characterization of lignin degradation and …...chemistry reu lignin is one of the most abundant...

Characterization of Lignin Degradation and Repolymerization ProductsShelly Lu, Honzík Bílek, Anastasia Andrianova, Alena Kubátová

Chemistry Department, University of North Dakota

❖ Lignin’s unique structure has the potential for the production of a

new generation of renewable materials

❖ Lignin is a sources of phenolic compounds, e.g., vanillin, phenol,

guaiacol, and vanillic acid

Phenol

❖ TCA confirmed that low MW fractions were rich

in monomeric species, whereas higher MW

fractions featured highly crosslinked polymers

❖ TCA corresponded with GPC and shown there is

non-lignin impurities which elute in GPC before

high MW lignin species

❖ TEM results also suggested that the first eluted

fraction in GPC was structurally different from

lignin

❖ Lignin nanoparticles of uniform size were

observed in narrow MW lignin fractions

❖ Repolymerization is occurring in concentrated

lignin solutions over

InterdisciplinaryRenewable & EnvironmentalChemistry REU

Lignin is one of the most abundant

biopolymers in the world; 50 million tons

produced annually from plants

I would like to thank Dr. Kozliak, Josh Hatton, Brett Nespor, Sarah Reagen, Audrey LaVallie, and Tyson Berg who have assisted and advised me throughout the program.

This material is based upon work supported by the National Science Foundation Research Experience for Undergraduates under Grant No. CHE 1460825. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Vanillin

Guaiacol

358

580

1480

2340

50306850

8450

19760

2.0

2.5

3.0

3.5

4.0

4.5

0

10000

20000

30000

40000

50000

60000

70000

80000

0 1 2 3 4 5 6 7 8 9 1011121314151617181920212223242526272829

Calibration curve is

composed of polystyrene

(PS) and polymethyl-

methacrylate (PMMA)

standards Fr. 1 Fr. 2 Fr. 3 Fr. 4 Fr. 5 Fr. 6

Log

MW

Absorb

ance (

230

–750 n

m),

mA

U

Time (min)

• Fraction 3 and 4 are the most

concentrated and they consist

mainly of oligomers

• Fraction 1 is anticipated to

have the highest MW, while

fraction 6 has the lowest MW

❖ Lignin fractionation preparation using gel permeation

chromatography (GPC)

❖ Fraction characterization by TCA

❖ Lignin visual analysis using transmission electron microscopy

(TEM)

❖ Weekly evaluation of extend of lignin repolymerization by

hydrotreated samples using TCA

❖ Characterize lignin heteropolymer to better understand the

composition of lignin for future renewable resource studies

❖ Observe lignin repolymerization to help understand and develop

methods to prevent this phenomenon

❖ Quantify the amount of carbon by thermal carbon analysis (TCA)

to evaluate contribution of monomers, oligomers, and elemental

carbon.

❖ TEM results confirmed that the first eluted

fraction in GPC was structurally different from

lignin

❖ Lignin nanoparticles (NPS) of the uniform size

were observed in fractions of defined

molecular weight (MW)

❖ Intact lignin consists of NPS of various MW

Fraction 3

GPC separation provides 6 fractions

❖The total amount of carbon recovered is 76%

❖Small amounts of carbon can be lost during the filter

drying process, low MW compounds in lignin can be

lost due to low boiling points

❖TCA results show most abundant carbon

concentrations in fractions 3 and 4

TEM Images of Lignin Nanoparticles Formed in Various MW Fractions

Preparative Size Exclusion Chromatography

Methods and Materials

Background

Objectives

Acknowledgement

Conclusions

Future Work

Low MW

Oligomers evolving

Elemental carbon evolving

1. Measure lignin nanoparticle size in the

solution by dynamic light scattering

2. Perform TD/pyr-GC/MS analysis of lignin MW

fractions and GC-MS analysis of low MW

fractions

3. Distinguish the predominant functionalities in

different lignin MW fractions by means of

NMR and FT-IR spectroscopy

4. Achieve the mass balance closure in lignin

fractionation by MW

❖Amount of carbon at 890 °C is decreasing for 25,000

ppm solutions

❖Amount of carbon at Coked is increasing for 25,000

ppm solutions

0

20

40

60

80

100

120

AmbientCO2

Ambientvolatiles

200 °C 300 °C 890 °C Coked Sum

% w

t. o

f In

itia

l Fee

dst

ock

Temperature Step

Day 1-3

Day 8-10

Day 15

Day 25

TCA of Concentrated Lignin Repolymerization

(25,000 ppm)

0

5

10

15

20

25

% w

t. o

f In

itia

l Lig

nin

Temperature Step

Fraction 1 (high MW)

Fraction 2

Fraction 3

Fraction 4

Fraction 5

Fraction 6 (low MW)

TCA Lignin Fractionation

Calibration curve

Carbon Distribution By TCA

THF Concentrated 5.00 µm

Fraction 4 5.00 µm

Fraction 6 5.00 µm

Fraction 2 5.00 µm

Intact Lignin 5.00 µm

5.00 µm

Fraction 5 5.00 µm

Fraction 1 5.00 µm

H

TEM ×8,000 Magnification

TCA Operational Principle TCA Thermogram

sample introduced to TCA