Method for preparing biofuel by lossless component separation and classified modification of straw bio-oil

Abstract

The invention relates to the technical field of biomass resource utilization, and discloses a method for preparing biofuel by lossless component separation and classified modification of straw bio-oil, which comprises the following steps: carrying out centrifugal pretreatment on original bio-oil to remove macromolecular particles, and then mutually dissolving the pretreated bio-oil and dichloromethane to prepare a mixed solution; and carrying out molecular distillation on the mixed solution through a molecular distillation device to obtain light distillate oil and heavy distillate oil, carrying out separate hydro-upgrading on the light distillate oil, and adding a hydrogen donor into the heavy distillate oil for co-hydro-upgrading to respectively obtain the modified oil. According to the method, nondestructive collection of straw bio-oil components is achieved, the problem that heavy fractions such as coking polymerization and the like are difficult to continue to be utilized in conventional distillation is solved, targeted classified modification can be implemented according to the characteristics of different fractions, and by adding the hydrogen donor, the yield of the straw bio-oil is improved. And the energy recovery efficiency in the process of converting the straw biomass raw material into the biofuel is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass resource utilization, and in particular relates to a method for lossless component separation and classification reforming of straw bio-oil to prepare biofuel. Background Art

[0002] Biomass energy is a green renewable energy source with a safe and gentle production process and excellent regional adaptability. It is also the only carbon-neutral and carbon-rich resource known to be directly converted into liquid fuel. Compared with gaseous energy such as natural gas and hydrogen, biofuel has the advantages of being easy to store and transport.

[0003] Straw is a high-quality and abundant biomass resource, composed of a large amount of organic matter, a small amount of inorganic matter and water, and rich in cellulose, hemicellulose and lignin. At present, pyrolysis and hydrothermal liquefaction technologies are widely used in the research of preparing bio-oil from lignocellulosic biomass. The C, H content and calorific value (HHVs) of the obtained crude bio-oil are significantly improved compared with the raw material. However, compared with fossil fuels, the high oxygen content of crude bio-oil will lead to its high acidity, high viscosity and low stability, and its nitrogen and sulfur content will produce NO when directly burned. x and SO x , causing air pollution. These negative characteristics become obstacles to the direct application of lignocellulosic bio-oil as liquid fuel. Therefore, it is necessary to modify and upgrade it to meet the quality requirements for direct use as liquid fuel. Among the current bio-oil modification methods, catalytic hydrogenation is a commonly used technical means. Catalytic hydrogenation usually uses hydrogen as the hydrogen source, and noble metals, transition metals and molybdenum-based sulfides as catalysts to remove N, O and S heteroatoms in crude oil through hydrodeoxygenation (HDO), hydrodenitrogenation (HDN) and hydrodesulfurization (HDS), usually accompanied by hydrogenation (saturation) of olefins and aromatics, thereby obtaining high-grade bio-liquid fuels with low O / C values ​​and high saturation.

[0004] The commonly used method at present is to hydrogenate and reform bio-oil as a whole, but carbon deposition is a common phenomenon in the catalytic hydrogenation process of bio-oil. The cause of carbon deposition and catalyst deactivation are not only closely related to the operating conditions, but also directly related to the chemical composition of bio-oil. Bio-oil contains hundreds of organic compounds, mainly composed of oxygen-containing and nitrogen-containing compounds. Oxygen-containing compounds are mainly ketones and phenolic compounds, in addition to a small amount of acids, alcohols, aldehydes, esters and ethers. Nitrogen-containing compounds mainly include pyridine, pyrrole, pyrazine and nicotine compounds, most of which are heterocyclic compounds. Phenols, aldehydes and nitrogen-containing heterocycles in bio-oil are more likely to cause carbon deposition. Phenols and aldehydes form carbon deposition through polymerization and polycondensation reactions. These carbon depositions will block the active pores on the catalyst surface, thereby causing catalyst deactivation and may further promote the formation of carbon deposition. Nitrogen-containing heterocyclic compounds easily diffuse into the micropores of the catalyst and adsorb on the acidic sites, thereby aggravating carbon deposition and causing serious poisoning of the catalyst. Polycyclic aromatic hydrocarbons are considered to be potential strong coke precursors. They can adsorb on the acidic sites of the catalyst and produce a large amount of carbon deposits during the catalytic hydrogenation process, which in turn leads to catalyst deactivation. It can be seen that if bio-oil is indiscriminately hydrogenated and modified as a whole, it will inevitably cause catalyst deactivation and carbon deposition, affecting the yield of modified oil and increasing operating costs.

[0005] Traditional distillation includes atmospheric distillation and vacuum distillation, which is a simple, mature and widely used separation technology. However, for bio-oil with high heat sensitivity, although atmospheric distillation has the advantages of relatively low cost and simple operation, it also has the disadvantages of long residence time, high temperature and low efficiency. Long-term high-temperature heating will lead to polymerization and aging coking in the heat-sensitive bio-oil components, which not only affects the yield of the final distillate oil, but also destroys the original composition of the bio-oil. The operating temperature of vacuum distillation is much lower than that of atmospheric distillation, but it only relatively reduces the occurrence of adverse reactions and aging reactions, not completely eliminating them. Under the conditions of vacuum distillation, faster steam discharge may lead to higher loss of light distillate oil, thereby reducing the yield of light distillate oil. In addition, these two bio-oil separation methods tend to obtain light fractions in bio-oil. For heavy fractions containing many macromolecular compounds, they often polymerize and coke during the distillation process, and cannot be subsequently processed and abandoned, which is bound to cause a cliff-like decrease in bio-oil conversion efficiency. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for lossless component separation and classification reforming of straw bio-oil to prepare biofuel, so as to solve the technical problems of decreased reformed oil yield and increased operating costs caused by carbon deposition and catalyst deactivation during the reforming bio-oil process.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil, comprising the following steps: S1, centrifugal pretreatment of raw bio-oil; S2, preparing a mixed solution by dissolving the pretreated bio-oil and dichloromethane; S3, performing molecular distillation on the mixed solution through a molecular distillation device to obtain light distillate oil and heavy distillate oil; S4, the light distillate oil is subjected to separate hydrogenation reforming, and the heavy distillate oil is subjected to co-hydrogenation reforming by adding a hydrogen donor, so as to obtain reformed oils respectively.

[0008] A further improvement of the present invention is that in the step S1, the original bio-oil is pre-treated by centrifugation at a speed of 4000-6000 r / min and a centrifugation time of 20-40 min.

[0009] A further improvement of the present invention is that in the step S2, 80-120 g of the pretreated bio-oil is dissolved in dichloromethane to make the total volume reach 300 mL to prepare a mixed solution.

[0010] A further improvement of the present invention is that in the step S3, the vacuum degree of the molecular distillation system is 120Pa and the temperature is 100-160°C.

[0011] A further improvement of the present invention is that in the step S3, the molecular distillation device includes a feeding device, an evaporation device, a primary condensation device, a secondary condensation device and a cold trap device.

[0012] A further improvement of the present invention is that in the step S4, Pt / C catalyst is used for both the hydrogenation reforming of the light distillate oil and the co-hydrogenation reforming of the heavy distillate oil.

[0013] A further improvement of the present invention is that in the step S4, the temperature of the hydrogenation reaction is 300-500°C.

[0014] A further improvement of the present invention is that in the step S4, a hydrogen donor is added when the heavy distillate oil is co-hydrogenated, wherein the mass ratio of the heavy distillate oil to the hydrogen donor is 1:1.

[0015] A further improvement of the present invention is that the hydrogen donor is one of waste engine oil, tetralin, decalin or indane.

[0016] A further improvement of the present invention is that after the hydrogenation and co-hydrogenation reactions are completed, dichloromethane is used to extract and clean the molecular distillation device.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil, wherein the original bio-oil is centrifugally pretreated to remove macromolecular particles, and then the pretreated bio-oil is mutually dissolved with dichloromethane to prepare a mixed solution, and then the mixed solution is molecularly distilled by a molecular distillation device to obtain light distillate oil and heavy distillate oil, and the light distillate oil is separately hydrogenated and reformed, and a hydrogen supply agent is added to the heavy distillate oil for co-hydrogenation and reforming to obtain reformed oils respectively. The method not only realizes the lossless collection of straw bio-oil components, but also overcomes the problem that heavy fractions such as coking and polymerization in conventional distillation are difficult to continue to use, and can implement targeted classification reforming according to the characteristics of different fractions, and significantly improves the energy recovery efficiency in the process of converting straw biomass raw materials into biofuels by adding a hydrogen supply agent. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0020] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0021] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0022] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0023] The present invention provides a method for lossless component separation and classification reforming of straw bio-oil to prepare biofuel, comprising the following steps: S1, using straw hydrothermal liquefaction oil or pyrolysis oil as raw material, and subjecting it to centrifugal pretreatment to remove macromolecular particles in the raw material, wherein the centrifugal pretreatment condition is 4000-6000r / min, and the centrifugal time is 20-40min.

[0024] S2, taking 80-120 g of the pretreated raw material and dissolving it in dichloromethane to make the total volume reach 300 mL, to prepare a mixed solution.

[0025] S3, under the conditions of system vacuum degree of 120Pa and temperature of 100-160°C, the mixed solution is molecularly distilled by a molecular distillation device to obtain light distillate oil and heavy distillate oil; The molecular distillation device comprises a feeding device, an evaporating device, a primary condensing device, a secondary condensing device and a cold trap device.

[0026] S4, performing separate hydro-upgrading on the light distillate oil; Specifically, light distillate oil was added to the reactor, and 0.6 g of Pt / C catalyst was added at the same time. The reactor was tightened symmetrically and heated with H 2 After exhausting for 25 min, fill with 6 MPa H 2 . After the leak test, put the reactor into a 400℃ salt bath pot, heat it to 400℃ after about 35min, start timing, and react for 2h. The pressure of the reactor when it is heated to 400℃ is 12~14 MPa, and the pressure of the reactor after the reaction is 10~12 MPa. After the reaction is completed, put the reactor into cold water for quenching for 1~2h, at which time the pressure of the reactor is 3~4 MPa. Use a vacuum collection bag to collect part of the gas produced by the reaction, and then discharge the remaining gas. The mass difference of the reactor before and after exhaust minus the mass of the H2O2 gas filled in is the mass difference of the reactor before and after exhaust. 2 The mass is the mass of the gas produced, and the gas yield is calculated. Open the reactor, extract the product with about 50 mL of dichloromethane, and repeatedly clean the inner wall and pipe of the reactor, then wipe the inner wall and contact surface of the reactor repeatedly with filter paper, and transfer it to a beaker. Then filter the mixture in the beaker, rinse the filter residue with about 20 mL of dichloromethane and rinse the edge of the filter paper several times, and the filtration ends when the filtrate turns light yellow. Put all the filter papers and filter residues into a blast drying oven at 105°C and dry them for 6 hours. After drying, subtract the mass of the filter paper and the catalyst to obtain the mass of the solid residue, and calculate the solid residue yield. Transfer the filtrate to a pre-weighed empty round-mouth flask for rotary evaporation. The mass difference between the round-mouth flask after rotary evaporation and the empty round-mouth flask is the mass of the obtained light modified oil.

[0027] S5, co-hydrogenation upgrading of heavy distillate oil; Specifically, the heavy distillate oil and the hydrogen donor were mixed in a ratio of 1:1 and added to the reactor. At the same time, 0.6 g of Pt / C catalyst was added. The reactor was tightened symmetrically and heated with H 2 After exhausting for 25 min, fill with 6 MPa H 2 . After the leak test, put the reactor into a 400℃ salt bath pot, heat it to 400℃ after about 35min, start timing, and react for 2h. The pressure of the reactor when it is heated to 400℃ is 12~14 MPa, and the pressure of the reactor after the reaction is 10~12 MPa. After the reaction is completed, put the reactor into cold water for quenching for 1~2h, at which time the pressure of the reactor is 3~4 MPa. Use a vacuum collection bag to collect part of the gas produced by the reaction, and then discharge the remaining gas. The mass difference of the reactor before and after exhaust minus the mass of the H2O2 gas filled in is the mass difference of the reactor before and after exhaust. 2 The mass is the mass of the gas produced, and the gas yield is calculated. Open the reactor, extract the product with about 50mL of dichloromethane, and repeatedly clean the inner wall and pipe of the reactor, then wipe the inner wall and contact surface of the reactor repeatedly with filter paper, and transfer it to a beaker. Then filter the mixture in the beaker, rinse the filter residue with about 20mL of dichloromethane and rinse the edge of the filter paper several times, and the filtration ends when the filtrate turns light yellow. Put all the filter papers and filter residues into a blast drying oven at 105℃ and dry them for 6h. After drying, subtract the mass of the filter paper and the catalyst to obtain the mass of the solid residue, and calculate the solid residue yield. Transfer the filtrate to a pre-weighed empty round-mouth flask for rotary evaporation. The mass difference between the round-mouth flask after rotary evaporation and the empty round-mouth flask is the mass of the obtained heavy modified oil.

[0028] As a preferred embodiment, the hydrogen donor is one of waste engine oil, tetralin, decalin or indane.

[0029] It should be noted that at the beginning of molecular distillation, the mixed solution enters the evaporator through the feed device, and flows downward along the inner wall of the double-layer jacket of the evaporator under the dual effects of gravity and heating. Since the distance between the inner wall of the double-layer jacket of the evaporator and the scraper is less than 0.5 mm, with the high-speed rotation of the scraper, the material is scraped into an extremely thin liquid film, which is pushed downward in a spiral shape under the action of the scraper. In the process of the spiral pushing downward, under the dual effects of the heating of the evaporator and the vacuum degree of the system, the molecules with a smaller mean free path pass through a shorter route and are almost not The collision condenses into liquid on the built-in primary condensation device, flows down along the spiral condenser tube, and is collected in the light fraction collection bottle; molecules with a smaller mean free path, such as dichloromethane and small molecular compounds in the original bio-oil, will enter the secondary condensation device and the cold trap device along the system, and are condensed and collected in the cold trap collection bottle and the secondary condensation device collection bottle respectively; molecules with a larger mean free path are not easy to evaporate, and under the dual effects of heating by the evaporation device and their own gravity, they flow down along the inner wall of the double-layer jacket and enter the heavy fraction collection bottle to be collected. After the mixed solution is fed, dichloromethane is used to extract and clean the molecular distillation device, so that the residue remaining on the surface of the condenser flows into the light fraction collection bottle, and the residue on the surface of the evaporator flows into the heavy fraction collection bottle. After the molecular distillation is completed, the liquids in the cold trap collection bottle, the secondary condensation device collection bottle and the light fraction collection bottle are mixed together for rotary evaporation. The bio-oil obtained after rotary evaporation is collectively referred to as light fraction oil; the bio-oil obtained by rotary evaporation of the liquid in the heavy fraction collection bottle is collectively referred to as heavy fraction oil.

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0031] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0032] Example 1 This embodiment uses straw hydrothermal liquefied oil as raw bio-oil, and a method for non-destructive component separation thereof includes the following steps: Step S1, performing centrifugal pretreatment on the straw hydrothermal liquefied oil, centrifuging at 5000 r / min for 30 min to remove macromolecular particles in the straw hydrothermal liquefied oil; Step S2, taking 100g of the pretreated straw hydrothermal liquefied oil, dissolving it with dichloromethane until the total volume reaches 300mL, preparing a mixed solution, pouring the mixed solution into a feeding device, adding anhydrous ethanol and dry ice into a cold trap device to reach a molten state, and inserting a thermometer to monitor the temperature in real time, when the system pressure reaches 120Pa and the temperature is 100°C, performing molecular distillation to collect light distillate oil and heavy distillate oil respectively.

[0033] Table 1 shows the yield distribution of molecular distillation products of straw hydrothermal liquefaction oil. It can be seen from Table 1 that when the system pressure reaches 120Pa and the temperature is 100℃, the yields of molecular distillation products of peanut straw hydrothermal liquefaction oil are light oil yield of 11.96wt.%, heavy oil yield of 86.64wt.%, and total yield of 98.38wt.%.

[0034] Example 2 This example uses straw hydrothermal liquefied oil as the original bio-oil, performs a non-destructive component separation method, sets the molecular distillation temperature to 130° C., and collects light distillate oil and heavy distillate oil separately. The contents not mentioned in this example are the same as those described in Example 1.

[0035] Table 1 shows the yield distribution of molecular distillation products of straw hydrothermal liquefaction oil. It can be seen from Table 1 that when the system pressure reaches 120Pa and the temperature is 130℃, the yields of molecular distillation products of peanut straw hydrothermal liquefaction oil are light oil yield 20.96wt.%, heavy oil yield 75.86wt.%, and total yield 96.82wt.%.

[0036] Example 3 This example uses straw hydrothermal liquefied oil as the original bio-oil, performs a non-destructive component separation method, sets the molecular distillation temperature to 160° C., and collects light distillate oil and heavy distillate oil separately. The contents not mentioned in this example are the same as those described in Example 1.

[0037] Table 1 shows the yield distribution of molecular distillation products of straw hydrothermal liquefaction oil. It can be seen from Table 1 that when the system pressure reaches 120Pa and the temperature is 160℃, the yields of molecular distillation products of peanut straw hydrothermal liquefaction oil are light oil yield 23.26wt.%, heavy oil yield 74.33wt.%, and total yield 97.59wt.%.

[0038] Table 1 Yield distribution of molecular distillation products of straw hydrothermal liquefaction oil (wt.%, operating pressure 120Pa)

[0039] Light oil is a brown liquid with strong volatility and pungent odor, containing a certain amount of water and strong fluidity. In contrast, heavy oil is close to solid at room temperature, has a low water content, and is a black liquid with poor fluidity and strong viscosity. The sum of the light oil and heavy oil yields obtained by molecular distillation at different temperatures is stable at 96.82~98.38 wt.%, which shows that molecular distillation can effectively avoid the problem of easy loss of light distillate oil and easy deterioration of heavy distillate oil in the traditional distillation process, and can realize the graded separation and lossless collection of straw bio-oil.

[0040] Example 4 In this example, straw hydrothermal liquefaction oil was used as the original bio-oil, and light oil was modified to prepare biofuel: 6 g of light oil was added to the reactor, and 0.6 g of Pt / C catalyst was added. The reactor was tightened symmetrically and heated with H 2 After exhausting for 25 minutes, fill with 6 MPa H 2 . After the leak test, put the reactor into a 400℃ salt bath pot, heat it to 400℃ after about 35min, start timing, and react for 2h. The pressure of the reactor when it is heated to 400℃ is 13±1 MPa, and the pressure of the reactor after the reaction is 11±1 MPa. After the reaction is completed, put the reactor into cold water for quenching for 1h, at which time the pressure of the reactor is 3.5±1 MPa. Use a vacuum collection bag to collect part of the gas produced by the reaction, and then discharge the remaining gas. The mass difference of the reactor before and after exhaust minus the mass of the H2 filled in is 2 The mass is the mass of the gas produced, and the gas yield is calculated. Open the reactor, extract the product with about 50 mL of dichloromethane, and repeatedly clean the inner wall and pipe of the reactor, then wipe the inner wall and contact surface of the reactor repeatedly with filter paper, and transfer it to a beaker. Then filter the mixture in the beaker, rinse the filter residue with about 20 mL of dichloromethane and rinse the edge of the filter paper several times, and the filtration is completed when the filtrate turns light yellow. Put all the filter papers and filter residues into a blast drying oven at 105°C and dry them for 6 hours. After drying, subtract the mass of the filter paper and the catalyst to obtain the mass of the solid residue, and calculate the solid residue yield. Transfer the filtrate to a pre-weighed empty round-mouth flask for rotary evaporation. The mass difference between the round-mouth flask after rotary evaporation and the empty round-mouth flask is the mass of the light oil modified oil obtained.

[0041] Example 5 In this example, straw hydrothermal liquefaction oil was used as the original bio-oil, and light oil + waste engine oil was modified to prepare biofuel: 3g of light oil and 3g of waste engine oil were added to the reactor, and 0.6g of Pt / C catalyst was added. The reactor was tightened symmetrically and heated with H 2 After exhausting for 25 minutes, fill with 6 MPa H 2. After the leak test, put the reactor into a 400℃ salt bath pot, heat it to 400℃ after about 35min, start timing, and react for 2h. The pressure of the reactor when it is heated to 400℃ is 13±1 MPa, and the pressure of the reactor after the reaction is 11±1 MPa. After the reaction is completed, put the reactor into cold water for quenching for 1h, at which time the pressure of the reactor is 3.5±1 MPa. Use a vacuum collection bag to collect part of the gas produced by the reaction, and then discharge the remaining gas. The mass difference of the reactor before and after exhaust minus the mass of the H2 filled in is 2 The mass of the gas produced is the mass of the gas, and the gas yield is calculated. Open the reactor, extract the product with about 50 mL of dichloromethane, and repeatedly clean the inner wall and pipe of the reactor, then wipe the inner wall and contact surface of the reactor repeatedly with filter paper, and transfer it to a beaker. Then filter the mixture in the beaker, rinse the filter residue with about 20 mL of dichloromethane and rinse the edge of the filter paper several times, and the filtration is completed when the filtrate turns light yellow. Put all the filter papers and filter residues into a blast drying oven at 105°C and dry them for 6 hours. After drying, subtract the mass of the filter paper and the catalyst to obtain the mass of the solid residue, and calculate the solid residue yield. Transfer the filtrate to a pre-weighed empty round-mouth flask for rotary evaporation. The mass difference between the round-mouth flask after rotary evaporation and the empty round-mouth flask is the mass of the light oil + waste oil modified oil obtained.

[0042] Example 6 In this example, straw hydrothermal liquefied oil is used as the original bio-oil, and 6g of heavy oil is reformed to prepare biofuel. The contents not mentioned in this example are the same as those described in Example 4.

[0043] Example 7 In this example, straw hydrothermal liquefied oil is used as the original bio-oil, and 3g of heavy oil + 3g of waste oil are reformed to prepare biofuel. The contents not mentioned in this example are the same as those described in Example 5.

[0044] Example 8 In this example, straw hydrothermal liquefied oil is used as the original bio-oil, and 3g of heavy oil + 3g of decalin are reformed to prepare biofuel. The contents not mentioned in this example are the same as those described in Example 5.

[0045] Example 9 In this example, straw hydrothermal liquefied oil is used as the original bio-oil, and 3g heavy oil + 3g tetralin are reformed to prepare biofuel. The contents not mentioned in this example are the same as those described in Example 5.

[0046] Example 10 In this example, straw hydrothermal liquefied oil is used as the original bio-oil, and 3g heavy oil + 3g indane are modified to prepare biofuel. The contents not mentioned in this example are the same as those described in Example 5.

[0047] Table 2 Distribution of hydrogenation products of molecular distillation products of straw hydrothermal liquefaction oil (wt.%)

[0048] Table 2 shows the distribution of hydrogenation products of the molecular distillation products of straw hydrothermal liquefaction oil. It can be seen from Table 2 that by molecular distillation, bio-oil is divided into light distillate oil and heavy distillate oil, and they are hydrogenated and modified respectively. It can be obtained that the modified oil yield of both light oil and heavy oil is higher than that of bio-oil. When it is co-hydrogenated and modified with waste engine oil at the same time, the modified oil yield of light oil and heavy oil is still higher than that of bio-oil. When waste engine oil, decahydronaphthalene, tetrahydronaphthalene and indane are added to heavy oil, its modified oil yield increases significantly compared with that without addition, and the corresponding solid yield drops to 4.32 wt.% at the lowest.

[0049] Table 3 Elemental composition of bio-oil and its fractions hydro-modified and co-hydro-modified with hydrogen donors (wt.%)

[0050] Table 3 shows the elemental composition of the modified oil obtained by hydrogenation and reforming of bio-oil and its fractions and co-hydrogenation and reforming with hydrogen donors. It can be seen from Table 3 that, compared with the overall hydrogenation and reforming of bio-oil, the C and H content and calorific value of the hydrogenation and reforming oil of its fractions (light oil and heavy oil) are significantly higher than those of the bio-oil reformed oil, and the heteroatom content is also significantly lower than that of the bio-oil reformed oil. This reflects the advantage of non-destructive separation and collection of bio-oil by molecular distillation and then classified hydrogenation and reforming. After the heavy oil is co-hydrogenated with hydrogen donors such as waste engine oil and decahydronaphthalene, not only the yield of the reformed oil is greatly improved (see Table 2), but its heteroatom content is also significantly reduced.

[0051] In summary, straw bio-oil can be obtained through molecular distillation to obtain light distillate oil and heavy distillate oil. Light distillate oil can be directly hydrogenated and reformed to obtain a higher reformed oil yield and a very low carbon deposition yield. Heavy distillate oil can be added with waste oil, tetralin, decalin or indane and other hydrogen donors during its reforming process, which can not only reduce the viscosity and corrosiveness of the bio-oil system, but also significantly improve the heat and mass transfer performance in the pyrolysis system. It can also play the role of hydrogen donor under supercritical conditions, thereby reducing the carbon deposition yield and increasing the reformed oil yield of heavy distillate oil. In short, through the graded separation and classified reforming of bio-oil, the high carbon deposition rate and catalyst deactivation in the overall hydrogenation reforming process of bio-oil can be effectively avoided, and the energy conversion and recovery efficiency of straw biomass in the preparation of biofuels can be improved.

[0052] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil, characterized in that: The following steps are involved: S1, centrifugal pretreatment of raw bio-oil; S2, preparing a mixed solution by dissolving the pretreated bio-oil and dichloromethane; S3, performing molecular distillation on the mixed solution through a molecular distillation device to obtain light distillate oil and heavy distillate oil; S4, the light distillate oil is subjected to separate hydrogenation reforming, and the heavy distillate oil is subjected to co-hydrogenation reforming by adding a hydrogen donor, so as to obtain reformed oils respectively.

2. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: In the step S1, the original bio-oil is pre-treated by centrifugation at a speed of 4000-6000 r / min and a centrifugation time of 20-40 min.

3. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: In the step S2, 80-120 g of the pretreated bio-oil is dissolved in dichloromethane to make the total volume reach 300 mL to prepare a mixed solution.

4. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: In the step S3, the system vacuum of the molecular distillation is 120 Pa and the temperature is 100-160°C.

5. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: In the step S3, the molecular distillation device includes a feeding device, an evaporation device, a primary condensation device, a secondary condensation device and a cold trap device.

6. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: In the step S4, Pt / C catalyst is used for both the hydrogenation reforming of the light distillate oil and the co-hydrogenation reforming of the heavy distillate oil.

7. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: In the step S4, the temperature of the hydrogenation reaction is 300-500°C.

8. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: In the step S4, a hydrogen donor is added to the heavy distillate oil during the co-hydrogenation reforming, wherein the mass ratio of the heavy distillate oil to the hydrogen donor is 1:

1.

9. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 8, characterized in that: The hydrogen donor is one of waste engine oil, tetralin, decalin or indane.

10. The method for preparing biofuel by lossless component separation and classification reforming of straw bio-oil according to claim 1, characterized in that: After the hydrogenation and co-hydrogenation reactions are completed, dichloromethane is used to extract and clean the molecular distillation device.

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