Carbohydrate Polymers 106 (2014) 60–70 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Thermal degradation behavior and kinetic analysis of spruce glucomannan and its methylated derivatives Rosana Moriana a , Yujia Zhang a , Petra Mischnick b , Jiebing Li a,c , Monica Ek a,∗ a Department of Fibre and Polymer Technology, Royal Institute of Technology-KTH, SE-100 44 Stockholm, Sweden b Department of Food Chemistry, Technische Universität Braunschweig, Schleinitzstraße 20, D-38106 Braunschweig, Germany c Wallenberg Wood Science Center, The Royal Institute of Technology and Chalmers University of Technology, SE-100 44 Stockholm, Sweden article info Article history: Received 13 December 2013 Received in revised form 22 January 2014 Accepted 25 January 2014 Available online 2 February 2014 Keywords: Spruce glucomannan Konjac glucomannan Methylated glucomannan Thermogravimetry Thermal degradation behavior Kinetic triplet abstract The thermal degradation behavior and kinetics of spruce glucomannan (SGM) and its methylated deriva- tives were investigated using thermogravimetric analysis to characterize its temperature-dependent changes for use in specific applications. The results were compared with those obtained for commer- cial konjac glucomannan (KGM). The SGM and the KGM exhibited two overlapping peaks from 200 to 375 ◦ C, which correspond to the intensive devolatilization of more than 59% of the total weight. Differ- ences in the pyrolysis-product distributions and thermal stabilities appeared as a result of the different chemical compositions and molecular weights of the two GMs. The Friedman and Flynn-Wall-Ozawa isoconversional methods and the Coats–Redfern were adopted to determine the kinetic triplet of the intensive devolatilization region. Both GMs can be modeled using a complex mechanism that involves both a Dn-type and an Fn-type reaction. The comparative study of partially methylated GM indicated higher homogeneity and thermal resistance for the material with the higher degree of substitution. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Hemicelluloses are structural carbohydrates of plant cell walls that, in close association with cellulose and lignin, form the lignocellulosic biomass. Hemicelluloses generally occur as het- eropolysaccharides, in which their main building units are hexoses (d-glucose, d-mannose and d-galactose) and pentoses (d-xylose and l-arabinose). Small amounts of deoxyhexoses (l-rhamnose and l-fucose) and uronic acids (4-O-methyl-d-glucuronic acid, d-galacturonic acid and d-glucuronic acid) are also present. Hemi- celluloses have a lower degree of polymerization (DP) and are more easily hydrolyzed and less thermally stable than cellulose. An understanding of their pyrolytic behavior is of paramount importance in improving process fundamentals and designing effective biomass-conversion technologies, such as the torrefaction process, which is carried out at the typical degradation tempera- ture of hemicelluloses (Branca, Di Blasi, Mango, & Hrablay, 2013; Chaouch, Pétrissans, Pétrissans, & Gérardin, 2010). In general, in ∗ Corresponding author at: Division of Wood Chemistry and Pulp Technology, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Teknikringen 56, SE 10044 Stockholm, Sweden. Tel.: +46 08 790 81 04; fax: +46 08 790 6166. E-mail address: monicaek@kth.se (M. Ek). thermochemical conversion technologies, pyrolysis plays a key role in determining the reaction kinetics, and it is therefore critical to reactor design and the determination of product distribution, composition and properties (Raveendran, Ganesh, & Khilar, 1995). Pyrolysis studies are also essential to implementing new biomass- conversion technologies, such as low-temperature carbonization and chemical production from solid fuels (Seo, Park, Hwang, & Yu, 2010). A significant number of studies are available concern- ing the pyrolysis of xylan from hardwood hemicelluloses (Bilbao, Millera, & Arauzo, 1989; Di Blasi & Lanzetta, 1997; Shen, Gu, & Bridgwater, 2010). In contrast, no study is available regarding the thermal behavior, thermal degradation kinetics and products of pyrolysis of softwood glucomannan, which is the main component of softwood hemicellulose. The thermal and kinetic aspects of solid state decomposition reactions are complex (Yang, Miranda, & Roy, 2001) and involve a large number of parameters to investigate. Thermogravimetric analysis (TGA) is one of the most widely used techniques to assess the thermal and kinetic behavior of carbohydrate polymers, allow- ing the determination of parameters such as the kinetic triplet, which includes (Nelson David, Hallen Richard, & Theander, 1988) the apparent activation energy, the reaction mechanism (f(˛)) and the pre-exponential factor (A)(Akbar, Iqbal, Massey, & Masih, 2012; Iqbal, Massey, Akbar, Ashraf, & Masih, 2013; Moriana, Vilaplana, Karlsson, & Ribes-Greus, 2011; Yao, Wu, Lei, Guo, & Xu, 2008; 0144-8617/$ – see front matter © 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbpol.2014.01.086