Bio-based surfactants and antioxidants

Abstract

The present invention relates to a compound of formula (I) JPEG2025531345000012.jpg51144, wherein R1 is hydrogen or —OCH3, R2 is linear or branched C1-C4 alkyl or linear or branched C1-C4 hydroxyalkyl, and R3 is hydrogen or Na, and the method comprises at least the following steps: a) providing a mixture containing lignin fragments; b) separating the mixture of step a) into a lignin oligomer-enriched fraction and a lignin monomer-enriched fraction; c) separating the solution comprising the compound according to formula (I), wherein R3 is hydrogen, from the lignin monomer enriched fraction of step b) by fractional distillation; d) adding an aqueous NaOH solution having a pH of 11 or greater to the solution of step c) comprising the compound according to formula (I), wherein R3 is a cation; e) isolating the precipitated compound of step d); optionally thereafter; f) dissolving the isolated compound of step e) in water and lowering the pH of the aqueous solution using an acid to a value below pH 10; g) isolating the compound according to formula (I), wherein R3 is hydrogen, from the solution of step f).

Description

[Technical Field]

[0001] The present invention relates to methods for isolating compounds from lignin compositions and their use as bio-based surfactants, antioxidants, UV light absorbers and stabilizers. [Background technology]

[0002] Surfactants, antioxidants, and stabilizers are a class of chemicals used in a wide range of applications in the home care, personal care, and agrochemical industries, food, medical, and health sectors, and in the formulation of materials such as polymer materials, fuels, engine oils, paints, inks, adhesives, and waxes. Given their diverse markets and significant demand, it is highly desirable for their production to be sourced from short-lived renewable feedstocks (especially for surfactants) to minimize global environmental concerns, rather than relying solely on fossil-based sources. Natural antioxidants and bio-based surfactants are commercially available. While the performance of these chemicals rivals or surpasses fossil-based benchmarks, their production often requires the use of food or virgin feedstocks (e.g., fruit or tropical plant fatty acids), which still poses environmental pressures due to inefficient extraction procedures and deforestation issues.

[0003] WO2018 / 134427A1 discloses the synthesis of alternative bisphenols using 4-alkylphenol derivatives (e.g., 2-methoxy-4-n-propylphenol and 2,6-dimethoxy-4-n-propylphenol), which are obtained by depolymerizing lignin encapsulated in lignocellulosic biomass.

[0004] US 2,888,503 A discloses the use of 2,6-dimethoxy-4-propylphenol as an antioxidant in light-colored rubber for stabilization against degradation by ozone.

[0005] Ren et al. (Green Chemistry 2022) disclose a method for the isolation of 4-propylsyringol and 4-propylguaiacol by extracting a monomer-enriched oil from lignin oil with a 0.3–0.1 mol / L KOH solution. In a second step, the extraction solution was rotary evaporated to partially remove water, increasing the KOH concentration to above 0.5 mL / L. The KOH solution was cooled to precipitate crystals. Furthermore, Ren et al. disclose in silico experiments that distillation of gas streams of 4-propylsyringol-enriched and 4-propylguaiacol-enriched solutions using two distillation units yielded 4-propylsyringol with 98.4% purity and 94.5% recovery, while all 4-propylguaiacol was recovered with a purity of 67.3%. Actual distillation experiments were not disclosed due to the difficulty of preparing sufficient feedstock for distillation. Ren et al. also disclose that NaOH solution is not suitable for purifying 4-propylsyringol by isolating the sodium salt of 4-propylsyringol. Summary of the Invention

[0006] It is therefore an object of the present invention to provide a method for isolating bio-based compounds with surfactant, antioxidant, UV light absorbing and stabilizing properties in several steps directly from sustainable sources. [Brief explanation of the drawings]

[0007] [Figure 1] NMR analysis of 4-propylsyringol sodium salt. [Figure 2] Scale-up data for pH-driven precipitation of 4-propylsyringol salts is presented. [Figure 3] 1 shows the results of testing 4-propylsyringol as an antioxidant. [Figure 4] 1 shows the results of testing 4-propylsyringol as an antioxidant. [Figure 5] 1 shows the test results of 4-propylsyringol as a surfactant. DETAILED DESCRIPTION OF THE INVENTION

[0008] This problem is solved by a method according to claim 1. Further preferred embodiments are the subject matter of the dependent claims.

[0009] The present invention relates to a compound represented by general formula (I) [ka] from a mixture containing lignin fragments, wherein R1 is hydrogen or -OCH3; R2 is a linear or branched C1-C4 alkyl or a linear or branched C1-C4 hydroxyalkyl; R3 is hydrogen or Na.

[0010] The method includes at least a first step of providing a mixture containing lignin fragments. In the context of the present invention, the term "mixture" can also be understood as a solution or a composition. Second, the mixture from the first step is separated into a lignin oligomer-enriched fraction and a lignin monomer-enriched fraction. Third, a solution containing a compound according to formula (I) in which R3 is hydrogen is separated from the lignin monomer-enriched fraction from the second step. Fourth, an aqueous NaOH solution having a pH of 11 or higher is added to the solution from the third step to initiate precipitation of the compound according to formula (I). After precipitation, the solution contains a compound according to formula (I) in which R3 is a cation. In a fifth step, the precipitated compound from the fourth step is isolated.

[0011] The method according to the present invention comprises the following optional steps 6 and 7. In the sixth step, the compound isolated in the fifth step is dissolved in water and the pH of the aqueous solution is reduced to a value below pH 10 using an acid. In the seventh step, the compound according to formula (I) in which R3 is hydrogen is isolated from the solution of step 6.

[0012] Preferably, the composition containing lignin fragments is obtained by reductive depolymerization of lignin.

[0013] In a preferred embodiment of the present invention, the lignin oligomer-enriched fraction and the lignin monomer-enriched fraction are separated in a second step by either distillation, at least one membrane, or liquid-liquid extraction using a low-polarity solvent such as diethyl ether. In distillation, light lignin fragments and other small fragments are evaporated from solution, and the remaining fraction is recovered as a powder containing heavier lignin fragments (e.g., lignin dimers and oligomers). In membrane separation, small lignin fragments and other small mixture components are ultrafiltered from large lignin fragments by size exclusion, which is enriched in lignin oligomers. In liquid-liquid extraction, the light phase containing lignin monomers and other small fragments is solubilized, and the remaining fraction is enriched in heavier fragments such as lignin oligomers.

[0014] The isolation of the compound of formula (I) in the third step is carried out by fractional distillation, in which the evaporation selectivity is driven by changes in pressure and / or temperature in a column consisting of stripping and / or rectification sections.

[0015] Preferably, the NaOH solution of the fourth step containing the compound according to formula (I) has a pH of 12-13.

[0016] In the fifth step, an emulsion is preferably formed when the pH is lowered. Preferably, the heavier phase of the emulsion contains lignin monomers which can be separated by decantation or centrifugation.

[0017] Surprisingly, it has been found that the method for isolating substituted guaiacol and / or syringol of formula (I) results in the production of these compounds in high yields, despite the use of fractional distillation to separate the compound of formula (I) from the lignin monomer-enriched fraction and the use of NaOH solution for precipitation. The method according to the present invention is easy to handle and control, allowing for industrial scale-up to produce inexpensive, high-quality compounds. Furthermore, the method according to the present invention allows for the continuous production of the compounds to be isolated. A further advantage is that the mixture containing the isolated compound in the method according to the present invention does not contain sugars, which greatly facilitates further processing and avoids the formation of humins and other degradation products.

[0018] In a preferred embodiment of the invention, R1 is hydrogen.

[0019] In another preferred embodiment of the present invention, R1 is -OCH3.

[0020] Preferably, R2 is selected from the group consisting of -(CH2)2-CH3, -(CH2)-CH3, -CH3 and -(CH2)3-OH.

[0021] In a preferred embodiment of the invention, the compound of formula (I) is selected from the group consisting of: [ka] [ka]

[0022] In a preferred embodiment of the present invention, the concentration of NaOH in the alkaline aqueous solution is 0.1 to 4 mol / L.

[0023] Preferably, the precipitation is carried out at room temperature.

[0024] In a preferred embodiment of the present invention, the method comprises the following steps 6 and 7. In the sixth step, the compound isolated in the fifth step is dissolved in water, and the pH of the aqueous solution is reduced to a value below pH 11 using an acid. In the seventh step, the compound of formula (I) in which R3 is hydrogen is isolated from the solution of step 6.

[0025] 10. The method according to claim 9, wherein in step f), the pH is adjusted to 4 to 7.

[0026] 11. The method according to claim 9 or 10, wherein in step f) the acid is HCl, p-TSA, acetic acid, H3PO4 or H2SO4.

[0027] The present invention also includes compositions comprising compounds according to formula (I) above.

[0028] The present invention also encompasses the use of the above compositions as surfactants, antioxidants, UV light absorbers or stabilizers.

[0029] Preferably, the composition comprises 4-propylsyringol as a surfactant, UV light absorber or stabilizer.

[0030] Preferably, the composition comprises a 4-propylsyringol salt as a surfactant, antioxidant, UV light absorber or stabilizer.

[0031] A preferred embodiment of the present invention is the use of 4-propylsyringol or 4-propylsyringol salts as UV light absorbers, for example for coatings in sunglasses, or as ingredients in sun creams.

[0032] Another preferred embodiment of the present invention is the use of 4-propylsyringol or a 4-propylsyringol salt as a stabilizer for emulsion stability. These compounds, similar to surfactants, have applications in minimizing the coalescence of colliding droplets, for example, in active pharmaceutical ingredients, foods such as ice cream or milk, and cosmetics.

[0033] The present invention also encompasses the use of 4-propylsyringol as a non-ionic surfactant.

[0034] The present invention further includes the use of 4-propylsyringol salts as ionic surfactants.

[0035] The present invention further encompasses the use of 4-propylsyringol and / or 4-propylsyringol salts as surfactants.

[0036] Preferably, 4-propyl syringol and 4-propyl syringol salts are used as surfactants in the baking industry, pulp and paper processing, pesticide formulations, fire fighting applications, pipelines, personal care products, cleaning products, petrochemical products, toothpaste, detergents, cosmetics, paints, adhesives, inks, waxes, laxatives and pharmaceutical products such as foods.

[0037] The present invention also encompasses the use of 4-propylguaiacol, 4-propanol syringol, 4-propanol guaiaol and combinations thereof as antioxidants.

[0038] The present invention also encompasses the use of 4-propylguaiacol, 4-propylsyringol and combinations thereof as UV light absorbers.

[0039] The present invention also encompasses the use of 4-propylguaiacol, 4-propylsyringol and combinations thereof as stabilizers.

[0040] The present invention also encompasses compositions comprising at least the surfactant components 4-propylsyringol and 4-propylsyringol salts.

[0041] The present invention also encompasses compositions comprising at least the surfactant components 4-propanol syringol and 4-propanol guaiacol. [Example]

[0042] Separation of lignin monomers and lignin oligomers from lignin oil The apparatus consists of two flasks (lignin mixture container and fraction collector) connected by a glass bridge. The collector is connected to a vacuum line and cooled using liquid nitrogen. After assembling the apparatus, the system is evacuated and the lignin mixture flask is heated to the desired temperature depending on the number of fractions to be collected and stirred using a stirring heating plate. Each fraction is collected after the other by changing the vacuum and temperature (fraction 0 at 50 °C and 0.7 mbar; fraction 1 at 210 °C starting at 50 °C and 0.2 mbar with a ramp of 1 °C / min). After all volatiles are removed, the heavier lignin fragments (fraction oligomers) are collected after cooling to room temperature. [Table 1] [Table 2]

[0043] Purification by fractional distillation The apparatus for fractional distillation consists of two flasks (a lignin mixture container and a fraction collector), a Vigreux column, and a glass bridge. The mixture container is connected to the Vigreux column, which is in turn connected to a glass bridge with a collector at the other end. The collector is connected to a vacuum line and cooled using liquid nitrogen. After assembling the apparatus, the system is evacuated and the lignin mixture is heated and stirred using a stirring heating plate. Each fraction is collected after the other by changing the vacuum and temperature (F0 at 135°C and 1.0 mbar; F1 at 145°C and 0.7 mbar; F2 at 150°C and 0.6 mbar; F3 at 155°C and 0.4 mbar; Fr is the residue from the distillation after collection of F3). [Table 3]

[0044] Purification by pH-driven precipitation The apparatus consists of a dropping funnel, one flask equipped with a magnetic stir bar, a stir plate, a Buchner filter, and an Erlenmeyer flask equipped with a vacuum connection. While stirring, the base solution is added dropwise to the lignin monomer mixture. The precipitate is then filtered and dried in a vacuum oven at 50°C and 100 mbar. Optionally, remaining monomers in the aqueous phase can be neutralized and extracted with ethyl acetate or hexane to recover other monomers. [Table 4]

[0045] NMR analysis of solids obtained by pH-driven precipitation using 1M NaOH and ddH2O as solvents 4-Propylsyringol sodium salt (Ib) 1H NMR(400MHz,D2O)δ6.48(s,1H),3.68(s,3H),2.39(t,J=7.6Hz,1H),1.50(h,J=7.4Hz,1H),0.82(t,J=7.4Hz,2H)

[0046] Scale-up data for pH-driven precipitation of 4-propylsyringol salts The apparatus consists of a dropping funnel, one flask equipped with a magnetic stir bar, a stir plate, a Buchner filter, and a conical flask equipped with a vacuum connection. While stirring, the base solution is added dropwise to the lignin monomer mixture. The precipitate is then filtered and dried in a vacuum oven at 50°C and 100 mbar. Optionally, remaining monomers in the aqueous phase can be neutralized and extracted with ethyl acetate or hexane to recover other monomers. [Table 5]

[0047] Testing 4-propylsyringol as an antioxidant Antioxidant activity was assessed by measuring the capacity of compounds to react with free radicals (herein 2,2-diphenyl-1-picrylhydrazyl, also known as DPPH). Measurements were based on the color difference of DPPH in solution upon addition of antioxidants at different compound compositions, measured by UV / visible spectrophotometry within the 400-700 nm range (517 nm being the preferred wavelength). Butylated hydroxytoluene (BHT) and vitamin E were used as rejection substances (positive controls), and glycerol was used as a negative control (see Figures 3 and 4). At a concentration of 5 μg / mL, 4-propylsyringol had a 65% inhibition rate, while BHT and vitamin E had 32% and 28%, respectively. At a concentration of 10 μg / mL, 4-propylsyringol had an 84% inhibition rate, while BHT and vitamin E had 54% and 61%, respectively. Only at a high concentration of 50 μg / mL, 4-propylsyringol, BHT, and vitamin E had similar inhibition rates of 85%, 85%, and 84%, respectively (Figure 3), clearly demonstrating the excellent activity of 4-propylsyringol as an antioxidant.

[0048] Testing 4-propylsyringol as a surfactant Surface tension measurements were performed using the pendant drop method with a Kruess EasyDrop Standard drop shape analysis system. Measurements were performed at the water / air interface to determine the surface tension of different compounds at application-relevant concentrations (0.1-1.0 wt%). [Table 6]

Claims

1. Formula (I) 【Chemical 1】 1. A method for isolating a substituted guaiacol and / or a substituted syringol from a mixture containing lignin fragments, comprising the steps of: R １ is hydrogen or —OCH ３ and R ２ is a linear or branched C １ ~C ４ Alkyl or linear or branched C １ ~C ４ is a hydroxyalkyl, R ３ is hydrogen or Na, At least the following steps: a) providing a mixture containing lignin fragments; b) separating the mixture of step a) into a lignin oligomer-enriched fraction and a lignin monomer-enriched fraction; c) R ３ separating the solution comprising the compound according to formula (I), wherein is hydrogen, from the lignin monomer enriched fraction of step b) by fractional distillation; d) R ３ adding aqueous NaOH to the solution of step c) comprising the compound according to formula (I), wherein is Na, to obtain a pH of at least 11; e) isolating the precipitated compound of step d); Including, Optionally thereafter; f) dissolving the isolated compound of step e) in water and lowering the pH of the aqueous solution to a value below pH 11 using an acid; g) R ３ isolating the compound according to formula (I), wherein is hydrogen, from the solution of step f); A method comprising:

2. R １ The method of claim 1 , wherein is hydrogen.

3. R １ Ga-OCH ３ The method of claim 1, wherein

4. R ２ But -(CH ２ ) ２ -CH ３ , -(CH ２ )-CH ３ , -CH ３ and -(CH ２ ) ３ The method of claim 2 or 3, wherein the alkyl group is selected from the group consisting of —OH.

5. 5. The method according to claim 1, wherein the concentration of NaOH in the solution of step d) is 0.1 to 4 mol / L.

6. The method according to any one of claims 1 to 5, wherein the precipitation is carried out at room temperature.

7. f) dissolving the isolated compound of step e) in water and lowering the pH of the aqueous solution to a value below pH 11 using an acid; g) R ３ isolating the compound according to formula (I), wherein is hydrogen, from the solution of step f); The method of any one of claims 1 to 6, further comprising:

8. 8. The method of claim 7, wherein in step f), the pH is adjusted to 4 to 7.

9. In step f), the acid is HCl, p-TSA, acetic acid, H ３ P.O. ４ or H ２ SO ４ The method according to claim 7 or 8, wherein

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