, tar, sulfur dioxide and nitrogen oxides, and significantly reduce the negative impact on the environment. In addition, the catalyst gives the fuel excellent antioxidant stability and extends its storage life. At the same time, the present invention optimizes the physical and chemical properties of the fuel, reduces viscosity, acid value and ash content, improves the liquefaction yield, reduces heavy oil components, and makes the fuel more convenient and efficient in storage, transportation and use.

[0034] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing liquid fuel based on biomass, characterized in that: The biomass-based liquid fuel is prepared from the following raw materials in parts by weight: 80-100 parts of straw, 6-10 parts of catalyst, 5-8 parts of complex enzyme preparation, 0.05-0.01 parts of BHA, and 0.5-1 parts of SDS; The biomass-based liquid fuel preparation method specifically comprises the following steps: S1, mechanically crushing the straw, and drying it after crushing to obtain crushed straw; S2, enzymatic hydrolysis reaction, mixing the crushed straw with the composite enzyme preparation, adding SDS, stirring at a constant temperature, maintaining pH, and obtaining a mixture; S3, catalytic pyrolysis, filtering the mixture to obtain a solid residue, adding a catalyst to the solid residue to perform catalytic pyrolysis to produce pyrolysis oil; S4, hydrogenation and upgrading, introducing hydrogen into the pyrolysis oil, adding BHA and catalyst, stirring, and obtaining a reaction product; S5, solid-liquid separation, filtering the reaction product to obtain a liquid portion, centrifuging the liquid portion to obtain a clarified crude liquid fuel; S6, distillation and refining, distilling and refining the crude liquid fuel to obtain biomass-based liquid fuel.

2. The method for preparing liquid fuel based on biomass according to claim 1, characterized in that: In step S2, the pH is 4.5-5.

5.

3. The method for preparing liquid fuel based on biomass according to claim 1, characterized in that: In step S3, the temperature of the catalytic pyrolysis is: the temperature is raised to 350-450°C at a heating rate of 10°C, and the pyrolysis time is 30-60 minutes.

4. The method for preparing liquid fuel based on biomass according to claim 1, characterized in that: In step S6, the distillation refining process is: first collect the light fraction with a boiling point of 60-200°C, then increase the temperature to 200-350°C, collect the heavy fraction with a boiling point of 200-350°C, and the light fraction and the heavy fraction together constitute the biomass-based liquid fuel.

5. The method for preparing liquid fuel based on biomass according to claim 1, characterized in that: The composite enzyme preparation is a mixed enzyme of cellulase, hemicellulase and xylanase in a mass ratio of 3:2:1; the straw is crop straw, including corn, wheat and rice straw.

6. The method for preparing liquid fuel based on biomass according to claim 1, characterized in that: The catalyst is prepared from the following raw materials in a weight ratio: sepiolite: Ce(NO3)3·6H2O: Ni(NO3)2·6H2O: PEG=12:1-4:1-2:1; The preparation method of the catalyst is specifically The following steps are involved: A1, weigh Ce(NO3)3·6H2O and Ni(NO3)2·6H2O and dissolve them in deionized water to form a mixed salt solution; A2, adding sepiolite to the mixed salt solution, stirring with a magnetic force, slowly dropping ammonia water, controlling the pH, and then slowly adding PEG, stirring, to obtain a mixture; A3, centrifugally washing the mixture, and then drying to obtain a precursor powder; A4, calcining the precursor powder to obtain a catalyst.

7. The method for preparing liquid fuel based on biomass according to claim 6, characterized in that: In step A1, the concentration of the mixed salt solution is 0.1-0.5 mol / L.

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