Impact of lignin and carbohydrate chemical structures on kraft pulping processes and biofuel production

Abstract

Most studies aimed at determining rates of hardwood delignification and carbohydrate degradation have focused on understanding the behavior of a single wood species. Such studies tend to determine either the delignification rate or the rate of carbohydrate degradation without examining the potential interactions resulting from related variables. The current study provides a comprehensive evaluation of lignin and carbohydrate degradation during kraft pulping of multiple hardwood species. The kraft delignification rates of Eucalyptus urograndis, E. nitens, E. globulus, sweet gum, maple, red oak, red alder, cottonwood, and acacia were obtained. The kinetics of glucan, xylan, and total carbohydrate dissolution during the bulk phase of the kraft pulping process for those species also were investigated. The wide ranges of delignification and carbohydrate degradation rates were correlated to wood chemical characteristics. It appears that the syringyl:guaiacyl lignin ratio and lignin-carbohydrate complexes are the main factors responsible for the differences in kraft pulping performance among the hardwoods studied.