from first principles PP-I-1

OP-IV-1Kinetic Study of Aspen-Wood Delignification by H 2 O 2 with Sulfuric AcidCatalyst under Mild ConditionsKuznetsov B.N. 1,2 , Sudakova I.G. 1 , Garyntseva N.V. 1 , Djakovitch L. 3 , Pinel C. 31 Institute of Chemistry and Chemical Technology SB RAS, Krasnoyarsk, Russia2 Siberian Federal University, Krasnoyarsk, Russia3 Institut de Recherches sur la Catalyse et l’Environnement de Lyon (IRCELYON), Lyon, Francebnk@icct.ruPreviously, it was shown that a significant intensification of oxidative delignification of woodby H 2 O 2 in acetic acid–water medium at 120–130 °C and increased pressure takes place in thepresence of sulfuric acid catalyst (SAC) [1]. The present communication describes the resultsof kinetic study of a “green” process of aspen-wood oxidative delignification by H 2 O 2 withSAC under mild conditions: temperature less 100 °C, atmospheric pressure.Kinetics of wood delignification process was investigated at variation of temperature(70–98.5 °C), concentration of H 2 O 2 (2–6 wt%), acetic acid (15–40 wt%), H 2 SO 4(1 wt% ), liquor ratio (5–15), time (1–4 h). The increase of temperature, concentrations ofH 2 O 2 and acetic acid, liquor ratio (LR) and time results in the acceleration of the rate ofdelignification process. Cellulose obtained under the optimal conditions (98.5 °C, H 2 O 2 4 wt %,CH 3 COOH 25 wt%, H 2 SO 4 1 wt%, LR 10, 4 h) contains only 0.6 wt% of residual lignin. Thedecomposition of hemicelluloses and amorphous part of cellulose is also intensified at theseprocess parameters. The time dependence of residual lignin content in cellulosic product andconcentration of dissolved LMML corresponds to first order equation. Rate constants ofaspen-wood delignification process vary from 0.25·10 -4 c -1 (70 °C) to 2.5·10 -4 c -1 (98.5 °C).The activation energy of aspen-wood delignification is 90.9 (13.0) kJ/mol. This value pointsthat delignification process goes predominantly in kinetic region.The possible mechanism of wood delignification in the medium “acetic acid – H 2 O 2 –water–SAC” is discussed. Some dependences between the delignification process parameters andreaction ability of main wood components (lignin, hemicelluloses, cellulose) and products oftheir oxidative and hydrolytic depolymerization are established. Optimal conditions of aspenwooddelignification were selected which allow to obtain by “green” method at atmosphericpressure the cellulosic products with a variable content of residual lignin, hemicelluloses,amorphous and crystalline cellulose.References:[1] B.N. Kuznetsov, S.A. Kuznetsova, V.G. Danilov et al. Reac Kinet Mech Cat. 104 (2011) 337.77