Determination of structural and thermal features of cellulose from different eucalyptus species

Abstract

Wood from Eucalyptus genus is an important raw material for pulp and cellulose derivatives production. With the aim to understand the differences and the further use for production of cellulose derivatives, eight six-year-old Eucalyptus species were sampled and analyzed for anatomical and chemical characterization. The species studied corresponded to E. badjensis, E. benthamii, E. dunnii, E. globulus, E. nitens, E. smithii and two hybrids of E. nitens x E. globulus (coded x64 and x65), which ranged a wood density of 420 – 484 kg/m3, being E. globulus and E. smithii the higher wood density trees, and E. badjensis the lower one. Different chemical and anatomical features were observed from the different wood species. Infrared spectroscopy (FTIR), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) data were obtained from wood, holocellulose and alphacellulose samples of the eight Eucalyptus studied in order to obtain information about their cellulose structure. From FTIR spectra, the total crystalline index (TCI) and the lateral order index (LOI), which is defined as an empirical crystallinity index, were calculated. In wood samples the TCI ranged 0.292 – 0.394, while LOI ranged 1.013 – 2.698. From XRD data, the crystallinity index (CrI) and crystallite size can be obtained. The CrI ranged 51.2 – 57.2% in wood samples. The highest TCI and CrI values were observed in E. dunnii; the lowest TCI values were observed in E. nitens and E. smithii, and the lowest CrI values were observed in E. badjensis, E. smithii and E. nitens. It was also observed that TCI and CrI values increase after holocellulose isolation, but both decrease again in alpha-cellulose samples. From TGA, the thermal degradation profiles obtained showed that the higher DTG peak temperature (related with cellulose degradation) was observed in x64 and E. dunnii (369ºC), while the lower DTG peak temperature was observed in E. smithii (352ºC). Therefore, Eucalyptus species showed different variation patterns for the structural features of cellulose, which could be attributed to chemical and structural properties of the inherent properties of wood components from each species.