Journal of Analytical and Applied Pyrolysis 107 (2014) 284–288 Contents lists available at ScienceDirect Journal of Analytical and Applied Pyrolysis journa l h om epage: ww w.elsevier.com/locate/jaap The relationship between Eucalyptus grandis lignin structure and kraft pulping parameters Luis Reina a,∗ , Alejandra Galetta a , Vittorio Vinciguerra b , Fernando Resquin c , Pilar Menéndez a a Departamento de Química Orgánica, Facultad de Química, Universidad de la República, Avenida General Flores 2124, Montevideo 11800, Uruguay b Dipartimento per la Innovazione nei sistemi Biologici, Agroalimentari e Forestali, Università della Tuscia, l.go dell’Università, 01100 Viterbo, Italy c Programa de Producción Forestal, Instituto Nacional de Investigación Agropecuaria Tacuarembó, Ruta 5 km 386, Tacuarembó 45000, Uruguay a r t i c l e i n f o Article history: Received 10 December 2013 Accepted 27 March 2014 Available online 4 April 2014 Keywords: Pulping Py-GC–MS Lignin structure Eucalyptus grandis a b s t r a c t The syringyl/guaiacyl (S/G) ratio of Eucalyputs grandis lignin was determined and its relation with kraft pulping parameters was studied. Twenty one wood samples obtained from 10-year-old trees grown in the same place were analyzed using Py-GC–MS to determine the syringyl/guaiacyl (S/G) ratio. The samples were pulped to the same final lignin content (Kappa number 18) obtaining pulp yields between 48.8% and 54.3%. Relationships were observed between pulp yield and S/G ratio (r = 0.51) also between alkali charge used in pulping and S/G ratio (r = -0.60). © 2014 Elsevier B.V. All rights reserved. 1. Introduction Pulpwood production involves different mechanical, chemico- physical and chemical steps, which affect the yield and quality of the pulp, such as the final quality of paper. In order to improve the knowledge of the relationship between wood characteristics and kraft pulp production it is necessary to determinate the factors related to wood that affect pulp production. One factor is wood chemical composition [1], that including the quantity of differ- ent chemical components (e.g. cellulose, hemicelluloses and lignin) and also the structural features of those components. The lignin, present in wood in the proportion of 15–25%, is a complex poly- mer, consisting of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) phenylpropanoid units. It is produced from polymerization of three monolignols, p-coumaryl alcohol (the less abundant compo- nent), coniferyl alcohol and sinapyl alcohol [2]. The structure of the polymer depends on the proportion of those units and the linkages among them [3]. In kraft pulping process wood chips are digested using a solu- tion of sodium hydroxide and sodium sulfide at 130–170 ◦ C. Lignin dissolution is the first objective of the process. When about 90% of lignin is dissolved fibers from wood can be separated [4]. ∗ Corresponding author. Tel.: +598 29244543. E-mail address: lmreina@fq.edu.uy (L. Reina). Cellulose and hemicelluloses are also dissolved in the propor- tions of 7–15% for cellulose and 60–70% for hemicelluloses [5–7]. As the delignification step of the pulpwood production con- siderably influences the pulpwood yield and paper quality, the knowledge of lignin structure represents an important subject of study to foresee the ability to remove lignin from the pulpwood. The relation between lignin removal and kraft pulping yield depends on the lignin quantity and its structure. Some authors have found a negative relationship between lignin content in wood and pulping yield [8–10], although other authors have found that pulp yield depends rather on lignin structure [8,11,12]. In these works they analyzed samples from different ages, sites [11] or species [12]. However, to carry out an efficient breeding program the wood sam- ples should be collected from trees grown in the same location so only their genetic potential can be expressed. In lignin the phenylpropanoid units are linked by ether bonds and carbon–carbon bonds and the latter are more difficult to break, in kraft pulping process, than ether bonds [13,14]. Therefore, when the lignin structure consists in high amounts of C C linkages a harder pulping process (high alkali requirements) will be required to achieve satisfactory delignification. In these conditions, one con- sequence is higher dissolution of cellulose and a drop of pulping yield [5]. Of the different analytical techniques to determine lignin structure [15] pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS) is considered a rapid and very sensitive method. It consists of a thermal degradation of lignin, the separation of the http://dx.doi.org/10.1016/j.jaap.2014.03.013 0165-2370/© 2014 Elsevier B.V. All rights reserved.