Delignification kinetics of corn stover in lime pretreatment

Abstract

Corn stover was pretreated with excess calcium hydroxide (0.5 g Ca(OH) 2/g raw biomass) in non-oxidative and oxidative conditions at 25, 35, 45, and 55 °C. The delignification kinetic model of corn stover used three first-order reactions with following forms: W L = 0.09 · exp(−∞ · t) + 0.28 · exp(− k 2 · t) + 0.63 · exp(− k 3 · t) in non-oxidative pretreatment; W L = 0.16 · exp(−∞ · t) + 0.27 · exp(− k 2 · t) + 0.57 · exp(− k 3 · t) in oxidative pretreatment. The first term corresponds to the initial phase, which is essentially infinite at the time scale of the reaction (weeks). The second and third terms correspond to the bulk and residual phases of delignification. The activation energies for delignification in the oxidative lime pretreatment reactions were estimated as 50.15 and 54.21 kJ/mol in the bulk and residual phases, respectively, which are similar to the Kraft delignification of bagasse, but much less than in Kraft delignification of wood.