Kinetic Study of the Thermochemical Degradation of Lignocellulosic Materials Based on TG-FTIR, Py-GC/MS and 13C NMR Experiments

I. Hrablay and L. Jelemenský

Abstract
Pyrolysis of a hardwood representative, beech sawdust (Fagus sylvatica), was investigated by thermogravimetry, a thermal analysis technique. A suitable kinetic approach for the determination of kinetic parameters was proposed. The model fitting method was used to optimize the kinetic parameters of the reaction pathways of the selected reaction mechanisms. The experiments were conducted starting from ambient temperature up to 600 °C using the following five heating rates: 2, 5, 10, 15, and 20 °C min–1. FTIR, Py-GC/MS, 13C NMR, and elemental analysis were also used to analyse the pyrolysis products. Differentiation among the reaction mechanisms of lignocellulosic material pyrolysis was performed. The three-step parallel mechanism containing an intermediate was the most suitable mechanism based on 13C NMR analysis of solid residues prepared at the selected temperatures from 230–500 °C. The NMR results showed that the inclusion of an intermediate into the reaction scheme was a reasonable step. It was concluded that the intermediate was connected with the lignin structure.

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Keywords
kinetics, wood pyrolysis, mechanism, TG-FTIR, NMR, Py-GC/MS