Characterization of Endocarp Biomass and Extracted Lignin Using Pyrolysis and Spectroscopic Methods

Abstract

Pyrolysis-GC/mass spectrometry (Py-GC/MS) and thermogravimetric analysis (TGA) was used to analyze the thermal decomposition of several endocarp sources, namely, coconut shells, walnut shells, peach pits, and olive pits, as well as their respective lignin fractions. To determine whether extraction procedures influenced pyrolysate composition and thermal decomposition processes, lignin was extracted from these feedstocks using two different procedures based on the use of formic acid and sulfuric acid (National Renewable Energy Laboratory (NREL) laboratory analytical procedure), after which the lignin-derived pyrolysates and TGA profiles were compared. Qualitative analysis of the distribution of pyrolysates provided predictive information about the structure and composition of the lignin in each sample. Results suggest that the lignin extract pyrolysates contained a different distribution of linkages and monomers in comparison to the non-extracted biomass, suggesting that lignin processing can influence bio-oil composition. Moreover, we identify the types of products obtainable by pyrolysis of these feedstocks and their lignin extracts. Heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (HSQC NMR) and Fourier transform infrared spectroscopy (FTIR) were also used to elucidate the structures of the extracted lignin samples.