Method for resource utilization of polycondensation byproduct humin in HMF production

Abstract

The invention discloses a method for resource utilization of a polycondensation by-product humin in HMF production. The method comprises the following steps: firstly, carrying out pretreatment such as cleaning, drying and crushing on a solid by-product humin in HMF industrial production; then carrying out copolymerization reaction on the treated humin fine powder and biomass alcohol (such as furfuryl alcohol) under acid catalysis to obtain humin-biomass alcohol copolymerization liquid; and finally, mixing the copolymerization liquid with a proper amount of solvent / assistant, coating a treated base material with the mixture, and curing to form the anticorrosive coating. The industrial waste residue humin is successfully converted into a high-value product, and the prepared coating has excellent acid corrosion resistance, good adhesive force, film-forming property and heat resistance, can be widely applied to protection of materials such as metal and wood, especially has huge potential in the field of corrosion prevention of vehicles and boats, and has wide application prospects. The organic combination of waste recycling and high-performance material preparation is realized.

Description

Technical Field

[0001] This invention belongs to the field of raw material resource utilization, specifically relating to a method for the resource utilization of humin, a polycondensation byproduct in HMF production. Background Technology

[0002] 5-Hydroxymethylfurfural (HMF), prepared from sugars through dehydration, is becoming an increasingly desirable platform chemical due to its unique furan ring and hydroxyl and aldehyde functional groups, especially in downstream markets where 2,5-furandicarboxylic acid (FDCA) is also attracting significant attention in the polymerization industry. However, a major challenge in actual industrial production is the inevitable generation of condensation byproducts (humins) during the dehydration of sugars to produce HMF, which reduces product selectivity and causes substantial carbon loss. The term humins can be traced back to 1849, when Muller et al. first used it to describe solid substances discovered during acid-catalyzed sucrose dehydration. After years of research and development, humins have become widely recognized as a class of solid byproducts of acid-catalyzed polymerization dehydration of carbohydrates.

[0003] The production of humin in HMF (Hydrogen Fumon Soap) results in a 10-50% carbon loss, with traditional landfilling being the primary method of disposal, which is costly and wasteful. Due to the lack of large-scale humin raw material sources, and the fact that the structure and yield of humin from acid-catalyzed carbohydrate dehydration in the laboratory can vary depending on various factors (such as temperature, catalyst, solvent, raw materials, concentration, and residence time), there are limitations in the utilization of humin. Currently, global HMF production capacity is rapidly expanding (such as the establishment of a 10,000-ton-level production line by Zhongke Guosheng), making large-scale utilization of byproducts urgent. Meanwhile, the utilization of highly polymerized solid humin has remained relatively limited.

[0004] Studies have found that humin can manifest as a black solid or a high-viscosity liquid. Higher temperatures, longer reaction times, higher acidity, and higher raw material concentrations often increase the degree of cross-linking of humin, resulting in solid black lumps composed of agglomerated spherical particles with a wide size distribution. Solid humin typically has very low solubility, while viscous liquid humin with a low degree of polymerization can often dissolve in some organic solvents. It can be modified and commercialized through various chemical methods, such as pyrolysis for oil extraction, pyrolysis for catalyst support, activated carbon adsorbents, and the preparation of thermosetting materials.

[0005] On the other hand, the preparation of bio-based coatings using carbohydrates is currently a hot topic in research and application. As an environmentally friendly material, bio-based coatings primarily derive their raw materials from renewable resources (such as vegetable oils, natural rubber, and rosin), and have a high bio-based carbon content (typically >20%). This reduces dependence on fossil fuels and helps lower the carbon footprint throughout the product's life cycle. Bio-based coatings have become very popular due to policy support, and solid humic acid is rich in carbon and is often treated as useless waste. Therefore, how to utilize the resources of this troublesome solid humic acid to prepare bio-based coatings is a very valuable research area. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for the resource utilization of humin, a solid byproduct of HMF production, thereby resolving the existing issues in the resource utilization of solid humin.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for the resource utilization of humin, a polycondensation byproduct in HMF production, includes the following process: S1: Pretreatment process of washing, drying, pulverizing and sieving humulin; S2: Introduce a copolymerization system and carry out a copolymerization reaction: Mix the humin fine powder obtained in step S1 with biomass alcohol, and carry out a heated copolymerization reaction under the action of an acid catalyst to obtain humin-biomass alcohol reaction copolymer liquid; S3: Take a certain mass of the reactive copolymer liquid, add a certain amount of solvent and additives, mix and stir to adjust the viscosity, and then obtain bio-based anti-corrosion coatings with different coating application viscosities; S4: After pre-treating and cleaning the substrates of different materials, apply the bio-based anti-corrosion coating obtained in step S3 to the surface of the pre-treated substrate, and cure it into a film after drying in an oven.

[0008] Furthermore, step S1 specifically includes: S11: After the solid humin is initially crushed, it is transferred to a vacuum filtration flask and washed with water to obtain water-washed humin. S12: Place the washed humectin in an oven to dry, and then pour the dried humectin into a pulverizer to pulverize it into black fine powder particles of different mesh sizes. S13: Collect the pulverized fine powder through a 100-120 mesh sieve, and continue to dry it in an oven to remove the remaining moisture; the drying temperature is 40~80℃.

[0009] Furthermore, step S2 specifically includes the following steps: S21: Premixing: Add the pretreated humin fine powder granules and biomass alcohol to a three-necked flask equipped with a stirrer at a certain mass ratio. Place the three-necked flask in an oil bath at 25~50℃ and stir to make it evenly mixed. The stirrer used is a stirrer with real-time torque and temperature display. S22: Catalyst addition and reaction: Raise the oil bath temperature to 50℃~60℃, add a certain proportion of acid catalyst, slowly raise the temperature to avoid the reaction being too fast, raise the temperature in increments of 10℃ to 105-115℃, keep the temperature constant for 1~2 hours, and monitor the viscosity of the system. S23: Once the reaction reaches its endpoint, immediately cool the temperature to below 40°C to temporarily terminate the reaction and prevent excessive reaction and gel formation; and terminate the reaction by neutralizing the residual acid catalyst using alkaline titration. S24: Product post-processing: The reaction slurry from step S23 is quickly filtered through a filter screen to remove larger unreacted particles, resulting in a reaction copolymer liquid with a certain viscosity.

[0010] Furthermore, in step S21, the biomass alcohol is selected from one or more of glycerol, furfuryl alcohol, sorbitol, isosorbide, bio-based ethylene glycol, and 1,3-propanediol.

[0011] Furthermore, in step S21, the mass ratio of added humic acid fine powder particles to biomass alcohol is 1:(1-4).

[0012] Furthermore, in step S21, 10-20 wt% of ethanol solvent, accounting for the total mass of the reaction system, is added during the stirring process to aid dissolution.

[0013] Furthermore, in step S22, the acid catalyst is p-toluenesulfonic acid, and its addition amount is 0.5~2wt% of the total mass of the reaction system. Furthermore, in step S23, the reaction endpoint is determined using the following process: The endpoint is determined by combining torque and temperature data from the stirrer. After the temperature rises to approximately 110 degrees Celsius, a significant reflux phenomenon occurs, and the real-time temperature display shows a significant temperature drop for a period. This is due to the ring-opening and direct bonding process of biomass alcohols, which leads to a rapid decrease in the biomass alcohol content in the system and a significant change in viscosity. A small amount of the reaction product from S22 is then dropped onto a hot plate, and the curing time is recorded. The reaction endpoint is determined based on the curing time; alternatively, it can be determined by viscosity testing. The reaction endpoint is determined when the viscosity reaches the target viscosity.

[0014] Furthermore, in step S23, after the temperature decreases, to prevent the residual acid catalyst from continuing to slowly catalyze the reaction, leading to storage instability, increased viscosity, and ultimately gelation, resulting in product spoilage or performance degradation, an alkaline neutralization step should be taken to terminate the reaction. The specific procedure is as follows: Prepare a 10%~30% NaOH solution. After the reaction temperature drops to room temperature or lower (below 40 degrees Celsius), if the system viscosity is too high, a small amount of solvent (such as ethanol) can be added first for dilution and to facilitate stirring and neutralization. Then, while continuously stirring vigorously, slowly add the pre-prepared NaOH solution dropwise using a dropping funnel. Take samples periodically and test them with precision pH paper. When the pH approaches 7, slow down the adding rate. When the pH stabilizes at around 7, stop adding. If necessary, vacuum dehydration can be performed to remove moisture and a small amount of volatile substances to obtain a product with high solids content.

[0015] Furthermore, in step S24, the mesh size of the filter is 60-100 mesh.

[0016] Furthermore, in step S3, the solvent additive is one or more of acetone, ethanol, ethylene glycol, methanol, epichlorohydrin, and bisphenol A type epoxy resin.

[0017] Furthermore, in step S4, the drying process is as follows: drying temperature 80~100℃, drying time 12~24h.

[0018] The present invention also proposes a bio-based anti-corrosion coating, which is prepared by the process described in steps S1-S3 above.

[0019] The technical solution of the present invention has the following beneficial effects: (1) Resource utilization and environmental protection: This invention is the first to use humic acid, a solid waste in HMF industrial production, as the main raw material to successfully prepare a high-value-added bio-based anti-corrosion coating, realizing the high-value utilization of industrial by-products, which is in line with the development concept of green chemistry and circular economy and solves the disposal problem.

[0020] (2) Excellent coating performance: Chemical corrosion resistance: Through copolymerization modification, humin and biomass alcohol (especially furfuryl alcohol) form a dense three-dimensional network cross-linked structure, which effectively blocks the hydrophilic groups of humin itself and significantly improves the acid resistance and water resistance of the coating. Examples show that after the metal sheet coated with this coating is immersed in 10% hydrochloric acid for one week, the base metal still maintains its original appearance, and the degree of corrosion is very light.

[0021] (3) Good adhesion and film-forming properties: Compared with the direct self-polymerization of humic acid to form a film (thick, rough, and easy to peel off), the copolymerized modified liquid has good fluidity and can form a thin, uniform, smooth, and strong dense coating, which effectively blocks the penetration of corrosive media.

[0022] (4) Heat resistance: Thermogravimetric analysis shows that the prepared coating can remain stable at close to 200℃, which has good heat resistance and broadens its application range.

[0023] (5) Wide range of applications: The coating prepared by this invention can be applied by brushing, pouring, spraying and other methods. It is suitable for a variety of materials such as metal (such as vehicle and ship hulls) and wood, and shows good application prospects, especially in the fields of car paint and ship protection.

[0024] (6) Simple process and low cost: The reaction conditions are mild, the process is simple, the raw materials are widely available and low cost, and it has good prospects for industrial application and economic benefits. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the homogeneous reactive copolymer liquid obtained after filtration in Example 2 of the present invention; Figure 2 A schematic diagram of a metal sheet coated with pure furfuryl alcohol resin; Figure 3 This is a schematic diagram of the metal sheet coating film formation according to the present invention; Figure 4 A schematic diagram showing the removal of a coated reactive copolymer liquid metal sheet after a week of immersion in an acid resistance test. Figure 5 for Figure 4 A schematic diagram of the surface of the metal sheet after the coating has been removed; Figure 6 Thermogravimetric analysis (TGA) curve of the coating prepared in this invention; Figure 7 This is a schematic diagram illustrating the effect of directly pouring and applying the dried car paint. The left image shows the paint before application, and the right image shows the paint after application. Figure 8 This is a schematic diagram showing the effect of car paint after being sprayed and left to dry overnight. The left image is before coating, and the right image is after coating. Figure 9 This diagram illustrates the effect of applying and drying car paint after adding gloss-enhancing additives. The left image shows the paint before application, and the right image shows the paint after application. Figure 10 This diagram illustrates the effect of coating and drying car paint after optimizing reaction conditions. The right image shows the paint before coating, and the left image shows the paint after coating. Figure 11 The image shows a comparison of the effect of the paint after the reaction conditions were improved and before the conditions were changed. The left image shows the effect after the reaction conditions were improved, and the right image shows the effect before the conditions were changed. Figure 12 This is a diagram illustrating the wrinkles that appear on the surface of wood after it has been coated and allowed to dry naturally. Figure 13A schematic diagram showing the smooth finish obtained by coating a wood surface and drying it in an oven. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] In this embodiment of the invention, humulin (a solid black rot produced in the industrial production of HMF by acid catalytic conversion of Zhongke Guosheng Company) is used as a raw material; furfuryl alcohol, glycerol, ethanol, acetone, p-toluenesulfonic acid (PTSA), epichlorohydrin, and bisphenol A epoxy resin (all analytical grade); 304 stainless steel sheet (50mm×50mm×1mm); car body model (ABS material); and pine wood block (50mm×50mm×10mm).

[0028] Example 1: Solid humin self-polymerizes into a film, as a comparison. First, the purchased 304 stainless steel sheet (50mm long, 50mm wide, and 1mm thick) is used as the substrate. It is then treated according to the Sa2.5 (very thorough blast cleaning) level of the steel surface treatment grades in the national standard SH / T 3022-2019 to remove oil, grease, and dirt from the surface, and to ensure that there is no scale, rust, coating, or foreign matter.

[0029] Afterwards, the solid humectant from the factory was simply crushed and transferred to a vacuum filtration flask. The solid was washed with water to obtain water-washed humectant. The water-washed humectant was then directly applied to the metal sheet to be coated and smoothed out. The sheet was then placed in an oven at 80°C and dried overnight to remove moisture, resulting in a coated metal sheet. The results showed that the coated surface was relatively thick and the particle size was obvious.

[0030] Acid resistance test: Uncoated and coated metal sheets were subjected to a one-week acid resistance test (immersion in 10% hydrochloric acid). The results showed that humulin self-polymerized into a film, which played a certain role in acid resistance. The uncoated metal sheet was corroded by acid and turned black, while the coated metal sheet showed less corrosion. This is because the adhesion between humulin and the metal sheet was not strong enough during the self-polymerization process. At the same time, the gaps in the film were relatively large, and liquid could easily enter the film interface and corrode, but to a slight degree. It was also observed that some porous structures were generated during the self-polymerization process of humulin, which may also lead to liquid ingress.

[0031] Water resistance test: The coated metal sheet was immersed in water for one week. The results showed that the water resistance of the coating formed by direct self-polymerization of humulin was poor. The film was easily peeled off in water because humulin itself carries many hydroxyl and carbonyl groups that easily react with water, resulting in poor water resistance.

[0032] Example 2: Film Formation by Introducing Solid Humin into Furfuryl Alcohol Copolymer System

[0033] The results in Example 1 show that although humin self-polymerization can form films, the film properties are poor, with insufficient acid resistance and water resistance. To address this issue, a copolymerization reaction was initiated using a solvent to modify the film and resolve the problems.

[0034] First, dried black humulin powder granules (passed through a 100-mesh sieve) and furfuryl alcohol (FA, pale yellow) were added to a three-necked flask equipped with a stirrer at a mass ratio of 1:2. During stirring, 15 wt% ethanol was added to aid dissolution. The flask was first placed in an oil bath below 40°C and stirred for 2 hours to ensure uniform mixing. The pale yellow furfuryl alcohol in the system rapidly turned black after the introduction of humulin. After uniform stirring, the oil bath temperature was raised to 55°C, and 1 wt% PTSA (based on total mass) was added. The temperature was slowly increased to avoid excessive reaction, with increments of 10°C to 110°C, which was then held for 2 hours. The viscosity of the system was monitored (increased stirring resistance and the appearance of stringing indicated that polymerization was proceeding).

[0035] Take a small amount of product and drop it onto a hot plate (150℃), record the curing time, and determine the reaction endpoint based on the curing time; or, when the viscosity reaches the target viscosity, immediately cool down to below 40℃, and neutralize the residual acid catalyst by adding 20% ​​NaOH solution until the pH reaches 7 to terminate the reaction and avoid over-reaction and gel formation. The quenched reaction viscous liquid is then rapidly filtered through 60-mesh and 100-mesh filters to remove larger unreacted particles, obtaining a homogeneous reactive copolymer liquid with a certain viscosity. Figure 1 (As shown).

[0036] A certain amount of reactive copolymer liquid and commercially available pure furfuryl alcohol resin were drop-coated onto the treated metal sheet. The coated metal sheet was then dried overnight at 80°C under ventilated conditions. Figure 2 and Figure 3 It can be observed that the pure furfuryl alcohol resin coating is transparent and pale yellow, with good film-forming properties; while the copolymer liquid coating is black. Compared with the self-polymerization film formation of humic acid, the introduction of the copolymer system results in better liquid film-forming performance, thinner film, and smoother surface.

[0037] Acid resistance test: Uncoated and coated metal sheets were subjected to an acid resistance test (immersion in 10% hydrochloric acid) for one week. After one week, the coated metal sheet was removed (e.g., Figure 4As shown), the coating layer was peeled off. The results showed that, compared to the metal sheet coated with humectant directly cured into a film, the liquid immersion color did not turn dark green. Upon removal, it was observed that the edges of the coating showed slight corrosion due to incomplete coating, but the center of the fully coated metal sheet was not corroded by acid into a black surface, instead retaining its original metallic color (as shown). Figure 5 As shown in the figure, this indicates that the copolymerized liquid coating provides acid resistance. This is because during the copolymerization process of solid humic acid, the hydroxymethyl (-CH2OH) group of FA undergoes protonation and dehydration under acid catalysis, forming a highly reactive furfural carbocation. This ion can attack the furan ring of another FA molecule, causing ring-opening polymerization and forming a linear polyfuran chain. Simultaneously, the solid humic acid is rich in aldehyde, carbonyl, and furan ring structures, which can act as a multifunctional crosslinking agent, combining with the FA polymer chain to form a three-dimensional network structure, thereby increasing the crosslinking density and rigidity, and thus improving the adhesion to the metal sheet. Furthermore, the polymerized liquid film does not form a porous structure, making it difficult for the immersion liquid to penetrate the film interface and cause corrosion.

[0038] Figure 6 The thermogravimetric curves of the obtained coatings from 40 to 800℃ were shown, and the results showed that the bio-based coatings prepared on the surface had a stability of nearly 200℃, indicating good heat resistance.

[0039] Example 3: Optimized application of humulin-furfuryl alcohol copolymer system in automotive paint

[0040] 1. Direct coating: Apply the reactive copolymer liquid from Example 2 ( Figure 1 (As shown) Try applying the paint directly to the car.

[0041] A certain mass of the reactive copolymer liquid was poured onto a purchased car body model and smoothed out. It was left to stand for 5 minutes in a ventilated area, then dried overnight in an oven at 80°C. The results showed that the directly applied paint was a matte black with a frosted surface. Figure 7 (As shown).

[0042] 2. Spraying application: Spray the reactive copolymer liquid from Example 2 onto the car paint and let it air dry.

[0043] Because the reactive copolymer liquid has a high viscosity, making it difficult to achieve the conditions required for spray gun application, a certain mass of the reactive copolymer liquid was taken and diluted with solvents such as hardener and acetone (not exceeding 30 wt% of total mass) for 30 minutes until the application viscosity was reached. Then, under ventilated conditions and with protective gear, the liquid was sprayed onto the car body surface and allowed to dry naturally overnight. The results showed that the sprayed paint was matte black with uniform particles and a frosted surface. Figure 8 (As shown).

[0044] 3. Improved gloss of automotive paint when coated with reactive copolymer liquid. To address the issue of insufficient gloss in car paint, we attempted to improve the application process (e.g., by adding a small amount of commonly used paint solvents). A certain mass of reactive copolymer liquid was taken and diluted with 20 wt% (of the total mass) of epichlorohydrin, bisphenol A type epoxy resin, and other solvents. The mixture was stirred for 30 minutes to obtain a homogeneous solution. This solution was then poured onto a purchased car body model and smoothed repeatedly. The model was left to stand for 5 minutes under ventilated conditions, and then dried overnight in an oven at 80°C. The results showed a significant improvement in the gloss of the car paint. Figure 9 (As shown).

[0045] 4. In order to reduce reaction costs, gloss can also be adjusted by optimizing the copolymerization reaction ratio, reducing the amount of catalyst, reducing the reaction time, and controlling the viscosity of the low reaction product.

[0046] The viscosity of the product was controlled by optimizing the copolymerization ratio (humulin:furfuryl alcohol = 1:3), reducing the catalyst dosage to 0.8 wt%, and shortening the reaction time to 2.5 hours. A certain mass of the optimized reaction liquid was taken and diluted with 15 wt% (percentage of total mass) of acetone / ethanol and other solvents, and stirred for 30 minutes to obtain a homogeneous solution. This solution was then poured onto a purchased car body model and smoothed multiple times. After standing for 5 minutes under ventilation, it was dried overnight in an oven at 80°C. The results showed that the gloss of the paint surface was also significantly improved. Figure 10-11 (As shown).

[0047] In conclusion, solid humic acid, through the introduction of a polymerization system, has great potential for application in fields such as automotive paint.

[0048] Example 4: Application of surface coating on wood

[0049] A certain mass of the reactive polymer liquid was poured onto two pine wood blocks and smoothed. After standing for 5 minutes in a ventilated area, one block was allowed to air dry naturally in the sun, while the other was dried overnight in an oven at 80°C. The results showed that the naturally dried paint surface had wrinkles (as shown in Figure 12). This was due to the different evaporation rates of the solvent between the inside and outside of the surface; the surface solvent evaporated quickly to form an outer film, while the internal solvent evaporated slowly, generating shrinkage stress from the inside out. In contrast, the sample dried overnight at 80°C had a smooth paint surface (as shown in Figure 13), indicating significant potential for application in the field of wood coatings.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for the resource utilization of humin, a polycondensation byproduct in HMF production, characterized in that, Including the following processes: S1: Pretreatment process of washing, drying, pulverizing and sieving humulin; S2: Introduce a copolymerization system and carry out a copolymerization reaction: Mix the humin fine powder obtained in step S1 with biomass alcohol, and carry out a heated copolymerization reaction under the action of an acid catalyst to obtain humin-biomass alcohol reaction copolymer liquid; S3: Take a certain mass of the reactive copolymer liquid, add a certain amount of solvent and additives, mix and stir to adjust the viscosity, and then obtain bio-based anti-corrosion coatings with different coating application viscosities; S4: After pre-treating and cleaning the substrates of different materials, apply the bio-based anti-corrosion coating obtained in step S3 to the surface of the pre-treated substrate, and cure it into a film after drying in an oven.

2. The method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 1, is characterized in that, Step S1 specifically includes: S11: After the solid humin is initially crushed, it is transferred to a vacuum filtration flask and washed with water to obtain water-washed humin. S12: Place the washed humectin in an oven to dry, and then pour the dried humectin into a pulverizer to pulverize it into black fine powder particles of different mesh sizes. S13: Collect the pulverized fine powder through a 100-120 mesh sieve, and continue to dry it in an oven to remove the remaining moisture; the drying temperature is 40~80℃.

3. A method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 1, characterized in that, Step S2 specifically includes the following steps: S21: Premixing: Add the pretreated humin fine powder granules and biomass alcohol to a three-necked flask equipped with a stirrer at a certain mass ratio. Place the three-necked flask in an oil bath at 25~50℃ and stir to make it evenly mixed. S22: Catalyst addition and reaction: Raise the oil bath temperature to 50℃~60℃, add a certain proportion of acid catalyst, slowly raise the temperature to 105-115℃ in a stepwise manner, keep the temperature constant for 1~2 hours, and monitor the viscosity of the system. S23: Once the reaction reaches its endpoint, immediately cool the temperature to below 40°C to temporarily terminate the reaction and prevent excessive reaction and gel formation; and terminate the reaction by neutralizing the residual acid catalyst using alkaline titration. S24: Product post-processing: The reaction slurry from step S23 is quickly filtered through a filter screen to remove larger unreacted particles, resulting in a reaction copolymer liquid with a certain viscosity.

4. A method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 3, characterized in that, In step S21, the biomass alcohol is selected from one or more of glycerol, furfuryl alcohol, sorbitol, isosorbide, bio-based ethylene glycol, and 1,3-propanediol.

5. A method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 4, characterized in that, The mass ratio of added humic acid fine powder particles to biomass alcohol is 1:(1-4).

6. A method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 3, characterized in that, In step S21, 10-20 wt% of ethanol solvent, accounting for the total mass of the reaction system, is added during stirring to aid dissolution.

7. A method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 3, characterized in that, In step S22, the acid catalyst is p-toluenesulfonic acid, and its addition amount is 0.5~2wt% of the total mass of the reaction system; in step S24, the filter mesh size is 60-100 mesh.

8. A method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 1, characterized in that, In step S3, the solvent additive is one or more of acetone, ethanol, ethylene glycol, methanol, epichlorohydrin, and bisphenol a type epoxy resin.

9. A method for resource utilization of humin, a polycondensation byproduct in HMF production, according to claim 1, characterized in that, In step S4, the drying process is as follows: drying temperature 80~100℃, drying time 12~24h.

10. A bio-based anti-corrosion coating, characterized in that, It is prepared using the process described in steps S1-S3 of claim 1.

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