A method for preparing a multi-phase product based on the directional pyrolysis of ginkgo biloba leaf dregs

Abstract

This invention belongs to the field of waste recycling technology, specifically relating to a method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue. The method includes the following steps: Ginkgo biloba leaf residue is heated to 400℃~600℃ under an inert gas atmosphere at a heating rate of 10℃ / min~20℃ / min, and then subjected to pyrolysis for 10min~20min. The solid product biochar, the condensed liquid product bio-oil, and the non-condensable gaseous product pyrolysis gas are collected separately. This invention systematically reveals the pyrolysis behavior and product distribution patterns of Ginkgo biloba leaf residue, overcoming the shortcomings of existing technologies that focus on single-factor optimization of pyrolysis process parameters and lack multi-factor coupled control, thus achieving precise directional conversion of pyrolysis products.

Description

Technical Field

[0001] This invention belongs to the field of waste recycling technology, specifically relating to a method for preparing multiphase products based on the directional pyrolysis of ginkgo leaf residue. Background Technology

[0002] Biomass resources, as a form of renewable energy, differ fundamentally from fossil fuels in their ability to be dynamically replenished through natural succession or artificial cultivation. The core reason biomass is considered key to future carbon neutrality and development lies in its construction of a dynamic closed-loop carbon cycle: if the carbon absorbed by biomass through photosynthesis during growth precisely offsets the carbon released during conversion (such as pyrolysis and gasification) or biological processes (such as fermentation), from a macroscopic carbon balance perspective, net emissions will approach zero. This attribute determines that biomass energy and bio-based fuels derived from it possess significant strategic value in supporting global warming control targets and fulfilling greenhouse gas emission reduction responsibilities. Simultaneously, in promoting the transformation of energy consumption structures towards low-carbonization, these resources also contribute to the formation of a diversified energy supply system that balances economic viability, stability, and cleanliness.

[0003] However, the direct use of forest biomass for large-scale energy production has raised systemic concerns regarding ecological protection, resource allocation, and social acceptance, and is gradually entering the policy agenda. In light of this, expanding the boundaries of raw material selection, promoting the development and utilization of non-woody biomass resources, and exploring their potential as energy conversion pathways to replace woody raw materials have become key policy focuses for optimizing biomass utilization structure and alleviating resource and environmental pressures. Pyrolysis and gasification technologies can achieve efficient conversion of biomass into high-value-added products such as tar, hydrogen-rich gas, and biochar. Compared to gasification, pyrolysis has advantages in terms of milder reaction conditions, simpler operation, and easier system control, and is therefore considered a promising bioenergy conversion method, receiving increasing attention. Under pyrolysis, biomass is efficiently decomposed into three different phases of products: combustible gas rich in calorific value, structurally stable biochar, and refinable bio-oil. This process transforms low-grade biomass waste into high-grade energy and materials, significantly enhancing resource value. There are still some problems in the field of biomass pyrolysis. Existing research focuses on traditional biomass such as wood and straw, while research on ginkgo leaf residue often only focuses on the extraction and separation of the main components. In addition, most studies focus on the acquisition of single pyrolysis components. Most importantly, the components of traditional Chinese medicine residue are complex, and many of them have certain biological toxicity. If they are not properly treated as solid waste, they will not only cause environmental pollution, but also pose certain safety hazards. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue. This invention achieves the production of multiphase products through the synergistic effect of three factors: heating rate, pyrolysis temperature, and pyrolysis time. This not only solves the problem of product homogeneity in existing technologies but also provides a new recycling pathway for traditional Chinese medicine waste, especially Ginkgo biloba leaf residue.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] A method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue includes the following steps: Ginkgo leaf residue was heated to 400℃~600℃ in an inert gas atmosphere at a heating rate of 10℃ / min~20℃ / min for 10min~20min for pyrolysis. During the pyrolysis process, volatiles were continuously collected and condensed. The condensed liquid was bio-oil, and the non-condensable gas was pyrolysis gas. The solid obtained after the pyrolysis reaction was biochar.

[0007] Preferably, the temperature is increased to 500°C at a heating rate of 10°C / min, and then the pyrolysis reaction is carried out for 15 min.

[0008] This invention selects heating rate, pyrolysis temperature, and pyrolysis time as the three most critical variables for achieving directional pyrolysis and multiphase product control. Through the synergistic control of these three key process parameters, this invention achieves directional optimization of the yield and composition of three-phase products. Temperature is the primary factor determining the inflection point of product distribution. Experiments revealed that the liquid yield peaks at 500℃, then decreases due to secondary cracking, while the gas yield monotonically increases with increasing temperature, and the solid yield continuously decreases. Therefore, 400℃~600℃ was determined as the suitable temperature range. Excessively high or low heating rates are detrimental to the stable progress of the dehydrogenation reaction. Therefore, a heating rate of 10℃ / min~20℃ / min is the time-dimensional parameter for controlling product selectivity, determining the kinetics and heat / mass transport coupling mechanism of the pyrolysis process. The pyrolysis time is chosen and limited to the range of 10min~20min primarily to determine the reaction endpoint and avoid excessive cracking, balancing the competition between liquid and gaseous products. The heating rate, pyrolysis temperature, and pyrolysis time together constitute the three core control knobs for controlling the direction of pyrolysis products of Ginkgo biloba residue. Only through the coordinated regulation of the three can the directional preparation of multiphase products be achieved.

[0009] In another preferred embodiment, the pyrolysis gas includes H2, CO, CO2, CH4, and C2-C3 hydrocarbon gases.

[0010] In another preferred embodiment, the solid product biochar has a porous structure, with a fixed carbon content of 35.71% to 46.20% and a carbon element content of 44.89% to 46.80%.

[0011] In another preferred embodiment, the inert gas is argon.

[0012] In another preferred embodiment, the flow rate of the inert gas is 100 mL / min to 200 mL / min.

[0013] In another preferred embodiment, the condensation temperature is -15°C to -10°C. This condensation temperature enables efficient condensation of pyrolysis volatiles and complete capture of liquid products. If the cold trap temperature is too high, some low-boiling-point organic compounds cannot be fully condensed and will enter the gas collection bag in gaseous form, resulting in low liquid-phase yield and deviations in gas composition measurement. If the cold trap temperature is too low, although the capture efficiency can be further improved, it will significantly increase refrigeration energy consumption and equipment costs, and may also lead to excessive condensation of moisture and extremely low-boiling-point components, affecting the composition and quality of the bio-oil. Therefore, controlling the cold trap temperature between -15°C and -10°C is a preferred range that balances capture efficiency, energy economy, and product purity.

[0014] In another preferred embodiment, the particle size of the ginkgo leaf residue is no greater than 0.15 mm.

[0015] In another preferred embodiment, the ginkgo leaf residue is the residue obtained after alcohol extraction and then dried.

[0016] In another preferred embodiment, the alcohol extraction refers to extraction at 70% ethanol at 60°C to 80°C for 20 to 30 minutes.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue. By synergistically controlling three key process parameters—pyrolysis temperature (400℃~600℃), heating rate (10℃ / min~20℃ / min), and pyrolysis reaction time (10min~20min)—the yield and composition of the three-phase products (solid phase: biochar), liquid phase: bio-oil, and gas phase: pyrolysis gas) are obtained. Using the pyrolysis method of this invention, the yield of the liquid product, bio-oil, reaches a peak of 48.07%, and the bio-oil is rich in high-value-added compounds such as phenols, ketones, and acids. The H2 content in the gaseous product is the highest at 26.54%. The fixed carbon content of the solid product, biochar, increases with increasing temperature, reaching a maximum of 46.2%, and a rich porous structure forms on its surface.

[0018] This invention utilizes the residue from ginkgo leaf extraction as raw material, effectively addressing the environmental safety risks posed by the toxicity of ginkgo acid in traditional Chinese medicine residue treatment methods such as landfilling, composting, and feed additives. Ginkgo leaf residue possesses excellent fuel characteristics, including high volatile matter (69.55%), low ash content (3.27%), low carbon-to-nitrogen ratio, and low sulfur content (0.35%). The method of this invention can efficiently convert it into three energy products: biochar, bio-oil, and pyrolysis gas, realizing the resource and energy utilization of agricultural waste. Specifically, biochar can be used as an adsorbent, soil conditioner, or solid fuel; bio-oil is rich in phenols and other chemical precursors; and pyrolysis gas is rich in combustible components such as H2, CO, and CH4. This invention combines ecological and socio-economic benefits, providing a new technological path for the high-value utilization of characteristic biomass waste such as Chinese medicine residue. Attached Figure Description

[0019] Figure 1 The graphs are thermogravimetric curves of ginkgo leaf residue. A is the TG curve and B is the DTG curve.

[0020] Figure 2 The graphs show the effects of different pyrolysis temperatures on product yield and gas composition; A is the pyrolysis product yield graph, and B is the gas composition graph.

[0021] Figure 3 The graphs show the effects of different reaction times on product yield and gas composition; A is the pyrolysis product yield graph, and B is the gas composition graph.

[0022] Figure 4 The graphs show the effects of different heating rates on product yield and gas composition; A is the pyrolysis product yield graph, and B is the gas composition graph.

[0023] Figure 5 Scanning electron microscope images of biochar at different temperatures; A represents 400℃, B represents 500℃, and C represents 600℃.

[0024] Figure 6 3D diagrams of the seven major components of the pyrolysis solution at different pyrolysis temperatures. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Ginkgo is an important medicinal plant resource in China, and its leaves can be used to extract ginkgolide esters, which have high medicinal value. However, the content of ginkgolide esters in ginkgo leaves is very low, only 2% of the leaf's weight, and 98% of ginkgo leaves are discarded as medicinal residue after extraction. However, due to the various biotoxicities of ginkgolic acid contained in ginkgo leaves, traditional methods of treating medicinal residue, such as landfilling, processing into cultivation substrates for edible fungi, or developing into feed additives, all pose significant safety risks. Ginkgo leaves are rich in lignin, cellulose, and hemicellulose, so the medicinal residue has great potential for development as a biomass resource.

[0028] This invention combines thermogravimetric analysis (TGA) with experiments using a biomass pyrolysis apparatus. Using pyrolysis temperature, reaction time, and heating rate as variables, and the yields of the three-phase products—biochar, bio-oil, and pyrolysis gas—as response indicators, it systematically analyzes the influence of various factors and their interactions on the distribution of pyrolysis products from Ginkgo biloba leaf residue. Two equal-conversion kinetic models, KAS and OFW, are employed to analyze the pyrolysis mechanism and thermodynamic characteristics. Scanning electron microscopy (SEM) is used to characterize the morphology and structure of the pyrolysis semi-coke. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC) are used for qualitative and quantitative analysis of the liquid and gas phase products, aiming to provide theoretical basis and technical reference for the resource utilization and pyrolysis process optimization of this type of agricultural waste.

[0029] 1. Experimental Section 1.1 Experimental Materials Ginkgo leaves were taken from ginkgo trees at the South Lake Campus of China University of Mining and Technology. After being extracted in 70% ethanol at 70℃ for 30 minutes, the residue was filtered and dried at 80℃ for 24 hours to obtain dried ginkgo leaf residue, which was then placed in a desiccator for later use.

[0030] 1.2 Experimental Methods 1.2.1 Raw material industrial analysis and elemental analysis Industrial analysis of Ginkgo biloba residue was conducted in accordance with the "Analytical Methods for Solid Biofuels" (GB / T2873-2012). The results of the industrial analysis are expressed on an air-dried basis, while the results of the elemental analysis are calculated on an ash-free dried basis. The elemental composition and content of the raw materials were determined using an elemental analyzer.

[0031] 1.2.2 Thermogravimetric Analysis Experiment 1.2.2.1 Analysis of Thermogravimetric Characteristics The decomposition characteristics of Ginkgo biloba leaf residue were determined by TAG. Argon was used as the carrier gas at a flow rate of 80 mL / min. 5 mg of sample was weighed and placed in a crucible. The sample was heated from room temperature to 800℃ by changing the heating rate (10℃ / min, 15℃ / min, 20℃ / min) and held at this temperature for 5 min. Data on the change of sample mass with temperature during this process were collected. The TG / DTG curve was obtained after processing the thermogravimetric data to study the effect of heating rate on the pyrolysis process.

[0032] 1.2.2.2 Kinetic Analysis of Biomass Pyrolysis Two equal conversion models, KAS and DAEM, were used (see equations (1) and (2). Based on the first-order reaction kinetic equation, the pyrolysis process of Ginkgo biloba residue was kinetically analyzed within the range of conversion α between 0.1 and 0.5.

[0033] = Equation (1); Equation (2).

[0034] In the formula: β—heating rate, in K / min; T—temperature, K; A—pre-exponential factor, min -1 R—molar gas constant, with a value of 8.314 J / (mol·K). Ea is the activation energy of the reaction, kJ / mol; F(α) is the reaction mechanism function, which is the integral form of f(α). ; f(α) is a first-order reaction kinetic model.

[0035] 1.2.3 Biomass pyrolysis experiment A biomass pyrolysis microreactor was used to conduct pyrolysis experiments under inert gas (Ar) conditions at a flow rate of 100 mL / min. 2 g of ginkgo leaf residue was weighed and placed on quartz wool in the reaction tube. The residue was pyrolyzed at different reaction temperatures (400℃, 500℃, 600℃), different reaction times (10 min, 15 min, 20 min), and different heating rates (10℃ / min, 15℃ / min, 20℃ / min). The liquid products from the pyrolysis were collected using a cold trap, while the solid char products were mainly concentrated in the lower middle part of the reaction tube. Non-condensable gases released during the pyrolysis process were collected using a gas collection bag. After the reaction, the apparatus had to be allowed to cool to room temperature before disassembly. The semi-coke and liquid products were then weighed separately. The yield of the gaseous products was indirectly obtained by subtraction based on the principle of mass conservation. To improve the confidence level of the experimental results, the final value was set as the average of three independent replicate experiments. The appearance characteristics of the semi-coke samples after weighing were measured using SEM.

[0036] 1.2.4 Analytical Methods for Biomass Pyrolysis Products Gas chromatography (GC) was used to analyze the non-condensable gases collected during pyrolysis to determine the composition and content of the gases from the pyrolysis of Ginkgo biloba leaf residue. Argon was used as the carrier gas, and flame ionization detector (FID) and thermal conductivity detector (TCD) were used to measure the components and contents of the gaseous products. The chemical composition of the pyrolysis oil obtained from pyrolysis was studied using GC-MS. The industrial and elemental analyses of the bio-coke were performed using the same methods as the raw materials, but the industrial analysis used a desiccated basis, and the elemental analysis used an ash-free desiccated basis. Its surface microstructure was characterized by SEM.

[0037] 2. Results 2.1 Physicochemical properties of Ginkgo leaf residue Table 1. Industrial composition and elemental content determination of Ginkgo leaf residue and other biomass * Subtraction method: ad, air-dried basis; daf, dry ash-free basis.

[0038] This invention compares and analyzes the combustion characteristics of ginkgo leaf residue and other typical biomass fuels. As shown in Table 1, ginkgo leaf residue exhibits typical fuel characteristics of high volatile matter (69.55%) and low ash content (3.27%), with a fixed carbon content of 17.91%, indicating that ginkgo leaf residue has significant energy conversion potential and environmentally friendly characteristics. Regarding ash content, ginkgo leaf residue has only 3.27%, far lower than high-ash biomass such as rice straw (19.19%). Lower ash content helps reduce residue formation during combustion, mitigating operational problems such as slagging and ash accumulation, thereby improving the stability and operating efficiency of the combustion system.

[0039] Further analysis of its elemental composition revealed that the carbon content of ginkgo leaf residue was 46.79%, significantly higher than that of rice husk (34.99%) and rice straw (38.24%). This higher carbon content directly contributes to its superior calorific value, as carbon, as the main combustible component, releases a large amount of energy during oxidation. The total proportion of carbon and oxygen was as high as 91.61%, further confirming the material's application potential in the field of energy utilization. In addition, the nitrogen and sulfur contents of ginkgo leaf residue were 1.50% and 0.35%, respectively, with the sulfur content significantly lower than that of oily sludge (1.9%). The lower nitrogen and sulfur content means that the formation of NOx and SOx pollutants can be effectively suppressed during thermochemical conversion, which is conducive to achieving clean combustion.

[0040] Ginkgo leaf residue exhibits excellent fuel characteristics in terms of ash content and elemental composition, combining high energy conversion efficiency with low environmental emission load, providing important evidence for its feasibility in industrial energy applications.

[0041] 2.2 Thermogravimetric and kinetic analysis of the pyrolysis process of Ginkgo leaf residue 2.2.1 Thermogravimetric analysis of Ginkgo leaf residue As shown by the TG and DTG curves, the pyrolysis behavior of Ginkgo biloba leaf residue exhibits significant stage-specific characteristics and is highly sensitive to changes in the heating rate.

[0042] Regarding the pyrolysis process, the entire process can be divided into four stages: the low-temperature zone (<200℃), mainly characterized by dehydration and volatilization of light components; the medium-temperature zone (200~340℃), corresponding to the branching and structural reorganization of hemicellulose; the high-temperature zone (340~500℃), which is the main cellulose pyrolysis stage, mainly releasing combustible gases such as H2 and CO; and the ultra-high-temperature zone (>500℃), which is the slow degradation process of lignin. This component has high thermal stability due to its rich oxygen-containing aromatic units, and its decomposition can continue to above 800℃, ultimately generating carbon-rich solid product biochar. Regarding the effect of heating rate, as the heating rate increases, the entire weight loss curve shifts towards the high-temperature side, with the maximum weight loss peak temperature Tm increasing from 348℃ (10℃ / min) to 359℃ (20℃ / min), exhibiting a significant thermal hysteresis effect. This phenomenon reflects the modulating effect of internal heat transfer limitations on pyrolysis kinetics. It is worth noting that the heating rate has a dual effect on the pyrolysis process: appropriately increasing the heating rate can shorten the reaction time and improve the processing efficiency; however, if the rate is too high, the uneven temperature distribution inside the particles will be aggravated, resulting in a significant internal and external temperature difference, which will have an adverse effect on the pyrolysis efficiency and the yield of the target product.

[0043] 2.2.2 Kinetic Analysis of Pyrolysis Reaction of Ginkgo Leaf Residue To comprehensively evaluate the kinetic characteristics of the pyrolysis reaction of Ginkgo biloba residue, two isoconversion models, KAS and DAEM, were used to fit and analyze the experimental data. Under three heating rates, data points with conversion rates in the range of 0.1 to 0.5 on the thermogravimetric curves were selected for analysis. The kinetic parameters of each model are summarized in Table 2.

[0044] Table 2. Pyrolysis kinetic parameters for two kinetic models Analysis of the pyrolysis process of Ginkgo biloba leaf residue using two kinetic models, KAS and DAEM, yielded the following conclusions: Within a conversion rate range of 0.1–0.5, the activation energy (Ea) in both the KAS and DAEM models increased with increasing conversion rate, indicating that the later stages of the pyrolysis reaction became more difficult. The Ea in the KAS model increased from 96.27 kJ·mol⁻¹ to 120.15 kJ·mol⁻¹, while that in the DAEM model increased from 96.86 kJ·mol⁻¹ to 122.05 kJ·mol⁻¹. The pre-exponential factor (A) also increased with increasing conversion rate, reflecting the kinetic compensation effect of the reaction. The correlation coefficient (R²) between the two models was [not specified in the original text]. 2 The values ​​of all values ​​were above 0.9, indicating that the KAS model and DAEM were chosen reasonably, and the results are reliable. The average activation energies were 108.62 kJ·mol⁻¹. -¹ (KAS) and 109.93 kJ·mol -¹ (DAEM) can provide a theoretical basis for the optimization of pyrolysis processes.

[0045] 2.3 Effects of pyrolysis conditions on the pyrolysis characteristics of Ginkgo biloba leaf residue 2.3.1 Effect of pyrolysis temperature on the pyrolysis of Ginkgo leaf residue To investigate the effect of pyrolysis temperature on the pyrolysis behavior of Ginkgo biloba leaf residue, under fixed conditions of a heating rate of 10℃ / min, particle size <0.15mm, and reaction time of 10min, the product distribution and gas composition at different pyrolysis temperatures were examined. The results are as follows: Figure 2 As shown.

[0046] Figure 2 (A) illustrates the effect of pyrolysis temperature on the distribution of three-phase products from Ginkgo biloba residue. As the pyrolysis temperature increases from 400℃ to 600℃, the yield of solid products continuously decreases. This is because the high temperature promotes more thorough thermal decomposition of recalcitrant components in biomass (such as lignin and macromolecular carbon skeletons), resulting in a reduction in solid phase residue. The gas yield shows a monotonically increasing trend, with a significantly faster rate of increase in the 500℃~600℃ range; the liquid yield reaches its peak at 500℃ and then gradually decreases. Combined with the fact that the weight loss of the Ginkgo biloba residue TG curve tends to level off after 500℃, it can be inferred that most of the primary pyrolysis reactions were completed before this temperature. When the temperature continues to rise, the primary liquid-phase products (tar / bio-oil) undergo secondary decomposition reactions, with macromolecular compounds breaking bonds to generate non-condensable small molecule gases H2 and CH4, leading to a decrease in liquid yield and an increase in gas yield. In conclusion, 500℃ is the suitable temperature for oil extraction from the pyrolysis of Ginkgo biloba residue.

[0047] Figure 2(B) reflects the effect of pyrolysis temperature on the composition of gaseous products. With increasing temperature, the volume fractions of CO2 and CO decrease, while the H2 content increases significantly, reaching its second-largest proportion after CO2 at 600℃. This phenomenon is attributed to the fact that in the low-temperature stage (400~500℃), oxygen-containing functional groups such as carboxyl and carbonyl groups in biomass readily undergo decarboxylation and decarbonylation reactions, mainly releasing CO2 and CO; while high temperatures promote homogeneous gas-phase reactions and gas-solid secondary reactions, such as tar cracking, the Boudouard reaction, and hydrocarbon reforming (e.g., CH4 + 2H2O → 4H2 + CO2), leading to further CO / CO2 conversion and a significant increase in the generation of hydrogen-rich gas. The effect of pyrolysis temperature on the composition characteristics of solid products is shown in Table 3. With increasing temperature, the volatile matter content continuously decreases, while the fixed carbon content increases accordingly. In terms of elemental composition, the relative carbon content increases, while hydrogen and oxygen show a decreasing trend, causing the C / O and C / H ratios to continuously increase. This evolutionary pattern corresponds well to the phenomenon of H enrichment in gaseous products at high temperatures. These changes stem from the phased characteristics of the biomass thermal conversion process. At low temperatures, small-molecule organic matter and water are preferentially released from the volatiles; as pyrolysis deepens, the decomposition of oxygen-containing components becomes more complete, leading to a continuous loss of oxygen. From a reaction mechanism perspective, high temperatures induce dehydration and deoxygenation reactions in the hydroxyl and carboxyl oxygen-containing functional groups of biomass, generating H2O, CO, and CO2 that escape from the system, resulting in a net reduction in oxygen. Meanwhile, aliphatic structures and aromatic units undergo dehydrogenation under high-temperature induction, releasing light gases H2 and CH4, thus reducing hydrogen content. Simultaneously, the increased aromaticity promotes the formation of carbon-rich ordered structures, further enhancing the carbon density of the solid products. The continuous increase in the carbon-oxygen ratio and carbon-hydrogen ratio reflects the optimization of the energy density and calorific value of the solid products, and their thermal stability as fuel is also enhanced.

[0048] Table 3. Industrial composition and elemental content determination of biochar at different pyrolysis temperatures. Note: *Subtraction method: d—dry basis; daf—dry ash-free basis.

[0049] 2.3.2 Effect of reaction time on the pyrolysis of Ginkgo biloba leaf residue Pyrolysis time is a key parameter affecting the carbonization behavior of biomass. Too short a time can lead to incomplete carbonization, while too long a residence time not only increases energy consumption but may also alter the physicochemical properties of the product. Therefore, this invention investigated the effect of different reaction times on biochar characteristics under fixed conditions of a pyrolysis temperature of 600℃, a particle size of less than 0.15 mm, and a heating rate of 10℃ / min. The results are as follows: Figure 3 As shown.

[0050] Combination Figure 3(A) indicates that the effect of pyrolysis time on the distribution of the three-phase products exhibits a phased characteristic. When the reaction time is extended from 10 min to 15 min, the gas and solid yields remain relatively stable; the liquid yield reaches its peak at 15 min, and after 15 min, the liquid yield shows a slight decreasing trend, while the gas yield increases accordingly, and the solid yield decreases. This suggests that at reaction times (>15 min), the liquid phase products have a longer residence time in the high-temperature region, undergoing a secondary pyrolysis reaction, and partially converting into small molecule gases, thus leading to the inverse relationship between the gas and liquid phase yields. Figure 3 As shown in (B), the evolution of gas components reveals that as the reaction time increased from 10 min to 15 min, the H2 content decreased significantly, while the CO2 content increased. After the reaction time exceeded 15 min, the H2 and CO2 concentrations stabilized, indicating that the main pyrolysis reaction was essentially completed at 15 min. To further verify the effect of pyrolysis time on the solid-phase products, industrial and elemental analyses were performed on the semi-coke obtained at different reaction times (Table 4). The results in Table 4 show that when the reaction time was extended from 10 min to 15 min, only the carbon content in the semi-coke increased slightly, while other components changed very little. This is consistent with... Figure 3 (A) shows that the solid yield is basically stable, which further confirms that the pyrolysis time has little effect on the solid semi-coke.

[0051] Table 4. Industrial composition and elemental content determination of biochar at different pyrolysis times. 2.3.3 Effect of heating rate on the pyrolysis of Ginkgo biloba leaf residue To investigate the effect of heating rate on the pyrolysis process, experiments were conducted under the conditions of a reaction temperature of 600℃, a particle size of less than 0.15 mm, and a reaction time of 10 min. The results are as follows: Figure 4 As shown. The effect of heating rate on the distribution of three-phase products from the pyrolysis of Ginkgo biloba leaf residue is as follows. Figure 4As shown in (A), with increasing heating rate, the yield of liquid products gradually increases, while the yield of gaseous products gradually decreases; the yield of solids, except for a slight decrease at 20℃ / min, does not change significantly at other heating rates. This phenomenon is closely related to the influence of heating rate on heat transfer and reaction process. Although a lower heating rate (10℃ / min) is beneficial for uniform heating of the bed and more complete pyrolysis of Ginkgo biloba residue, this often comes at the cost of sacrificing liquid yield, resulting in a reduction in the yield of the target bio-oil. Conversely, an excessively high heating rate leads to an increase in the temperature difference between the inside and outside of the particles, uneven heat transfer in the bed, and a lag in the pyrolysis inside the particles; the liquid products generated inside also undergo secondary cracking when they come into contact with the high-temperature surface during outward diffusion, resulting in a decrease in liquid yield and an increase in gaseous yield. Considering the effective suppression of secondary cracking and the completeness of the pyrolysis reaction, a heating rate of 10℃ / min shows significant process advantages. At this rate, the reaction system avoids excessive gasification, allowing more organic matter in the feedstock to be distributed into the liquid char and solid residue. Based on the optimization results of product yield, 10℃ / min was determined to be the optimal heating parameter under the conditions of this invention.

[0052] according to Figure 4 (B) shows the gas component analysis results, indicating that the heating rate significantly regulates the generation of CO2, CO, and H2. At a heating rate of 10 °C / min, CO2 and CO contents are lowest, while H2 content is highest, indicating that the gas component distribution reaches its optimal state at this rate. From the reaction mechanism perspective, the generation of CO2 and CO is mainly attributed to the decarboxylation and decarbonylation reactions of cellulose, hemicellulose, and lignin. When the heating rate increases to 10 °C / min, the reaction time shortens, the secondary cracking reaction is suppressed, and the generation of CO2 and CO decreases accordingly. In contrast, H2 generation mainly originates from the dehydrogenation behavior of lignin macromolecules and the synergistic effect of aromatic structure recombination. When the heating rate is maintained at 10 °C / min, the reaction system provides a sufficient time window and ideal temperature field for the dehydrogenation process, promoting effective recombination and enrichment of hydrogen free radicals, thereby increasing the yield of H2. Both excessively low and excessively high heating rates are detrimental to H2 generation: when the rate is too low, the secondary cracking reaction consumes H2 and generates more CO2 / CO; when the rate is too high, the reaction process is too violent, the dehydrogenation reaction is difficult to proceed stably, and the H2 concentration decreases.

[0053] Table 5. Determination of industrial composition and elemental content of biochar at different heating rates. Table 5 shows that the heating rate has a significant regulatory effect on the compositional properties of biochar. As the heating rate increases from 10℃ / min to 20℃ / min, the volatile matter content first increases and then decreases, while the fixed carbon content first decreases and then increases; the C and H contents show a trend of first increasing and then decreasing, while the O content continues to decrease. Therefore, at 10℃ / min, the fixed carbon content is the highest, the C / O ratio is the lowest, and the C / H ratio is the highest. This variation is closely related to the reaction mechanism during pyrolysis. At low heating rates, the longer pyrolysis time allows for the full release of volatiles, resulting in a relative enrichment of fixed carbon. As the heating rate increases, the reaction pathway and the types of intermediate products may change, thus affecting the C / O and C / H ratios. When the heating rate continues to increase (15~20℃ / min), the diffusion time of pyrolysis gas within the particles is insufficient, and some volatile elements (O, H) fail to escape completely and remain in the biochar. Therefore, the effect of the heating rate on the composition of biochar is the result of the combined action of pyrolysis kinetics and heat and mass transport mechanisms.

[0054] 2.4 Characteristics of pyrolysis semi-coke and liquid products at different temperatures 2.4.1 Surface morphology analysis of solid products To investigate the effect of pyrolysis temperature on the apparent morphology of pyrolysis semi-char from Ginkgo biloba leaf residue, SEM was used to characterize the pyrolysis semi-char prepared at 400℃, 500℃, and 600℃. The results are as follows: Figure 5 As shown in the image, comparing SEM images of pyrolyzed semi-coke at different temperatures reveals that pyrolysis induces the formation of numerous irregular channels on the semi-coke surface. With the gradual increase in pyrolysis temperature, the pore size of these irregular channels on the semi-coke surface significantly increases, gradually evolving into a microstructure with lamellar stacking and honeycomb characteristics. Simultaneously, when the pyrolysis temperature reaches 500℃–600℃, significant pore collapse occurs on the semi-coke surface. This high-porosity structure facilitates the adsorption of metal ions or the storage of gases and liquids, primarily attributed to the deep pyrolysis of cellulose and hemicellulose under high-temperature conditions. Excessive temperature increases damage the pore structure, inducing pore wall ablation and framework collapse, further increasing the pore size on the biochar surface and consequently reducing the biochar's adsorption or storage capacity.

[0055] 2.4.2 Compositional Analysis of Liquid Products As shown in Tables 6 and 7, the types of compounds in the pyrolysis oil products are basically the same at different pyrolysis temperatures. The main compounds are phenol, acetic acid, 5-methylfurfural, furfural, 4-ethylphenol, (Z)-8-oxetane-heptadec-8-en-2-one, and (Z)-3-(heptadec-10-en-1-yl)phenol. With the increase of pyrolysis temperature, the acetic acid content decreased from 9.612% to 4.872%, and the phenol content decreased from 3.906% to 2.428%. The main reason for the decrease in acetic acid is probably that the main source, hemicellulose, is completely decomposed and decomposes into gas at high temperature. The change in phenol content is the result of the dynamic balance between its generation (from the conversion of lignin and complex phenols) and consumption (polymerization into coke or deep cracking).

[0056] Table 6 Chemical composition of Ginkgo leaf residue pyrolysis liquid at different pyrolysis temperatures Note: In the table, "*" indicates that the content of the compound at this temperature is less than 1%, and the same applies below.

[0057] Tables 7 and 6 (continued) Figure 6 This indicates that pyrolysis temperature has a significant impact on the chemical composition of the pyrolysis solution of Ginkgo biloba leaf residue. Within the investigated temperature range, the content of other compounds gradually increased with increasing pyrolysis temperature, with relative contents ranging from 35.05% to 51.07%. Apart from other compounds (hydrocarbons, heteroatom-containing compounds (N / S), furans, and sugar derivatives), phenols remained the most abundant component in the pyrolysis solution, with relative contents ranging from 20.36% to 22.93%. This was followed by ketones (3.79%–12.58%) and acids (8.73%–11.53%). The content of each component exhibited different changing patterns with increasing pyrolysis temperature. Specifically, with gradually increasing pyrolysis temperature, the contents of acids and esters showed an evolutionary characteristic of first increasing and then decreasing, with peak values ​​appearing around 500℃, at 11.53% and 10.3%, respectively. With increasing pyrolysis temperature, the content of ketones first increased and then decreased. This change can be attributed to the fact that ketones at 400℃ likely originate primarily from specific cleavage pathways of cellulose / hemicellulose (such as the formation of L-glucanone). These pathways are inhibited at 500℃, reducing ketone formation. The rebound at 600℃ may stem from new formation pathways: such as high-temperature decarboxylation / ketolation reactions of carboxylic acids (acetic acid, hexadecanoic acid), or partial oxidation of hydrocarbons. Further research revealed that different pyrolysis temperatures lead to significant differences in the liquid product composition of Ginkgo biloba leaf residue. 500℃ is the optimal pyrolysis temperature, under which the formation of target products such as aldehydes, ketones, phenols, and esters in the pyrolysis solution is most complete.

[0058] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue, characterized in that, Includes the following steps: Ginkgo leaf residue was heated to 400℃~600℃ in an inert gas atmosphere at a heating rate of 10℃ / min~20℃ / min for 10min~20min for pyrolysis. During the pyrolysis process, volatiles were continuously collected and condensed. The condensed liquid was bio-oil, and the non-condensable gas was pyrolysis gas. The solid obtained after the pyrolysis reaction was biochar.

2. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 1, characterized in that, The pyrolysis gas includes H2, CO, CO2, CH4, and C2-C3 hydrocarbon gases.

3. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 1, characterized in that, The biochar has a porous structure, with a fixed carbon content of 35.71% to 46.20% and an elemental carbon content of 44.89% to 46.80%.

4. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 1, characterized in that, The inert gas is argon.

5. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 1, characterized in that, The flow rate of the inert gas is 100 mL / min to 200 mL / min.

6. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 1, characterized in that, The condensation temperature is -15℃ to -10℃.

7. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 1, characterized in that, The particle size of the ginkgo leaf residue is no greater than 0.15 mm.

8. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 1, characterized in that, The ginkgo leaf residue is the residue obtained after alcohol extraction and drying.

9. The method for preparing multiphase products based on the directional pyrolysis of Ginkgo biloba leaf residue according to claim 8, characterized in that, The alcohol extraction refers to extraction at 70% ethanol at 60℃~80℃ for 20min~30min.

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