sg ratio - spark_2007.pdf

7/29/2019 SG ratio - Spark_2007.pdf

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Presented to SACI

by

Prof. Andrew Sparkfor

Mark Govender and Tammy Bush

7 December 2006

Analysis of Syringyl and

Guaiacyl (S/G) ratio in lignin


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Acknowledgements

SAPPI

MONDI

CSIR

UKZN


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Aim Develop a quick and accurate method

to measure S/G ratio

Characterise and identify the acidolysis

products

Validate the new S/G ratio method


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Why are S/G ratios important?

Gives a good indication of the reactivity

of the lignin


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Experimental design

Literature ReviewEstablishing

Acidolysis conditions

Permanganate oxidation Lignin isolation

Characterisation andidentification of

acidolysis products

Inter-lab study(Method validation)


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Introduction

Lignin is the second most abundant

polymeric substance known to man

Lignin has not been isolated in its pure

form which makes both quantitative and

qualitative determinations difficult

Lignin are polymers of phenylpropaneunits


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Lignin is amorphous

Figure 1: Model structure of lignin (Lin and Dence,1992)


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Methods of oxidising lignin

into its subunits:

Acidolysis-method is quick

Permanganate oxidation-method is slowbut it is the standard method used at

present

Nitrobenzene Oxidation, Pyrolysis,Cupric Oxidation and Thioacidolysis


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Lignin can be broken down to

syringyl and guaiacyl subunits:

OCH3

OH

OCH3

OH

OCH3

Guaiacyl Syringyl


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Advantages of Acidolysis

Quick sample preparation times

Reagents used for the samplepreparation are relatively cheap

Sample preparation is simple


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Acidolysis

Present definition-the heating at 105 C oflignin or sawdust with 0.2 M HCl indioxane-water (9:1, v/v)

Acidolysis degradation products areformed by the selective cleavage ofarylglycerol--aryl ethers and other weak

ether linkages


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Lignin

O

C O

CH O

CH2OH

OH

O

OH

OO

+

0.2 M HCl105 C

4hrs

Guaiacyl Syringyl


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Experimental

Sampling and

sample preparation

Lignin isolation

(Klason Lignin)

Acidolysis

and extraction

GC-MS

analysis

Wood Chips

S/G Ratio

Sawdust


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Results

Acidolysis products were separated

using column chromatography

Characterised and identified usingGC-MS together with 1H-Nuclear

Magnetic Resonance (NMR) and 13C-

Nuclear Magnetic Resonance (NMR)


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Column chromatography

Solvent system of 15% ethyl acetate and 85%

methylene chloride gave the best separation

Thin layer Chromatography (TLC) was used to

determine best eluent


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GC Chromatogram

Klason lignin

SyringylGuaiacyl


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Mass Spectrum of Syringyl


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Mass Spectral Analysis of Syringyl

181

153

43

Fragmentm/z

C CH3

O

OCH3CH3O

OH

OCH3CH3O

OH

C O


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1H-Nuclear Magnetic Resonance (NMR)

Aromatic

CHs

OH

2xOCH3

CH3

}


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13C-Nuclear Magnetic Resonance (NMR)

C=O=C-O

=CH

}} }

=C and 2xO-CH3

CO

CH3


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1,2-Propanedione, 1-(4-hydroxy-3,5-

dimethoxyphenyl)

MeMe

Me

C C

O O

O

O

HO

Syringyl


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Mass Spectrum of Guaiacyl


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Mass Spectral Analysis of Guaiacyl

151

123

43

FragmentMass/charge (m/z)

CH3O

OH

CH3O

OH

C O

C CH3

O


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1H-Nuclear Magnetic Resonance (NMR) - Guaiacyl

X

}

Aromatic HsOH

OCH3CH3


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13C-Nuclear Magnetic Resonance (NMR) - guaiacyl

} }

}C=O

=C

=CHCO

CH3

X


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1,2-Propanedione, 1-(4-hydroxy-3-

methoxyphenyl)

Me

Me

C C

O O

O

HO

Guaiacyl


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Repeatability Study

0.052.60Grandis

0.061.74GxT

0.012.88Smithii0.052.50Fastigata

0.022.15GxC

0.032.48Dunnii

0.042.30Nitens

Standard

deviation

(4 replicates)

S/G ratioEucalyptus

species


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Internal standard(Butylated Hydroxy Toluene) vs S/G ratio

2

2.1

2.2

2.3

2.4

0 0.02 0.04 0.06 0.08 0.1

BUTYLATED HYDROXY TOLUENE(g)

S/GR

ATI


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Klason lignin preparation methods

T222om-88- preparation of

Acid-insoluble lignin

(Klason lignin)

15 ml H2SO4 (72%) added

to 1 g sawdust

2 hours at 20oC

Boil for 4 hours Filter off Klason lignin

T249cm-85- carbohydrate

analysis

(Isolation of Klason lignin)

3 ml H2SO4 (72%) added to

0.35 g sawdust

1 hour in water bath set at 30oC

1 hour in autoclave at 121oC

Filter off Klason lignin


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S/G ratios of Klason lignin from TAPPI method

T222 om-88vs. TAPPI method T249 cm-85

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

1.3 1.5 1.7 1.9 2.1 2.3 2.5

T249 cm-85 (S/G ratio)

T222om-8

8(S/G

rati

T222 om-88= 6 hours T249 cm-85= 3 hours

R2= 0.8401


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Inter-lab. study

Aim: To compare theAcidolysis(CSIR-

FFP) method for oxidising lignin with the

Nitrobenzene Oxidation method used at(Syracuse University, NY)


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Comparison of lignin oxidation methods

Acidolysis Method

Acidolysis reagent (2 ml ) isadded to 0.0150 g Klason

lignin Acidolysis mixture kept at 105oC for 4 hours

Acidolysis mixture isneutralised and then solvent

extracted Acidolysis products analysedon GC to obtain S/G ratio

Nitrobenzene Oxidation

0.4 g of wood meal is addedto a bottle containing 2.5 ml

nitrobenzene and 2 M NaOH(40ml) Bottle placed in an oil bath

(170C ) for 2.5 hours 1 hour in autoclave at 121oC

Autoclave mixture is solventextracted and the pH isadjusted to 3

Nitrobenzene oxidationproducts analysed on the GC-

MS to obtain S/G ratio


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Comparison of S/G ratios measured using

Nitrobenzene Oxidation with Acidolysis (Klason lignin

prepared using TAPPI method T222 om-88)

0.9

1

1.1

1.2

1.3

1.41.5

1.6

1.7

1.8

1.5 1.7 1.9 2.1 2.3 2.5 2.7

Acidolysis(S/G ratio)

NitrobenzeneOxidatio

n(S/G

ratio

R2= 0.8283


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Comparison of S/G ratios measured using

Nitrobenzene Oxidation with Acidolysis (Klason lignin

prepared using TAPPI method T249 cm-85)

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.2 1.4 1.6 1.8 2 2.2 2.4 2.6

Acidolysis(S/G ratio)

Nitrob

enzeneOxida

tion(S/G

R2= 0.8847


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Conclusions

Acidolysis of Klason lignin produces:

Syringyl unit

1,2-Propanedione, 1-(4-hydroxy-3,5-dimethoxyphenyl)

Guaiacyl unit

1,2-Propanedione, 1-(4-hydroxy-3-methoxyphenyl)


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Internal standard BHT plays a major

role in preventing the guaiacyl groups

from polymerising

Inter-lab. study was a success with

good correlations of the S/G ratios from

acidolysis and nitrobenzene oxidation of

the lignin

Conclusions cont..


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The preferred lignin isolation method is

T249 cm-85 due to quicker preparation

times and better correlation withnitrobenzene oxidation than T222 om-

88

Conclusions cont..

sg ratio - spark_2007.pdf

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