A method for preparing lignin amine cationic surfactant from high-value water phase of papermaking by-product black liquor

Abstract

The present application relates to biomass high-value utilization technical field, more specifically to a kind of papermaking by-product black liquor high-value water phase preparation lignin amine cationic surfactant method, comprising the following steps: pulping black liquor is adjusted pH with acid or alkali, centrifugal to take upper clear liquid, add epoxy chloropropane, temperature is raised to certain temperature and is reacted for 30min.Then, add amine reagent and react for a certain time, after cooling, centrifugal, wash after the lower layer precipitate is dried to obtain lignin amine cationic surfactant.The present application not only can make papermaking by-product black liquor waste into treasure-high-value water phase synthesis lignin amine cationic surfactant, and the preparation process of the lignin amine cationic surfactant is simple, energy consumption is low, the whole process is green, no waste water discharge, without black liquor purification, without adding formaldehyde, also without alkali recovery;Easy to realize industrial production, with broad market prospect.

Description

Technical Field

[0001] This invention relates to the field of biomass high-value utilization technology, and more specifically to a method for preparing lignin amine cationic surfactants from the aqueous phase of black liquor produced as a byproduct of papermaking. Background Technology

[0002] Concerns about excessive greenhouse gas emissions and the depletion of fossil fuel resources have prompted a more urgent shift towards renewable and relatively clean energy sources to replace fossil fuels. Black liquor, a byproduct of alkaline pulping in pulp production, is rich in lignin and is the largest natural source of aromatic hydrocarbons such as phenolic hydroxyl groups. The composition of pulping black liquor varies greatly between different plants, depending on the cooking process and the type of wood used, but the pollution it causes is the same. Due to its high alkalinity and high COD content, pulping black liquor poses serious harm to the environment and human health. Therefore, converting pulping black liquor waste into useful products is of great significance. We know that pulping black liquor is a black, viscous liquid with a distinctive odor, rich in lignin. Lignin has a complex structure and is difficult to biodegrade, making it one of the world's major sources of pollution. Utilizing lignin-based pulping black liquor to synthesize high-value-added products is the best way to reduce pollution.

[0003] Lignin is the second most abundant renewable macromolecule on Earth after cellulose, and is considered one of the most promising organic resources among natural polymers. Lignin is abundant in plant cells and wood tissues, with its content varying depending on the plant species, accounting for 15%–30% of biomass. Strengthening research on the application of lignin is crucial and necessary, as it is significant for eliminating the pollution of the ecological environment caused by pulping and expanding the utilization of renewable resources. Lignin can be used as a raw material for benzene derivatives, benzene, and aromatic compounds, and can also serve as a surfactant, synthetic adhesive, or fuel for paper mills, offering significant economic benefits. As a biomass, lignin is widely available, inexpensive, environmentally friendly, biodegradable, and has high surface activity, making it one of the best raw materials for preparing biomass surfactants. Initially, lignin salts were used as anionic organic compounds, possessing both hydrophilic and hydrophobic components, thus exhibiting the properties of anionic surfactants. Although lignin salts possess certain surface activity, their wide molecular weight distribution, complex molecular structure, and lack of regular lipophilic and hydrophilic groups limit their surface activity and application performance at the interface between two phases. Among various surfactants, cationic surfactants possess emulsifying and bactericidal properties, as well as multifunctional applications in cosmetics and pharmaceutical formulations, making them promising candidates for future surfactant development. Therefore, it is necessary to appropriately modify lignin to meet the conditions for surface activity.

[0004] Patent CN201280066901.X provides a method for preparing lignin-amine. Kraft paper lignin or sulfate lignin is dissolved in a polar solvent (dimethylformamide, tetrahydrofuran, acetone, N-methyl-2-pyrrolidone, dimethyl sulfoxide, or methanol, etc.), and an organic amine and an acyl-containing compound are added to react and obtain lignin-amine. Patent CN201611100373.1 dissolves lignin in an alkaline solution, adds a solid alkaline catalyst and an organic amine, heats to the desired temperature, and then adds formaldehyde dropwise while maintaining the temperature to obtain lignin-amine.

[0005] Patent CN201510005045.2 discloses a method for preparing a phenolic lignin amine cationic emulsifier. First, phenol and alkali lignin are reacted under alkaline conditions to obtain phenolic lignin through phenolization modification without significantly increasing the molecular weight of the lignin. Then, the phenolic lignin is reacted with diethylenetriamine and formaldehyde under alkaline conditions to obtain a phenolic lignin amine cationic emulsifier solution. The phenolic alkali lignin amine cationic emulsifier exhibits better surface activity, higher zeta potential, and better emulsifying performance than the control sample without phenolization modification, and can be applied in fields such as asphalt emulsification.

[0006] Patent CN202010446957.4 discloses a lignin-based cationic surfactant and its preparation method, as well as a long-acting antibacterial agent and its preparation method. A tertiary amine is acidified under acidic conditions, followed by the addition of epichlorohydrin. The pH of the system is adjusted to neutral, and the reaction continues to obtain an intermediate product. Lignin is added to the intermediate product, and the pH of the solution is adjusted to alkaline to carry out a grafting reaction to obtain the lignin-based cationic surfactant. The prepared surfactant exhibits good hydrophilicity and stability.

[0007] The inventions described above all utilize pure lignin solids instead of directly using undried pulping black liquor to synthesize lignin amines; moreover, the synthesis environment is mostly organic or contains formaldehyde, and organic solvent synthesis presents difficulties in subsequent separation and recovery, while formaldehyde is an unfriendly reagent that can harm human health. Summary of the Invention

[0008] To address the above problems, this invention provides a method for high-value preparation of lignin amine cationic surfactants from black liquor produced as a byproduct of papermaking. This method can directly transform the high-pH, highly polluting pulping black liquor discharged from the papermaking industry into a valuable resource by synthesizing lignin amine cationic surfactants in an aqueous phase. The entire process is green and environmentally friendly, with no wastewater discharge, and requires no purification of the black liquor, no addition of formaldehyde, and no alkali recovery.

[0009] The present invention specifically adopts the following technical solution:

[0010] A method for preparing lignin-amine cationic surfactants from the aqueous phase of black liquor, a byproduct of papermaking, includes the following steps:

[0011] Take an appropriate amount of papermaking black liquor, adjust the pH of the pulping black liquor to a certain range with acid or alkali, centrifuge and take the supernatant, add an appropriate amount of epichlorohydrin, heat to a certain temperature and react for 30 minutes. Then add an appropriate amount of amine reagent, react for a certain time, cool, centrifuge, and dry the solid precipitate to obtain lignin amine cationic surfactant.

[0012] Furthermore, the pH of the pulping black liquor is adjusted to 8-13 using acid or alkali.

[0013] Furthermore, the amount of epichlorohydrin added is 1.0-10.0 times the amount of hydroxyl groups in the lignin of the papermaking black liquor, based on the molar ratio.

[0014] Furthermore, the reaction temperature is 40-100℃.

[0015] Furthermore, the amount of amine reagent added is 1.0-10.0 times the amount of hydroxyl groups contained in lignin in papermaking black liquor, based on the molar ratio.

[0016] Furthermore, the reaction time is 10-300 min.

[0017] Furthermore, after centrifugation and washing, the resulting lower precipitate is dried to obtain a lignin amine cationic surfactant.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) This invention can directly synthesize lignin amine cationic surfactants into high-value-added pulping black liquor with high alkalinity and high COD content discharged in the papermaking industry. There is no need to purify the black liquor, add formaldehyde, or recover alkali. The whole process is green and environmentally friendly with no wastewater discharge.

[0020] (2) The method of synthesizing lignin amine cationic surfactants in this invention is in an aqueous system rather than an organic system, which reduces production costs; the raw materials for synthesizing cationic surfactants are renewable, which effectively reduces the consumption of fossil energy and helps to achieve the goal of carbon neutrality.

[0021] (3) The lignin amine cationic surfactant synthesized in this invention can not only act as a surfactant to reduce surface tension, but also act as a curing agent for epoxy asphalt, thus having multifunctional application properties.

[0022] (4) This invention turns highly polluting pulping black liquor into valuable lignin amine cationic surfactants. The process is simple, energy consumption is low, and the production cycle is short, providing technical support for the large-scale production of lignin amine cationic surfactants. Attached Figure Description

[0023] Figure 1 This is a process route diagram for the aqueous phase synthesis of lignin amine cationic surfactants for high-value papermaking black liquor according to the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following embodiments are commercially available unless otherwise specified.

[0025] Example 1

[0026] 50 mL of pulping black liquor was taken to adjust the pH to 11, and 0.5 mL of epichlorohydrin was added. The mixture was heated to 60 °C and reacted for 30 min. Then, 0.9 mL of n-butylamine was added and reacted for 30 min. After cooling, centrifugation, washing, and drying of the lower precipitate, a lignin amine cationic surfactant was obtained. The surface tension (2.5 mg / mL) of this lignin amine cationic surfactant was 49.83 mN / m.

[0027] Example 2

[0028] 50 mL of pulping black liquor was taken to adjust the pH to 12, and 0.7 mL of epichlorohydrin was added. The mixture was heated to 50 °C and reacted for 30 min. Then, 0.7 mL of n-butylamine was added and reacted for another 30 min. After cooling, centrifugation, washing, and drying of the lower precipitate, a lignin amine cationic surfactant was obtained. The surface tension (2.5 mg / mL) of this lignin amine cationic surfactant was 48.71 mN / m.

[0029] Example 3

[0030] 50 mL of pulping black liquor was taken to adjust the pH to 10, and 0.5 mL of epichlorohydrin was added. The mixture was heated to 80 °C and reacted for 30 min. Then, 0.7 mL of n-butylamine was added and reacted for 1 h. After cooling, centrifugation, washing, and drying of the lower precipitate, a lignin amine cationic surfactant was obtained. The surface tension (2.5 mg / mL) of this lignin amine cationic surfactant was 47.45 mN / m.

[0031] Example 4

[0032] 50 mL of pulping black liquor was taken to adjust the pH to 11, and 0.9 mL of epichlorohydrin was added. The mixture was heated to 60 °C and reacted for 30 min. Then, 0.9 mL of n-butylamine was added and reacted for 2 h. After cooling, centrifugation, washing, and drying of the lower precipitate, a lignin amine cationic surfactant was obtained. The surface tension (2.5 mg / mL) of this lignin amine cationic surfactant was 46.81 mN / m.

[0033] Example 5

[0034] 50 mL of pulping black liquor was taken and the pH was adjusted to 12. 1 mL of epichlorohydrin was added, and the mixture was heated to 70 °C and reacted for 30 min. Then, 1 mL of n-butylamine was added, and the mixture was reacted for 2 h. After cooling, centrifugation, washing, and drying of the lower precipitate, a lignin amine cationic surfactant was obtained. The surface tension (2.5 mg / mL) of this lignin amine cationic surfactant was 47.47 mN / m.

[0035] As shown in Table 1, the surface tension (2.5 mg / L) of the lignin amine cationic surfactants prepared in Examples 1-5 is lower than that of deionized water and the solid after drying pulping black liquor. This indicates that lignin amine cationic surfactants with good surface activity can also be obtained from pulping black liquor in an aqueous phase under aldehyde-free conditions.

[0036] It should be noted that when numerical ranges are mentioned in the claims of this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. To avoid redundancy, the present invention describes preferred embodiments.

[0037] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0038] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0039] Table 1. Surface tension of the samples (2.5 mg / L)

[0040] sample Surface tension (mN / m) Example 1 49.83 Example 2 48.71 Example 3 47.45 Example 4 46.81 Example 5 47.47 Solids after drying of pulping black liquor 64.84

[0041] *The surface tension of deionized water is 72.81 mN / m.

Claims

1. A method for preparing lignin-amine cationic surfactants from the aqueous phase of high-value black liquor produced as a byproduct of papermaking, characterized in that, Includes the following steps: Take an appropriate amount of pulping black liquor, adjust the pH of the pulping black liquor to 8-13 with acid or alkali, centrifuge and take the supernatant, add an appropriate amount of epichlorohydrin, heat to a certain temperature and react for 30 min, then add an appropriate amount of amine reagent and react for a certain time, cool and centrifuge, and dry the solid precipitate to obtain lignin amine cationic surfactant.

2. The method for preparing lignin-amine cationic surfactants from high-value black liquor produced as a byproduct of papermaking according to claim 1, characterized in that, The acid is an inorganic acid or an organic acid, or a combination of both.

3. The method for preparing lignin-amine cationic surfactants from high-value black liquor produced as a byproduct of papermaking according to claim 1, characterized in that, The amount of epichlorohydrin added is 1.0-10.0 times the amount of hydroxyl groups in the lignin of the black liquor produced as a by-product of papermaking, based on the molar ratio.

4. The method for preparing lignin-amine cationic surfactants from high-value black liquor produced as a byproduct of papermaking according to claim 1, characterized in that, The reaction temperature is 40-100 ℃.

5. The method for preparing lignin-amine cationic surfactants from high-value black liquor produced as a byproduct of papermaking according to claim 1, characterized in that, The amount of amine reagent added is 1.0-10.0 times the hydroxyl groups contained in the lignin of the papermaking black liquor, based on the molar ratio; the amine reagent is one or a combination of n-butylamine, n-propylamine, and cashew phenol-modified amine.

6. The method for preparing lignin-amine cationic surfactants from high-value black liquor produced as a byproduct of papermaking according to claim 1, characterized in that, The reaction time after adding amine reagents is 10-300 min.

7. The method for preparing lignin-amine cationic surfactants from high-value black liquor produced as a byproduct of papermaking according to claim 1, characterized in that, After centrifugation and washing, the resulting lower precipitate was dried to obtain a lignin amine cationic surfactant.

8. The application of the lignin amine cationic surfactant according to any one of claims 1-7, characterized in that, The lignin amine cationic surfactant described herein is used in the fields of textile softeners, antistatic agents, oil emulsifiers, bactericides, and disinfectants.

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