Relevance of chemical structure in different wood wastes to pyrolysis behavior: Kinetics and hydrogen release

Abstract

Relevance of chemical structure to pyrolysis behavior from different wood wastes was elaborated in this study. Chemical structure was analyzed by solid 13C nuclear magnetic resonance (13C-NMR) and Fourier transform infrared spectrometer (FTIR). Pyrolysis kinetics was analyzed according to thermogravimetric (TG) data. Results showed that the highest content of C1, 4 carbons in cellulose and weak functional groups in hemicellulose in poplar are leading to the lowest Tm and highest weight loss to increase CO release and decrease hydrogen generation. Amorphous C6 of cellulose in cedar with 12.00% has a remarkable impact on formation of more degree of polymerization during pyrolysis leading to activation energy (Eα) of 199.39 kJ/mol at conversion of 0.8, which is further to the highest hydrogen release. Hydrogen generation is dominated by contracting volume and diffusional theory during pyrolysis controlled by C–O structure in wood waste. The methoxy of lignin in cedar is abundant to produce CH4 for hydrogen generation by gas reaction. Torrefaction of cedar decreases the C–O structure and methoxy so that hydrogen generation from torrefied cedar is lower than that from raw cedar. Due to the different chemical structure with different pyrolysis behavior, hydrogen release rate from three wood wastes by pyrolysis follows the order: cedar > fir > poplar.