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Forest Biomaterials nc state university nc state university Modification of Kraft Lignin for Use as a Replacement for Phenol Formaldehyde in Adhesives Hasan Jameel Hou-min Chang Zhoujian Hu Jie Lu Jing Du

Outline Introduction 1 Experimental 2 Results and Discussion 3 Modification of lignin and properties of modified lignin Optimization of parameters for preparation of modified lignin Use of lignin for adhesives 4 Conclusions an Future plan Department of Forest Biomaterials

Background  Recovery of lignin from black liquor, is being evaluated at many locations o Improve pulp mill efficiency o Use of lignin as a low cost source of fuel in the mill  However the recovery of lignin will need for the development of higher value uses of lignin than use as a fuel  Current production of lignin is about 1.1 million tons globally, with only about 70,000 tons of it being kraft lignin Department of Forest Biomaterials

Introduction • Around 50 million metric tons of lignin is produced annually by the pulp and paper industry, most of which are kraft lignin • Most current industrial applications of technical lignin are lignosulfonates, amounting to 1 million tons annually • Potentially, 5 million tones of kraft lignin could be extracted from the pulp and paper industry if higher value products can be derived above the fuel value of the kraft lignin.

Background  Uses of lignin Types of Products Source lignin Non- Alkali Adhesives woody lignin Binders biomass Carbon Hydrolysis Softwood fibers lignin Hardwood Kraft Surfactants lignin Dispersants Organosolv Aromatics lignin Phenols Sulfite Plastics lignin Vanillin Department of Forest Biomaterials

Lignin Wisdom “You can make anYthing lignin except moneY” $

Adhesives from Lignin  Phenol-formaldehyde (PF) adhesive is widely used due to its high weather-resistance and water-resistance, which is expected to have a production of 18.1 million tons by 2018 (Transparency Market Research).  Numerous efforts have been carried out to reduce the dependence of this industry on phenol, the cost of which is subject to fluctuations in the price of oil  Many attempts have been made to replace phenol by lignin due to structural similarity and lower cost Department of Forest Biomaterials

 Factors limiting utilization of lignin  Reactivity Available reaction sites/unit = 0.3 Available reaction sites/unit = 3 Typical sites/unit used = 1.9 Typical sites/unit used = 0.2  Molecular Weight One site/unit need to be a. Viscosity left/unoccupied for polymerization b. Shelf-life [1] Thielemans W. J. Appl. Polym. Sci. 2002, 83, 2, 323-331. Department of Forest Biomaterials

 Lignin-based PF resins in literatures--- unmodified lignin (1) Conventional technical lignin (kraft lignin; lignosulfonate)  Kraft softwood lignin is suggested to be the most promising substitute among all technical lignin based on the reactivity  Up to 25% substitution rate can be achieved without significant sacrifice of physical properties. (2) Enzymatic hydrolysis lignin  Up to 15% substitution rate can be achieved with comparable performances (3) Bio-oil  Up to 30% substitution rate can be achieved with comparable performances Tejado, A., Pena, C., Labidi, J., Echeverria, J. M., & Mondragon, I. (2007). Physico-chemical characterization of lignins from different sources for use in phenol-formaldehyde resin synthesis. Bioresour Technol, 98 (8), 1655-1663. doi: 10.1016/j.biortech.2006.05.042 B. Sukhbaatar, Philip H. Steele, Leonard I. Ingram, Moon G. Kim. Use of Lignin Separated From Bio-oil in Oriented Stradn Board Binder Phenol-formaldehyde Resins . Bioresources. 2009.4(2). Department of Forest Biomaterials

 Lignin-based PF resins in literatures--- modified lignin Introducing reactive functional groups Producing reactive sites on lignin Methylolation  Introduce – CH 2 OH group on C5  0.33 mole/C9 unit  Up to 40% of phenol can be replaced by methylolated lignin to get similar performances with PF  Better for SW than HW  Cons: Free formaldehyde Malutan, T (2007). "Contribution to the study of hydroxymetylation reaction of alkali lignin". Bioresources (1930-2126) , 3 (1), p. 13. YouBing, M (2009). "Study on composite adhesive of hydroxymethylated lignosulfonate/phenol-formaldehyde resin with low free formaldehyde.". Línchăn huàxué yŭ gōngyè (0253-2417) , 29(3), p. 38. Department of Forest Biomaterials

 Lignin-based PF resins in literatures--- modified lignin Phenolation  Introduce phenolic structure on lignin  Up to 30% of phenol can be substituted by phenolated lignin with similar performances compared to PF  Cons: Ethanol solvent, high P to L ratio Nihat S Çetin, Nilgül Özmen, Use of organosolv lignin in phenol – formaldehyde resins for particleboard production: I. Organosolv lignin modified resins, International Journal of Adhesion and Adhesives, Volume 22, Issue 6, 2002, Pages 477-480 Department of Forest Biomaterials

 Lignin-based PF resins in literatures--- modified lignin Demethylation  Produce reactive sites   Cons: expensive!!! few adhesive work Li, K., and X. Geng. 2005. Formaldehyde-free wood adhesives from decayed wood. Macromol. Rapid Commun. 26:529-532. Department of Forest Biomaterials

 Lignin-based PF resins in literatures--- modified lignin Thermo-chemical depolymerization • Pyrolysis • Hydrogenolysis • Oxidation • Hydrolysis  Lower MW  Increase phenolic -OH groups compared to unmodified kraft softwood lignin Homaira Siddiqui, 2013. Thesis. Production of Lignin-Based Phenolic Resins Using De-Polymerized Kraft Lignin and Process Optimization. Department of Forest Biomaterials

Phenolation of Lignin • Reactivity of kraft lignin towards formaldehyde can be improved by phenolation • Phenolation of kraft lignin also results in degradation of lignin, leading to lower molecular weight and lower polydispersity • Excess phenol is needed to prevent lignin condensation during phenolation • Phenolations of lignin were previously done with concentrated sulfuric acid in methanol or ethanol which is not commercially viable • Normally, excess acid (50% on lignin) was used Phenolation of kraft lignin  Low acid dosage  Without solvent

Phenolation of Lignin • Under acidic conditions, lignin normally undergoes self- condensation and form an insoluble residue. Klason lignin being a good example. • In the excess amount of phenols, self-condensation is prevented and lignin reacts with the phenol. • At low acid dosage and temperature (5% at 90 O C for example), most ethers , α -carbonyl, stilbene and vinyl ethers are protonated and reacts with phenol. • Hydrolysis of α - ethers, vinyl ethers and remaining β -aryl ethers decreases the molecular weight and MW polydispersity. • Without the presence of acid, reaction of phenol with α - carbonyl, stilbene and vinyl ethers may occurs to some extent, but little degradation of lignin takes place.

Acid Catalyzed Reactions of Kraft Lignin with Phenol

Acid Catalyzed Reactions of Kraft Lignin with Phenol

Phenolation of Lignin • Kraft lignin is soluble in phenol (1 g lignin/10mL of phenol) • Acid was added directly to the dissolved lignin – BF 3 – H2SO4 • Reaction was carried out in a capped glass centrifuge tube head in an aluminum block (temperature controlled) • The tube was shaken vigorously every 10 minutes • Reaction terminated by cooling the tube in ice water bath

Phenolation of lignin using acid catalyst 98% sulfuric acid or BF 3 Kraft lignin, 10% in phenol 1. 98% sulfuric acid or BF 3 2. Extract with saturated NaCl Organic layer Aqueous layer 1. Dissolved In 2N NaOH 2. Adjust pH to 7 with 2 N HCl 3. Extract with ethyl ether Aqueous layer Ether layer Adjust pH to 2.5 Precipitated in petroleum ether Aqueous layer PPT Organic Modified lignin 1 PPT layer PL 1 Modified lignin 2 Ether Insoluble PL 2 Ether Soluble

Yield of Phenolation Reaction Products Acid Temp. Yield PL 1 Yield PL 2 Guaiacol Total yield O C % of BCL % of BCL % of BCL % of BCL % of BCL BF 3 50% 80 59 15 9 83 BF 3 5% 90 66 52 2 110 No acid 90 86 10 2 98 H 2 SO 4 2% 90 84 20 0 109 H 2 SO 4 5% 90 83 27 1 111 68 62 1 131 H 2 SO 4 15% 90 Time = 2 hours

Functional Groups of Phenolation Products using UV-vis α -Carbonyl % Acid Lignin Phenolic Stilbene/C 9 Methoxyl Temperature Sample /C 9 OH/C 9 % % Wt % 0 BCL 7.8 43 5.8 12.6 50% BF 3 PL 1 4.7 70 2.4 8.5 80 O C PL 2 3.0 75 2.3 9.1 4.1 63 1.8 7.7 5% BF 3 PL 1 1.6 66 1.0 3.4 90 O C PL 2 0% acid PL 1 6.0 42 2.5 8.7 90 O C PL 2 2.6 50 2.0 4.4 2% H 2 SO 4 PL 1 3.8 63 2.0 10.4 90 O C PL 2 3.1 77 1.5 5.9 21 5% H 2 SO 4 PL 1 2.9 53 1.5 10.1 90 O C PL 2 2.5 78 1.3 8.0 15% H 2 SO 4 PL 1 4.9 58 2.1 8.7 90 O C PL 2 2.6 69 1.0 2.9

Phenolation of BCL with 5% BF 3 at 90 o C Molecular weight distribution of lignin 0.20 Original Lignin PL1 PL2 UV absorption, Au 0.15 Original 0.10 0.05 0.00 19 21 23 25 27 29 31 Retention time, min

Phenolation of BCL with 5% Sulfuric acid at 90 o C Molecular weight distribution of lignin 0.20 Original Lignin PL1 PL2 UV absorption, Au 0.15 Original 0.10 0.05 0.00 19 21 23 25 27 29 31 Retention time, min