Forest Biomaterials nc state university nc state university - - PowerPoint PPT Presentation

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 nc state university

Forest Biomaterials

nc state university

Outline

Introduction Experimental

1 2 3

Results and Discussion Conclusions an Future plan

4 Modification of lignin and properties of modified lignin Optimization of parameters for preparation of modified lignin

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Use of lignin for adhesives

Background

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• Recovery of lignin from black liquor, is being

evaluated at many locations

• Improve pulp mill efficiency
• 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

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

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• Uses of lignin

Non- woody biomass Softwood Hardwood Alkali lignin Hydrolysis lignin Kraft lignin Organosolv lignin Sulfite lignin Adhesives Binders Carbon fibers Surfactants Dispersants Aromatics Phenols Plastics

Source Types of lignin Products

Vanillin

Lignin Wisdom

“You can make anYthing lignin except moneY”

$

 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

Adhesives from Lignin

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• Reactivity

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• Factors limiting utilization of lignin

Available reaction sites/unit = 3 Typical sites/unit used = 1.9 Available reaction sites/unit = 0.3 Typical sites/unit used = 0.2

[1] Thielemans W. J. Appl. Polym. Sci. 2002, 83, 2, 323-331.

• Molecular Weight
• a. Viscosity
• b. Shelf-life

One site/unit need to be left/unoccupied for polymerization

• 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

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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).

• Lignin-based PF resins in literatures--- modified

lignin

Introducing reactive functional groups

Producing reactive sites on lignin

Methylolation

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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.

• Introduce –CH2OH 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

• Lignin-based PF resins in literatures--- modified

lignin

Phenolation

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• 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

• Lignin-based PF resins in literatures--- modified

lignin

Demethylation

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Li, K., and X. Geng. 2005. Formaldehyde-free wood adhesives from decayed wood. Macromol. Rapid Commun. 26:529-532.

• Produce reactive sites
• Cons:

expensive!!!  few adhesive work

• 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

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Homaira Siddiqui, 2013. Thesis. Production of Lignin-Based Phenolic Resins Using De-Polymerized Kraft Lignin and Process Optimization.

• 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 Lignin

Phenolation of kraft lignin

• Low acid dosage
• Without solvent

• 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 90OC 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.

Phenolation of Lignin

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

– BF3 –

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

Kraft lignin, 10% in phenol Aqueous layer Organic layer

Phenolation of lignin using acid catalyst

98% sulfuric acid or BF3

• 2. Adjust pH to 7 with 2 N HCl
• 1. 98% sulfuric acid or BF3
• 2. Extract with saturated NaCl

Adjust pH to 2.5

• 3. Extract with ethyl ether

Ether layer Aqueous layer Aqueous layer PPT Modified lignin 1 PL 1 Ether Insoluble

• 1. Dissolved In 2N NaOH

Precipitated in petroleum ether Organic layer PPT Modified lignin 2 PL 2 Ether Soluble

Acid % of BCL Temp.

OC

Yield PL 1 % of BCL Yield PL 2 % of BCL Guaiacol % of BCL Total yield % of BCL BF3 50% 80 59 15 9 83 BF3 5% 90 66 52 2 110 No acid 90 86 10 2 98 H2SO4 2% 90 84 20 109 H2SO4 5% 90 83 27 1 111 H2SO4 15% 90 68 62 1 131

Yield of Phenolation Reaction Products

Time = 2 hours

Functional Groups of Phenolation Products using UV-vis

21

% Acid Temperature Lignin Sample α-Carbonyl /C9 Phenolic OH/C9 % Stilbene/C9 % Methoxyl Wt % BCL 7.8 43 5.8 12.6 50% BF3 80OC PL 1 PL 2 4.7 3.0 70 75 2.4 2.3 8.5 9.1 5% BF3 90OC PL 1 PL 2 4.1 1.6 63 66 1.8 1.0 7.7 3.4 0% acid 90OC PL 1 PL 2 6.0 2.6 42 50 2.5 2.0 8.7 4.4 2% H2SO4 90OC PL 1 PL 2 3.8 3.1 63 77 2.0 1.5 10.4 5.9 5% H2SO4 90OC PL 1 PL 2 2.9 2.5 53 78 1.5 1.3 10.1 8.0 15% H2SO4 90OC PL 1 PL 2 4.9 2.6 58 69 2.1 1.0 8.7 2.9

Phenolation of BCL with 5% BF3 at 90 oC

0.00 0.05 0.10 0.15 0.20 19 21 23 25 27 29 31 UV absorption, Au Retention time, min

Molecular weight distribution of lignin

Original Lignin PL1 PL2 Original

Phenolation of BCL with 5% Sulfuric acid at 90oC

0.00 0.05 0.10 0.15 0.20 19 21 23 25 27 29 31 UV absorption, Au Retention time, min

Molecular weight distribution of lignin

Original Lignin PL1 PL2 Original

Summary

• Phenolation of kraft lignin with excess phenols in the presence of

catalytic amount of acid (BF3 or H2SO4) occurs at 60-100 OC, resulting in

– Condensation of phenol with α-hydroxy/-ether, addition of phenol to α- carbonyl, stilbene and vinyl ether structure – Substantial increase of phenolic hydroxyl content of modified lignin – Degradation of ether linkages in lignin, resulting in lower molecular weight and lower dispersity

• No solvent is needed for the phenolation reactions
• Using 5% H2SO4 incorporates around 30% of phenol into the

lignin

Summary

• Reacting with BF3 produces phenolated lignin, it

is however too expensive for commercialization

• Reaction with low dosages of sulfuric acid has

higher potential for commercialization

• However the process needs to be simplified
• Simplified Process

– No fractionation into PL 1 and PL 2 – No pH adjustment – Improved mixing during reaction

Wash with saturated NaCl No pH adjustment Evaporate to dryness Dissolved in EtOAC Precipitated in petroleum ether Organic layer Reaction conditions: 90oC, 2 hours Phenolated Lignin

Simplified Procedure for Phenolating Lignin

Kraft lignin and phenol 5% sulfuric acid (5:3 phenol to lignin ) Low MW Phenolic Compounds Precipitate

Properties of Phenolated Lignin Produced by Simplified Procedure

α- carbonyl %C9 ph-OH %C9 Stilbene %C9 Mn, g/mol Mw, g/mol Mw/Mn

BCL 15.8 45 3.5 970 8850 7.0 BCL 5% H2SO4 3.9 58 1.1 1210 4130 2.6

Molecular Weight

Phenolated Lignin PL 2 PL 1 BCL

Original PL

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Objectives

Study and compare the performances of BCL and PL in adhesives

• Preparation of PF:

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Formulation of PF resin( F:P=1.9:1)

Component MW(g) Purity Mass Solids Moles Phenol 94.11 1.00 30.0 30.0 0.32 CH2O 30.03 0.37 49.4 18.3 0.61 40% NaOH-1 40.00 0.40 4.6 1.84 0.046 40% NaOH-2 40.00 0.40 5.2 2.08 0.052 water 18.00 1.00 10.0 Totals 100.00 52.2 *: Formulation provided by USDA Forest Product Lab

Experimental

85oC 3h 85oC 1h

• Curing process

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Experimental

 Plywood: yellow poplar, 10 in X 10 in  Amount: 13.9 g on 10 in X 10 in plywood  Assembly time: open: 5 min, closed: 15 min  Curing condition: 175℃, 5 min, 125 psi  Conditioning: 23oC, 50 RH for 7 days

• Cutting

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Experimental

Shear strength test

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Vacuum system for wetting samples

Experimental

Important parameters for PF

Important parameters of PF formulation

• Formaldehyde to phenol molar ratio
• Catalyst concentration
• Reaction time and temp.

Key properties of adhesives

• Viscosity
• Nonvolatile solid content
• Storage life
• Shear strength (dry& wet)
• Wood failure
• Free formaldehyde

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ASTM standards

Processing& Penetration Performance

• Preparation of LPF:

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Experimental

F: free phenol= adjusted Solid content=50% Reaction conditions the same Formulation of LPF resin

Component MW(g) Purity Mass Solids Moles BCL N 1.00 7.5 7.5 N Phenol 94.11 1.00 22.5 22.5 0.24 CH2O 30.03 0.37 36.9 13.6 0.45 40% NaOH-1 40.00 0.40 3.1 1.24 0.031 40% NaOH-2 40.00 0.40 3.6 1.44 0.036 water 18.0 1.00 18.9 Totals 92.6 46.3

• PL-LPF-adjusted:

25% L-LPF-adjusted 38% L-LPF-adjusted (P+PL+F) VS (PF+PL solution)

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Experimental

Adjust F: free phenol ratio Keep Solid content=50% Keep Reaction conditions the same

Solids Content and Viscosity of Adhesive

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properties samples

Solid Content, % Viscosity, cP PF 51.4 502 25% BCL-LPF 48.2 926 25% PL-LPF 50.3 708 38% BCL-LPF 49.4 4096 38% PL-LPF 49.6 2022 50% BCL-LPF Get gel around 3 hr 50% PL-LPF Partial Gel Partial Gel

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Sample

Dry, psi Wood Failure,% Wet, psi Wood Failure,% PF 307±11.5 35 273±6.1 83 25% BCL-LPF 299±14.1 73 241±11.0 86 25% PL-LPF-a 312±9.5 72 285±7.6 83 38% BCL-LPF 250±13.1 56 188±10.9 72 38% PL-LPF-a 309±11.1 55 256±8.4 68

Strength Testing of Wood

 SW Kraft lignin may be activated for adhesive application by dissolving BCL in excess phenol and reacting at 90OC with 5%

• f acid (BF3 or H2SO4).

 The resulting phenolated lignin has lower MW and narrower MW distribution and presumably higher reactivity than the

• riginal lignin.

 With unmodified technical kraft softwood lignin, up to 25%

• f substitution rate can be achieved without significant

sacrifice of shear strength, and with higher wood failure.  With phenolated lignin after adjustment, up to 38% of phenol can be replaced with comparable shear strength.

Conclusions

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40

Phenolation Process

*Phenolation Unit 233,680 BDt/year Lignin Residue Fluidized Bed Dryer Phenolation Tank Precipitation Centrifugation Solvent Recovery Vacuum Bed Dryer Power & Steam Bagging Product Storage Brine Treatment Treated Effluent 175,600 BDt/year Phenolated Lignin 350,670 mt/yr Petroleum Ether (make-up) 17,475 mt/yr Ethyl Acetate (make-up) 220,500 mt/year Phenol, 6,890 mt/year Sulfuric Acid 6,615,000 mt/year Brine Landfill Residue

 Demonstrate improved reactivity of the phenolated lignin

• DSC+DMA  thermal behavior
• Study the changes of structure with changes of temp.

 Optimization of curing conditions for PL-LPF at different replacement ratio  Different lignin resources (hardwood kraft lignin and enzymatic hydrolysis lignin) will be modified and compared for potential adhesive applications  Perform techno-econmoic analysis for phenolated lignin and its use in adhesives

• Is improved substitution worth the cost?

Future work

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Lignin Wisdom

“You can make anYthing lignin except moneY”

$

?

On-going Lignin Modification Projects

• Lignin Fractionation

– Using successive precipitation in solvent systems

• Catalytic Cracking of Kraft Lignin in Supercritical

Methanol with/without Catalyst/H2

• Oxidation with catalysts

Special Thanks to: Domtar US Department of Agriculture Biomass to Biomaterial and Biochemical Consortium

BTB2 Consortium

• Georgia Pacific
• International Paper
• Moorim Paper
• YFY
• Tralin Paper
• API
• Novozymes