A method for straw-assisted heavy bio-oil heat treatment separation-in-situ coating-coupling pyrolysis upgrading carbon sequestration

Abstract

The present application belongs to the field of biomass resource utilization, and discloses a method for straw assisted heavy bio-oil heat treatment separation-in-situ coating-coupled pyrolysis upgrading and carbon sequestration, which comprises: preparation of self-source coating material: taking straw as raw material, heavy bio-oil is prepared by pyrolysis under nitrogen atmosphere; the same source straw powder as that for preparing heavy bio-oil is coated with heavy bio-oil to obtain self-source coating material; coupled pyrolysis upgrading and carbon sequestration: under inert or nitrogen atmosphere, the self-source coating material is pyrolyzed to obtain gas product, bio-oil and biochar, respectively. The present application coats straw with heavy bio-oil generated in the process of biomass thermochemical conversion, separates the light components in heavy bio-oil through heat treatment, simultaneously completes in-situ coating of straw powder, and uses the self-source coating material for coupled pyrolysis carbon sequestration, thereby realizing high-value utilization of biomass waste.

Description

Technical Field

[0001] This invention belongs to the field of biomass resource utilization and relates to a method for separating, in-situ coating, and synergistic pyrolysis of heavy bio-oil using straw-assisted thermal treatment, specifically a method based on self-sourced coating materials for separating, in-situ coating, and synergistic pyrolysis of heavy bio-oil using straw-assisted thermal treatment, in-situ coating, and synergistic pyrolysis of heavy bio-oil. Background Technology

[0002] Straw is one of the main components of agricultural and forestry waste, but its resource utilization rate is low. Large quantities of straw are burned in the open or discarded indiscriminately, causing serious resource waste and environmental pollution. Straw pyrolysis is an important way to utilize straw resources; pyrolysis char can be used as a soil conditioner, activated carbon precursor, carbon-based fertilizer, and other high-value-added products. However, due to the loose and porous structure of straw, volatile matter escapes rapidly during pyrolysis, resulting in a low final char yield, which severely restricts the economic viability and industrialization of straw pyrolysis technology.

[0003] Heavy bio-oil is the heavy component of bio-oil produced during biomass pyrolysis. It is an unavoidable byproduct, a brown or dark brown viscous liquid with a pungent odor, and an extremely complex composition containing hundreds of organic compounds. Due to its high viscosity and complex composition, it has been difficult to utilize, and its utilization value has long been underestimated. However, heavy bio-oil is rich in phenolic compounds (approximately 20-30 wt%), which are crucial chemical raw materials for producing high-value-added chemicals (such as phenolic resins, antioxidants, and pharmaceutical intermediates). Realizing the resource utilization of heavy bio-oil has significant industrial and economic value. Summary of the Invention

[0004] The purpose of this invention is to address the problems of difficulty in separating and utilizing heavy bio-oil in existing biomass pyrolysis processes, low char yield from straw pyrolysis alone, lack of structural control in amorphous mixed reactions, and poor product component selectivity. Based on the principle of biomass pyrolysis-in-situ self-adsorption coupling process, this invention provides a method for straw-assisted heavy bio-oil thermal treatment separation, in-situ coating, and synergistic pyrolysis for quality improvement and carbon fixation. Through thermal treatment component separation, in-situ self-assembly coating, and programmed temperature rise synergistic pyrolysis coupling, the heavy bio-oil generated during the biomass thermochemical conversion process is used to coat the straw. Thermal treatment achieves the separation of light components from the heavy bio-oil, while simultaneously completing the in-situ coating of straw powder, constructing a self-sourced coating material with a stable core-shell coating structure. This self-sourced coating material is then used for synergistic pyrolysis carbon fixation, achieving simultaneous multi-stage product preparation including light component recovery, heavy component coating and shaping, biochar quality improvement and carbon fixation, and enrichment of aromatic components in bio-oil. This fills the technological gap in self-sourced coating structure coupled pyrolysis processes and realizes the high-value utilization of biomass waste.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for straw-assisted thermal treatment separation, in-situ coating, and synergistic pyrolysis for upgrading and carbon fixation of heavy bio-oil includes the following steps:

[0007] Step (1) Preparation of self-sourced coating material: Heavy bio-oil is obtained by pyrolysis of straw under nitrogen atmosphere; the same type of straw powder as the one used to prepare the heavy bio-oil is coated with the heavy bio-oil to obtain self-sourced coating material.

[0008] Step (2), Synergistic pyrolysis for upgrading and carbon fixation: Under an inert or nitrogen atmosphere, the self-sourced coating material is pyrolyzed to obtain gaseous products, bio-oil (liquid products) and biochar (solid products).

[0009] The porous structure and oxygen-containing functional groups on the surface of straw powder preferentially promote the volatilization and precipitation of light components such as water and low-boiling-point phenols in heavy bio-oil. After condensation, these components can be recovered and used as liquid fuel or chemical feedstock. Simultaneously, the remaining heavy components, due to their reduced viscosity and increased fluidity, gradually wet, spread, and coat the surface of the straw powder, forming a self-sourced coating material with a "core-shell" structure: straw powder as the core (continuous or porous discrete framework) and heavy bio-oil components as the shell. This self-sourced coating material requires no external binder and is assembled in situ. The self-sourced coating material features "external hydrophobic barrier and internal hydrophilic conduction": the dense external heavy oil layer inhibits the rapid escape of volatiles during subsequent pyrolysis, while the internal straw framework provides hydrophilic channels and maintains structural stability.

[0010] In step (1), the straw is any one of wheat straw, corn straw, rice straw, or cotton straw.

[0011] Preferably, the straw powder has a particle size of 20-80 mesh and a moisture content of ≤20 wt%.

[0012] The method for preparing the heavy bio-oil is as follows: Straw is used as raw material and pyrolyzed at 500–600℃ for 2 hours under a nitrogen atmosphere. The volatiles produced by pyrolysis are condensed to obtain a condensate. The condensate is allowed to stand and separate into layers. The lower layer, a water-insoluble viscous liquid phase, is taken as the heavy bio-oil. The heavy bio-oil contains water and volatile components such as phenols.

[0013] To prepare heavy bio-oil, straw is first crushed to 20-80 mesh, dried at 105℃ for 12 hours, and then pyrolyzed under a nitrogen atmosphere.

[0014] The condensation temperature is 10–25 °C.

[0015] The straw powder mentioned is powder from any one of the following: wheat straw, corn straw, rice straw, and cotton straw.

[0016] The straw powder has a particle size of 20-80 mesh.

[0017] The mass ratio of the heavy bio-oil to the straw powder is 10:3 to 10:15.

[0018] Preferably, the mass ratio of the heavy bio-oil to the straw powder is 10:5 to 10:15.

[0019] More preferably, the mass ratio of the heavy bio-oil to the straw powder is 10:5 to 10:7.

[0020] The device used for coating is equipped with a mechanical stirring device and a condensation recovery device.

[0021] The coating is carried out under stirring at a stirring rate of 60–100 r / min.

[0022] The coating temperature is 80–150°C, and the coating time is 0.5–6 hours.

[0023] Preferably, the coating temperature is 100-150°C.

[0024] More preferably, the coating temperature is 105–150°C.

[0025] Preferably, the light components that overflow during the coating process are collected and condensed at room temperature (25 °C) to obtain a light component rich in phenolic compounds.

[0026] In step (2), preferably, the self-sourced coating material is placed in a pyrolysis furnace and pyrolyzed under an inert or nitrogen atmosphere.

[0027] Preferably, under an inert or nitrogen atmosphere, the temperature is increased from room temperature to 500–700°C at a rate of 3–20°C / min, and pyrolysis is performed at 500–700°C for 0.5–2 h, collecting the gaseous products, bio-oil, and biochar. These pyrolysis conditions allow volatiles to escape orderly from the self-sourced coating material and promote the secondary carbonization reaction of the self-sourced coating material, further increasing the char yield.

[0028] Preferably, the heating rate is 10°C / min.

[0029] Preferably, the pyrolysis temperature is 500–600°C.

[0030] The bio-oil exhibits an aromatic component selectivity (percentage) greater than 60%, achieving selective enrichment of high-value-added aromatic components.

[0031] The beneficial effects of this invention are as follows:

[0032] (1) This invention uses straw to assist in the heat treatment of heavy bio-oil. The porous structure and internal components of straw promote the preferential escape of light components from the perspective of activation energy, thereby separating them from the heavy components. At the same time, the porous hydrophilic skeleton of straw coupled with the high viscosity of heavy bio-oil produces a self-sourced coating material with the characteristics of "external hydrophobic barrier and internal hydrophilic flow guide". This self-sourced coating material utilizes the "complementary physical properties and functional regeneration" of waste to build a "heavy bio-oil-straw coating configuration", enabling the heavy bio-oil to be rapidly formed, thereby effectively improving the added value of the product. The self-sourced coating material was pyrolyzed. During the pyrolysis process, due to the volatile matter barrier effect of the "core-shell" structure and the physical support of the straw skeleton, the volatile matter escape rate was slow and controllable, with no foaming expansion or coking. This resulted in a significant increase in char yield and excellent carbon fixation and quality improvement effects, with a biochar yield of no less than 35% (calculated based on the total mass of the coating material). Compared to the weighted average yield of pyrolysis of straw alone and pyrolysis of heavy bio-oil alone at the same mass, the relative increase was no less than 10 wt%. Through the technology of "straw-assisted heavy bio-oil thermal treatment - in-situ coating," the resource utilization of waste biomass was realized, the treatment efficiency of biomass was improved, and the goal of generating high-value-added products was achieved.

[0033] (2) Kinetic studies of the coating process show that the activation energy for the separation of light components in pure heavy bio-oil is 150–160 kJ / mol. The introduction of straw powder has a significant promoting effect, reducing the apparent activation energy of light components by more than 20%, thereby achieving the selective and preferential separation of light components.

[0034] (3) This invention is convenient and practical, requiring only a coating device for technical application, making it easy to promote. Various crop straws can be used as coating carriers; the process parameters are adjustable and highly versatile, suitable for large-scale centralized treatment of agricultural and forestry waste. This invention provides a new path for the resource utilization of agricultural waste straw and heavy bio-oil, which will strongly promote the value reconstruction of the agricultural and forestry waste and biomass pyrolysis by-product recycling industry, opening up new directions for the resource circular economy and biomass resource utilization field under the "dual carbon" goal. Attached Figure Description

[0035] Figure 1 Images of straw and self-sourced coating materials prepared by "heavy bio-oil-straw powder coating"; where A is a scanning electron microscope image of straw and B is a scanning electron microscope image of self-sourced coating materials.

[0036] Figure 2 The trend of quality change during the drying of pure heavy bio-oil and the coating process of "heavy bio-oil-straw powder coating".

[0037] Figure 3 The activation energy is the result of drying pure heavy bio-oil and coating with a mixture of "heavy bio-oil and straw powder".

[0038] Figure 4 Transmission electron microscopy (TEM) image of biochar obtained from the pyrolysis of self-sourced coating materials.

[0039] Figure 5 The effect of the mass ratio of heavy bio-oil to straw powder on the yield of pyrolytic char from self-sourced coating materials was investigated.

[0040] Figure 6 The selectivity of liquid bio-oil components obtained from the pyrolysis of self-sourced coating materials. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solution of the present invention, further explanation is provided below with reference to specific embodiments.

[0042] Those skilled in the art can optimize the process by appropriately modifying the process parameters under the guidance of the invention. It should be particularly noted that all similar substitutions and modifications, which are obvious to those skilled in the art, are considered to be included within the scope of this invention.

[0043] Example 1

[0044] Preparation and microstructure characterization of self-sourced coating materials:

[0045] The corn stalks were crushed, passed through a 40-mesh sieve, and dried to a moisture content of about 20 wt% to obtain corn stalk powder.

[0046] Corn stalk powder was placed in a pyrolysis furnace and heated from room temperature to 600 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere. The temperature was then maintained at 600 ℃ for 2 h. The pyrolysis of corn stalks produced volatiles, which were condensed at room temperature (25 ℃) to obtain condensate. The condensate was allowed to stand and separate into layers. The lower layer of viscous liquid was taken as the self-sourced heavy bio-oil, while the solid residue was collected as straw biochar.

[0047] Heavy bio-oil and corn stalk powder were added to a coating device at a mass ratio of 10:5 and mixed and coated for 6 h at a drying temperature of 105℃ and a stirring rate of 60 r / min to obtain a self-sourced coating material of "heavy bio-oil-stalk powder coating". The surface morphology of the corn stalk powder and the self-sourced coating material was observed using scanning electron microscopy (SEM). Figure 1 A shows that the original corn stalk powder has a rough surface with obvious fiber texture and open pore structure; Figure 1B shows that after coating with heavy bio-oil, a dense, smooth, and continuous coating layer was formed on the surface of the straw, completely covering the fiber texture and effectively sealing the pore structure. BET testing indicates that the specific surface area of ​​the self-sourced coating material is significantly reduced compared to the original straw, proving that the heavy bio-oil forms a complete coating structure on the straw surface.

[0048] Table 1: Comparison of specific surface area between straw and self-sourced coating materials

[0049]

[0050] Example 2

[0051] Corn stalks were crushed to 40 mesh, placed in an oven, and dried at 105℃ for 12 hours to obtain corn stalk powder.

[0052] Corn stalk powder was placed in a pyrolysis furnace and heated from room temperature to 600 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere. The mixture was then kept at 600 ℃ for 2 hours to produce volatiles. The volatiles were condensed to room temperature (25 ℃). The resulting condensate was allowed to stand and separate into layers. The lower layer was then removed to obtain the self-sourced heavy bio-oil.

[0053] The system includes a pure heavy bio-oil drying group and a heavy bio-oil mixed with straw powder coating group.

[0054] Pure heavy bio-oil drying group: The raw heavy bio-oil was dried for 6 hours at a temperature of 105℃ and a stirring rate of 60r / min.

[0055] Heavy bio-oil and straw powder mixed coating group: According to the mass ratio of heavy bio-oil to straw of 10:5, the self-sourced heavy bio-oil and corn straw powder were put into the coating device and mixed and coated for 6 hours at a temperature of 105 ℃ and a stirring rate of 60 r / min to obtain the self-sourced coating material of "heavy bio-oil-straw powder coating".

[0056] like Figure 2 As shown, compared with drying heavy bio-oil alone, the weight loss rate of the mixed coating of heavy bio-oil and straw powder during the drying process was faster, decreasing by 10% in the initial 20 minutes, resulting in better drying effect. After 6 hours of drying, the weight loss rate of the mixed coating group was more than twice that of the pure heavy bio-oil drying group. This indicates that the "heavy bio-oil-straw powder coating" drying process facilitates the volatilization of volatiles in the heavy bio-oil, enabling the heavy bio-oil to form quickly.

[0057] Example 3

[0058] The effect of coating structure on drying activation energy during the "heavy bio-oil-straw powder coating" process was tested. Corn straw was used as raw material. The corn straw was crushed, passed through a 40-mesh sieve, and dried to a moisture content of 20 wt% to obtain corn straw powder, which was then set aside. The corn straw powder was placed in a pyrolysis furnace and heated from room temperature to 600 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere. Pyrolysis at 600 ℃ was carried out for 2 h, producing volatiles. These volatiles were condensed (at 25 ℃), allowed to stand, and separated into layers. The lower layer was removed to obtain the self-sourced heavy bio-oil. The heavy bio-oil and corn straw powder were added to a coating device at a mass ratio of 10:5. Coating was carried out at 105 ℃ and a stirring rate of 60 r / min for 6 min. The activation energy was calculated, and the results are shown below. Figure 3 Straw powder can significantly promote the removal of volatile components such as water and phenols from heavy bio-oils. The activation energy for drying was calculated using mass change curves, and a comparison showed that the activation energy decreased from 141.9 kJ / mol to 59.1 kJ / mol, a reduction of over 58%.

[0059] Example 4

[0060] This study investigated the effects of three key parameters—straw type, straw particle size, coating temperature, and the mass ratio of heavy bio-oil to straw powder—on the separation efficiency of the light components (volatiles) in heavy bio-oil.

[0061] The effect of straw type on the separation of light components from heavy bio-oil: Straw was crushed to 40 mesh and dried at 105℃ for 12 h to obtain straw powder. The straw powder and its homologous heavy bio-oil (prepared by the same method as in Example 3) were placed in a coating device at a mass ratio of 5:10. The coating was carried out at 105℃ and a stirring rate of 60 r / min for 20 min. The light components (volatiles) precipitated during the coating process were collected by condensing at room temperature (25℃) using a condenser. The recovery rate of the light components was calculated by weighing (the recovery rate of the light components is the mass of the collected light components divided by the mass of the heavy bio-oil). The collected light components were analyzed by gas chromatography-mass spectrometry (GC-MS). The results are shown in Table 2.

[0062] Effect of straw particle size on the separation of light components of heavy bio-oil: Corn straw was crushed to 20, 60 and 80 mesh respectively, and dried at 105℃ for 12h to obtain corn straw powder. The straw powder and its homologous heavy bio-oil (preparation method as in Example 3) were placed in a coating device at a mass ratio of 5:10. The coating was carried out at a temperature of 105℃ and a stirring rate of 60 r / min for 20 min. The light components (volatiles) precipitated during the coating process were condensed and collected using a condenser tube. The recovery rate of light components was measured, and the results are shown in Table 2.

[0063] Effect of coating temperature on the separation of light components from heavy bio-oil: Wheat straw was crushed to 40 mesh and dried at 105℃ for 12 h to obtain straw powder. The straw powder and its homologous heavy bio-oil (prepared by the same method as in Example 3) were placed in a coating device at a mass ratio of 5:10. The coating was carried out for 20 min under different temperatures and stirring speeds of 60 r / min. The light components precipitated during the coating process were collected by condensation using a condenser tube, and the recovery rate of light components in each group was measured. The results are shown in Table 2.

[0064] Effect of the mass ratio of heavy bio-oil to straw powder on the separation of light components from heavy bio-oil: Wheat straw was crushed to 40 mesh and dried at 105℃ for 12 h to obtain straw powder. The straw powder and its homologous heavy bio-oil (prepared by the same method as in Example 3) were placed in a coating device at different mass ratios and coated for 20 min at a temperature of 105℃ and a stirring rate of 60 r / min. The light components precipitated during the coating process were collected by condensation using a condenser tube, and the recovery rate of light components in each group was measured. The results are shown in Table 2.

[0065] Experimental results show that crop straw can yield good yields of light components, especially corn straw, which is more conducive to the precipitation and recovery of light components from heavy bio-oil. The particle size of straw powder has little effect on the mixing and coating process; particles larger than 20 mesh have good coating effects. Regarding coating temperature, the recovery rate of light components reaches its highest value of 17.83% when the coating temperature is 150℃, indicating that higher temperatures are more conducive to breaking the binding force of components, reducing the volatilization activation energy, and promoting the rapid escape and separation of light components such as water and phenols. The high-temperature range is preferred. As the mass ratio of heavy bio-oil to straw powder increases from 10:3 to 10:15, the recovery rate of light components gradually increases, possibly because a higher proportion of straw powder results in stronger porous adsorption and flow conduction, which is more conducive to the volatilization and separation of light components.

[0066] Table 2. Effects of different influencing factors on the recovery rate of light components

[0067]

[0068] Example 5

[0069] The effect of coating structure on subsequent pyrolysis carbon fixation effect.

[0070] Self-sourced coating material: Corn stalks are crushed, passed through a 40-mesh sieve, and dried at 105℃ for 12 hours to obtain corn stalk powder. The corn stalk powder is placed in a pyrolysis furnace and heated from room temperature to 600℃ at a rate of 10℃ / min under a nitrogen atmosphere. It is then pyrolyzed at 600℃ for 2 hours. The pyrolysis of corn stalks produces volatiles, which are condensed (at 25℃), allowed to stand and separate into layers, and the lower layer is removed to obtain self-sourced heavy bio-oil. The heavy bio-oil and corn stalk powder are added to a coating device at a mass ratio of 10:3, 10:5, and 10:7, and coated for 20 minutes at a temperature of 105℃ and a stirring rate of 60r / min to obtain the self-sourced coating material.

[0071] Heavy bio-oil-straw physical mixture sample: Self-sourced heavy bio-oil was prepared according to the "self-sourced coating material" in this embodiment. The heavy bio-oil and corn straw powder were mixed evenly at a mass ratio of 10:5.

[0072] Heavy bio-oil solids: Self-sourced heavy bio-oil was prepared according to the “self-sourced coating material” in this embodiment, and dried at 120°C for 24 hours to obtain heavy bio-oil solids.

[0073] Pyrolysis experiments were conducted on samples of self-sourced coating materials, corn stalk powder, heavy bio-oil-straw physical mixtures, and heavy bio-oil solids. The samples of self-sourced coating materials, corn stalk powder, heavy bio-oil-straw physical mixtures, or heavy bio-oil solids were placed in a pyrolysis furnace and heated from room temperature to 600℃ at a rate of 10℃ / min under a nitrogen atmosphere. The samples were then pyrolyzed at 600℃ for 2 hours. The pyrolysis solid products (biochar) were collected, and the char yield of different samples was calculated. At the same time, gases (H2, CH4, etc.) were collected using a gas bag.

[0074] Microscopic morphology tests of straw biochar and pyrolytic char of self-sourced coating materials, such as... Figure 4 As shown, the self-sourced coating material pyrolytic char has a distinct core-shell structure, and the blue area is the coating layer after the pyrolysis of heavy bio-oil.

[0075] The graph shows the variation in char yield of self-prototype coated materials prepared by different mass ratios of heavy bio-oil and corn stalk powder, as shown in the figure. Figure 5 As shown, compared with the carbon yield of pure straw samples, the carbon yield of the self-sourced coating material increased by 13.77% to 17.41%, a significant increase, indicating that the addition of heavy bio-oil has a significant carbon fixation capacity.

[0076] As shown in Table 3, the carbon yield of the self-sourced coated material with the coating structure reached 38.15%, which is 13.41% higher than that of the physical mixture system. This is significantly higher than the carbon yield of pure straw (22.12%), heavy bio-oil solids (28.5%), and the physical mixture of the two (24.74%). This indicates that the increase in carbon yield is not only due to the addition of heavy bio-oil, but more importantly, the presence of the coating structure promotes carbon fixation.

[0077] Table 3. Comparison of pyrolysis biochar yield

[0078]

[0079] Example 6

[0080] The selectivity of liquid bio-oil components prepared by pyrolysis and condensation of the coating material obtained by "heavy bio-oil-straw powder coating" was analyzed.

[0081] Following the method described in Example 5, "Heavy bio-oil-corn stalk powder coating", a self-sourced coating material was prepared. The sample of the self-sourced coating material was placed in a pyrolysis furnace and heated from room temperature to 600°C at a rate of 10°C / min under a nitrogen atmosphere. The material was then pyrolyzed at 600°C for 2 hours. The liquid bio-oil was collected at room temperature (25°C) using a condenser and analyzed using a gas chromatography-mass spectrometry (GC-MS, Agilent 7890B-5977B).

[0082] like Figure 6 As shown, the products in liquid bio-oil are mainly aromatic compounds such as aromatic aldehydes, aromatic acids, and polycyclic aromatic rings. The highest content is phenolic compounds at 54.79%, followed by polycyclic aromatic hydrocarbons at 33.59%, with an aromatic component selectivity exceeding 88.38%. This indicates that bio-oil prepared through the pyrolysis of resource-coated materials has a rich aromatic character.

[0083] Example 7

[0084] The effects of using corn straw, wheat straw, rice straw, and cotton straw as raw materials on biochar yield, liquid product yield, and selectivity of aromatic components were evaluated.

[0085] Raw material preparation: Crop straw (corn straw, wheat straw, rice straw or cotton straw) is crushed to 40 mesh and dried at 105℃ for 12 hours to obtain corresponding straw powder with a moisture content of 20 wt%.

[0086] Preparation of heavy bio-oil: Take straw powder and heat it from room temperature to 600 ℃ at a rate of 10 ℃ / min under nitrogen atmosphere. Pyrolyze it at 600 ℃ for 2 h. The volatiles obtained from the pyrolysis are condensed in a condenser (condensation temperature 10~25℃) to obtain condensate. The condensate is allowed to stand and separate into layers. The lower viscous liquid phase is taken to obtain the self-sourced heavy bio-oil.

[0087] Preparation of self-sourced coating materials: The heavy bio-oil and homologous straw powder were mixed and coated in a coating device equipped with mechanical stirring and condensation recovery device at a mass ratio of 10:5. The mixture was mixed and coated for 6 h at a temperature of 105 ℃ and a stirring rate of 60 r / min. Light components were collected during the coating process to obtain four self-sourced coating materials with core-shell structure from different straw sources.

[0088] Synergistic pyrolysis experiment: The self-sourced coating material and four corresponding pure straw powders (control group) were placed in a pyrolysis furnace. Under a nitrogen atmosphere, the temperature was increased from room temperature to 600℃ at a rate of 10℃ / min, and pyrolyzed at 600℃ for 2 hours. The pyrolysis volatiles were collected through a condenser (condensation temperature 10-25℃) to obtain the liquid product (bio-oil). Non-condensable gases were collected using a gas bag, and the solid product was biochar. The char yield and liquid product yield of each group were calculated, and the relative content (selectivity) of aromatic components in the liquid product was analyzed by GC-MS.

[0089] The experimental results are shown in Table 4. The data indicate that:

[0090] (1) Significant and universal carbon fixation effect: The biochar yield is greatly improved and the carbon fixation capacity is increased by more than 58%, proving that the method of the present invention has wide applicability to straw from different sources.

[0091] (2) Simultaneous upgrading of liquid product quality: Although the yield of liquid bio-oil decreased slightly (due to more carbon remaining in the solid phase), the product quality was fundamentally improved. In the liquid products obtained by synergistic pyrolysis of self-sourced coating materials, the selectivity of aromatic components (phenols, polycyclic aromatic hydrocarbons, etc.) exceeded 70%. Compared with pure straw pyrolysis oil, the selectivity of aromatic components was improved, achieving selective enrichment of high-value-added aromatic components.

[0092] Table 4. Comparison of the distribution and effects of synergistic pyrolysis products of self-sourced coating materials from straw of different sources.

[0093]

[0094] Example 8

[0095] The effect of pyrolysis temperature on the carbon yield and aromatic component selectivity of self-sourced coating materials was investigated.

[0096] Corn stalks were used, and the experimental and testing methods were the same as in Example 7, except that the pyrolysis temperatures were adjusted to 500, 600, and 700℃. The results are shown in Table 5. As the pyrolysis temperature increased from 500℃ to 700℃, the char yield of all samples decreased due to the increased release of volatile matter. However, the char yield of the self-sourced coating material was significantly higher than that of pure straw at each temperature. More importantly, the absolute increase in char yield further expanded with increasing temperature (from +12.10% at 500℃ to +19.55% at 700℃), indicating that the carbon fixation advantage of the coating structure is more prominent at high temperatures. At the same time, the selectivity of aromatic components in the pyrolysis oil of the self-sourced coating material remained >70% at all temperatures, which was significantly better than that of the pure straw pyrolysis oil. This proves that the method of the present invention can effectively achieve quality improvement, carbon fixation, and aromatic component enrichment within a wide temperature range of 500–700℃.

[0097] Table 5. Comparison of carbon yield and aroma selectivity of self-sourced coated materials at different pyrolysis temperatures

[0098]

Claims

1. A method for separating, in-situ coating, and synergistic pyrolysis of straw-assisted heavy bio-oil through thermal treatment, characterized in that: Includes the following steps: Step (1) Preparation of self-sourced coating material: Heavy bio-oil is obtained by pyrolysis of straw under nitrogen atmosphere; the same type of straw powder as the one used to prepare the heavy bio-oil is coated with the heavy bio-oil to obtain self-sourced coating material. Step (2), Synergistic pyrolysis for upgrading and carbon fixation: Under an inert or nitrogen atmosphere, the self-sourced coating material is pyrolyzed to obtain gaseous products, bio-oil and biochar respectively.

2. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 1, characterized in that: In step (1), the straw is any one of wheat straw, corn straw, rice straw, and cotton straw; the straw powder is any one of wheat straw, corn straw, rice straw, and cotton straw powder; and the particle size of the straw powder is 20-80 mesh.

3. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 1, characterized in that: In step (1), the mass ratio of the heavy bio-oil to the straw powder is 10:3 to 10:

15.

4. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 3, characterized in that: In step (1), the mass ratio of the heavy bio-oil to the straw powder is 10:5 to 10:15, preferably 10:5 to 10:

7.

5. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 1, characterized in that: In step (1), the coating temperature is 80-150°C and the coating time is 0.5-6 hours.

6. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 5, characterized in that: In step (1), the coating temperature is 100-150°C.

7. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 5, characterized in that: In step (1), the coating is carried out under stirring at a stirring rate of 60-100 r / min.

8. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 1, characterized in that: In step (1), the light components that overflow during the coating process are collected.

9. The method for separating, in-situ coating, and synergistic pyrolysis of straw-assisted heavy bio-oil through thermal treatment, characterized in that: In step (2), under an inert or nitrogen atmosphere, the temperature is increased from room temperature to 500-700℃ at a heating rate of 3-20℃ / min, and pyrolyzed at 500-700℃ for 0.5-2 h, and gaseous products, bio-oil and biochar are collected.

10. The method for straw-assisted heavy bio-oil thermal treatment separation-in-situ coating-synergistic pyrolysis upgrading and carbon fixation according to claim 1 or 9, characterized in that: In step (2), the pyrolysis temperature is 500-600℃.

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