Cateto, C.A., Barreiro, M.F., Rodrigues, A.E., Brochier-Salon, M.C., Thielemans, W., Belgacem,

M.N., "FTIR and NMR studies on lignin acetylation" 9th European Workshop on

Lignocellulosics and Pulp- EWLP 2006, Vienna, Austria, 27-30 August (2006) (poster).

NINTH EUROPEAN WORKSHOP ON LIGNOCELLULOSICS AND PULP-TABLE OF CONTENTS

POSTER PRESENTATIONS

INFLUENCE OF CARBONYL GROUPS ON THE BRIGHTNESS REVERSION OF EUCALYPTUS KRAFT PULP lmmanuel Adorjan, Zhen Zhou, Anna-Stiina JaaskeHiinen, Antje Potthast, Tapani Vuorinen

134

SYNTHESIS AND APPLICATION OF THE HexA MODEL METHYL 138 4-DEOXY -P-L-THREO-HEX-4-ENOPYRANOSIDURONIC ACID Immanuel Adorjan, Anna-Stiina JaaskeHiinen, Zhen Zhou, Tapani Vuorinen

BIRCH LIGNIN MACROMOLECULAR STRUCTURE TRANSFORMATION 142 IN ALKALINE WATER-ETHANOL DELIGNIFICATION N.l. Afanasiev, A.V. Phesenko, G. F. Prokshin, Vishnjakova A.P.

MACROMOLECULAR AND SPECTRAL CHARACTERISTICS OF LIGNINS, 146 ISOLATED DURING MODIFIED ALKALINE DELIGNIFICATION OF HARDWOOD Afanasyev N., Gusakova M., Pazuhina G., Brovko 0.

GENERATION OF PERACETIC ACID FROM HYDROGEN PEROXIDE 150 AND ACETYL-CONTAINING ACTIVATORS Stefan Backa, Martin Ragnar

LONG-TIME IMPACT OF SALT SEA WATER UPON CONIFEROUS WOOD 154 Lubova Be1kova, Galina Dobele, Boguslava Waliszewska, JosefKudela

IMPROVING SEMI-EMPIRICAL MATHEMATICAL MODELING OF CHLORINE DIOXIDE DELIGNIFICATION N. Benattar, G. Mortha, C. Calais

CHEMICAL IDENTIFICATION OF EXTRACTIVE COMPONENTS IN BARKS OF SOME HARDWOOD AND SOFTWOOD SPECIES Frederique Bertaud, Markku Reunanen, Linda Nisula, Bjarne Holmbom, Patrick Chareyre, Christian Masure

MULTI-PURPOSE APPLICATIONS OF BIO-ACTIVE EXTRACTIVES FROM KNOTS AND BARK: ASSESSMENT OF INNOVATIVE EXPLOITATION OF INDUSTRIAL WOOD PULPING BY-PRODUCTS Frederique Bertaud, Delphine Craperi, Gilles Lenon, Maria CURRAS-LINO, Romeo Radman, Tajalli Keshavarz, Linda Nisula, Bjame Holmbom, Abir lsam Nazer, Romain Briandet, Markku Ahotupa

CHEMICAL MODIFICATION OF LIGNOCELLULOSIC WASTES AND ITS APPLICATION TO WOOD-PVC COMPOSITE MATERIALS Ruxanda Bodirlau, Iuliana Spiridon, and Carmen-Alice Teaca

SOLVATION EFFECTS INFLUENCE ON REDOX PROPERTIES OF LIGNIN'S GUAIACYL STRUCTURES IN WATER-ETHANOL MEDIA K. Bogolitsyn, A. Malkov

IV

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162

166

170

174

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·6

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NINTH EUROPEAN WORKSHOP ON LIGNOCELLULOSICS AND PULP- TABLE OF CONTENTS

HOMOGENOUS CATALYTIC OXIDATION OF LIGNIN MODEL COMPOUNDS IN WATER-ETHANOL MEDIUM K. Bogolitsyn, A. Koshe1eva, N. Popova

178

ELECTROCHEMICAL OXIDATION OF LIGNIN MODEL COMPOUNDS 181 K.G.Bogolitsyn, N.L.Ivanchenko, A.N.Shkaev, E.F.Potapova

KINETICS OF FORMATION AND DEGRADATION OF HEXENURONIC ACID IN PINE WOOD MEAL UNDER ALKALINE CONDITIONS Johannes Bogren, Harald Brelid

INITIAL STUDY OF THE RELATION BETWEEN THE THERMAL PROPERTIES OF KRAFT LIGNIN AND ITS CHEMICAL COMPOSITION Ida Brodin, Anders Uhlin, Elisabeth Sjoholm

FTIR AND NMR STUDIES ON LIGNIN ACETYLATION C.A. Cateto, M.F. Barreiro, A.E. Rodrigues M.C. Brochier-Salon, W. Thielemans, M.N. Belgacem

STRUCTURAL AND CHEMICAL CHANGES IN WOOD AND LIGNIN AT LOW TEMPERATURE TREATMENT Jelena Chirkova, Galina Dobele, Igor Urbanovich, Ingeborga Andersone, Bruno Andersons

STRUCTURAL MODIFICATIONS OF CELLULOSE ALLOMORPHS DURING THE ENZYMATIC HYDROLYSIS REACTION Diana Ciolacu

DSC INVESTIGATIONS ON THE CELLULOSE POLYMORPHS ACCESSIBILITY Diana Ciolacu, Georgeta Cazacu

BEHAVIOUR OF QUATERNARY COMPOSITES BASED ON NATURAL POLYMERS AND POLYETHYLENE MATRIX Gabriela Constantinescu, Georgeta Cazacu

ECO-FRIENDLY COMPOSITES OBTAINED FROM NATURALPOLYMERSANDPOLYETHYLENEMATrux Gabriela Constantinescu, Valentin I. Popa

SURFACE MODIFICATION OF CELLULOSE FIBRES WITH FLUORINE-CONTAINING COMPOUNDS G. Cunha, C. S. R. Freire, A. J. D. Silvestre, C. Pascoa1 Neto, A. Gandini

HOW DOES WOOD VARIABILITY IMPACT KRAFT PULPING ? D.da Si1va Perez, P. Nougier, A. Guillemain, G. Chantre, J.C.Rodrigues, M. Petit-Conil

STUDYING THE STRUCTURE OF NATIVE, RESIDUAL AND DISSOLVED LIGNINS BY FT -IR SPECTROSCOPY METHOD Olga Derkacheva, Dmitry Sukhov

184

188

192

196

200

204

208

212

216

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Ecole Française de Papeterie et des Industries Graphiques (2)

Institut National Polytechnique de Grenoble

FTIR AND NMR STUDIES ON LIGNIN ACETYLATIONC.A. Cateto1a, 2, M.F. Barreiro1a, A.E. Rodrigues1b,

M.C. Brochier-Salon2, W. Thielemans2, M.N. Belgacem2

Acetylation is a widely used technique for lignin characterization. Total hydroxyl

content, structural analysis by 1H and 13C NMR spectroscopy, and molecular weight

determination using SEC, are usually based on acetylation procedures. Acetylation

of lignin introduces some structural features in the molecule that could be detected

both by FTIR and 13C NMR spectroscopy. The direct quantification of the total

hydroxyl content using FTIR spectroscopy is not a current practice but 13C NMR

spectroscopy is a widely used technique for that purpose. However both techniques,

are useful to monitor the acetylation process.

Introduction

Figure 1. Lignin structural model: (i) original sample and (ii) partially acetylated sample.

(i) (ii)

Study of the reliability of an acetylation procedure by FTIR and 13C NMR

spectroscopy through the examination of samples subjected to the acetylation

process during 1 and 2 hours;

Determination of the total hydroxyl content using the standard titration

procedure and 13C NMR results.

Four technical lignin samples, representing guaiacyl and guaiacyl-syringyl type, and

two pulp processes, Kraft and Organosolv, were used: Alcell, Indulin AT, Sarkanda

and Curan 27-11P.

Experimental

Objectives

Elemental analysis: Elemental analysis was carried out by CNRS (Vernaison,

France). The content of C, H, N, S and O (by difference) was determined.

Acetylation procedure: The general procedure followed the method described in

the international standard ISO 14900:2001.

Lignin recovery procedure: The procedure to recover the acetylated lignin

samples to perform FTIR and NMR analysis was adapted from the procedure

described by Glasser et al. (1993).

FTIR analysis: FTIR measurements were taken on a FTIR Bomen model MB 104

working in transmittance mode using KBr pellets. Forty eight scans per spectrum

were taken in the range from 4000 to 650 cm-1 with a resolution of 4 cm-1. KBr

pellets were prepared with a lignin concentration of 1% (w/w) using a Specac

hydraulic press.13C NMR analysis: 13C NMR spectra were recorded on a MERCURY Varian

spectrometer, equipped with a 10-mm BB probe operating at 100.624 MHz.

Experiments were conducted at 50ºC in DMSO-d6 99.8% (SDS). 13C chemical shifts

are given relative to tetramethylsilane (TMS). The positions of the peaks were

referenced to the residual solvent peak DMSO-d6 (δ=39.5 ppm). Spectra were

quantitative (proton broad band decoupling only during the acquisition time. 13C

spectra were obtained using a 23 kHz (228ppm) spectral width, 32K data points, 11s

relaxation delay, and 12ms for a 75° pulse, zero-filling and 10Hz line broadening.

600 1000 1400 1800 2200 2600 3000 3400 3800

Wavenumbers (cm-1)

Tra

nsm

itan

ce

Original1 hour2 hour

Indulin AT

600 1000 1400 1800 2200 2600 3000 3400 3800

Wavenumbers (cm-1)

Tra

nsm

itan

ce

Original1 hour2 hour

Alcell

600 1000 1400 1800 2200 2600 3000 3400 3800

Wavenumbers (cm-1)

Tra

nsm

itan

ce

Original1 hour2 hour

Sarkanda

600 1000 1400 1800 2200 2600 3000 3400 3800

Wavenumbers (cm-1)

Tra

nsm

itan

ce

Original1 hour2 hour

Curan 27-11P

Figure 2. FTIR spectra of lignin samples (Indulin AT, Curan 27 11P, Alcell and Sarkanda) before and after

acetylation (acetylation time of 1 hour and 2 hours).

Figure 3. 13 C NMR spectroscopy spectra of the acetylated lignins, hydroxyl signals.

165 167 169 171 173ppm

Original

1 hour

2 hoursCuran 27-11P

165 167 169 171 173ppm

Original

1 hour

2 hoursAlcell

165 167 169 171 173ppm

Original

1 hour

2 hoursIndulin AT

165 167 169 171 173ppm

Original

1 hour

2 hoursSarkanda

Results and DiscussionFTIR Analysis:

In order to correct for concentration fluctuations, the spectra were corrected

according to the area of the band assigned at 1507 cm-1 in the original sample. This

vibration was not affected by the acetylation procedure. This procedure was tested

with success for the Indulin AT in a previous work (Cateto et al., 2005). For the

other samples analysed in this work, some difficulties were encountered and the

method is being reviewed and improved.

13C Analysis:

The following approximate integration limits were used:

Primary hydroxyls from 170.4 to 169.4 ppm;

Secondary hydroxyls from 169.4 to 168.5 ppm;

Phenolic hydroxyl from 168.5 to 165.8 ppm.

For all the samples, except for Sarkanda lignin, the original spectrum is free of

of contributions in the analysed region. A correction was made.

Reaction time = 1 hr Reaction time = 2 hr

OH (I) OH (II) OH () OH (total) OH (I) OH (II) OH () OH (total)

Indulin AT 0.33 0.22 0.72 1.27 0.28 0.20 0.67 1.15

Curan

27 11P

0.29 0.19 0.69 1.17 0.27 0.18 0.67 1.12

Alcell 0.16 0.10 0.70 0.96 0.19 0.12 0.68 0.99

Sarkanda 0.25 0.32 0.54 1.11 0.24 0.33 0.58 1.15

Table 1. Number of C atoms associated with OH groups per C9 unit (acetylated lignins).

4

5

6

7

8

4 5 6 7 8

Total OH (mmol/g)-13C

Tot

al O

H (

mm

ol/g

)- T

itra

tion

------- Diagonal

Figure 4. Total OH content calculated based on 13C NMR data against total OH content achieved by titration.

Acknowledgements:We thank the French-Portuguese Scientific Cooperation Programme and FCT for financial support within action F-13/06 and grant SFRH/BD/18415/2004, respectively; to MeadWestvaco for supplying us the Indulin AT samples and BooregaardLignoTech for supplying us the Curan 27-11 P samples.

References:C.A. Cateto, M.N. Belgacem, A.E. Rodrigues, M.F. Barreiro, Lignin characterization by acetylation procedures, Proceedings of 9th International Chemical Engineering Conference – CHEMPOR’05, 2005, CD publication – ISBN 972-8055-13-7.D. Pasquini, Estudo de filmes de Langmuir de lenhinas de bagaço de cana-de-açúcar, 2000, Tese de doutoramento, USP-IQSC, São Paulo – Brasil.ISO 14900 – Plastics – Polyols for use in the production of polyurethane – Determination of hydroxyl number.W. G. Glasser, V. Davé, C.E. Frazier, Molecular weight distribution of semi-commercial lignin derivatives, 1993, J. of Wood Chemistry and Technology, 13(4), 545-559.

ConclusionsFor all the cases studied, an incomplete acetylation yield was achieved as verified by the

presence of a residual OH band in the FTIR spectra;

The maximum reaction yield was reached for reaction time of 1 hour as was indicated by the

FTIR experiments and confirmed by the 13C NMR results;

Total OH content was determined both by titration and using the 13C NMR results and found to

be in close agreement.

Laboratory of Separation and Reaction Engineering (1b)

School of Engineering – University of Porto

Laboratory of Separation and Reaction Engineering (1a)

Bragança Polytechnic Institute

Total OH content using 13C NMR results:

The C9 empirical formula was determined based on the results achieved by

elemental analysis (content of C, H and O) and 13C NMR (content of OCH3) according

to Pasquini (2000). Based on this empirical formula, the molecular weight of the C9

unit was determined and thus, allows for the calculation of the of the total OH

content (mmol/g) using the 13C NMR results (OH/C9 unit).

Table 2. Comparison of the total OH content (mmol/g) determined based on 13C NMR and titration results.

(*) obtained after alcalinity correction

NMR results

(reaction time = 1 h)

Titration results

(reaction time = 1 h)

Lignin

Empirical formula

M

(g/mol) Total

OH/C9

Total OH

(mmol/g) Total OH(mmol/g)

Indulin AT C9H8.7O2.81(OCH3)0.77 185.53 1.27 6.85 7.10

Alcell C9H7.22O2.06(OCH3)1.11 182.59 0.96 5.26 5.04

Curan

27-11P C9H9.31O4.33(OCH3)0.83 212.32 1.17 5.51 5.42 (*)

Sarkanda C9H9.20O3.31(OCH3)0.98 236.54 1.05 4.44 4.30