Integrated process for separation and upgrading of corn stalk-spirulina co-liquefaction

Abstract

The application discloses a corn straw-spirulina co-liquefaction separation and upgrading integrated process, a step-by-step extraction process is designed, the gas-liquid-solid three-phase product of the corn straw and spirulina co-hydrothermal liquefaction is processed in different solvent systems without adding a catalyst or in an EWCS system with adding Fe catalyst, and water-soluble oil, water-insoluble oil and biochar are sequentially separated and collected. The fine separation of bio-oil is realized, the corn straw and spirulina co-hydrothermal liquefaction is first processed, the bio-oil is split into WSB and WISB through step-by-step extraction, and a foundation is laid for targeted research. The step-by-step extraction path can directly distinguish the selective influence of the solvent type and the addition of Fe powder catalyst in the EWCS system on different oil components, so as to reveal the specific action site of the process conditions. According to the actual demand of different target products of WSB or WISB, the reaction conditions can be accurately controlled, and the yield and quality are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of synergistic resource utilization of agricultural waste and microalgae biomass and high-value utilization of biomass energy, specifically involving an integrated separation and upgrading process of corn straw-spirulina co-liquefaction. Background Technology

[0002] Hydrothermal liquefaction (HTL) is one of the core technologies for biomass energy conversion. Because it can directly process wet materials, eliminating the need for drying energy, and its oil products have lower oxygen content and higher energy efficiency, it has become a research hotspot for the resource utilization of agricultural and forestry waste and microalgae. Current research often focuses on co-hydrothermal liquefaction of different biomass (co-HTL), introducing organic solvents, or adding catalysts to optimize the reaction and improve the yield and quality of bio-oil. Existing technologies mostly focus on increasing the total bio-oil yield, collecting the liquid products as a whole mixed oil phase, without specifically separating and analyzing water-soluble oils (WSB) and water-insoluble oils (WISB) of different polar components. For example, CN105733693A discloses a method for co-liquefying algae and woody biomass in alcohol-water, which focuses on increasing the total oil yield and collects the liquefied liquid phase products as a whole mixed oil phase without finely separating all liquid phase products; CN109022057A discloses a method for co-liquefying kitchen waste and microalgae to achieve energy. Self-balancing systems, whose core lies in energy cycling, do not involve the separation and targeted upgrading of components in the bio-oil phase; or they simply classify water-soluble products as byproducts without extracting the soluble oil components. For example, CN110114317A describes the co-liquefaction of wastewater sludge and lignocellulose, which only separates bio-oil, water-soluble byproducts (WSP), and biochar. WSP is a water-soluble product obtained directly through simple centrifugation and filtration, without extracting the soluble oil components. This results in a loss of the actual total oil yield and waste of high-value small molecule compounds in WSB.

[0003] In fact, among the products of corn stalk + spirulina co-HTL, WSB is rich in nitrogen-containing compounds and small phenolic molecules, showing potential as a fine chemical intermediate; WISB, on the other hand, is mainly composed of esters and hydrocarbon macromolecules, making it a high-quality clean biomass fuel feedstock. Meanwhile, the process conditions have significantly different effects on the formation and quality control of the two types of oil. Therefore, developing a co-HTL process that can achieve fine separation and targeted upgrading of WSB and WISB, and construct a resource recycling system, is key to overcoming the shortcomings of existing technologies. Summary of the Invention

[0004] To address the aforementioned issues, embodiments of the present invention propose an integrated separation and upgrading process for corn stalk-spirulina co-liquefaction.

[0005] The integrated separation and upgrading process of corn stalk-spirulina co-liquefaction of the present invention includes the following steps:

[0006] S1. Raw material pretreatment and hydrothermal liquefaction: Corn stalks, spirulina, and Fe powder catalyst are mixed as raw materials. The raw materials are placed in a closed high-pressure reactor. Solvent is added to the closed high-pressure reactor. Under high temperature and high pressure conditions, a co-hydrothermal liquefaction reaction is carried out. After the reaction is completed, a gas-liquid-solid three-phase mixed hydrothermal liquefaction product is obtained.

[0007] S2. Gas phase product treatment: The gas phase products obtained in S1 are directly vented and not included in the analysis and collection.

[0008] S3. Extraction of WSB and recycling of DCM: The solid-liquid mixture that can be directly poured out of the reactor is taken out and filtered to obtain all the liquid phase filtrate. DCM is added for extraction to separate the DCM phase from the aqueous phase. The DCM phase is collected and concentrated by rotary evaporation to obtain WSB. After constant weight, the yield is calculated by weighing and sealed in a bottle for later use.

[0009] S4. WISB Extraction and DCM Recycling: DCM was used to thoroughly wash and extract the solid residue obtained from S3 filtration and the inner wall of the reactor. The washing liquid was filtered and separated, and the obtained solid was a mixture of biochar and Fe powder. The obtained filtrate was extracted and separated by DCM. The DCM phase was concentrated by rotary evaporation to obtain WISB. After constant weight, the yield was calculated by weighing and sealed in a bottle for later use.

[0010] S5. Preparation of biochar: The biochar-Fe powder mixture obtained in S4 was placed in an oven and dried to constant weight. After constant weight, it was weighed to calculate the char yield, and then sealed and bagged for later use.

[0011] S6. Catalyst recovery and recycling: The biochar-Fe powder mixture obtained in S5 is treated by magnetic separation to separate and recover the Fe powder and biochar. The recovered Fe powder can be recycled and reused in its process.

[0012] If the catalyst is removed in S1, the biochar-Fe powder mixture in S4 and S5 will be replaced with crude biochar and biochar product, respectively.

[0013] The solvent in S1 is 100 mL of pure water or EWCS, the mass ratio of corn straw to spirulina is 1:1, and the amount of Fe powder added is 10 wt% (based on the dry weight of the raw materials).

[0014] The EWCS is an ethanol-water cosolvent, i.e., 50 mL of ethanol + 50 mL of water.

[0015] The hydrothermal liquefaction reaction conditions are: reaction temperature 240-340℃, residence time 30min, stirring speed 800rpm, and initial reaction pressure 1MPa.

[0016] The washing solution used in S4 is DCM, and the extraction agent used in S3 and S4 is also DCM. The amount of washing solution and extraction agent used should be based on sufficient extraction and washing.

[0017] The process parameters for rotary evaporation concentration in S3 and S4 are: rotary evaporation temperature 45℃, rotation speed 45rpm, and rotary evaporation concentration until there is no obvious flow dynamics.

[0018] The process parameters for oven drying in S5 are: drying temperature 105℃, drying time 12h.

[0019] When calculating the biochar-Fe powder mixture, the initial mass of the Fe powder catalyst must be deducted.

[0020] The magnetic separation process in S6 needs to be carried out on the dried biochar-Fe powder mixture. After the magnetic separation is completed, the recovered Fe powder and biochar products are collected separately.

[0021] The rotary evaporation temperature is 45℃ to avoid excessive temperature causing the decomposition and boiling of heat-sensitive compounds in the oil phase, thus ensuring the integrity of the oil phase components; the oven drying temperature is 105℃, and the temperature should not be too high to avoid pyrolysis of the biochar and ensure the quality of the biochar.

[0022] The beneficial effects of this invention are:

[0023] 1. Achieving refined separation of bio-oil, for the first time targeting corn stalk + spirulina co-HTL, the bio-oil was separated into WSB and WISB through stepwise extraction, laying the foundation for targeted research. This stepwise extraction pathway allows for a direct differentiation of the selective effects of solvent type (pure water, EWCS) and the addition of Fe powder catalyst in the EWCS system on the formation of different oil components, thus revealing the specific sites of action of process conditions. Based on this method, reaction conditions can be precisely controlled according to the actual needs of different target products of WSB or WISB, improving their yield and quality.

[0024] 2. This technology achieves a closed loop of fine separation, targeted upgrading, and resource recycling of bio-oil. It clarifies the synergistic regulatory effects of co-solvents and catalysts, providing theoretical and technical support for process optimization. It enables the reduction, harmlessness, and high-value utilization of agricultural waste and microalgae, demonstrating significant benefits and large-scale industrial potential. This not only aids in understanding the co-HTL reaction mechanism but also provides technical support for the targeted regulation and process optimization of target bio-oil components, further reducing production costs through resource recycling. Attached Figure Description

[0025] Figure 1 This is a flowchart of the bio-oil distribution and separation process with catalyst added according to the present invention.

[0026] Figure 2 This is a flowchart of the distribution and separation process of bio-oil without catalyst according to the present invention.

[0027] Figure 3 This is a product distribution diagram of all embodiments of the present invention.

[0028] Figure 4 The results are GC-MS analysis of oil products in all embodiments of the present invention: (a) WSB and (b) WISB. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] like Figure 1 As shown, the integrated separation and upgrading process of corn stalk-spirulina co-liquefaction of the present invention includes the following steps in the process of adding a catalyst:

[0031] S1. Raw material pretreatment and hydrothermal liquefaction: Corn stalks, spirulina and Fe powder catalyst are mixed as raw materials. The amount of each raw material is: 5g corn stalks, 5g spirulina, and 1g Fe powder. The raw materials are placed in a closed high-pressure reactor. Solvent is added to the closed high-pressure reactor. The solvent is 100ml pure water (or EWCS: 50ml ethanol + 50ml water). The co-hydrothermal liquefaction reaction is carried out under high temperature and high pressure conditions. The reaction temperature is 240-340°C, the residence time is 30min, the stirring speed is 800rpm, and the initial reaction pressure is 1MPa. After the reaction is completed, a gas-liquid-solid three-phase mixed hydrothermal liquefaction product is obtained.

[0032] S2. Gas phase product treatment: The gas phase products obtained in S1 are directly vented and not included in the analysis and collection.

[0033] S3. Extraction of WSB and recycling of DCM: The solid-liquid mixture that can be directly poured out of the reactor is taken out and filtered to obtain all the liquid phase filtrate. DCM is added for extraction to separate the DCM phase from the aqueous phase. The DCM phase is collected and concentrated by rotary evaporation to obtain WSB. After constant weight, the yield is calculated by weighing and sealed in a bottle for later use.

[0034] S4. WISB Extraction and DCM Recycling: DCM was used to thoroughly wash and extract the solid residue obtained from S3 filtration and the inner wall of the reactor. The washing liquid was filtered and separated, and the obtained solid was a mixture of biochar and Fe powder. The obtained filtrate was extracted and separated by DCM. The DCM phase was concentrated by rotary evaporation to obtain WISB. After constant weight, the yield was calculated by weighing and sealed in a bottle for later use.

[0035] S5. Preparation of biochar: The biochar-Fe powder mixture obtained in S4 was placed in an oven and dried to constant weight. After constant weight, it was weighed to calculate the char yield, and then sealed and bagged for later use.

[0036] S6. Catalyst recovery and recycling: The biochar-Fe powder mixture obtained in S5 is treated by magnetic separation to separate and recover the Fe powder and biochar. The recovered Fe powder can be recycled and reused in its process.

[0037] like Figure 2 As shown, the integrated separation and upgrading process of corn stalk-spirulina co-liquefaction of the present invention, without the addition of a catalyst, includes the following steps:

[0038] S1. Raw material pretreatment and hydrothermal liquefaction: Corn stalks and spirulina are mixed as raw materials. The amount of each raw material is: 5g of corn stalks and 5g of spirulina. The raw materials are placed in a closed high-pressure reactor. Solvent is added to the closed high-pressure reactor. The solvent is 100ml of pure water (or EWCS: 50ml of ethanol + 50ml of water). The co-hydrothermal liquefaction reaction is carried out under high temperature and high pressure conditions. The reaction temperature is 240-340°C, the residence time is 30min, and the stirring speed is 800rpm. After the reaction is completed, a gas-liquid-solid three-phase mixed hydrothermal liquefaction product is obtained.

[0039] S2. Gas phase product treatment: The gas phase products obtained in S1 are directly vented and not included in the analysis and collection.

[0040] S3. Extraction of WSB and recycling of DCM: The solid-liquid mixture that can be directly poured out of the reactor is taken out and filtered to obtain all the liquid phase filtrate. DCM is added for extraction to separate the DCM phase from the aqueous phase. The DCM phase is collected and concentrated by rotary evaporation to obtain WSB. After constant weight, the yield is calculated by weighing and sealed in a bottle for later use.

[0041] S4. Extraction of WISB and recycling of DCM: DCM was used to thoroughly wash and extract the solid residue obtained from S3 filtration and the inner wall of the reactor. The washing liquid was filtered and separated, and the obtained solid was crude biochar. The obtained filtrate was extracted and separated by DCM. The DCM phase was concentrated by rotary evaporation to obtain WISB. After constant weight, the yield was calculated by weighing and sealed in a bottle for later use.

[0042] S5. Preparation of biochar: The crude biochar obtained in S4 is placed in an oven and dried to constant weight to obtain the biochar product. After constant weight, the product is weighed to calculate the char yield, and then sealed and bagged for later use.

[0043] Water-soluble oils ( Yield, water-insoluble oil ( The yield and biochar yield are calculated using the following formulas:

[0044]

[0045]

[0046] Biochar yield without catalyst:

[0047]

[0048] Biochar yield with catalyst:

[0049]

[0050] In the formula,

[0051] M: Total mass of biomass raw materials (corn straw + spirulina);

[0052] M1: Mass after WSB constant weight, in g;

[0053] M2:W The mass of SB after constant weight, in g;

[0054] M3: Mass of dried crude biochar or biochar-Fe powder mixture, in g;

[0055] M4: Initial mass of Fe powder added, in g.

[0056] Example 1

[0057] Spirulina and corn stalks were used as raw materials, and pure water was used as the reaction solvent. No catalyst was added during the experiment. Specifically, 5g of spirulina, 5g of corn stalks, and 100ml of pure water were added to a reaction vessel. The reaction temperature was 300℃, and the residence time was 30min. Since gaseous products were not considered, the gas phase products were removed by venting in a fume hood after the reaction. The solid-liquid mixture that could be directly poured out of the reaction vessel was filtered. The filtrate was extracted with sufficient DCM. After standing and separating into layers, the DCM phase was concentrated by rotary evaporation (45rpm, 45℃) until there was no obvious flow. After constant weight, WSB was obtained. The inner wall of the reaction vessel and the solid residue obtained from the previous filtration step were washed with sufficient DCM. The washing liquid was concentrated by rotary evaporation to constant weight to obtain WISB. The crude biochar was dried in an oven at 105℃ for 12h to obtain biochar.

[0058] Experimental results showed that the yield of WSB was 3.42%, the yield of WISB was 18.94%, the total oil yield was 22.36%, and the biochar yield was 13.16%. Under these conditions, the oil was mainly composed of WISB, with a moderate total oil yield and a relatively high biochar yield. Its compound composition was mainly composed of nitrogen-containing compounds, phenols, and aldehydes / ketones, but WISB contained higher levels of esters and hydrocarbons.

[0059] Example 2

[0060] The specific steps are the same as in Example 1, except that the solvent is replaced with an ethanol-water co-solvent (EWCS: 50ml ethanol + 50ml water).

[0061] Experimental results showed that the WSB yield was 26.39%, the WISB yield was 14.40%, and the total oil yield increased to 40.79%, while the biochar yield was 6.00%. The introduction of ethanol significantly promoted WSB formation, increasing the total oil yield by approximately 11.26%, while simultaneously reducing biochar yield, indicating that EWCS has a significant selective effect on the reaction pathway. The compound composition was as follows: nitrogen-containing compounds and phenols were predominant in WSB; esters were predominant in WISB.

[0062] Example 3

[0063] The specific operating steps are the same as in Example 2, except that Fe powder catalyst (10wt%, i.e., 1g) is added to the system, and the other operating conditions are the same. However, the final solid product is not just crude biochar, but a mixture containing Fe powder, which needs to be separated by magnetic separation after drying in an oven to obtain biochar and Fe powder.

[0064] Experimental results showed that the WSB yield was 25.37%, the WISB yield was 21.83%, and the total oil yield further increased to 47.20%, while the biochar yield was 7.89%. The addition of Fe powder catalyst increased the total oil yield by approximately 6.41% compared to the uncatalyzed system, mainly due to the promotion of the WISB pathway. At this point, the WSB was still dominated by nitrogen-containing compounds and phenols, while the WISB was dominated by esters, but the nitrogen-containing compound content was slightly higher compared to the uncatalyzed EWCS.

[0065] The elemental analysis results of the products of each embodiment are shown in Table 1.

[0066] Table 1 Elemental analysis results of products from each example

[0067]

[0068] Based on the yields of the three embodiments described above, such as Figure 3 and Figure 4 As shown, the following results can be obtained through intuitive analysis.

[0069] By comparing and analyzing Examples 1 and 2, the "solvent effect" in the EWCS system under catalyst-free conditions can be understood. Specifically, ethanol promotes the formation of water-soluble bio-oil (WSB) and moderately inhibits the formation of water-insoluble bio-oil (WISB). This is because ethanol has a lower dielectric constant than water. The introduction of ethanol can reduce solvent polarity, thereby promoting the depolymerization and fragmentation of high molecular weight biomass intermediates, while inhibiting free radical polymerization and coking, increasing oil yield, and reducing biochar formation. GC-MS results conform to general patterns: ethanol, acting as an in-situ hydrogen donor, can reduce aldehyde / ketone intermediates to alcohols via hydrogenation, and then undergo esterification with carboxylic acids. This competes with the alcoholysis of amides / amines, leading to the enrichment of esters in the WISB and a decrease in the overall nitrogen content. Simultaneously, ethanol promotes the cleavage of ether bonds between lignin units, generating small-molecule phenolic monomers that accumulate in the WSB, thus increasing the phenol content. Due to polarity, isopolar nitrogen compounds have increased solubility in EWCS and tend to partition into the WSB phase, resulting in a significant decrease in nitrogen content in the WISB, which is highly consistent with the characterization results. In summary, EWCS has a significant synergistic effect, improving bio-oil yield and optimizing oil composition.

[0070] By comparing and analyzing Examples 2 and 3, the synergistic mechanism of EWCS and Fe powder catalyst can be understood. Specifically, the introduction of Fe powder into the EWCS system further improves the total oil yield and optimizes its compound composition. Combined with GC-MS and elemental analysis results, Fe powder exhibits a differentiated catalytic upgrading mechanism for WSB and WISB: For WSB, Fe powder plays a hydrodeoxygenation catalytic role due to the in-situ hydrogen effect, promoting the hydrodeoxygenation of oxygen-containing functional groups such as carboxyl groups in WSB, resulting in a significant decrease in O content and an increase in H content, thus improving the higher heating value, which is corroborated by a slight increase in aldehyde / ketone content; however, the compound composition of WSB under Fe catalysis is not significantly affected, indicating that the catalytic effect of Fe is mainly aimed at large oxygen-containing polymers, and the addition of Fe can stabilize small molecule components to prevent their repolymerization and stabilize the component composition. For WISB, the addition of Fe catalyst leads to a decrease in ester content, a slight increase in nitrogen-containing compound content and acid content, and an increase in O and H content and a decrease in N content. This may be because the introduction of Fe promotes ester cracking, converting esters into alcohols and acids. The incomplete deoxygenation of ester cracking products increases the O content of the system. At the same time, Fe catalysis promotes denitrification, thus reducing the N content. The increase in nitrogen-containing compound content can be understood as a decrease in the relative content of esters in the system, thereby increasing their relative proportion.

[0071] Based on the aforementioned specific implementation examples, this invention innovatively separates the products of corn straw + spirulina synergistic hydrothermal liquefaction (co-HTL) into two independent components: water-soluble oil (WSB) and water-insoluble oil (WISB). Using the pure water system of Example 1 as a blank control, ethanol solvent is introduced, and a catalyst is further added for comparative research. This systematically reveals the "solvent effect" and the specific action sites of the catalyst, clearly elucidating the synergistic regulatory mechanism between the two in the co-HTL process. Addressing the dual demands of current biomass liquefaction technology for increased oil yield and optimized oil quality, this invention adopts an integrated strategy of fine separation and targeted quality improvement, providing a feasible technical route for simultaneously achieving high oil yield and high-quality bio-oil. Simultaneously, a recycling system for the catalyst and extraction solvent is constructed, forming a complete closed-loop process that effectively reduces production costs. This technology achieves the synergistic high-value utilization of agricultural straw waste and nitrogen-rich microalgae. The differences in component composition and chemical properties between WSB and WISB allow for targeted adaptation to the fields of refined chemical industry and clean biomass fuels, respectively. In summary, this study provides a novel technical approach and theoretical support for the resource utilization of agricultural and forestry waste and microalgae, as well as the high-value transformation of biomass.

[0072] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. An integrated separation and upgrading process for corn stalk-spirulina co-liquefaction, characterized in that, Includes the following steps: S1. Raw material pretreatment and hydrothermal liquefaction: Corn stalks, spirulina, and Fe powder catalyst are mixed as raw materials. The raw materials are placed in a closed high-pressure reactor. Solvent is added to the closed high-pressure reactor. Under high temperature and high pressure conditions, a co-hydrothermal liquefaction reaction is carried out. After the reaction is completed, a gas-liquid-solid three-phase mixed hydrothermal liquefaction product is obtained. S2. Gas phase product treatment: The gas phase products obtained in S1 are directly vented and not included in the analysis and collection. S3. Extraction of WSB and recycling of DCM: The solid-liquid mixture that can be directly poured out of the reactor is taken out and filtered to obtain all the liquid phase filtrate. DCM is added for extraction to separate the DCM phase from the aqueous phase. The DCM phase is collected and concentrated by rotary evaporation to obtain WSB. After constant weight, the yield is calculated by weighing and sealed in a bottle for later use. S4. WISB Extraction and DCM Recycling: DCM was used to thoroughly wash and extract the solid residue obtained from S3 filtration and the inner wall of the reactor. The washing liquid was filtered and separated, and the obtained solid was a mixture of biochar and Fe powder. The obtained filtrate was extracted and separated by DCM. The DCM phase was concentrated by rotary evaporation to obtain WISB. After constant weight, the yield was calculated by weighing and sealed in a bottle for later use. S5. Preparation of biochar: The biochar-Fe powder mixture obtained in S4 was placed in an oven and dried to constant weight. After constant weight, it was weighed to calculate the char yield, and then sealed and bagged for later use. S6. Catalyst recovery and recycling: The biochar-Fe powder mixture obtained in S5 is treated by magnetic separation to separate and recover the Fe powder and biochar. The recovered Fe powder can be recycled and reused in its process.

2. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 1, characterized in that, If the catalyst is removed in S1, the biochar-Fe powder mixture in S4 and S5 will be replaced with crude biochar.

3. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 2, characterized in that, The solvent in S1 is 100 mL of pure water or an ethanol-water co-solvent. The amount of corn stalks and spirulina added is 1:1 by mass ratio of corn stalks to spirulina. The amount of Fe powder added is 10 wt% (based on the dry basis of the raw materials).

4. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 3, characterized in that, The ethanol-water co-solvent is 50 mL of ethanol + 50 mL of water.

5. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 1, characterized in that, The hydrothermal liquefaction reaction conditions are: reaction temperature 240-340℃, residence time 30min, stirring speed 800rpm, and initial reaction pressure 1MPa.

6. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 1, characterized in that, The washing solution used in S4 is DCM, and the extraction agent used in S3 and S4 is also DCM. The amount of washing solution and extraction agent used should be based on sufficient extraction and washing.

7. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 1, characterized in that, The process parameters for rotary evaporation concentration in S3 and S4 are: rotary evaporation temperature 45℃, rotation speed 45rpm, and rotary evaporation concentration until there is no obvious flow dynamics.

8. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 1, characterized in that, The process parameters for oven drying in S5 are: drying temperature 105℃, drying time 12h.

9. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 1, characterized in that, When calculating the biochar-Fe powder mixture, the initial mass of the Fe powder catalyst must be deducted.

10. The integrated separation and upgrading process of corn straw-spirulina co-liquefaction according to claim 1, characterized in that, The magnetic separation process in S6 needs to be carried out on the dried biochar-Fe powder mixture. After the magnetic separation is completed, the recovered Fe powder and biochar products are collected separately.

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