Preparation method of lignin-based potassium fulvate
The preparation of lignin-based potassium humate by a one-pot method using potassium hydroxide/sulfate/paraformaldehyde under mild conditions solves the problems of low conversion efficiency and pollution in existing technologies, achieving efficient and environmentally friendly preparation of potassium humate with superior performance compared to traditional coal-based products.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-02
- Publication Date
- 2026-03-31
AI Technical Summary
Existing methods for synthesizing fulvic acid suffer from problems such as low conversion efficiency, low fulvic acid content, harsh process conditions, high energy consumption, easy generation of secondary pollution, and poor product stability, making it difficult to meet the requirements of industrial production and agricultural applications.
Using lignin as raw material, potassium humate was prepared by heating and reacting in a closed environment at 100℃~140℃ using a one-pot method of potassium hydroxide/sulfate/paraformaldehyde, adjusting the pH value to 4~7, and then drying.
It achieves efficient and targeted conversion into highly active potassium humate, with key quality indicators meeting the HG/T 5334-2018 standard. The process is green, reducing energy consumption and emissions of waste gas, wastewater, and solid waste. Its performance is comparable to or even better than that of traditional high-end coal-based products.
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Figure CN121758769A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing potassium humate. Background Technology
[0002] Humic acids (including fulvic acid) are an important component of soil organic matter. Due to their multiple benefits, such as improving soil structure, enhancing crop resistance, promoting nutrient absorption, and stimulating plant growth, they are widely used in green agriculture and ecological restoration. Among them, potassium fulvate, with its small molecular weight, good water solubility, high physiological activity, and ease of absorption and utilization by plants, has become a high-end product among humic acid fertilizers and regulators.
[0003] Currently, commercially available potassium humate is mainly extracted and processed from non-renewable coal resources (such as weathered coal and lignite). However, the mining and utilization of coal resources face significant challenges, including dwindling resources, significant environmental pressure during mining, complex extraction processes that are prone to pollution, and product quality that fluctuates considerably depending on the coal source. This not only limits the sustainable development of the potassium humate industry but also contradicts the global advocacy of a green, low-carbon, and circular economy.
[0004] On the other hand, lignin is the second most abundant renewable aromatic polymer in nature after cellulose. It mainly originates from black liquor from the paper industry and biorefining residues, resulting in huge annual production but low utilization rates. Most of it is incinerated or discarded, causing resource waste and environmental pollution. Lignin possesses aromatic structural units similar to fulvic acid, theoretically possessing the potential to be converted into high-value fulvic acid-like substances. However, natural lignin has a complex structure, large molecular weight, poor solubility, and uneven reactivity, making its direct, efficient, and targeted conversion into highly bioactive potassium fulvate a significant technological challenge.
[0005] Li et al. (H. Li, Q. Zeng, J. Zhu, Y. Zhu and Y. Xu, Integrated production of humic-like acid, fulvic-like acid, and fermentable sugars from industrial xylooligosaccharides manufacturing waste residues via hydrothermal pretreatment, Ind. Crop. Prod., 2023, 205, 117514.) found that the humic acid content of xylooligosaccharides residue after hydrothermal pretreatment reached 9.6 g / L. Pan et al. (S. Pan, Z. Zhang, Z. Liu, L. Wu, Q. Gao and H. Cai, The combination of hydrothermal humification and biological fermentation converts straw lignocellulose into artificial fulvic acid, Int. J. Biol. Macromol., 2025, 314, 144359) found that even with a combination of hydrothermal humification and biological fermentation under low alkaline conditions, the yield of rice straw converted into fulvic acid was only around 39%. Cai et al. (D. Cai, Y. Lu, Y. Zhu, D. Wang, J. Shi, L. Liu, J. Li, X. Zhan, W. Zhang and H. Xu, Inducing hour-level humification of Enteromorpha prolifera to fabricate fulvic-like acidfertilizer with Fenton's reagent, Nat. Commun., 2025, 16, 5860.) achieved a fulvic acid yield of 25.5 ± 4.3 wt% by inducing hour-level humification of Enteromorpha prolifera with the addition of FeSO4·7H2O and H2O2. Although the above-mentioned hydrothermal treatment as a means of humification can improve the utilization rate of biomass waste, temperature has a great influence on the efficiency of humification reaction, and excessively high temperatures will increase the environmental burden; in addition, from the perspective of raw materials, the yield of fulvic acid is generally low; and the oxidation of biomass raw materials using Fenton's reagent has the drawback of over-oxidation, which is very easy to over-oxidize into carbon dioxide.Therefore, existing methods for synthesizing fulvic acid suffer from problems such as low conversion efficiency, low content of active ingredients (small molecule fulvic acid) in the product, harsh process conditions, high energy consumption, easy generation of secondary pollution, and poor product stability, making it difficult to meet the requirements of industrial production and agricultural applications. Summary of the Invention
[0006] This invention aims to address the problems of low conversion efficiency, low fulvic acid content, harsh process conditions, high energy consumption, easy secondary pollution, and poor product stability in existing fulvic acid synthesis methods, and provides a method for preparing lignin-based potassium fulvicate.
[0007] A method for preparing lignin-based potassium humate, comprising the following steps:
[0008] Lignin was added to a mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde, and heated in a closed environment at 100℃~140℃. After the reaction was completed, the mixture was cooled and the pH was adjusted to 4~7. Finally, it was dried to obtain potassium lignin-based humate.
[0009] The beneficial effects of this invention are:
[0010] This invention uses lignin as raw material and employs a one-pot method of potassium hydroxide / sulfate / paraformaldehyde to efficiently and directionally convert it into highly active potassium humate using hydrothermal humification technology. This achieves efficient humification of lignin (including industrial grade, enzymatic grade, and organic solvent grade) extracted from various biomass raw materials (such as poplar, fir, eucalyptus, straw, or bamboo), converting it into high-value potassium humate products. Moreover, the key quality indicators of the obtained lignin-based potassium humate (fulvic acid content, potassium oxide content, water-insoluble matter, moisture content, and pH value) all meet and comply with the requirements of the HG / T 5334-2018 standard.
[0011] (1) Abandoning the traditional path of relying on non-renewable coal resources, it innovatively utilizes lignin (such as black liquor from papermaking and biomass refining residue), which has huge reserves, is renewable and often discarded, as the core raw material, realizing the transformation of agricultural and forestry waste into high value-added products, with significant cutting-edge nature and environmental benefits.
[0012] (2) Based on the core technologies of mild directional catalysis and precise molecular regulation, a process system for efficiently depolymerizing lignin ether bonds and carbon-carbon bond networks has been successfully developed, realizing the controllable conversion of lignin into small molecule fulvic acid, and significantly increasing the proportion of low molecular weight (<1000Da) high-activity component fulvic acid in the lignin humification process.
[0013] (3) The key quality indicators of the lignin-based potassium humate (humic acid content, potassium oxide content, water-insoluble matter, moisture content and pH value) all meet and comply with the requirements of HG / T 5334-2018 standard; and the process is green and carried out under mild conditions (such as normal pressure, medium and low temperature, and avoidance of strong acids and alkalis), which significantly reduces energy consumption and emissions of waste, and greatly improves production safety.
[0014] (4) The prepared lignin-based potassium humate not only has good water solubility and high physiological activity (stimulates plant growth, enhances stress resistance, and has a strong ability to chelate trace elements), but its molecular structure characteristics (such as small molecular weight and high functional group density) make its performance comparable to or even better than traditional coal-based high-end potassium humate products in terms of soil improvement, nutrient efficiency enhancement and leaf absorption. Attached Figure Description
[0015] Figure 1 A schematic diagram illustrating the route and application of potassium humate prepared by lignin humification according to the present invention.
[0016] Figure 2 The image shows the physical sample of potassium lignin-based humate prepared in Example 3, along with its three-dimensional fluorescence spectrum (3DEEM).
[0017] Figure 3 The XPS spectral structural characteristics of the organic solvent lignin and the prepared lignin-based potassium humate described in Example 3 are shown in Figure 3. a and c are organic solvent lignin, and b and d are lignin-based potassium humate. Detailed Implementation
[0018] Specific implementation method one, combined with Figure 1 Detailed explanation: This embodiment describes a method for preparing potassium lignin-based humate, which is carried out according to the following steps:
[0019] Lignin was added to a mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde, and heated in a closed environment at 100℃~140℃. After the reaction was completed, the mixture was cooled and the pH was adjusted to 4~7. Finally, it was dried to obtain potassium lignin-based humate.
[0020] The closed environment described in this specific embodiment is a closed reaction vessel with a certain pressure resistance, such as a hydrothermal reactor.
[0021] The beneficial effects of this embodiment are:
[0022] This embodiment uses lignin as raw material and employs a one-pot method of potassium hydroxide / sulfate / paraformaldehyde to efficiently and directionally convert it into highly active potassium fulvate using hydrothermal humification technology. This achieves efficient humification of lignin (including industrial grade, enzymatic grade, and organic solvent grade) extracted from various biomass raw materials (such as poplar, fir, eucalyptus, straw, or bamboo), converting it into high-value potassium fulvate products. Moreover, the key quality indicators of the lignin-based potassium fulvate (fulvic acid content, potassium oxide content, water-insoluble matter, moisture content, and pH value) all meet and comply with the requirements of the HG / T 5334-2018 standard.
[0023] (1) Abandoning the traditional path of relying on non-renewable coal resources, it innovatively utilizes lignin (such as black liquor from papermaking and biomass refining residue), which has huge reserves, is renewable and often discarded, as the core raw material, realizing the transformation of agricultural and forestry waste into high value-added products, with significant cutting-edge nature and environmental benefits.
[0024] (2) Based on the core technologies of mild directional catalysis and precise molecular regulation, a process system for efficiently depolymerizing lignin ether bonds and carbon-carbon bond networks has been successfully developed, realizing the controllable conversion of lignin into small molecule fulvic acid, and significantly increasing the proportion of low molecular weight (<1000Da) high-activity component fulvic acid in the lignin humification process.
[0025] (3) The key quality indicators of the lignin-based potassium humate (humic acid content, potassium oxide content, water-insoluble matter, moisture content and pH value) all meet and comply with the requirements of HG / T 5334-2018 standard; and the process is green and carried out under mild conditions (such as normal pressure, medium and low temperature, and avoidance of strong acids and alkalis), which significantly reduces energy consumption and emissions of waste, and greatly improves production safety.
[0026] (4) The prepared lignin-based potassium humate not only has good water solubility and high physiological activity (stimulates plant growth, enhances stress resistance, and has a strong ability to chelate trace elements), but its molecular structure characteristics (such as small molecular weight and high functional group density) make its performance comparable to or even better than traditional coal-based high-end potassium humate products in terms of soil improvement, nutrient efficiency enhancement and leaf absorption.
[0027] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass percentage of potassium hydroxide in the mixed aqueous solution containing potassium hydroxide, sulfate, and paraformaldehyde is 9%~12%, the mass percentage of sulfate is 5%~8%, and the mass percentage of paraformaldehyde is 2%~4%. Everything else is the same as in Specific Implementation Method One.
[0028] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the mass ratio of the lignin to the mixed aqueous solution containing potassium hydroxide, sulfate, and paraformaldehyde is 1:(4~6). Everything else is the same as in Specific Implementation Method One or Two.
[0029] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the sulfate mentioned is one or a combination of several of sodium sulfite, sodium metabisulfite, and sodium persulfate. Everything else is the same as in Specific Implementation Method Three.
[0030] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the reaction is carried out in a closed environment at a temperature of 100℃~140℃ for 2 hours. Everything else is the same as Specific Implementation Methods One to Four.
[0031] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the reaction is carried out in a closed environment at 140°C for 1 to 4 hours. Everything else is the same as Specific Implementation Methods One to Five.
[0032] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the lignin mentioned is industrial lignin, organic solvent lignin, or enzymatically hydrolyzed lignin. Everything else is the same as in Specific Implementation Methods One to Six.
[0033] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the lignin is derived from fir, eucalyptus, poplar, straw, or bamboo. Otherwise, it is the same as Specific Implementation Methods One to Seven.
[0034] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that it uses sulfuric acid with a mass percentage of 70% to 98% to adjust the pH value to 4 to 7. Everything else is the same as Specific Implementation Methods One to Eight.
[0035] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the drying process is specifically carried out at a temperature of 40℃ to 60℃ for 4 to 6 hours. Everything else is the same as in Specific Implementation Methods One to Nine.
[0036] The beneficial effects of the present invention are verified using the following embodiments:
[0037] Example 1:
[0038] A method for preparing lignin-based potassium humate, comprising the following steps:
[0039] Lignin was added to a mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde, and the reaction was carried out in a closed environment at 140°C for 2 hours. After the reaction was completed, the mixture was cooled and the pH was adjusted to 5 with 72% sulfuric acid. Finally, the mixture was dried at 60°C for 4 hours to obtain potassium lignin-based humate.
[0040] The mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde has a mass percentage of 11.5% for potassium hydroxide, 6.75% for sulfate and 2.7% for paraformaldehyde.
[0041] The mass ratio of the lignin to the mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde is 1:4.
[0042] The sulfate mentioned is sodium sulfite.
[0043] The lignin mentioned is sulfate lignin (derived from eucalyptus).
[0044] Example 2: This example differs from Example 1 in that the lignin used is sulfate lignin (derived from cedar). Everything else is the same as in Example 1.
[0045] Example 3: This example differs from Example 1 in that the lignin is an organic solvent lignin (derived from poplar); and the sulfate is sodium metabisulfite. Everything else is the same as in Example 1.
[0046] Comparative Experiment 1:
[0047] Lignin was added to an aqueous solution of potassium hydroxide and heated in a closed environment at 140°C for 2 hours. After the reaction was completed, the solution was cooled and the pH was adjusted to 5 using 72% sulfuric acid. Finally, the solution was dried at 60°C for 4 hours to obtain potassium lignin-based humate.
[0048] The aqueous solution of potassium hydroxide contains 11.5% potassium hydroxide by mass.
[0049] The mass ratio of lignin to potassium hydroxide aqueous solution is 1:4.
[0050] The lignin mentioned is organic solvent lignin (derived from poplar).
[0051] Comparative Experiment 2:
[0052] Lignin was added to a mixed aqueous solution containing potassium hydroxide and paraformaldehyde. The mixture was heated and stirred for 2 hours in a closed environment at 140°C. After the reaction was completed, the mixture was cooled and the pH was adjusted to 5 using 72% sulfuric acid. Finally, the mixture was dried at 60°C for 4 hours to obtain potassium lignin-based humate.
[0053] The mass percentage of potassium hydroxide in the mixed aqueous solution containing potassium hydroxide and paraformaldehyde is 11.5%, and the mass percentage of paraformaldehyde is 2.7%.
[0054] The mass ratio of the lignin to the mixed aqueous solution containing potassium hydroxide and paraformaldehyde is 1:4.
[0055] The lignin mentioned is organic solvent lignin (derived from poplar).
[0056] Comparative Experiment 3:
[0057] Lignin was added to a mixed aqueous solution containing potassium hydroxide and sulfate. The mixture was heated and stirred for 2 hours in a closed environment at 140°C. After the reaction was completed, the mixture was cooled and the pH was adjusted to 5 using 72% sulfuric acid. Finally, the mixture was dried at 60°C for 4 hours to obtain potassium lignin-based humate.
[0058] The mass percentage of potassium hydroxide in the mixed aqueous solution containing potassium hydroxide and sulfate is 11.5%, and the mass percentage of sulfate is 6.75%.
[0059] The mass ratio of the lignin to the mixed aqueous solution containing potassium hydroxide and sulfate is 1:4.
[0060] The sulfate mentioned is sodium metabisulfite.
[0061] The lignin mentioned is organic solvent lignin (derived from poplar).
[0062] The lignin-based potassium humate prepared in Examples 1 to 3 and Comparative Experiments 1 to 3 were tested for humic acid content, potassium oxide content, water-insoluble matter content, moisture content, and pH value according to the methods specified in HG / T5334-2018. Qualitative characterization was performed using three-dimensional fluorescence spectroscopy (3D EEM) and X-ray photoelectron spectroscopy (XPS).
[0063] Table 1. Compliance Analysis of Product Quality Indicators Based on HG / T 5334-2018 Standard
[0064]
[0065] Table 2. Role of each reagent in the hydrothermal humification reaction (taking organic solvent lignin as an example)
[0066]
[0067] By systematically comparing various additives in the humification process, it was confirmed that the synergistic effect of potassium hydroxide, paraformaldehyde and sulfate can not only efficiently and directionally convert fulvic acid, but also that the product is comparable to mineral-derived potassium fulvicate in key indicators.
[0068] Figure 2 The image shows the physical sample of potassium fulvicate prepared in Example 3 and its three-dimensional fluorescence spectrum (3DEEM). As can be seen from the image, the fluorescence peaks of potassium fulvicate are all located in the range of λEx / Em = 210-380 / 330-550 nm, which is consistent with the typical characteristic range of fulvic acid. Moreover, potassium fulvicate has a flaky appearance, so the humification product can be identified as potassium fulvicate.
[0069] Figure 3 The XPS spectral structural characteristics of the organic solvent lignin and the prepared lignin-based potassium humate described in Example 3 are shown in Figures a and c, where lignin is the organic solvent and potassium humate is the lignin-based potassium humate. Compared with organic solvent lignin, the newly added OC=O characteristic peak in the C 1s spectrum and the obvious carboxyl oxygen (C=O) characteristic peak in the O 1s spectrum of potassium humate confirm that lignin successfully generates fulvic acid containing the characteristic structure during the humification process.
Claims
1. A method for preparing potassium lignin-based humate, characterized in that... It is done in the following steps: Lignin was added to a mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde, and heated in a closed environment at 100℃~140℃. After the reaction was completed, the mixture was cooled and the pH was adjusted to 4~7. Finally, it was dried to obtain potassium lignin-based humate.
2. The method for preparing lignin-based potassium humate according to claim 1, characterized in that... The mass percentage of potassium hydroxide in the mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde is 9%~12%, the mass percentage of sulfate is 5%~8%, and the mass percentage of paraformaldehyde is 2%~4%.
3. The method for preparing potassium lignin-based humate according to claim 1, characterized in that... The mass ratio of the lignin to the mixed aqueous solution containing potassium hydroxide, sulfate and paraformaldehyde is 1:(4~6).
4. The method for preparing lignin-based potassium humate according to claim 1, characterized in that... The sulfate is one or a combination of sodium sulfite, sodium metabisulfite and sodium persulfate.
5. The method for preparing lignin-based potassium humate according to claim 1, characterized in that... The reaction was carried out in a closed environment at a temperature of 100℃~140℃ for 2 hours.
6. The method for preparing potassium lignin-based humate according to claim 1, characterized in that... The reaction is carried out in a closed environment at 140℃ for 1 to 4 hours.
7. The method for preparing potassium lignin-based humate according to claim 1, characterized in that... The lignin mentioned is industrial lignin, organic solvent lignin, and enzymatically hydrolyzed lignin.
8. The method for preparing potassium lignin-based humate according to claim 1, characterized in that... The lignin is derived from fir, eucalyptus, poplar, straw, or bamboo.
9. The method for preparing potassium lignin-based humate according to claim 1, characterized in that... The pH value is adjusted to 4-7 using sulfuric acid with a mass percentage of 70%-98%.
10. The method for preparing potassium lignin-based humate according to claim 1, characterized in that... The drying process specifically involves drying at a temperature of 40℃ to 60℃ for 4 to 6 hours.